CAMRT exam prep
3 factors contributing to increased scatter - ANS-1. High kV
2. Increase xray field size
3. Increased patient thickness
3 reasons why Tungsten is the material of choice - ANS-1. High atomic #: increase xray
production efficiency
2. Thermal Conductivity: Effective at dissipating heat
3. High melting Point: Can withstand high current without pitting/bubbling/melting
90% of man made radiation to the population is related to? - ANS-Medical Radiography
and Dental
Adjustments to kV and mAs for a small/medium or large plaster cast - ANS-Small/
Medium: +5-7kV or +50%-60% mAs
Large: +8-10kV or + 100%mAs
After a BE if there is barium in the ileum, what caused this? - ANS-Inefficient ileoceccal
valve
At what vertebral level does the trachea bifurcate? - ANS-T4-T5
Bit conversions for part thickness - ANS-Every 5cm change = 1 bit
Bones that make up the skull floor - ANS-Temporal bones, ethmoid, sphenoid, occipital
CR angle for an AP coccyx is - ANS-10 degrees caudad
Describe mild, moderate, and severe contrast reactions - ANS-Mild: flushing, itching,
cough, pale, nasal stuffiness
Describe the 2 fontanelles of the skull and when they close - ANS-Anterior fontanelle
occurs at the bregma suture, closes at 18 months
Posterior fontanelle occurs at the lambda suture, closes at 8 weeks
,Describe the 3 components of each step (capture, coupling, collecting) for:
-Indirect DR
-Direct DR - ANS-Indirect DR
-Capture: Cesium Iodide
- Coupling: Fiber optics
-Collect: CCD
Direct DR:
-Capture: a-Se
-Coupling: none (also a-Se)
-Collecting: TFT
Describe the Circle of Willis from posterior to anterior - ANS-
Describe the CR image readout process - ANS-1. Red laser light strikes IP
2. Light gives energy to trapped electrons --> emission of light (Photo stimulated
luminescence)
3. Trapped electrons return to original state
4. Energy emitted in form of blue light
5.Light collected and converted to an electric signal
(When rollers position the IP to be read its called translation
Describe the layers of the CR cassette from front to back - ANS--Protective layer
-Phosphor layer (F center) where the latent image is stored (made with Barium Flour
Halide Crystals)
-Conductive layer (light reflective layer)
-Support layer
-Anti-halation layer (avoid light spread)
-Backing layer with lead
Describe the mnemonic for the carpals - ANS-Some (scaphoid)
Lovers (Lunate)
Try (Triquetral)
Positions (Pisiform)
That (Trapezium)
They (Trapezoid)
Cant (Capitate)
, Handle (Hamate)
Do you need to adjust technique for a fiber glass cast? - ANS-No adjustment needed
Explain bit conversions for grids - ANS-5:1 Grid: 1 bit
8:1 / air gap: 2 bits
12:1 grid: 2.5 bits
Explain compton scatter - ANS-When an xray interacts with an outer shell e- and ejects
it from the atom. Xray changes direction and loses energy
Explain differential absorption - ANS-xrays that undergo photoelectric absorption show
on the image as light areas (xrays did not reach IR)
xrays that penetrate the body and are transmitted to the IR produce dark areas on an
image
Xray image results because of the difference between the 2
-increase mAs
-increase kV
-increase SID
-increase filtration - ANS-mAs: no change
kV: increase quality
SID: no change
Filters: increase
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