1. What is a radiographer?

A radiographer or medical imaging technologist is a trained health professional who performs medical imaging by producing high quality X-ray pictures or images used to diagnose and treat injury or disease. It is an important part of medicine and a patient’s diagnosis and treatment is often dependent on the X-ray images produced.

2. What does a radiographer do?

A radiographer is an important member of the diagnostic health care team. They are responsible for producing high quality medical images that assist medical specialists and doctors to diagnose or monitor a patient's injury or illness.

They operate extremely technologically advanced equipment such as CT (Computed Tomography), MRI (Magnetic Resonance Imaging) and mobile X-ray machines. Their roles are diverse and challenging, as radiographers are often trained in several specialist areas such as:

Trauma radiography - challenging examinations on injured individuals.

Mobile radiography - for patients too sick to travel to the X-ray department.

Computed tomography - three dimensional X-ray imaging test.

Magnetic resonance imaging - three dimensional imaging test powered by a large magnet.

Fluoroscopy – X-ray test that examines the internal body and shows moving images on a screen like a movie.

Angiography - imaging of blood vessels and the heart.

Operating theatre - assisting surgeons during operations with special X-ray equipment.

Radiographers need to show care, compassion and empathy to their patients. Whilst the role is highly technical, radiographers focus their efforts on patient care and welfare to ensure positive patient experiences. The radiographer works in a highly advanced technical profession that also requires excellent people skills. It is an exciting and rewarding profession to be a part of.

Radiographers have an extremely thorough understanding of the structure of the body, how the body can be affected by injury, and causes and effects of disease when taking X-ray images. However, they are not responsible for interpreting the images they produce. This is the role of a radiologist, who is a specialist doctor with a medical degree, and who has also completed clinical training and

then specialised in interpreting images and writing a diagnostic report for referring doctors. Radiologists rely on the input of radiographers and there is a very close working relationship.

Radiographers work in a variety of situations including radiography/medical imaging departments of large public hospitals with busy emergency departments, private hospitals and large and small private radiology practices, sometimes with only a couple of rooms and a few staff.

Radiology or medical imaging departments are extremely safe places to work and to spend time in. There are state and federal regulations governing safe work practices and radiation safety within all X-ray departments and private imaging clinics. See Radiation Risk of Medical Imaging in Adults and Children for more information.

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3. Why become a radiographer?

A radiographer’s role is challenging, rewarding and highly skilled. Radiographers become part of a vital group of medical professionals with specialist training and highly developed skills. There is significant patient contact and a radiographer plays an important part in improving patient outcomes and experiences. The profession offers excellent career prospects with qualified staff in high demand. There are many benefits in becoming a radiographer such as:

Excellent job prospects in a highly skilled and rewarding job.

The opportunity to work in a diverse range of specialist areas, e.g. CT, MRI, etc.

Using cutting edge technology.

On-going training (radiographers are constantly improving their knowledge and skills).

Great travelling opportunities (radiographers are in high demand both nationally and internationally).

A financially rewarding career.

Flexible working arrangements (full-time, part-time and locum work is available).

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4. How do you become a radiographer?

A radiographer must become a graduate of a Medical Imaging Degree program. There are several courses throughout Australia available to prospective radiography students. The admission requirements vary between universities. Generally there are options available for school leavers, non-school leavers, mature students and overseas students.

All courses demand a high degree of academic study, as well as clinical expertise in routine and advanced medical imaging procedures. Most courses are three years in duration with a graduate needing to undertake one year of mentored clinical experience to complement their university studies (called an intern year). This intern year may vary in duration, structure and name depending on the State and university.

The Australian Institute of Radiography website has more information about radiographers.

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5. Where does a radiographer study?

Diagnostic radiography courses are available in most states in Australia. The Universities currently running the courses include:

NSW:

The University of Newcastle: (www.newcastle.edu.au/)

The University of Sydney: (www.fhs.usyd.edu.au/mrs/)

Charles Sturt University: (www.csu.edu.au/faculty/science/)

VIC:

RMIT University: (www.rmit.edu.au/medical-sciences)

Monash University: (www.med.monash.edu.au/radiography/)

QLD:

Queensland University of Technology: (www.sci.qut.edu.au/)

SA:

University of South Australia: (www.unisa.edu.au/hls/)

WA:

Curtin University of Technology: (www.medicalimaging.curtin.edu.au/)

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6. What else can a radiographer do?

One of the greatest benefits in this profession is the variety and scope for progression. Apart from performing plain examinations like chest X-rays, radiographers have the opportunity to become expert in areas like CT, MRI, angiography, fluoroscopy, trauma (injury) radiography, mobile radiography, and operating theatre radiography. Radiographers also have the opportunity to take on roles in the following areas:

Clinical leadership - within most environments there are supervisory positions and clinical education (tutoring) careers for experienced staff.

Corporate management - Radiographers are recruited to management roles.

Education - university lecturing (see section above on Where does a Radiographer study?).

Research - advanced qualifications in research such as graduate diplomas, masters degrees, and PhDs can be pursued by radiographers or medical imaging technologists.

Corporate applications - Radiographers are recruited by radiographic equipment companies to train users in clinical practice.

Corporate sales - X-ray equipment companies require radiographers to sell their equipment to private radiology groups and hospitals.

Sonography - many radiographers choose a career in sonography (a person who performs diagnostic ultrasound procedures). This does require further training and the completion of a graduate diploma.

Some radiographers run their own business in partnership with other imaging professionals like radiologists.

Abstract

Rapidly evolving changes in the way that healthcare is administered, coupled with the amazing recent advances within imaging, has necessitated a review of the way in which radiology should be regarded. This review considers some aspects of these changes and offers some recommendations.

Keywords: Radiology, Training, Subspecialisation, Teleradiology, Interventional radiology

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Introduction

Radiology has been a distinct medical specialty with unique technical challenges from its inception. The origins of specialisation can be traced back to the technical nature of X-ray image capture and perhaps more significantly the difficulty of exposing, transporting and developing images on fragile glass plates for subsequent interpretation. Despite pressure in the early 1900s to define radiology as a technical service, radiographic image interpretation and reporting required medically trained specialists. Therefore, radiologists have been clinical specialists, who have been obliged to also become experts in image capture technology, broad-based advances in engineering and, more recently, applications of information technology for healthcare, which continue to drive and be driven by radiology.

Radiology is now the key diagnostic tool for many diseases and has an important role in monitoring treatment and predicting outcome. It has a number of imaging modalities in its armamentarium which have differing physical principles of varying complexity. The anatomical detail and sensitivity of these techniques is now of a high order and the use of imaging for ultrastructural diagnostics, nanotechnology, functional and quantitative diagnostics and molecular medicine is steadily increasing. Technological advances in digital imaging have also enabled the images produced to be post-processed, manipulated and also transmitted rapidly all over the world to be viewed simultaneously with the transmitting centre.

Radiologists have been strongly involved in these technological developments and have been responsible for much of the evaluation of the strengths and weaknesses of different investigations. Radiologists have developed the knowledge of the appropriate integrated imaging algorithms to maximise clinical effectiveness. They have also been responsible for the implementation of these developments into the clinical setting and for ensuring the best use of assets and healthcare resources.

The improved image clarity and tissue differentiation in a number of situations has dramatically increased the range of diagnostic information and in many cases the demonstration of pathology without the requirement of invasive tissue sampling (histology). This increased information also requires careful interpretation without preconception to avoid prejudging the findings. The use of imaging for functional evaluation and cellular activity has created a new challenge for radiologists

whose training has predominantly been based on the anatomical and pathological model with limited experience in physiology and cell function. It has therefore been the case that in some super specialist areas of work, clinician specialists may believe that radiologists have not contributed sufficiently to the care of patients [1]. It is therefore incumbent on radiologists to mobilise their skills to utilise these new approaches to evaluate clinical questions in the most effective way. For this reason the radiological training programme for Europe is now mainly system- and disease-focussed to ensure that radiologists can respond to the multiple interactions of patient care.

Although the training programmes are repositioning radiology in this way, these developments are now occurring and are affecting all radiologists who in general, at present, are satisfied with their overall position within the respective health care system in most European countries. Radiologists have no difficulties in finding professionally fulfilling and well-paid employment. Indeed the rapid rise in workload and complexity of examinations have resulted in a shortage of radiologists in most countries which may reduce the opportunity or desire to move and up-date sufficiently with these advances. The availability of high-speed internet transfer of images may affect the requirement and role of local radiologists by transferring images to major centres for rapid specialist interpretation. Thus the rapidly developing and expanding field of imaging becomes a challenge to our specialty, especially as it has also become so attractive to others. We should therefore be concerned to ensure the future of radiology as a medical specialty and take into consideration the forces and the dynamics surrounding our profession by meeting them with foresight and flexibility.

Although as a specialty we must embrace the opportunities that these developments create, the requirements to embrace all aspects of the speciality are now considered unattainable for any individual, especially in an environment where the clinicians themselves are focussed on specific anatomical or disease-related areas as specialists. Therefore the dilemma for radiology and radiologists is how to achieve the objectives of the specialty and still provide a comprehensive service within the confines of a radiology department where so many of the tasks previously undertaken by clinicians are now the province of radiology.

The need for change

Numerous facilities in clinical services are collectively used by different specialties: operating rooms are not owned by surgeons anymore, ICUs have become independent of departments of cardiology, internal medicine, or neurology, while emergency rooms are not part of traumatology departments. Hospital beds are no longer dedicated to individual specialists or specialties and are available for radiologists for one or two nights following interventional procedures in some hospitals. At present the radiology department remains predominantly the domain of the radiologist, but this is changing and there is no specific reason why imaging facilities should not be used by other clinical specialists trained in imaging, and images produced in these departments may also be reported remotely.

New knowledge in imaging is being developed at an increasingly rapid rate. The field of radiology has expanded dramatically. The range of radiology covers diseases from the foetus through to the multi-morbid aging population, from prostate to the pituitary gland and from pancreatic neoplasia to bone dysplasia. No single person can master all the available knowledge. However, the referring physicians need a clinical interface with the imaging specialist. In order to create added value for the referring clinician, the radiologist must fully understand the clinical problem. The radiologist is expected to be able to do this at a different level and for all medical specialties. Therefore clinical experience is required before embarking training in imaging, and appropriate training in specific clinical specialties may also be needed. If not, imaging may increasingly be regarded as a sub-entity within the clinical specialty and in that setting each specialty will take care of its own specialised imaging and training, and the influence of the radiological expertise would diminish.

Public recognition of the clinical role of radiology is essential and is very much dependent on contact with the patients [2]. However, over the past years radiologists reading more and more complex examinations have become less and less visible for patients and the public. Moreover, in some health care systems the emphasis of radiology work is placed on the in-patient referrals to major general (secondary) and university (tertiary) hospitals where the role of the radiologist as part of the team is less obvious to the patient. There has been less focus on the provision of radiology services to primary care (including general practitioners and office based specialists), where the requirements are different, with a need for a more general service but still involving a range of imaging services, and where the individual role of the radiologist is more obvious to the patient.

In some countries clinical specialists may be the primary providers and interpreters of imaging in their offices. This has potential disadvantages for the patients. The self-reporting clinician may focus on the images to confirm or refute a preconceived clinical diagnosis whereas the interface of a radiologist, reporting the images, provides an independent opinion. It is also suboptimal for funding healthcare, as self-referral has been shown to increase numbers of radiological procedures and consequently costs. Moreover, radiologists will ensure the appropriate use of equipment and quality control, and apply radiation protection principles which are particularly pertinent with the massive increase in the use of multi-detector CT [3].

Radiology has prospered by staying ahead of the wave of progress. But radiologists will have to change many of their attitudes and rethink their professional training to accommodate to the dramatic revolution and evolution of radiology [4]. Radiologists need to adapt to the changes in technology in order for the profession to deliver the service that patients expect and medical progress requires.

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Specialisation in radiology

One solution has been a gradual increase in the degree of specialisation of radiologists along systems and disease-related specialties, which has been strongly advocated by the ESR in its curriculum. Some radiologists have focussed on particular imaging modalities which may have assisted the development of these modalities, but the range of imaging techniques to evaluate particular clinical scenarios is such that this approach is not appropriate when dealing with clinicians who have all specialised along systems and disease-based pathways. The current curriculum for training has been adapted to take this process into account. It now separates radiologists, following training to a core level in all aspects of radiology including all techniques, into two main categories:

Radiologists who have additional dedicated training to provide special interests in two or possibly three system-based specialties. These radiologists work in teams to provide a 24/7 comprehensive radiological service and at present represent the largest radiological community.

Radiologists who have subsequently focussed on one field of radiology which parallels a medical or surgical specialty and who work primarily in that subspecialty in secondary or tertiary referral centres.

It is however still debated how far subspecialisation should proceed and how enthusiastically it should be promoted. It is also unclear how the process should be managed in order to provide an integrated cohesive imaging service to the patients and their clinicians.

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Reasons for subspecialisation

The argument for subspecialisation is strong and a number of factors should be taken into account.

Information overload:

Our field has become so complex that no individual can maintain the level of expertise needed to practice the entire field of radiology. At present we insist that radiologists become at least minimally competent in the entire field although it is virtually impossible today to remain a radiologist with competence in all areas of our specialty [5]. However, in interventional radiology, for example, sub-specialist training is needed to gain deeper knowledge, new techniques and practical experience to provide a high level of clinical service. The technical demands for procedural skills and familiarity with new devices mean that only a few members of a group can develop the expertise to practice interventional radiology. Mammography quality standards require that physicians practising mammography interpret a minimum number of cases and attain specific breast-related continuing medical education to continue the practice.

Developments too rapid:

There are many examples of the effect of rapid developments but the increase in the temporal and spatial resolution of acquisition in CT and the complexities of new software packages in MR have been paramount. The former has involved radiologists in many non-invasive vascular imaging interpretations that were previously the domain of the sub-specialist. The latter has resulted in functional imaging, spectroscopy and diffusion imaging requiring specialist knowledge to conditions which hitherto have been the responsibility of the clinical radiologist such as the early evaluation of stroke patients. The emergence of fusion imaging presents further challenges to staying abreast of this evolving technology. As the field of radiology expands, the degree of sub-specialisation requires maintaining competence increases [5]. Thus the growing array of radiological tools will require radiologists in various practice settings to make fundamental decisions about how to focus and balance their areas of expertise [6]. It is impossible for the radiologist, who is providing a busy comprehensive service, to assimilate these advances.

Clinicians in secondary and tertiary referral centres are all specialised:

Secondary and tertiary based clinicians have long since abandoned the concept of the generalist and focus on particular systems or disease-related areas. While the imaging of disease becomes ever more complex, the clinical conditions remain mainly unchanged although the ability of the clinical specialist to treat these conditions is advancing. This reduced pace of change enables the clinicians to assimilate and often develop new ways of addressing the diseases in their special area, thus posing a challenge to the radiologist who is not aware of these developments.

Now better and faster imaging machines enable more accurate diagnosis with less risk and at lower costs than ever before so that radiologists will not be the only specialty to be able to identify disease sites and morphology. The developments also apply to clinical sciences such as the rapid growth of anti-cancer drugs requiring a new insight by imaging of tumour response, or to developments in laparoscopic surgery which need detailed staging of disease by radiology.

The referring clinician’s role changed by imaging:

The patient characteristics, clinical history and examination remain important to guide the investigative choices and are an integral part of the clinical examination. Clinical information is important to correlate with the imaging findings, especially to avoid false positive imaging diagnoses. However, in many circumstances a long differential diagnosis may be resolved by modern objective imaging which can provide a precise diagnosis in a few minutes. The role of surgeons has also been changed by the emergence of laproscopic surgery and by image-guided endoscopic and interventional techniques. These developments require even more precise delineation of the lesion before intervention and yet even closer collaboration between radiologists and referring clinicians.

Patients and clinicians require comprehensive information and the most accurate diagnosis:

A reduced level of expertise of the non sub-specialised radiologists may reduce the quality of patient care, and also the respect radiologists are accorded by their colleagues in other medical disciplines. For example an experienced neurologist or orthopaedic surgeon is unlikely to rely on a diagnosis made on a MR study by a radiologist who has had only 3–4 months of training in neuroradiology or musculoskeletal imaging. This lack of confidence in radiologists would force them to rely on their

own interpretations. They no longer want radiologists to report back with generalised observations about the abnormalities.

Teleradiology can provide instant access to sub-specialist opinion:

Teleradiology is becoming a significant component in the delivery of radiological services due to the high quality and speed of image transmission. Communication of images between radiologists, via local or distant networks is now a widely available option to solicit a specialised opinion in selected cases. This enables subspecialty opinions to be provided easily and quickly, thus undermining the role of the radiologist who does not possess a specialised knowledge. The patients and their clinicians are now rightly expecting an expert opinion and it is possible now to obtain one through teleradiology services.

Technological developments:

There are often short innovation cycles of radiological equipment and it is important that there are specialist radiologists who are able to assist the manufacturers with technological developments and clinical implementation. It is also important to emphasise that radiologists have special expertise in technology not possessed by other clinicians, which provide an indispensable link with other disciplines such as physicists, experts in information technology, molecular biology and engineering. It is essential that knowledge of the technology used is included in radiological core and subspecialty training.

Research:

It is imperative that radiologists are engaged in research in their own discipline. Research in radiology is part of the huge domain of clinical research requiring imaging and at present much of this research is undertaken through multidisciplinary protocols led by clinicians and scientists with radiologists seen as a relatively small contributor. Unless specialisation occurs, radiologists will be unable to reverse this situation and thus risk a further loss of influence in the future of imaging at a time when there is a major transformation to functional and molecular imaging. The breadth of research topics relevant to radiology is constantly expanding and includes development in technology and its applications, epidemiology, molecular biology, computer science and other basic research fields.

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Reasons for maintaining radiology with special interest(s)

In most secondary care centres and large private radiological offices radiologists have developed additional expertise in two or three clinical disciplines which supplement the delivery of a general service and complement each other within the department or practice. This enables the practice and individual radiologists to add value to the clinicians and provide support to each other.

Diseases are not always restricted to one system:

While a number of disorders may be confined to one organ or system, such as musculoskeletal or intra-cerebral abnormalities, others may involve a number of systems such as diabetes, some

neoplastic disorders or inflammatory diseases. There may also be circumstances were the initial patient imaging examination may reveal other abnormalities, which were unsuspected and potentially life-threatening. A patient, who may have a specific lesion directly related to the individual specialty, may have co-morbidity that will affect their management, while other abnormalities and disease processes can and are demonstrated incidentally by radiology, and the radiologist is essential to avoid assumptions and also false positive conclusions. In these circumstances the radiologist needs to have a broad perspective and a wide knowledge of anatomy, pathology and imaging signs. This is difficult to maintain, even when the initial training is broad-based, if the subsequent work is highly specialised. It is important that there is good joined-up thinking to avoid the patient having unnecessary examinations and being referred to a variety of physicians.

The majority of illness is due to a few common disorders:

Some imaging examinations are commonly performed in most hospitals and all radiologists should be sufficiently experienced to manage and interpret them.

A knowledge of all modalities is important:

The value of different modalities varies by disease and clinical question and some modalities have considerable limitations in some organ systems. Radiographs, ultrasound, computed tomography (CT), magnetic resonance (MR) and nuclear medicine techniques are all of value in different clinical situations in musculoskeletal radiology while in neuroradiology MR and CT are predominant.

Radiology is a 24/7 speciality:

If all radiologists are sub-specialists, it requires a large staff to cover all emergency work in-house. Sub-specialist staffing requirements are also increased to cover sickness and leave of absence, if continuity of service is to be achieved. Teleradiology may be of value but there is a resultant loss of contact between the radiologists and clinicians, if this is used extensively. The use of this technology is under scrutiny and is being restricted in some countries to ensure that quality issues are robust. Emergency radiology is now becoming a specialist area and the presence of radiologists on site in major accident and emergency departments is essential for the smooth running of the service and although some local emergency radiology reporting has been replaced by teleradiology.

Integrated nature of radiology should not be lost:

If all radiologists are sub-specialists, there may be a loss of unity in the department and a loss of interest in discussing cases. Satellite organ- or disease-based departments may become an expectation with a potential duplication and under use of expensive capital equipment and clinicians may set up their own subspecialty radiology departments in conjunction with either the sub-specialist radiologist or a clinician who has done some imaging training as part of their specialist clinical training.

Access to subspecialty training is limited in some parts of Europe:

In many countries in Europe sub-specialisation and access to complex equipment is limited. Therefore no opportunities are available to train or practice in a subspecialty. This situation is

changing by implementing fellowship programmes and by the use of electronic teaching files and internet-accessible case collections but it may be resource-limited and the complex sub-specialisation model may not be appropriate outside the major university hospital setting.

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How should sub-specialisation be implemented in radiological practice?

Subspecialisation is established in university hospital settings and large hospital-based non-academic practice groups, who are increasingly appreciating the value of having this high level of expertise within their groups, and the process towards increasing super-specialisation is already upon us and is continuing. Neuroradiologists focus on spinal, paediatric, interventional, or head and neck radiology. Interventional radiologists may concentrate on vascular procedures, non-vascular intervention, or oncologic procedures, such as percutaneous tumour ablation or chemo-embolisation. Thoracic radiologists are often divided into those who provide cardiac imaging and those limiting their practice to the lungs and mediastinum.

However the primary care physician will need help from radiologists to decide which imaging procedure will most likely provide the diagnosis without having to go through the escalating sequence of imaging or other tests. Radiologists will also be expected to manage and report these examinations, many of which will cover a spectrum of common disorders which form the mainstay of any primary care service. To be able to render these consultative services, the radiologist will need to keep abreast with the new key developments in most subspecialties [1].

It is therefore likely that more than one model of practice will continue, depending on the physical circumstances of the service required, but in order to be valuable to the clinicians, the radiologists must have sufficient insight into the clinical problems being investigated and greater skills in interpreting more complex images than the clinicians themselves. In areas where there are significant ‘turf strains’, of which there are an increasing number, subspecialty qualifications may be a requirement. Radiologists should therefore have areas of subspecialty competence, even if they still provide a broad service most of the time.

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Clinical competence

One of the main reasons why radiologists are losing many turf issues is their inadequate clinical culture. A high level of technical training is not sufficient for dealing with clinicians and their clinical queries. Medical practice is becoming increasingly interdisciplinary due to the vastness of knowledge involved. The importance of clinical training has been emphasised previously by the ESR but it is still not a requirement for entry into radiology in a number of European countries. It is essential that, if radiologists are expected to understand the clinical features and treatment of sub-specialist areas, they have a good clinical base on which to build that knowledge. Good clinical training will enable

radiologists to interact at the appropriate level with clinicians. Therefore radiologists, to be able to take part in an interdisciplinary discussion as a key player, will not only have to be specialised in the imaging of a specific organ system but also to be able to discuss complex clinical cases. Clinicians require radiologists who understand the clinical questions, keep updated with the most recent advances in the disease processes and have knowledge of the relevant therapies.

A basic clinical experience and knowledge should be achieved prior to entering radiology. A 1–2 year programme of clinical work would ensure a sound basic knowledge and give the appropriate skills for caring for patients and interacting with clinicians. Attempting to develop a sound clinical base during radiological training may be difficult to organise and will distract and potentially dilute the radiological training programme. Further subspecialty clinical knowledge and experience may then be achieved in a number of different ways, which are not mutually exclusive, including combined clinical and radiological rounds, interdisciplinary meetings, scientific literature and research and where possible clinical secondments.

As part of this clinical knowledge and experience, radiologists in specialised situations must have a good understanding of the physiology, pathology, and up-to-date therapies applicable to their respective organ system. They must also be experts in the multiple imaging modalities applicable to the clinical problem addressed [1]. Whatever methodology is adopted to develop the necessary clinical experience, it should be focussed in the area in which a radiologist will practice, and would be more appropriately embedded in the subspecialty training.

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Interventional radiology

The field of interventional radiology has moved at great speed over the last few years, and there is no evidence of a reduction in the pace. Indeed quite the opposite is true as more and more surgical procedures are performed with minimal invasion. Radiology has led the field but is being overwhelmed by the volume of work and the desire of surgeons and physicians to take over this work. In order to preserve radiology’s place, it is essential that a radiologist’s training in interventional radiology is structured in such a way to ensure that they not only have the core diagnostic imaging skills, knowledge and technical interventional competence, but also have sufficient clinical skills and training to care for their patients. Interventional radiologists must also be given the necessary resources of clinic time, hospital facilities and support to take and treat direct referrals. An innovative approach to training in conjunction with our surgical, cardiological and oncological colleagues is required to ensure that radiologists remain key operators in this subspecialty. Interventional radiology should also be funded and recognised for the clinical work they provide. In health economies that use Diagnostic Related Groups (DRG) for payment purposes, it is of utmost importance that patients admitted for an interventional procedure create income for the radiology department in due proportion to the gain provided to the hospital by the intervention and the hospital stay.

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Training implications

The European Training Charter for Clinical Radiology [7] identifies the first 3 years devoted to developing the core skills and knowledge in all aspects of diagnostic radiology. The following 2 years may be spent either undertaking subspecialty training or gaining further experience while developing areas of special interest by focussing more time in two or three organ- or disease-related specialties.

In a report of the 2005 Intersociety Conference, Reed Dunnick et al. also advocate that the first 3 years of training in radiology could constitute a core curriculum. However, they suggest that this would be followed by a three-year focused programme. In America, this would replace their traditional fellowship and could include clinical training. During this period of training each resident would be required to focus on one or perhaps two subspecialty areas. A variety of choices would be available depending on an individual’s interest.

There may be organisational challenges to obtaining subsequent clinical experience during subspecialty training although this could be on the basis of supernumerary status which would provide clinical exposure without taking clinicians resident positions, but gaining a sound clinical base prior to starting radiology is entirely possible given the acquiescence of national policies. Additional clinical experience should follow a structured curriculum individualised for each subspecialty.

There is a fundamental requirement to increase the exposure of medical students to imaging taught by radiologists. Presently, the number of radiologists involved in undergraduate training is low. As a result the potentials and excitement of radiology as a career are not transmitted and the realisation that radiologists are key players in the patient care pathway is not embedded in the medical student’s psyche at an early stage. There are a number of initiatives that have been developed in Europe for increasing the teaching of radiology at undergraduate level and these should be further promoted.

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Teleradiology: an opportunity

Teleradiology is now an established method of providing radiological services. It is well developed in the provision of on-call emergency reporting being used by over 70% of radiological practices in the US both by groups in the US and by Night hawk services around the world. Teleradiology is also established for the provision of radiological services to remote rural communities and for sub-specialist opinions and for specialist case transfers. In the UK it is now used to provide primary reporting services from centres both in Europe and by international providers.

With the costs of data transmission decreasing as fast as the costs of computing power, practical opportunities for global teleradiology are rapidly increasing as the cost effectiveness of PACS and digital radiology increases. In our financially constrained world, the clinical losses associated with generalised use of teleradiology may be accepted by governments and health care insurers as a means of cost containment [1].

However, exchanges of information with referring physicians in conferences or reading rooms are an integral part of delivering a clinical radiological service. It would be a great loss to the profession if radiologists were to be identified by other physicians and patients only as image readers sitting exclusively in front of workstation screens and ceasing to be clinicians [1].

The obligation or responsibility or opportunity of a radiologist to go beyond the dictated report and to offer consultant services to his or her clinical colleagues is what allows the specialty to be more than a technical service. This will be even more significant as computer-assisted diagnostic programmes extend to more body parts. If a radiologist provides nothing more than an observation of abnormal densities, radiology will be minimised or eliminated [8]. Similarly the role of laboratory medicine was minimised when chemical autoanalyzers provided results cheaply and accurately and the printed values were significant to the referring physician without any interpretation or consultation with a laboratory physician.

With so many technological advances it is not surprising that radiology utilisation of high-cost studies such as CT and MR is expanding rapidly worldwide. This has resulted in a larger and more complex workload. However the number of radiologists worldwide has not increased at the same rate as the number of examinations. Radiologists have only been able to manage this increase by improved workflow and productivity due in part to digital technology. Digital imaging, workstations, speech recognition technology, PACS and ease of communication via the internet have all facilitated workflow. Teleradiology may increase productivity in some circumstances such as night cover in smaller practices and provision of radiology reporting services to rural communities. It has also been used in some countries to compensate for manpower shortages and when used in a proactive and controlled fashion may help to avoid loosing turf to clinical colleagues. It is not however the ultimate solution to manpower problems which are better resolved by training sufficient radiologists to provide the service within the locality of the clinicians and patients. Teleradiology must not be allowed to commoditise imaging services and should only be used to support the comprehensive diagnostic service provided by radiologists within groups or local area networks.

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Patient relations

Radiological societies maintain (and radiologists do not publicly disagree) that to improve the public perception of the role radiologists play in patient care, closer contact with patients is essential [9]

Radiological services are essential to the care of patients. To the patients, however, radiological services may seem somewhat inconvenient, mysterious or frightening, or may even be a painful intrusion of their privacy. The perception is further altered by the fact that patients typically do not choose their radiologist; the referring physician, the health plan or another intermediary usually makes that choice. Often patients and their diagnostic radiologist never meet. This situation substantially alters the service bond between them, actually making the relationship more demanding in a number of ways [10]. Moreover, nurses, technologists and others are increasingly participating in the performance of imaging examinations. For many patients, radiologists are identified only with the equipment used and not as physicians who play a vital role in the decisions that affect them. The use of technologists, nurses, and physician assistants for intravenous injection of contrast material makes radiologist-patient contact even less common [2]

Patients believe that the clinician who requested the examination and has received the report is actually the physician who has interpreted the study [2]. On the other hand, there is widespread agreement that patients prefer to hear the results of imaging examinations from the radiologist at the time of the procedure rather than to hear them later from the referring physician, regardless of the findings [11]. And in another study it has been shown that radiologists and referring physicians alike tend to support the proposition that, if asked, radiologists should disclose the results of imaging studies to patients [12].

It seems to be important for the future of the specialty for radiologists to have more contact with patients in the setting of high-cost, high-impact imaging procedures. The very position of radiology in a variety of hierarchies ranging from political to economic may depend on increased recognition by the public of radiologists as physicians. However, results of a survey by Margulis and Sostman [2] show that more than a half of the injections of contrast medium in radiological practices are performed by non-physicians. Radiologists are often but by no means always present in the facility during performance of the study and radiologists rarely introduce themselves to the patient. Radiologists should always introduce themselves to patients before any interventional procedure. This is not only good manners but it also establishes the radiologist’s clinical role in the whole spectrum of planning the treatment and assessing the prognosis and the response during follow-up.

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Involvement in primary care (general practice (GP) and office based practice)

Primary care is the point of first patient contact and offers continuous comprehensive and coordinated care to populations undifferentiated by gender, disease or organ system. In order for

comprehensive care to take place in the primary care setting, the GP often requires access to a wide range of imaging services. This enables the GP to diagnose and treat the more common diseases without recourse to hospital services. It also empowers the GP to investigate the patient more fully so that, if a transfer to a hospital specialist is required, such referral can, in many cases be for therapeutic care rather than for further investigation.

A GP may wish to work up a patient more fully in conjunction with the clinical radiologist, who may be a sub-specialist or a radiologist with special interests, so that the requirement for outpatient referral to specialty services may be avoided or may be a more focussed and constructive consultation. For such a means of referral to be effective, the radiologist will need to establish preferred investigation pathways with the clinicians to whom ultimately the patients may be referred. Finally, the GP may be able to treat a patient directly with the assistance of the radiologists and some image-guided therapeutic procedures can be undertaken by radiologists directly for GPs on an outpatient, day-case or short-stay basis.

In the past the workload of departments of radiology was concentrated primarily on supporting the care of hospital patients and on providing imaging services for outpatients attending consultant clinics. GPs’ rights to request radiological examinations should be however similar to those enjoyed by hospital specialists. The concept that expensive investigation should be limited to clinical specialists is not sustainable. Specialists and GPs should have similar rights to request examinations. This is particularly highlighted with MRI or CT, where a single examination may avoid the need for an outpatient visit or an invasive procedure, which would cost considerably more. If GPs are undertaking primary diagnosis and management of patients, then clinical radiologists are acting as first-line clinicians and it is entirely reasonable for the radiologist to undertake the most appropriate examination. The radiologist also possesses the knowledge and competence to ensure compliance with all aspects of radiation protection and justification of investigations which is particularly relevant regarding CT. They should therefore recommend additional examinations where appropriate and manage the imaging diagnostic process in conjunction with the primary care clinician. The value of investigation which does not show an abnormality but reduces uncertainty and provides reassurance to the patient and to the GP, should also not be underestimated by the radiologist [13].

However, radiological investigations available to GPs must be determined by local radiologists in consultation with their GP colleagues as availability of new, often complex investigations may be limited in some countries and areas.

Electronic transfer has also developed rapidly over the last few years and the transmission of images and reports between radiology departments and surrounding GPs is now easily undertaken.

Closer working relationships with GPs and a stronger involvement of imaging in primary care will also increase contact of radiologists to their patients and particularly raise public awareness.

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Maximising the use of resources

There has been a tendency in teaching and large regional hospitals for subspecialty services to pursue the development of satellite departments isolating radiologists from each other. While this may be essential in some clinical situations such as emergency departments, it potentially reduces the interaction between sub-specialist radiologists to the detriment of their wider knowledge and technological development. It may also reinforce the desire for clinicians to set up their own units and encourages the concept of radiologists working in clinical groups rather than providing a comprehensive imaging service. Radiologists should work towards a single strong well-staffed and funded department which is able to accommodate those clinicians who justifiably need prompt access to expert imaging [3].

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Conclusion

The world of radiology is changing rapidly and radiologists have to be proactive in this process to survive. The subject is now too broad and complex for an individual to remain a comprehensive provider. As a result radiologists need to group themselves as specialists in particular systems or disease-based areas while finding a mechanism to provide a high-quality service. Radiologists must also be clinicians and understand the clinical features, natural history and treatments of the diseases that they are requested to investigate. Therefore, if radiologists want to add value to the chain of healthcare they need to sub-specialise to a greater or lesser extent according to their working circumstances. Teleradiology services may be appropriate for small and rural practices as part of an area network especially during nights and weekends and for interaction with GPs and patients. Radiologists must also interact more directly with patients and primary care physicians to provide a comprehensive diagnostic and advisory service prior to the patient entering the secondary care service by managing the investigations of the patients themselves. This will increase efficiency, clinical effectiveness of the service and speed up the referral process. Radiologists in the teaching hospitals will also need to specialise to a higher degree in order to provide a tertiary referral service, communicate and advise clinical experts and to conduct and drive imaging research as true experts in their field.

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Recommendations

Sufficient radiologists are in training to ensure that the workforce is large enough to undertake the workload.

System- (or disease-) based subspecialisation or the development of system- (or disease-) based areas of special interest is essential for all radiologists to respond to the complexity and technological advances of imaging.

Encouraging radiologists to build strong networks with clinicians. In order to achieve this, all radiologists should have sufficient clinical knowledge in order to understand the fundamentals of clinical presentations, natural history, treatment and prognosis of all common and/or severe diseases. They should also obtain a more in-depth clinical knowledge of particular diseases related to any subspecialty in which they wish to practice. This may involve a number of strategies, but subspecialty and special interest curricula should ensure that trainees participate in clinical rounds, multidisciplinary meetings and provide opportunities for interaction with relevant clinicians.

Wide clinical experience should be obtained before entering radiology. In such circumstances further clinical experience may only be required in a chosen subspecialty and to a level dependent on previous experience.

Expanding consulting activities of radiologists with clinical specialists in multidisciplinary conferences.

Intensifying relations with GPs offering diagnostic management of their patients including referral to clinical specialists if needed or full work-up in conjunction with the GP.

Communicating with the patient and discussing options particularly in cases of primary care (patient referred by GP).

Making use of teleradiology services in a proactive way through local area networks under the control of radiologists to incorporate general and sub-specialist radiologists in a comprehensive coverage of clinical scenarios.

Ensuring that all radiologists involved in such networks keep close contact with referring physicians through both personal interaction and video conferencing.

Encouraging radiologists to network with interventional radiologists to learn the basic aspect of the techniques, indications and imaging follow-up in order to increase the quality of care to patients and the potential referral to both.

Ensuring that radiologists are conversant with the technical aspects of the equipment they are utilising and that sub-specialists involve themselves where possible in the development and implementation of new innovations.

Reinforcing the clinical role of radiologists to use resources to increase day-case work, to make decisions regarding imaging strategies, and to explain the results and further examinations to the patients.

Reinforcing the status of the radiologist with special interests.

Training programmes are always subject to country by country variations but should be structured with these principles in mind. Possible combinations include:

System- or disease-oriented sub-specialisation during the last 2 years of residency training (3+2). This may be followed by an additional 1 year fellowship training where appropriate.

Additional clinical experience fitting to the radiological sub-specialisation within the subspecialty training period and fellowship.

System- or disease-oriented training in two areas of special interest in the final 2 years of residency. This may be followed if appropriate by an additional 1 year fellowship training gaining further experience which may include an understanding of general practice medicine.

Medical imaging is the technique and process of creating visual representations of the interior of a body for clinical analysis and medical intervention. Medical imaging seeks to reveal internal structures hidden by the skin and bones, as well as to diagnose and treat disease. Medical imaging also establishes a database of normal anatomy and physiology to make it possible to identify abnormalities. Although imaging of removed organs and tissues can be performed for medical reasons, such procedures are usually considered part of pathology instead of medical imaging.

As a discipline and in its widest sense, it is part of biological imaging and incorporates radiology which uses the imaging technologies of X-ray radiography, magnetic resonance imaging, medical ultrasonography or ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography and nuclear medicine functional imaging techniques as positron emission tomography.

Measurement and recording techniques which are not primarily designed to produce images, such as electroencephalography (EEG), magnetoencephalography (MEG), electrocardiography (ECG), and others represent other technologies which produce data susceptible to representation as a parameter graph vs. time or maps which contain information about the measurement locations. In a limited comparison these technologies can be considered as forms of medical imaging in another discipline.

Up until 2010, 5 billion medical imaging studies had been conducted worldwide.[1] Radiation exposure from medical imaging in 2006 made up about 50% of total ionizing radiation exposure in the United States.[2]

In the clinical context, "invisible light" medical imaging is generally equated to radiology or "clinical imaging" and the medical practitioner responsible for interpreting (and sometimes acquiring) the images is a radiologist. "Visible light" medical imaging involves digital video or still pictures that can be seen without special equipment. Dermatology and wound care are two modalities that use visible light imagery. Diagnostic radiography designates the technical aspects of medical imaging and in particular the acquisition of medical images. The radiographer or radiologic technologist is usually responsible for acquiring medical images of diagnostic quality, although some radiological

interventions are performed by radiologists. While radiology is an evaluation of anatomy, nuclear medicine provides functional assessment.

As a field of scientific investigation, medical imaging constitutes a sub-discipline of biomedical engineering, medical physics or medicine depending on the context: Research and development in the area of instrumentation, image acquisition (e.g. radiography), modeling and quantification are usually the preserve of biomedical engineering, medical physics, and computer science; Research into the application and interpretation of medical images is usually the preserve of radiology and the medical sub-discipline relevant to medical condition or area of medical science (neuroscience, cardiology, psychiatry, psychology, etc.) under investigation. Many of the techniques developed for medical imaging also have scientific and industrial applications.[3]

Medical imaging is often perceived to designate the set of techniques that noninvasively produce images of the internal aspect of the body. In this restricted sense, medical imaging can be seen as the solution of mathematical inverse problems. This means that cause (the properties of living tissue) is inferred from effect (the observed signal). In the case of medical ultrasonography, the probe consists of ultrasonic pressure waves and echoes that go inside the tissue to show the internal structure. In the case of projectional radiography, the probe uses X-ray radiation, which is absorbed at different rates by different tissue types such as bone, muscle and fat.

The term noninvasive is used to denote a procedure where no instrument is introduced into a patient's body which is the case for most imaging techniques used.

Contents [hide]

1 Imaging modalities

1.1 Radiography

1.2 Magnetic Resonance Imaging (MRI)

1.3 Nuclear medicine

1.4 Ultrasound

1.5 Elastography

1.6 Tactile imaging

1.7 Photoacoustic imaging

1.8 Thermography

1.9 Tomography

1.9.1 Conventional tomography

1.9.2 Computer-assisted tomography

1.10 Echocardiography

1.11 Functional near-infrared spectroscopy

2 Medical imaging topics

2.1 Image Gently and Image Wisely Campaigns

2.2 Maximizing imaging procedure use

2.3 Creation of three-dimensional images

2.4 Compression of medical images

2.5 Non-diagnostic imaging

2.6 Archiving and recording

2.7 Medical Imaging in the Cloud

2.8 Use in pharmaceutical clinical trials

2.9 Shielding

3 Further reading

4 See also

5 References

6 External links

Imaging modalities[edit]

(a) The results of a CT scan of the head are shown as successive transverse sections. (b) An MRI machine generates a magnetic field around a patient. (c) PET scans use radiopharmaceuticals to create images of active blood flow and physiologic activity of the organ or organs being targeted. (d) Ultrasound technology is used to monitor pregnancies because it is the least invasive of imaging techniques and uses no electromagnetic radiation.[3]

Radiography[edit]

Main article: Medical radiography

Two forms of radiographic images are in use in medical imaging; projection radiography and fluoroscopy, with the latter being useful for catheter guidance. These 2D techniques are still in wide use despite the advance of 3D tomography due to the low cost, high resolution, and depending on application, lower radiation dosages. This imaging modality utilizes a wide beam of x rays for image acquisition and is the first imaging technique available in modern medicine.

Fluoroscopy produces real-time images of internal structures of the body in a similar fashion to radiography, but employs a constant input of x-rays, at a lower dose rate. Contrast media, such as barium, iodine, and air are used to visualize internal organs as they work. Fluoroscopy is also used in image-guided procedures when constant feedback during a procedure is required. An image receptor is required to convert the radiation into an image after it has passed through the area of interest. Early on this was a fluorescing screen, which gave way to an Image Amplifier (IA) which was a large vacuum tube that had the receiving end coated with cesium iodide, and a mirror at the opposite end. Eventually the mirror was replaced with a TV camera.

Projectional radiographs, more commonly known as x-rays, are often used to determine the type and extent of a fracture as well as for detecting pathological changes in the lungs. With the use of radio-opaque contrast media, such as barium, they can also be used to visualize the structure of the stomach and intestines - this can help diagnose ulcers or certain types of colon cancer.

Magnetic Resonance Imaging (MRI)[edit]

Main article: Magnetic resonance imaging

A brain MRI representation

A magnetic resonance imaging instrument (MRI scanner), or "nuclear magnetic resonance (NMR) imaging" scanner as it was originally known, uses powerful magnets to polarise and excite hydrogen nuclei (single proton) in water molecules in human tissue, producing a detectable signal which is spatially encoded, resulting in images of the body.[4] The MRI machine emits a RF (radio frequency) pulse that specifically binds to hydrogen. The system sends the pulse to the area of the body to be examined. The pulse makes the protons in that area absorb the energy needed to make them spin in a different direction. This is the "resonance" part of MRI. The RF pulse makes them (only the one or two extra unmatched protons per million) spin at a specific frequency, in a specific direction. The particular frequency of resonance is called the Larmour frequency and is calculated based on the particular tissue being imaged and the strength of the main magnetic field. MRI uses three electromagnetic fields: a very strong (on the order of units of teslas) static magnetic field to polarize the hydrogen nuclei, called the static field; a weaker time-varying (on the order of 1 kHz) field(s) for spatial encoding, called the gradient field(s); and a weak radio-frequency (RF) field for manipulation of the hydrogen nuclei to produce measurable signals, collected through an RF antenna.

Like CT, MRI traditionally creates a two dimensional image of a thin "slice" of the body and is therefore considered a tomographic imaging technique. Modern MRI instruments are capable of producing images in the form of 3D blocks, which may be considered a generalisation of the single-slice, tomographic, concept. Unlike CT, MRI does not involve the use of ionizing radiation and is therefore not associated with the same health hazards. For example, because MRI has only been in use since the early 1980s, there are no known long-term effects of exposure to strong static fields (this is the subject of some debate; see 'Safety' in MRI) and therefore there is no limit to the number of scans to which an individual can be subjected, in contrast with X-ray and CT. However, there are well-identified health risks associated with tissue heating from exposure to the RF field and the presence of implanted devices in the body, such as pace makers. These risks are strictly controlled as part of the design of the instrument and the scanning protocols used.

Because CT and MRI are sensitive to different tissue properties, the appearance of the images obtained with the two techniques differ markedly. In CT, X-rays must be blocked by some form of dense tissue to create an image, so the image quality when looking at soft tissues will be poor. In MRI, while any nucleus with a net nuclear spin can be used, the proton of the hydrogen atom remains the most widely used, especially in the clinical setting, because it is so ubiquitous and returns a large signal. This nucleus, present in water molecules, allows the excellent soft-tissue contrast achievable with MRI.

Nuclear medicine[edit]

Main article: Nuclear medicine

Nuclear medicine encompasses both diagnostic imaging and treatment of disease, and may also be referred to as molecular medicine or molecular imaging & therapeutics.[5] Nuclear medicine uses certain properties of isotopes and the energetic particles emitted from radioactive material to diagnose or treat various pathology. Different from the typical concept of anatomic radiology, nuclear medicine enables assessment of physiology. This function-based approach to medical evaluation has useful applications in most subspecialties, notably oncology, neurology, and cardiology. Gamma cameras are used in e.g. scintigraphy, SPECT and PET to detect regions of biologic activity that may be associated with disease. Relatively short lived isotope, such as 123I is administered to the patient. Isotopes are often preferentially absorbed by biologically active tissue in the body, and can be used to identify tumors or fracture points in bone. Images are acquired after collimated photons are detected by a crystal that gives off a light signal, which is in turn amplified and converted into count data.

Scintigraphy ("scint") is a form of diagnostic test wherein radioisotopes are taken internally, for example intravenously or orally. Then, gamma cameras capture and form two-dimensional[6] images from the radiation emitted by the radiopharmaceuticals.

SPECT is a 3D tomographic technique that uses gamma camera data from many projections and can be reconstructed in different planes. A dual detector head gamma camera combined with a CT scanner, which provides localization of functional SPECT data, is termed a SPECT-CT camera, and has shown utility in advancing the field of molecular imaging. In most other medical imaging modalities, energy is passed through the body and the reaction or result is read by detectors. In SPECT imaging, the patient is injected with a radioisotope, most commonly Thallium 201TI, Technetium 99mTC, Iodine 123I, and Gallium 67Ga.[7] The radioactive gamma rays are emitted through the body as the natural decaying process of these isotopes takes place. The emissions of the gamma rays are captured by detectors that surround the body. This essentially means that the human is now the source of the radioactivity, rather than the medical imaging devices such as X-Ray or CT.

Positron emission tomography (PET) uses coincidence detection to image functional processes. Short-lived positron emitting isotope, such as 18F, is incorporated with an organic substance such as glucose, creating F18-fluorodeoxyglucose, which can be used as a marker of metabolic utilization. Images of activity distribution throughout the body can show rapidly growing tissue, like tumor, metastasis, or infection. PET images can be viewed in comparison to computed tomography scans to determine an anatomic correlate. Modern scanners may integrate PET, allowing PET-CT, or PET-MRI to optimize the image reconstruction involved with positron imaging. This is performed on the same equipment without physically moving the patient off of the gantry. The resultant hybrid of functional and anatomic imaging information is a useful tool in non-invasive diagnosis and patient management.

Fiduciary markers are used in a wide range of medical imaging applications. Images of the same subject produced with two different imaging systems may be correlated (called image registration) by placing a fiduciary marker in the area imaged by both systems. In this case, a marker which is visible in the images produced by both imaging modalities must be used. By this method, functional information from SPECT or positron emission tomography can be related to anatomical information provided by magnetic resonance imaging (MRI).[8] Similarly, fiducial points established during MRI can be correlated with brain images generated by magnetoencephalography to localize the source of brain activity.

Ultrasound representation of Urinary bladder (black butterfly-like shape) and hyperplastic prostate

Ultrasound[edit]

Main article: Medical ultrasonography

Medical ultrasonography uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce (up to 3D) images. This is commonly associated with imaging the fetus in pregnant women. Uses of ultrasound are much broader, however. Other important uses include imaging the abdominal organs, heart, breast, muscles, tendons, arteries and veins. While it may provide less anatomical detail than techniques such as CT or MRI, it has several advantages which make it ideal in numerous situations, in particular that it studies the function of moving structures in real-time, emits no ionizing radiation, and contains speckle that can be used in

elastography. Ultrasound is also used as a popular research tool for capturing raw data, that can be made available through an ultrasound research interface, for the purpose of tissue characterization and implementation of new image processing techniques. The concepts of ultrasound differ from other medical imaging modalities in the fact that it is operated by the transmission and receipt of sound waves. The high frequency sound waves are sent into the tissue and depending on the composition of the different tissues; the signal will be attenuated and returned at separate intervals. A path of reflected sound waves in a multilayered structure can be defined by an input acoustic impedance (ultrasound sound wave) and the Reflection and transmission coefficients of the relative structures.[7] It is very safe to use and does not appear to cause any adverse effects. It is also relatively inexpensive and quick to perform. Ultrasound scanners can be taken to critically ill patients in intensive care units, avoiding the danger caused while moving the patient to the radiology department. The real time moving image obtained can be used to guide drainage and biopsy procedures. Doppler capabilities on modern scanners allow the blood flow in arteries and veins to be assessed.

Elastography[edit]

Main article: Elastography

Elastography is a new imaging modality that maps the elastic properties of soft tissue. This modality emerged in the last decade. Elastography can use ultrasound, magnetic resonance imaging and tactile imaging.

3D tactile image (C) is composed from 2D pressure maps (B) recorded in the process of tissue phantom examination (A).

Tactile imaging[edit]

Main article: Tactile imaging

Tactile imaging is a medical imaging modality that translates the sense of touch into a digital image. The tactile image is a function of P(x,y,z), where P is the pressure on soft tissue surface under applied deformation and x,y,z are coordinates where pressure P was measured. Tactile imaging closely mimics manual palpation, since the probe of the device with a pressure sensor array mounted on its face acts similar to human fingers during clinical examination, slightly deforming soft tissue by the probe and detecting resulting changes in the pressure pattern. Figure on the right presents an experiment on a composite tissue phantom examined by a tactile imaging probe illustrating the ability of tactile imaging to visualize in 3D the structure of the object.

This modality is used for imaging of the prostate,[9] breast,[10] vagina and pelvic floor support structures,[11] and myofascial trigger points in muscle.[12]

Photoacoustic imaging[edit]

Main article: Photoacoustic imaging in biomedicine

Photoacoustic imaging is a recently developed hybrid biomedical imaging modality based on the photoacoustic effect. It combines the advantages of optical absorption contrast with ultrasonic spatial resolution for deep imaging in (optical) diffusive or quasi-diffusive regime. Recent studies have shown that photoacoustic imaging can be used in vivo for tumor angiogenesis monitoring, blood oxygenation mapping, functional brain imaging, and skin melanoma detection, etc.

Thermography[edit]

Primarily used for breast imaging. There are three approaches: tele-thermography, contact thermography and dynamic angiothermography. These digital infrared imaging thermographic techniques are based on the principle that metabolic activity and vascular circulation in both pre-cancerous tissue and the area surrounding a developing breast cancer is almost always higher than in normal breast tissue. Cancerous tumors require an ever-increasing supply of nutrients and therefore increase circulation to their cells by holding open existing blood vessels, opening dormant vessels, and creating new ones (neo-angiogenesis theory).

Tele-thermography and contact thermography supporters claim this process results in an increase in regional surface temperatures of the breast, however there is little evidence that thermography is an accurate means of identifying breast tumours. Thermography is not approved for breast cancer screening in the United States or Canada, and medical authorities have issued warnings against thermography in both countries.[13]

Dynamic angiothermography utilizes thermal imaging but with important differences with the tele-thermography and contact thermography, that impact detection performance. First, the probes are improved over the previous liquid crystal plates; they include better spatial resolution, contrastive performance, and the image is formed more quickly. The more significant difference[14] lies in identifying the thermal changes due to changes in vascular network to support the growth of the tumor/lesion. Instead of just recording the change in heat generated by the tumor, the image is now able to identify changes due to the vascularization of the mammary gland. It is currently used in combination with other techniques for diagnosis of breast cancer. This diagnostic method is a low cost one compared with other techniques. The angiothermography is not a test that substitutes for other tests, but stands in relation to them as a technique that gives additional information to clarify the clinical picture and improve the quality of diagnosis.

Tomography[edit]

Tomography is the method of imaging a single plane, or slice, of an object resulting in a tomogram. There are two principal methods of obtaining such images, conventional and computer assisted tomography. Conventional tomography uses mechanical means to record an image directly onto X-ray film, while in computer assisted tomography, a computer processes information fed to it from detectors then constructs a virtual image which can be stored in digital format and can be displayed on a screen, or printed on paper or film.

Conventional tomography[edit]

In conventional tomography, mechanical movement of an X-ray source and film in unison generates a tomogram using the principles of projective geometry.[15] Synchronizing the movement of the radiation source and detector which are situated in the opposite direction from each other causes structures which are not in the focal plane being studied to blur out. This was the main method of obtaining tomogaphic images until the late-1970s. It is now considered obsolete (except for certain dental applications), having been replaced with computer assisted tomographic techniques. Historically, there have been various techniques involved in conventional tomography:

Linear tomography: This is the most basic form of conventional tomography. The X-ray tube moved from point "A" to point "B" above the patient, while the cassette holder (or "bucky") moves simultaneously under the patient from point "B" to point "A." The fulcrum, or pivot point, is set to the area of interest. In this manner, the points above and below the focal plane are blurred out, just as the background is blurred when panning a camera during exposure. Rarely used, and has largely been replaced by computed tomography (CT).

Poly tomography: This was achieved using a more advanced X-ray apparatus that allows for more sophisticated and continuous movements of the X-ray tube and film. With this technique, a number of complex synchronous geometrical movements could be programmed, such as hypocycloidic, circular, figure 8, and elliptical. Philips Medical Systems for example produced one such device called the 'Polytome'.[15] This pluridirectional unit was still in use into the 1990s, as its resulting images for small or difficult physiology, such as the inner ear, was still difficult to image with CTs at that time. As the resolution of CTs got better, this procedure was taken over by CT.

Zonography: This is a variant of linear tomography, where a limited arc of movement is used. It is still used in some centres for visualising the kidney during an intravenous urogram (IVU), though it too is being supplanted by CT.

Orthopantomography (OPT or OPG): The only common tomographic examination still in use. This makes use of a complex movement to allow the radiographic examination of the mandible, as if it were a flat bone. It is commonly performed in dental practices and is often referred to as a "Panorex", but this is incorrect, as it is a trademark of a specific company.

Computer-assisted tomography[edit]

In computer-assisted tomography, a computer processes data received from radiation detectors and computationally constructs an image of the structures being scanned. Imaging techniques using this method are far superior to conventional tomography as they can readily image both soft and hard tissues (while conventional tomography is quite poor at imaging soft tissues). The following techniques exist:

X-ray computed tomography (CT), or Computed Axial Tomography (CAT) scan, is a helical tomography technique (latest generation), which traditionally produces a 2D image of the structures in a thin section of the body. In CT, a beam of X-rays spins around an object being examined and is picked up by sensitive radiation detectors after having penetrated the object from multiple angles. A computer then analyses the information received from the scanner's detectors and constructs a detailed image of the object and its contents using the mathematical principles laid out in the Radon transform. It has a greater ionizing radiation dose burden than projection radiography; repeated scans must be limited to avoid health effects. CT is based on the same principles as X-Ray projections but in this case, the patient is enclosed in a surrounding ring of detectors assigned with 500-1000 scintillation detectors[7] (fourth-generation X-Ray CT scanner geometry). Previously in older generation scanners, the X-Ray beam was paired by a translating source and detector.

Positron emission tomography (PET) also used in conjunction with computed tomography, PET-CT, and magnetic resonance imaging PET-MRI.

Magnetic resonance imaging (MRI) commonly produces tomographic images of cross-sections of the body. (See separate MRI section in this article.)

Echocardiography[edit]

Main article: Echocardiography

When ultrasound is used to image the heart it is referred to as an echocardiogram. Echocardiography allows detailed structures of the heart, including chamber size, heart function, the valves of the heart, as well as the pericardium (the sac around the heart) to be seen. Echocardiography uses 2D, 3D, and Doppler imaging to create pictures of the heart and visualize the blood flowing through each of the four heart valves. Echocardiography is widely used in an array of patients ranging from those experiencing symptoms, such as shortness of breath or chest pain, to those undergoing cancer treatments. Transthoracic ultrasound has been proven to be safe for patients of all ages, from infants to the elderly, without risk of harmful side effects or radiation, differentiating it from other imaging modalities. Echocardiography is one of the most commonly used imaging modalities in the world due to its portability and use in a variety of applications. In emergency situations, echocardiography is quick, easily accessible, and able to be performed at the bedside, making it the modality of choice for many physicians.

Functional near-infrared spectroscopy[edit]

Main article: Functional near-infrared spectroscopy

FNIR Is a relatively new non-invasive imaging technique. NIRS (near infrared spectroscopy) is used for the purpose of functional neuroimaging and has been widely accepted as a brain imaging technique.[16]

Medical imaging topics[edit]

Image Gently and Image Wisely Campaigns[edit]

In response to increased concern by the public over radiation doses and the ongoing progress of best practices, The Alliance for Radiation Safety in Pediatric Imaging was formed within the Society for Pediatric Radiology. In concert with The American Society of Radiologic Technologists, The American College of Radiology and The American Association of Physicists in Medicine, the Society for Pediatric Radiology developed and launched the Image Gently Campaign which is designed to maintain high quality imaging studies while using the lowest doses and best radiation safety practices available on pediatric patients.[17] This initiative has been endorsed and applied by a growing list of various Professional Medical organizations around the world and has received support and assistance from companies that manufacture equipment used in Radiology.

Following upon the success of the Image Gently campaign, the American College of Radiology, the Radiological Society of North America, the American Association of Physicists in Medicine and the American Society of Radiologic Technologists have launched a similar campaign to address this issue in the adult population called Image Wisely.[18] The World Health Organization and International Atomic Energy Agency (IAEA) of the United Nations have also been working in this area and have ongoing projects designed to broaden best practices and lower patient radiation dose.[19][20][21]

Maximizing imaging procedure use[edit]

The amount of data obtained in a single MR or CT scan is very extensive. Some of the data that radiologists discard could save patients time and money, while reducing their exposure to radiation and risk of complications from invasive procedures.[22]

Creation of three-dimensional images[edit]

Recently, techniques have been developed to enable CT, MRI and ultrasound scanning software to produce 3D images for the physician.[23] Traditionally CT and MRI scans produced 2D static output on film. To produce 3D images, many scans are made, then combined by computers to produce a 3D model, which can then be manipulated by the physician. 3D ultrasounds are produced using a somewhat similar technique. In diagnosing disease of the viscera of abdomen, ultrasound is particularly sensitive on imaging of biliary tract, urinary tract and female reproductive organs (ovary, fallopian tubes). As for example, diagnosis of gall stone by dilatation of common bile duct and stone in common bile duct. With the ability to visualize important structures in great detail, 3D visualization

methods are a valuable resource for the diagnosis and surgical treatment of many pathologies. It was a key resource for the famous, but ultimately unsuccessful attempt by Singaporean surgeons to separate Iranian twins Ladan and Laleh Bijani in 2003. The 3D equipment was used previously for similar operations with great success.

Other proposed or developed techniques include:

Diffuse optical tomography

Elastography

Electrical impedance tomography

Optoacoustic imaging

Ophthalmology

A-scan

B-scan

Corneal topography

Optical coherence tomography

Scanning laser ophthalmoscopy

Some of these techniques are still at a research stage and not yet used in clinical routines.

Compression of medical images[edit]

Medical imaging techniques produce very large amounts of data, especially from CT, MRI and PET modalities. As a result, storage and communications of electronic image data are prohibitive without the use of compression. JPEG 2000 is the state-of-the-art image compression DICOM standard for storage and transmission of medical images. The cost and feasibility of accessing large image data sets over low or various bandwidths are further addressed by use of another DICOM standard, called JPIP, to enable efficient streaming of the JPEG 2000 compressed image data.

Non-diagnostic imaging[edit]

Neuroimaging has also been used in experimental circumstances to allow people (especially disabled persons) to control outside devices, acting as a brain computer interface.

Many medical imaging software applications (3DSlicer, ImageJ, MIPAV [3], etc.) are used for non-diagnostic imaging, specifically because they don't have an FDA approval[24] and not allowed to use in clinical research for patient diagnosis.[25] Note that many clinical research studies are not designed for patient diagnosis anyway.[26]

Archiving and recording[edit]

Used primarily in ultrasound imaging, capturing the image produced by a medical imaging device is required for archiving and telemedicine applications. In most scenarios, a frame grabber is used in order to capture the video signal from the medical device and relay it to a computer for further processing and operations.[27]

Medical Imaging in the Cloud[edit]

There has been growing trend to migrate from PACS to a Cloud Based RIS. A recent article by Applied Radiology said, "As the digital-imaging realm is embraced across the healthcare enterprise, the swift transition from terabytes to petabytes of data has put radiology on the brink of information overload. Cloud computing offers the imaging department of the future the tools to manage data much more intelligently."[28]

Use in pharmaceutical clinical trials[edit]

Medical imaging has become a major tool in clinical trials since it enables rapid diagnosis with visualization and quantitative assessment.

A typical clinical trial goes through multiple phases and can take up to eight years. Clinical endpoints or outcomes are used to determine whether the therapy is safe and effective. Once a patient reaches the endpoint, he or she is generally excluded from further experimental interaction. Trials that rely solely on clinical endpoints are very costly as they have long durations and tend to need large numbers of patients.

In contrast to clinical endpoints, surrogate endpoints have been shown to cut down the time required to confirm whether a drug has clinical benefits. Imaging biomarkers (a characteristic that is objectively measured by an imaging technique, which is used as an indicator of pharmacological response to a therapy) and surrogate endpoints have shown to facilitate the use of small group sizes, obtaining quick results with good statistical power.[29]

Imaging is able to reveal subtle change that is indicative of the progression of therapy that may be missed out by more subjective, traditional approaches. Statistical bias is reduced as the findings are evaluated without any direct patient contact.

Imaging techniques such as positron emission tomography (PET) and magnetic resonance imaging (MRI) are routinely used in oncology and neuroscience areas,.[30][31][32][33] For example, measurement of tumour shrinkage is a commonly used surrogate endpoint in solid tumour response evaluation. This allows for faster and more objective assessment of the effects of anticancer drugs. In Alzheimer's disease, MRI scans of the entire brain can accurately assess the rate of hippocampal atrophy, while PET scans can measure the brain's metabolic activity by measuring regional glucose metabolism,[29] and beta-amyloid plaques using tracers such as Pittsburgh compound B (PiB). Historically less use has been made of quantitative medical imaging in other areas of drug development although interest is growing.[34]

An imaging-based trial will usually be made up of three components:

A realistic imaging protocol. The protocol is an outline that standardizes (as far as practically possible) the way in which the images are acquired using the various modalities (PET, SPECT, CT, MRI). It covers the specifics in which images are to be stored, processed and evaluated.

An imaging centre that is responsible for collecting the images, perform quality control and provide tools for data storage, distribution and analysis. It is important for images acquired at different time points are displayed in a standardised format to maintain the reliability of the evaluation. Certain specialised imaging contract research organizations provide to end medical imaging services, from protocol design and site management through to data quality assurance and image analysis.

Clinical sites that recruit patients to generate the images to send back to the imaging centre.

Shielding[edit]

X-rays generated by peak voltages below Minimum thickness

of lead

75 kV 1.0 mm

100 kV 1.5 mm

125 kV 2.0 mm

150 kV 2.5 mm

175 kV 3.0 mm

200 kV 4.0 mm

225 kV 5.0 mm

300 kV 9.0 mm

400 kV 15.0 mm

500 kV 22.0 mm

600 kV 34.0 mm

900 kV 51.0 mm

Lead is the most common shield against X-rays because of its high density (11340 kg/m3), stopping power, ease of installation and low cost. The maximum range of a high-energy photon such as an X-ray in matter is infinite; at every point in the matter traversed by the photon, there is a probability of interaction. Thus there is a very small probability of no interaction over very large distances. The shielding of photon beam is therefore exponential (with an attenuation length being close to the radiation length of the material); doubling the thickness of shielding will square the shielding effect.

The following table shows the recommended thickness of lead shielding in function of X-ray energy, from the Recommendations by the Second International Congress of Radiology.[35]

See also: MRI RF shielding

Radiology is the branch or specialty of medicine that deals with the study and application of imaging technology like x-ray and radiation to diagnosing and treating disease.

Radiologists direct an array of imaging technologies (such as ultrasound, computed tomography (CT), nuclear medicine, positron emission tomography (PET) and magnetic resonance imaging (MRI)) to diagnose or treat disease. Interventional radiology is the performance of (usually minimally invasive) medical procedures with the guidance of imaging technologies. The acquisition of medical imaging is usually carried out by the radiographer or radiologic technologist.

The following imaging modalities are used in the field of diagnostic radiology:

Projection (plain) radiography

Radiographs (or Roentgenographs, named after the discoverer of X-rays, Wilhelm Conrad Röntgen) are produced by the transmission of X-Rays through a patient to a capture device then converted into an image for diagnosis. The original and still common imaging produces silver impregnated films. In Film - Screen radiography an x-ray tube generates a beam of x-rays which is aimed at the patient.

The x-rays which pass through the patient are filtered to reduce scatter and noise and then strike an undeveloped film, held tight to a screen of light emitting phosphors in a light-tight cassette. The film is then developed chemically and an image appears on the film. Now replacing Film-Screen radiography is Digital Radiography, DR, in which x-rays strike a plate of sensors which then converts the signals generated into digital information and an image on computer screen.

Plain radiography was the only imaging modality available during the first 50 years of radiology. It is still the first study ordered in evaluation of the lungs, heart and skeleton because of its wide availability, speed and relative low cost.

Fluoroscopy

Fluoroscopy and angiography are special applications of X-ray imaging, in which a fluorescent screen and image intensifier tube is connected to a closed-circuit television system. This allows real-time imaging of structures in motion or augmented with a radiocontrast agent. Radiocontrast agents are administered, often swallowed or injected into the body of the patient, to delineate anatomy and functioning of the blood vessels, the genitourinary system or the gastrointestinal tract. Two radiocontrasts are presently in use. Barium (as BaSO4) may be given orally or rectally for evaluation of the GI tract. Iodine, in multiple proprietary forms, may be given by oral, rectal, intraarterial or intravenous routes. These radiocontrast agents strongly absorb or scatter X-ray radiation, and in conjunction with the real-time imaging allows demonstration of dynamic processes, such as peristalsis in the digestive tract or blood flow in arteries and veins. Iodine contrast may also be concentrated in abnormal areas more or less than in normal tissues and make abnormalities (tumors, cysts, inflammation) more conspicuous. Additionally, in specific circumstances air can be used as a contrast agent for the gastrointestinal system and carbon dioxide can be used as a contrast agent in the venous system; in these cases, the contrast agent attenuates the X-ray radiation less than the surrounding tissues.

CT scanning

CT imaging uses X-rays in conjunction with computing algorithms to image the body. In CT, an X-ray generating tube opposite an X-ray detector (or detectors) in a ring shaped apparatus rotate around a patient producing a computer generated cross-sectional image (tomogram). CT is acquired in the axial plane, while coronal and sagittal images can be rendered by computer reconstruction. Radiocontrast agents are often used with CT for enhanced delineation of anatomy. Although radiographs provide higher spatial resolution, CT can detect more subtle variations in attenuation of X-rays. CT exposes the patient to more ionizing radiation than a radiograph. Spiral Multi-detector CT utilizes 8,16 or 64 detectors during continuous motion of the patient through the radiation beam to obtain much finer detail images in a shorter exam time. With rapid administration of IV contrast during the CT scan these fine detail images can be reconstructed into 3D images of carotid, cerebral and coronary arteries, CTA, CT angiography. CT scanning has become the test of choice in diagnosing some urgent and emergent conditions such as cerebral hemorrhage, pulmonary embolism (clots in

the arteries of the lungs), aortic dissection (tearing of the aortic wall), appendicitis, diverticulitis, and obstructing kidney stones. Continuing improvements in CT technology including faster scanning times and improved resolution have dramatically increased the accuracy and usefulness of CT scanning and consequently increased utilization in medical diagnosis.

The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield at EMI Central Research Labs, Great Britain in 1972. EMI owned the distribution rights to The Beatles music and it was their profits which funded the research. Sir Hounsfield and Alan McLeod McCormick shared the Nobel Prize for Medicine in 1979 for the invention of CT scanning. The first CT scanner in North America was installed at the Mayo Clinic in Rochester, MN in 1972.

Ultrasound

Medical ultrasonography uses ultrasound (high-frequency sound waves) to visualize soft tissue structures in the body in real time. No ionizing radiation is involved, but the quality of the images obtained using ultrasound is highly dependent on the skill of the person (ultrasonographer) performing the exam. Ultrasound is also limited by its inability to image through air (lungs, bowel loops) or bone. The use of ultrasound in medical imaging has developed mostly within the last 30 years. The first ultrasound images were static and two dimensional (2D), but with modern-day ultrasonography 3D reconstructions can be observed in real-time; effectively becoming 4D.

Because ultrasound does not utilize ionizing radiation, unlike radiography, CT scans, and nuclear medicine imaging techniques, it is generally considered safer. For this reason, this modality plays a vital role in obstetrical imaging. Fetal anatomic development can be thoroughly evaluated allowing early diagnosis of many fetal anomalies. Growth can be assessed over time, important in patients with chronic disease or gestation-induced disease, and in multiple gestations (twins, triplets etc.). Color-Flow Doppler Ultrasound measures the severity of peripheral vascular disease and is used by Cardiology for dynamic evaluation of the heart, heart valves and major vessels. Stenosis of the carotid arteries can presage cerebral infarcts (strokes). DVT in the legs can be found via ultrasound before it dislodges and travels to the lungs (pulmonary embolism), which can be fatal if left untreated. Ultrasound is useful for image-guided interventions like biopsies and drainages such as thoracentesis). Small portable ultrasound devices now replace peritoneal lavage in the triage of trauma victims by directly assessing for the presence of hemorrhage in the peritoneum and the integrity of the major viscera including the liver, spleen and kidneys. Extensive hemoperitoneum (bleeding inside the body cavity) or injury to the major organs may require emergent surgical exploration and repair.

MRI (Magnetic Resonance Imaging)

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MRI uses strong magnetic fields to align atomic nuclei (usually hydrogen protons) within body tissues, then uses a radio signal to disturb the axis of rotation of these nuclei and observes the radio frequency signal generated as the nuclei return to their baseline states plus all surrounding areas. The radio signals are collected by small antennae, called coils, placed near the area of interest. An advantage of MRI is its ability to produce images in axial, coronal, sagittal and multiple oblique planes with equal ease. MRI scans give the best soft tissue contrast of all the imaging modalities. With advances in scanning speed and spatial resolution, and improvements in computer 3D algorithms and hardware, MRI has become a tool in musculoskeletal radiology and neuroradiology.

One disadvantage is that the patient has to hold still for long periods of time in a noisy, cramped space while the imaging is performed. Claustrophobia severe enough to terminate the MRI exam is reported in up to 5% of patients. Recent improvements in magnet design including stronger magnetic fields (3 teslas), shortening exam times, wider, shorter magnet bores and more open magnet designs, have brought some relief for claustrophobic patients. However, in magnets of equal field strength there is often a trade-off between image quality and open design. MRI has great benefit in imaging the brain, spine, and musculoskeletal system. The modality is currently contraindicated for patients with pacemakers, cochlear implants, some indwelling medication pumps, certain types of cerebral aneurysm clips, metal fragments in the eyes and some metallic hardware due to the powerful magnetic fields and strong fluctuating radio signals the body is exposed to. Areas of potential advancement include functional imaging, cardiovascular MRI, as well as MR image guided therapy.

Nuclear Medicine

Nuclear medicine imaging involves the administration into the patient of radiopharmaceuticals consisting of substances with affinity for certain body tissues labeled with radioactive tracer. The most commonly used tracers are Technetium-99m, Iodine-123, Iodine-131, Gallium-67 and Thallium-201. The heart, lungs, thyroid, liver, gallbladder, and bones are commonly evaluated for particular conditions using these techniques. While anatomical detail is limited in these studies, nuclear medicine is useful in displaying physiological function. The excretory function of the kidneys, iodine concentrating ability of the thyroid, blood flow to heart muscle, etc. can be measured. The principal imaging device is the gamma camera which detects the radiation emitted by the tracer in the body and displays it as an image. With computer processing, the information can be displayed as axial, coronal and sagittal images (SPECT images, single-photon emission computed tomography). In the most modern devices Nuclear Medicine images can be fused with a CT scan taken quasi-simultaneously so that the physiological information can be overlaid or co-registered with the anatomical structures to improve diagnostic accuracy.

PET,(positron emission tomography), scanning also falls under "nuclear medicine." In PET scanning, a radioactive biologically-active substance, most often Fluorine-18 Fluorodeoxyglucose, is injected into a patient and the radiation emitted by the patient is detected to produce multi-planar images of the body. Metabolically more active tissues, such as cancer, concentrate the active substance more than normal tissues. PET images can be combined with CT images to improve diagnostic accuracy.

The applications of nuclear medicine can include bone scanning which traditionally has had a strong role in the work-up/staging of cancers. Myocardial perfusion imaging is a sensitive and specific screening exam for reversible myocardial ischemia. Molecular Imaging is the new and exciting frontier in this field.

Further Reading