Imaging

Question 1

List mechanism, common uses, and toxicity

Xray

Answer 1

X-ray, two-dimensional
 Can visualize down to 2-4 mm
 Differentiate air, fat, fluid/solid organ, bone
 Toxicity – radiation, minimal
 Common uses – chest, abdomen, bones
 Problem – all organ/fluid density looks similar
(e.g. tumor, fluid, liver, pneumonia)
 Fairly cheap, ≈$100

Question 2

Describe ultrasound

Answer 2

Sound wave reflection, two-dimensional
 Can visualize down to 2-4 mm, fluid vs. solid
 Sound
 reflected back by air and hard objects (bones and stones)
 travels unimpeded through fluid
 partially reflected by solid organs
 Toxicity – thought to be nil (no radiation)
 Common uses – heart, gallbladder, pregnancy
 Problem – areas with bone (brain) and lots of air
(lungs/abd) can be hard to visualize
 Fairly cheap, ≈$300, often available on site

Question 3

Angiography

Answer 3

 X-ray with intravascular contrast, two- dimensional or three-dimensional
 Can visualize to <1mm
 Differentiates blood in vessel (or rupture) from
surrounding tissues
 Toxicity – radiation: (much higher), contrast: (nephropathy, allergy, iodine), vessel puncture
 Common uses – atherosclerosis, bleeding (often
interventional)
 Very expensive, variable ≈$1,000-$8,000

More therapeutic than diagnostic
 For purposes of :embolization to stop bleeding dilitation of narrowed artery
chemoembolization

Question 4

Describe CT

Answer 4

X-ray – three-dimensional
 Can visualize to 1mm
 Differentiates tissues of differing Hounsfield
units (many more gradations than plain Xray)
 Contrast shows areas of increased blood flow or
inflammation, can do angiography
 Toxicity – radiation (much higher), contrast
 Common uses – trauma, brain, tumors
 Fairly expensive, ≈$1,000

Question 5

Nuclear Medicine

Answer 5

Nuclear Medicine
 Administration of radiation-emitting material,
with subsequent scanning for emission
 Two- or three- dimensional
 Visualization often less fine than other modalities (esp the two-dimensional)
 Differentiates tissues with more vs. less uptake
 Toxicity – radiation (often less than CT)
 Common uses – myocardium, pulmonary
embolism, cancer/inflammation
 Fairly expensive, variable ≈$500-$1,500

Question 6

MRI

Answer 6

Three-dimensional MR
 Can visualize <1mm
 Mostly differentiates tissues by water content and
arrangement
 Gadolinium highlights areas of inflammation, can use for
angiography
 Toxicity——————–
 Ferromagnetic material inside patients could move or heat
 Gadolinium rarely causes permanent systemic sclerosis (renal)
 Gadolinium concerns in pregnancy
 Common uses – brain, spinal cord
 Quite expensive, ≈$1,500