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Radiology and Medical

Image Department

Dr. Mohamed Abdel-Monem El- Sakhawy

Introduction to

Overview about Radiology

Radiology is one of the modern science, just

over a 130 years and a specific since November 1895

when the physicist William Roentgen conduct some

tests on the elevator and the landing pad during the

experiments and he noted the presence of flash on the

sensitive paper used for testing. Since that time, he

began to think of something in unknown places and

others were visible by X-X-RAY.

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•Radiological and Medical Imaging Technology is a

health care profession which uses ionizing and non-

ionizing radiation in diagnosis and treatment of

diseases.

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•Radiology is a medical

specialty using medical

imaging technologies to

diagnose and treat

patients.

What are our tools?

• X-rays

• CT

• MRI

• Ultrasound

• Nuclear Medicine

• Radiotherapy

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The aim of the department

• The aim of the department of the radiological sciences and

medical photography is to seek to graduate qualified medical

technicians with high standards in knowledge and skills that

enable them to operate variety of radiological instruments.

• The departmental programs focus to provide students with

knowledge of the human body’s structure and function, under

normal and pathological conditions, using variety of techniques

of electromagnetic radiation such as x-rays, computed

tomography (CT), magnetic resonance imaging (MRI), nuclear

medicine well as sound waves (ultrasound). 5

•The department offers courses in anatomy, histology,

physiology, pathology, medical applications of

computer, electromagnetic radiation, and applications

of physics in medical biotechnology, and radiological

science and medical photography .

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Side effects of radiations

• The danger of radiation (ionizing) exposure is to stop the

growth of cells or changes in cytoplasm and DNA within

cells and are dangerous, where these cells are vulnerable

to random growth that called cancers.

• To avoid such risks are special techniques to protect

patients and workers from the dangers of radiation

parameters such as the use of lead shields and protective

measures and personal dose.

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Radiologist

Medical practitioner responsible for interpreting and

acquiring the images

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History

X-rays and radioactivity were

discovered by accident

Wilhelm Roentgen (1895)

X-rays is a part of electromagnetic

spectrum

X-rays energetic enough to ionise

atoms and break molecular bonds

as they penetrate tissues

therefore called ionising radiation9

X- ray radiation

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Plain x-rays

Wilhelm Roentgen discovered x-rays in 1895. X-rays

form part of the electromagnetic spectrum with

microwaves and radiowaves lying at the low energy

end, visible light in the middle and x-rays at the high

energy end. They are energetic enough to ionise

atoms and break molecular bonds as they penetrate

tissues and therefore called ionising radiation.

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Production of X- ray

•A high voltage is passed across two tungsten terminals. One

terminal (cathode) is heated until it liberates free electrons.

• When a high voltage is applied across the terminals the electrons

accelerate towards the anode at high speed.

• On hitting the anode target x-rays are produced.

• X-rays are produced when high energy electrons strike a high

atomic number material. This interaction is produced within an x-

ray tube.

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• The bombardment of targets of heavy atoms by fast

moving electrons causing energy levels in the target to

change.

• The energy released from K shell transition by electrons

returning to the ground state.

• Transitions of orbital electrons from outer to inner

shells.

• Bombarding electrons can release electrons from inner

energy level orbits.13

Glass tube of x-ray

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X-ray Production

• Electrons accelerated towards target

• Electrons strike a target.

• Energy released as high frequency electromagnetic radiation

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X-ray application protocol

• Transmission

– Photons passing through the body

• Absorption

– Partial or total absorption of energy in the patient

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Screen-film cassette

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Properties of film

• The x-ray beam leaving the patient carries absorption pattern

dependent on the thickness and composition of the body

• Image captured on phosphor screen: captured X-Rays and

transfer into visible light.

• After exposure, film can be viewed as a semitransparent on a

light screen

• Imaging in 2 ways:

– Recording on film (negative image)

– Display on video monitor (positive image)

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X- ray and interactions with tissue •The x-ray picture is a result of the interaction of the

ionising radiation with tissues as it passes through thebody. Tissues of different densities are displayed asdistinct areas depending on the amount of radiationabsorbed.•There are 4 basic densities in conventional

radiography: gas (air), soft tissue and fluid, andcalcified structures and bone.• Air absorbs the least amount of x-rays and therefore

appears black on the radiograph, whereas calcifiedstructures and bone absorb the most, resulting in awhite density. Soft tissues and fluid have a similarabsorptive capacity and therefore appear grey on aradiograph.

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Basic Radiographic Densities

• Air.

• Bone.

• Soft tissue.

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• Energy per unit mass

Expressed in Gray’s: 1 Gy

How do x-rays passing through the body create an image?

•X-rays that pass through the body to the film render the film dark (black).

•X-rays that are totally blocked do not reach the film and render the film light (white).

•Air = low atomic # = x-rays get through = image is dark.

•Metal = high atomic # = x-rays blocked = image is light (white).

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Thorax v Fractures

Abdominal Breast imagingx-ray Mammography

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Computed tomography (CT)

used to generate a three-dimensional image of the inside of an

object from a large series of two-dimensional X-ray images

taken around a single axis of rotation.

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Applications

CNS/spine:

CT remains the tool for primary diagnosis, pre-surgical

assessment, treatment monitoring and detection of relapse in

many CNS disease conditions.

Oncology/radiotherapy:

CT is particular value in obtaining whole body scans in oncology

due to the speed and ease of use. CT is used for radiotherapy

treatment planning to allow more precise targeting of treatment.

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CT – step by step

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Indications

CT is often the most diagnostic cross-sectionalexamination and more definitive than Ultrasound inmany instances.

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Contraindications

Due to the relatively high radiation dose, CT should beavoided in pregnancy, high density foreign material, e.g.dental amalgam and barium, may limit the diagnosticquality of the examination.

Chest:

CT is excellent for detecting both acute and chronicchanges in the lung parenchyma as pneumonia) orcancer.

Abdomen:

applications include the diagnosis of abdominalpathology which may be inflammatory or infectiveorigin. CT is particularly useful for masses, pancreaticand hepatic disease.

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Medical ultrasonography

High frequency broadband sound

waves in the megahertz range

that are reflected by tissue to

varying degrees.

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•No radiation

•Can be portable

•Relatively

inexpensiveespecially

when compared with

modalities such as MRI

and CT.

Ultrasound

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Ultrasound (Sonography)

• It is used to visualize muscles, tendons, and many internal

organs, their size, structure and any pathological lesions.

They are also used to visualize a fetus during routine and

emergency.

• It poses no known risks to the patient, it is generally described

as a "safe test" because it does not use ionizing radiation,

which imposes hazards (e.g. cancer production and

chromosome breakage).

• However, it has two potential physiological effects: it

enhances inflammatory response; and it can heat soft tissue.

• The same principles involved in the sonar used

by bats, ships and fishermen.

• Sound is a mechanical wave, which requires a

medium in which to travel.

• The wavelength is the distance traveled during

one cycle, the frequency of the wave is

measured in cycles per second or Hertz

(Cycles/s, Hz)

• For humans audible sound ranges between 16

Hz and 20.000 Hz (20 kHz).

Ultrasound – how does it work?

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• when a sound wave (frequency 2.0 to 10.0 megahertz ) strikesan object, it bounces backward or echoes.

• by measuring these echo waves it is possible to determine howfar away the object is and its size, shape, consistency (solid,filled with fluid, or both) and uniformity.

• a transducer both sends the sound waves and records theechoing waves. When the transducer is pressed against theskin, it directs a stream of inaudible, high-frequency soundwaves into the body. As the sound waves bounce off of internalorgans, fluids and tissues, the sensitive microphone in thetransducer records tiny changes in the sound's pitch anddirection. These signature waves are instantly measured anddisplayed by a computer, which in turn creates a real-timepicture on the monitor.

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Ultrasound waves do not pass through air; therefore an evaluation ofthe stomach, small intestine and large intestine may be limited.Intestinal gas may also prevent visualization of deeper structures suchas the pancreas and aorta.

Patients who are obese are more difficult to image because tissueattenuates (weakens) the sound waves as they pass deeper into thebody.

Ultrasound has difficulty penetrating bone and therefore can only seethe outer surface of bony structures and not what lies within.

Ultrasound – limitations

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Some applications of USS

• Head and neck:

may be used for evaluation of the thyroid, lymph nodes andclinically suspected masses.

Limbs:

musculoskeletal USS has been revolutionized by advances inhigh frequency probes which enable characterization of softtissue masses and collections.

Abdomen:

This is the main use of USS. Useful for assessment of

solid organs, e.g. liver, kidneys, spleen, gallbladder, pancreas,and uterus. Retroperitoneal masses and lymph nodes. USS isuseful for directing biopsy of solid organs/masses and fordrainage of ascites, abscesses and collections.

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Ultrasound - biomedical applications

• heart and blood vessels, incl. the abdominal aorta and its major branches

• liver

• gallbladder

• spleen

• pancreas

• kidneys

• bladder

• uterus, ovaries, and unborn child (fetus) in pregnant patients

• eyes

• thyroid and parathyroid glands

• scrotum (testicles)

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A magnetic resonance

imaging instrument (MRI

scanner), or "nuclear magnetic

resonance (NMR) imaging"

scanner.

MRI

A magnetic resonance imaging (MRI)

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uses powerful magnets to polarize 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.

MRI

Magnetic resonance imaging (MRI)

This is a non-invasive technique which displays internal

structure whilst avoiding the use of ionising radiation. The

nuclei of certain elements align with the magnetic force

when placed in a strong magnetic field. These are usually

hydrogen nuclei in water and lipid, which resonate to

produce a signal when a radiofrequency pulse is applied

and display anatomical information.

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Indications

There are a wide variety of indications. MR is especiallyuseful in imaging the brain, spine, peripheral limbs andjoints, neck and pelvis.

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Contraindications

• These largely apply to patients with magnetically susceptible

devices or materials whose movement

• These include cardiac pacemakers, metallic fragments and

prosthetic heart valves. Relative contraindications include

pregnancy.

MRI has limited use in the chest and increasing use in the

abdomen particularly with regard to the liver, pancreas and

adrenals.

Applications

The spine:

MRI imaging is superior to other techniques indisplaying anatomy and is the technique of choice inassessing disc disease and the post-operative back.

CNS:

imaging of the CNS is used to evaluate mass lesions,white matter disease, cerebrovascular disease andvisual and endocrine disorders such as pituitarydysfunction.

In trauma/acute haemorrhage CT is the preferredtechnique.

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Abdominal/pelvic MRI:

Within the abdomen MR is often a problem solving tool and can

be used to more confidently characterise focal liver and

pancreatic lesions as well as assess diffuse liver disease. It is

also of use in evaluating indeterminate adrenal masses.

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• No radiation

• Strong magnetic field• No pacemakers

• No electronic implants

• Small, loud tube

• Patients must hold still

• Relatively expensive

Magnetic Resonance Imaging (MRI)

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CT scanning versus MRI imaging

CT• Radiation exposure

• Easy use

• Good soft tissue contrast

• Fast scans available

• Limited plane

MRI• No radiation exposure

• Technically difficult

• Excellent soft tissue contrast, better than CT and shows internal structure of some organs in better detail

• Faster sequences still slower than CT

• Multiplanar imaging capability

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Percutaneous biopsy:

biopsy needle placement may be done under CT, MRI and

ultrasound especially ultrasound. This provides non-

operative confirmation of suspected malignancy and with

the aid of a tissue diagnosis it is possible to accurately plan

treatment. For histology and cytology a needle is used.

Using imaging guidance, there is avoidance of damage to

vital structures such as blood vessels and solid organs like

liver biopsy.

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Interventional radiology

Interventional radiology is a sub-speciality where a varietyof imaging modalities are used to guide percutaneousprocedures. This may obviate alternative surgicalprocedures and consequently result in lower morbidity.Interventional procedures are usually carried out underlocal anaesthesia and on an outpatient basis, therebyconsiderably reducing bed occupancy. There is a hugerange of procedures that are currently performed.

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DSA = Digital subtraction angiography (using contrast agent)

use of film and movies, and

especially for imaging the heart

and blood vessels.

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Nuclear Medicine (NM)[gamma camera]

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• Terms:• Counts or Activity

• Physiologic imaging

• Radioactivity stays with the patient until cleared or decayed

Nuclear Medicine (NM)[gamma camera]

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Academic planCourse name

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Radiation Physics Basic radiographic Positioning

Radiographic Anatomy&Physiology Patient care in medical Imaging

Principles of image formation y Computerized tomography Physics

Radiation Protection Image reading (1&2)

Radiation Physics Nuclear medicine Physics and

equipment

General Radiography Clinical

Practice

Ultrasound Procedures (1& 2)

Contrast media in Medical Imaging Magnetic Resonance Physics &

Equipment

Fluoroscopic Procedures Nuclear medicine Procedures (1&2)

Ultrasound Physics and equipment Principles of Radiation Therapy

Computerized tomography

Procedures

Magnetic Resonance

Quality Management in Medical

Imaging

Imaging Procedures

Directed study Nuclear medicine Procedures (1&2)