Diagnostic Imaging
What this domain tests
Diagnostic imaging covers radiography, positioning, exposure, contrast, ultrasound, safety, and artifacts. The exam tests image quality and patient protection.
Core rules
- mAs controls the number of x-rays and density; kVp controls penetration and contrast.
- Measure patient thickness, collimate to the area of interest, and use orthogonal views.
- Position for the view requested: lateral and ventrodorsal or dorsoventral; keep limbs out of the field.
- Use PPE: lead apron, gloves, thyroid shield, and dosimeter; follow ALARA.
- Artifacts include motion, grid lines, poor positioning, scratches, and contrast in the wrong place.
- Ultrasound needs clipping, gel, and a good acoustic window; fasting helps for some studies.
Worked example
A technique chart orders 200 mA at 0.05 s. mAs = 200 × 0.05 = 10 mAs. If the image is underexposed, the technologist can increase mAs or kVp according to the chart, but must not simply repeat without changing technique and recording it. Repeat views should be limited and logged.
Traps that cost marks
No orthogonal view; not measuring; collimating too widely; holding a patient without PPE; confusing kVp with mAs; failing to label the image.