DIAGNOSTIC RADIOLOGY
&
BODY SCANS
CHAPTERS 20 & 21
X-RAYS
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Electromagnetic radiation of short
wavelength.
Penetrate most substances,
including tissue.
Also called ionizing radiation.
Cause fluorescence (emission of
light) on photographic plates.
Harmful, in a dose-dependent
fashion.
X-RAYS AS A DIAGNOSTIC TOOL
3 PRIMARY WAYS
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1) Radiography.
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2) Fluoroscopy.
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3) Tomography.
RADIOGRAPHY
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Radiograph = an X-Ray image (picture), or
what we call “the X-Ray.”
“Like negatives of photographs.”
X-Rays that penetrate the tissues and
reach the film turn the film black. As such:
AIR = BLACK (ISH)
FAT = DARK GRAY
WATER = LIGHTER GRAY
BONE = WHITE (ISH)
FLUOROSCOPY
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See text. Not recommended
A real-time X-Ray
Typically used with dye studies such
as barium swallow, angiography,
etc.
Prolongs radiation exposure.
TOMOGRAPHY
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A tomogram is a radiograph that
generates cross-sectional images at
different tissue planes.
CT = computed tomography, or CAT
scan = computed axial tomography
– uses computers, produces digital
images. (More later)
DIGITAL RADIOGRAPH
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A digital image without film.
Stored in a computer database.
Can be accessed by anyone with
access to the database, can be
emailed, etc.
No need to chase down the hard
copy films.
RADIATION SAFETY
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Exposure is cumulative.
RISKS
1) Genetic damage, cancer.
2) Sterility.
3) Alterations in the composition of
individual cells.
4) Bone marrow production.
RADIATION SAFETY

Occupational exposure to ionizing
radiation is associated with:
1) Leukemia.
2) Skin cancer.
See text re:

The “rem,” the “rad”, and the “gray.”
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X-Ray exposure is measured in millirads.
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RADIATION SAFETY
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3 ways to protect against ionizing
radiation:
1) Time - as short as possible.
2) Distance - as far away as
possible.
3) Shielding.
RADIATION SAFETY
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PREGNANCY – potential for
teratogenesis etc. is highest during
organogenesis, which occurs during
the 1st 12 weeks.
Need to ask about pregnancy.
In a perfect world, X-Rays would be
done between menses and
ovulation.
Shielding the pelvis advised when
uncertain.
BODY SCANS
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CT
MRI
DEXA
PET
SPECT
CT / CAT
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Computed tomography, computerized
axial tomography.
Uses X-Rays in a 180° fashion.
Radiation exposure is “small.”
Image generated based on amount of
radiation absorbed.
Can depict all types of tissues except
nerves.
CT / CAT
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ADVANTAGES
1) Excellent detail.
2) Quick results.
DISADVANTAGES
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1) Cost.
2) Time of exposure to radiation.
CT / CAT
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1st CT developed in 1972 to evaluate
brain abnormalities.
Now in widespread use for other organ
systems.
USES: evaluation of neoplasms /
masses, hematomas, abscesses, foreign
body localization, trauma.
Quicker than MRI.
MRI
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Magnetic resonance imaging.
See text for details of the physics
involved.
In short, uses radio waves and a
magnetic field that detects changes in
absorption of energy by hydrogen ions.
As such, no radiation exposure.
MRI
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ADVANTAGES
1) No radiation exposure. Can be used
during pregnancy.
2) Better detail than CT.
3) Imaging modality of choice for the
CNS.
DISADVANTAGES
1) Cost – 1/3 more than CT.
2) Takes longer, results not available as
fast as CT.
→
CIRRHOSIS
STONE RIGHT URETER
←
MRI Absolute Contraindications
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Brain Aneurysm Clip
Implanted neural stimulator
Implanted cardiac pacemaker or
defibrillator
Cochlear implant
Ocular foreign body (e.g. metal shavings)
Other implanted medical devices: (e.g.
Swan Ganz catheter)
Insulin pump
Metal shrapnel or bullet.
MRI Relative Contraindications
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1) Penile and non metallic valve prosthesis
2) Pregnancy: We try to avoid scanning in the
first trimester since we are not sure if there are
any adverse effects to MRI. (Pregnant women
never receive the contrast agent gadolinium)
3) Claustrophobic or anxious patients can not
tolerate the MRI scanner.
4) Obese patients may not fit into the small
opening of the scanner. In addition the
maximum weight that the MRI table can sustain
is 350 lbs.
DEXA
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Dual Energy X-Ray Absorptiometry.
The modality of choice for
measuring bone mineral density
(BMD) in evaluating osteoporosis.
Low radiation exposure, quick.
Dexa T Scores
Normal
Osteopaenia
Osteoporosis
A normal bone density is
when the T score measures
greater than –1.0 (greater
than minus 1.0)
If the bone mineral density
is measured as a T score
between –1.0 and –2.5
(minus 1.0 and minus 2.5)
this indicates the presence
of osteopaenia.
Osteopaenia is not
osteoporosis.
It does however indicate that
there is a reduction in bone
mineral density, which is not
as severe as osteoporosis.
This condition represents an
earlier phase of bone mineral
density loss in the skeleton.
If the bone mineral
density is measured as a
T score of
–2.5 or less
(minus 2.5 or less)
this indicates the
presence of
osteoporosis at the site
of measurement.
PET SCAN
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Positron emission tomography.
The positron is the antiparticle or
the antimatter counterpart of the
electron. The positron has an
electric charge of +1, a spin of 1/2,
and the same mass as an electron.
(Wikipedia)
Measures function rather than
structure.
PET SCAN
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Patient is injected with a metabolically active
biochemical substance, such as glucose, water,
ammonia, which has been tagged with a
radioactive isotope that emits a positron.
Binding of these substances with electrons
found in the tissue being studied causes
emission of gamma rays, which are converted
into color-coded images.
Degree of gamma ray production reflects
cellular utilization / metabolism of the tagged
substance.
PET SCAN
APPLICATIONS OF PET SCANS
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High dollar machine, high dollar
test.
Costs 1/3 more than MRI.
Availability typically limited to
research institutions, and used
more as a research tool than a
diagnostic one.
Findings of altered metabolic
function can direct innovations in
treatment.
APPLICATIONS OF PET SCANS
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Neuroimaging - dementia, stroke,
epilepsy, Parkinson’s disease.
Cardiac – to assess myocardial viability.
Psychiatric – schizophrenia, mood
disorders, substance abuse.
See
http://en.wikipedia.org/wiki/Positron_emi
ssion_tomography
SPECT
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Single Photon Emission Computed Tomography
Uses radiopharmaceuticals labeled with a
positron-emitting isotope such as Technitium –
99 (Tc-99m).
Detects gamma rays emitted by the natural
radioactive decay of the isotope.
Degree of gamma ray production reflects more
the degree of perfusion of the organ being
studied than its function.
APPLICATIONS OF SPECT SCANS
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Neuroimaging- dementia,
neoplasms, infection, epilepsy.
Cardiac- ischemic heart disease.
Others- thyroid, bone, white cells.
See:
http://en.wikipedia.org/wiki/SPECT
63 YOM W/
PROSTATE
CANCER
Tc-99 Scan
FUNCTIONAL MRI
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Measures signal changes in the brain that
are due to changes in neural activity.
Increased neural activity → need for
increased oxygen → increased
oxygenated hemoglobin as relative to
deoxygenated hemoglobin.
Because deoxygenated hemoglobin
attenuates the MR signal, the vascular
response leads to a signal increase that is
related to the neural activity.
FUNCTIONAL MRI
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A fMRI scan showing regions of
activation in orange, including the
primary visual cortex.
IMAGES
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Images compliments of the
Department of Radiology at the
Uniformed Services University of
the Health Sciences (USUHS),
Bethesda, Md.
See: www.rad.usuhs.edu
THE CHEST X-RAY
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Can be used to assess a wide variety of
pathologic conditions of the chest: heart,
lungs, mediastinum, bone, esophagus,
trachea, diaphragm.
Such as: infection, tumor, lymphoma,
foreign bodies, rib fractures, cardiac
enlargement, presence of free air
(pneumothorax, pneumomediastinum),
fluid accumulation (pulmonary edema,
pleural effusion), changes such as
sarcoid, amyloid.
THE CHEST X-RAY
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Usually take an AP (antero-posterior), or
PA (postero-anterior), and a lateral view.
Can also take an oblique view.
If known, the part you’re interested in
should be closest to the film.
To assess free air or fluid, patients
position can be manipulated to allow
gravity to affect layering of the fluid or
air.
←
22 YEAR OLD SMOKER
W/ COUGH, WHEEZING
←
22 YEAR OLD SMOKER W/
COUGH, WHEEZING
← CYSTIC
TERATOMA
22 YEAR OLD SMOKER W/
COUGH, WHEEZING
←
←
46 YOF W/ CHEST PAIN
AFTER A ROUND OF GOLF
→
22 YOM W/ NIGHT
SWEATS, WT LOSS
←
ABDOMINAL X-RAYS
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The “flat plate,” or scout film, done as
the sole diagnostic film or prior to a
contrast study.
Manipulation of position of the patient
can assess presence of free air (under
the diaphragm), fluid, or the presence of
“air-fluid levels” as seen in bowel
obstruction.
KUB- kidneys, ureter, bladder. Term used
interchangeably w/ flat plate.
AIR-FLUID
LEVELS IN
BOWEL
OBSTRUCTION
43 YOF W/
ABDOMINAL
PAIN
32 YOF W/
G. E.
REFLUX
32 YOF W/
REFLUX
32 YOF W/
REFLUX
32 YOF W/
REFLUX
SKELETAL X-RAYS
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Most useful in assessing fractures,
but also good for: joint dislocation /
subluxation, changes in bone
architecture (erosions, thickening,
density), presence of abnormal
calcifications / deposits
(osteophytes, tophi), etc
18 YOM W/
RIGHT THIGH
PAIN
18 YOM W/
RIGHT THIGH
PAIN
OSTEOSARCOMA
53 YOM W/
SWELLING, LEFT
MIDDLE FINGER
TOPHACEOUS
GOUT
→
18 YOM FELT
SOMETHING
“POP” WHEN
THROWING A
SPLIT-FINGER
FASTBALL
UNICAMERAL
BONE CYST W/
PATHOLOGIC
FRACTURE
MAMMOGRAPHY
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Radiographic images of the breast,
primarily for early detection of breast
cancer, prior to the appearance of a
palpable mass.
Also useful for evaluation of palpable
masses: benign neoplasms, fibrocystic
breast disease, etc.
Used as an aid in placement of the biopsy
needle.
SCREENING MAMMOGRAPHY
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For early detection of breast cancer.
Guidelines as to who, when, and how
often vary by organization, and depend
on the patients risk status.
American Cancer Society: baseline
between 35 and 40, every 1-2 years
between 40-50, and yearly after 50,
along with monthly self-breast
examination and annual physical exam.
SCREENING MAMMOGRAPHY
↓
CONTRAST STUDIES
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Involves the introduction of a
radiopaque substance (barium, dye,
etc) into an organ, vessel, duct, etc
Allows for the identification of the
anatomy of the structure being
studied, its shape, contour, size,
etc.
“Filling defect” – describes an area
where dye should be but isn’t.
CONTRAST STUDIES
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Barium swallow, upper GI, small bowel series.
Barium enema (B.E.)
Oral cholecystograms (OCG).
Cholangiograms.
Intravenous pyelogram (IVP).
Angiograms- arteriograms, venograms.
Lymphangiograms.
Hysterosalpingograms (HSG).
Myelograms.
Arthrograms.
AIR-CONTRAST B.E.
“APPLE CORE” LESION OF
ADVANCED COLON CANCER
→
←
ACHALASIA
2 DAY OLD INFANT W/ INCREASING ABDOMINAL
DISTENTION
2 DAY OLD INFANT W/ INCREASING ABDOMINAL
DISTENTION
16 YOF W/ RLQ PAIN
←
16 YOF W/ RLQ PAIN
↓
HSG
BICORNUATE
UTERUS
30 YOF W/
NEW ONSET
SEIZURES
ANGIOGRAM
MENINGIOMA
ANGIOGRAM
19 YOF W/
HYPERTENSION
RENAL
ARTERY
STENOSIS