DIAGNOSTIC RADIOLOGY & BODY SCANS

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DIAGNOSTIC RADIOLOGYBODY SCANS

• CHAPTERS 20 21

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X-RAYS

• 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.

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X-RAYS AS A DIAGNOSTIC TOOL

• 3 PRIMARY WAYS
• 1) Radiography.
• 2) Fluoroscopy.
• 3) Tomography.

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RADIOGRAPHY

• 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)

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FLUOROSCOPY

• See text. Not recommended
• A real-time X-Ray
• Typically used with dye studies such as barium
  swallow, angiography, etc.
• Prolongs radiation exposure.

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TOMOGRAPHY

• 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)

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DIGITAL RADIOGRAPH

• 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.

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RADIATION SAFETY

• Exposure is cumulative.
• RISKS
• 1) Genetic damage, cancer.
• 2) Sterility.
• 3) Alterations in the composition of individual
  cells.
• 4) Bone marrow production.

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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.
• X-Ray exposure is measured in millirads.

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RADIATION SAFETY

• 3 ways to protect against ionizing radiation
• 1) Time - as short as possible.
• 2) Distance - as far away as possible.
• 3) Shielding.

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RADIATION SAFETY

• 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.

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BODY SCANS

• CT
• MRI
• DEXA
• PET
• SPECT

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CT / CAT

• 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.

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CT / CAT

• ADVANTAGES
• 1) Excellent detail.
• 2) Quick results.
• DISADVANTAGES
• 1) Cost.
• 2) Time of exposure to radiation.

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CT / CAT

• 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.

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MRI

• 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.

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MRI

• 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.

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CIRRHOSIS
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STONE RIGHT URETER
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MRI Absolute Contraindications

• 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.

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MRI Relative Contraindications

• 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.

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DEXA

• Dual Energy X-Ray Absorptiometry.
• The modality of choice for measuring bone mineral
  density (BMD) in evaluating osteoporosis.
• Low radiation exposure, quick.

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Dexa T Scores
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PET SCAN

• 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.

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PET SCAN

• 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.

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PET SCAN
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APPLICATIONS OF PET SCANS

• 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.

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APPLICATIONS OF PET SCANS

• Neuroimaging - dementia, stroke, epilepsy,
  Parkinsons disease.
• Cardiac to assess myocardial viability.
• Psychiatric schizophrenia, mood disorders,
  substance abuse.
• See http//en.wikipedia.org/wiki/Positron_emission
  _tomography

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SPECT

• 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.

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APPLICATIONS OF SPECT SCANS

• Neuroimaging- dementia, neoplasms, infection,
  epilepsy.
• Cardiac- ischemic heart disease.
• Others- thyroid, bone, white cells.
• See http//en.wikipedia.org/wiki/SPECT

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63 YOM W/ PROSTATE CANCER
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Tc-99 Scan
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FUNCTIONAL MRI

• 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.

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FUNCTIONAL MRI

• A fMRI scan showing regions of activation in
  orange, including the primary visual cortex.

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IMAGES

• Images compliments of the Department of Radiology
  at the Uniformed Services University of the
  Health Sciences (USUHS), Bethesda, Md.
• See www.rad.usuhs.edu

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THE CHEST X-RAY

• 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.

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THE CHEST X-RAY

• Usually take an AP (antero-posterior), or PA
  (postero-anterior), and a lateral view.
• Can also take an oblique view.
• If known, the part youre 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.

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22 YEAR OLD SMOKER W/ COUGH, WHEEZING
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22 YEAR OLD SMOKER W/ COUGH, WHEEZING
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CYSTIC TERATOMA
22 YEAR OLD SMOKER W/ COUGH, WHEEZING
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46 YOF W/ CHEST PAIN AFTER A ROUND OF GOLF
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22 YOM W/ NIGHT SWEATS, WT LOSS
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ABDOMINAL X-RAYS

• 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.

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AIR-FLUID LEVELS IN BOWEL OBSTRUCTION
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43 YOF W/ ABDOMINAL PAIN
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32 YOF W/ G. E. REFLUX
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32 YOF W/ REFLUX
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32 YOF W/ REFLUX
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32 YOF W/ REFLUX
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SKELETAL X-RAYS

• 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

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18 YOM W/ RIGHT THIGH PAIN
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18 YOM W/ RIGHT THIGH PAIN
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OSTEOSARCOMA
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53 YOM W/ SWELLING, LEFT MIDDLE FINGER
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TOPHACEOUS GOUT ?
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18 YOM FELT SOMETHING POP WHEN THROWING A
SPLIT-FINGER FASTBALL
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UNICAMERAL BONE CYST W/ PATHOLOGIC FRACTURE
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MAMMOGRAPHY

• 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.

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SCREENING MAMMOGRAPHY

• 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.

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SCREENING MAMMOGRAPHY
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CONTRAST STUDIES

• 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 isnt.

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CONTRAST STUDIES

• 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.

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AIR-CONTRAST B.E.
APPLE CORE LESION OF ADVANCED COLON CANCER
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ACHALASIA
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2 DAY OLD INFANT W/ INCREASING ABDOMINAL
DISTENTION
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2 DAY OLD INFANT W/ INCREASING ABDOMINAL
DISTENTION
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16 YOF W/ RLQ PAIN
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16 YOF W/ RLQ PAIN
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HSG BICORNUATE UTERUS
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30 YOF W/ NEW ONSET SEIZURES
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ANGIOGRAM MENINGIOMA
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ANGIOGRAM 19 YOF W/ HYPERTENSION
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RENAL ARTERY STENOSIS