BASIS OF
RADIOLOGICAL
INVESTIGATION
Basic methods of radiological
examination
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US (ultrasound)
Plain X-ray
CT (computed tomography)
MRI (magnetic resonance imaging)
Nuclear medicine (scintigraphy)
Contrast studies
RADIOLOGY TOOLS
X- RAY
ULTRASOUND
NUCLEAR MEDICINE
MAGNETIC RESONANCE
COMPUTED TOMOGRAPHY
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HOW IS IMAGING DONE?
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IONIZING RADIATION
X-ray, CT, Nuclear Medicine
SOUND WAVES
Ultrasound
MAGNETIC FIELDS / RADIO WAVES
Magnetic Resonance
X-RAY
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DISCOVERED AND
NAMED BY Wilhelm
Conrad Röntgen AT
UNIVERSITY OF
WÜRZBURG, 1895
AWARDED FIRST
NOBEL PRIZE FOR
PHYSICS, 1901
X-RAYS
PLAIN FILM RADIOGRAPHY
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CHEST
MAMMOGRAPHY
GIT (contrast is
necessary!)
SPINE
EXTREMITIES,
BONES & JOINTS
SKULL
X - RAY -- FOUR BASIC DENSITIES
▪ BONE
▪ SOFT
TISSUE
▪ FAT
▪ AIR
STOMACH
UPPER GI – ORAL BARIUM CONTRAST
(GASTRO INTESTINAL)
WITHOUT CONTRASTplain or scout film
COLON
BARIUM ENEMA - RECTAL BARIUM CONTRAST
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INTRAVENOUS PYELOGRAM – IVP
INTRAVENOUS IODINE CONTRAST
WITHOUT CONTRASTplain or scout film
ARTERIOGRAM
INTRAARTERIAL IODINE CONTRAST
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Advantages of plain x-rays
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Quick
Not expensive
Relatively low radiation
Disadvantages of plain x-rays
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Not 3 dimensional
Can miss pathology
May still require other imaging studies
Princeples of CT imaging
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A CT scanner emits a series of narrow beams through the
human body as it moves through an arc, unlike an X-ray
machine which sends just one radiation beam. The final
picture is far more detailed than an X-ray one.
Inside the CT scanner there is an X-ray detector which
can see hundreds of different levels of density. It can see
tissues inside a solid organ. This data is transmitted to a
computer, which builds up a 3-D cross-sectional picture of
the part of the body and displays it on the screen.
Contrast dye is used because it shows up much more
clearly on the screen.
CT planes
CT planes
AXIAL
CORONAL
SAGITTAL
3D-reconstruction
Three-dimensional modeling of kidney on CT
Projection
of slice
Right kidney
Left kidney
CT – diagnostic windows
Head and neck
Brain
Chest
Lungs
Abdomen and pelvis
Bones
Advantages of CT scanning of the
musculoskeletal system
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Excellent anatomic detail
Will detect almost all pathology related
to cortical bone injury
Great for showing displacement or joint
involvement
Now multiplanar
Disadvantages of CT
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Expensive
More radiation
Often not necessary
Principles of MRI
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The patient is
placed in a
strong
electromagnetic
field of 0.3 to 3
teslas
The magnetic field of an MRI machine is typically 3 Tesla!
The Earth’s magnetic field is less that 30 microtesla (0.00003 Ts).
Principles of MRI
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The billions of Hatoms in the body
align themselves
parallel with the
magnetic field,
either in the same
direction or
opposite to the
direction of the
field.
MAGNETIC
RESONANCE
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HYDROGEN
PROTONS IN A
MAGNETIC FIELD
RADIO WAVE
SIGNAL
TRANSMISSION
NO IONIZING
RADIATION
MAGNETIC RESONANCE
EXAMPLES
BRAIN
SPINE
KNEE
Kidneys on MRI
Coronal, bilateral
renal ectopia
Axial, norm
Advantages of MRI
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No radiation
We can slice through the body using
any imaging plane
Looks “inside” bone. Marrow
evaluation.
MRI is very good for looking at the soft
tissues (muscles, ligaments, tendons
and cartilage)
MRI is very sensitive in detecting water
Disadvantages of MRI
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Very expensive
Not as good as CT for cortical bone
Is MRI Better Than CT?
MRI and CT are very different and used for different needs and
reasons; both are valuable and both have specific applications;
they are not interchangeable and one is not a better test than the
other for all things.
The decision whether to use one or the other is based according
to the density of the body tissue that needs to be seen. Softer
tissues that have more water molecules or hydrogen atoms in
them are better seen by MRI because of the physics used.
When MRI is preferable?
Brain
Spinal cord
Soft tissues (muscles, ligaments, intervertebral discs ets.)
Ultrasound
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SOUND WAVE-high
frequency
NO IONIZING
RADIATION
TRANSMITTER/
RECEIVER
TOMOGRAPHIC DATA
28
US – EXAMPLES
GALLBLADDER
KIDNEY
OBSTETRICS