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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)