Diagnostic Imaging
Domain focus
Diagnostic Imaging tests radiography, positioning, exposure technique, radiation safety, ultrasound basics, contrast studies, and image labeling. The exam focuses on producing diagnostic images without unnecessary radiation.
Core rules and concepts
- Follow ALARA: as low as reasonably achievable. Collimate to the area of interest, wear lead gloves and aprons, use personal dosimeters, and restrain with sandbags or ties rather than hands.
- Orthogonal views are standard: at least two views at 90 degrees. A single view can hide a lesion or make a foreign body look present.
- Exposure is controlled by kVp and mAs. mAs = milliamperes × exposure time in seconds. Increasing kVp raises penetration and scatter; increasing mAs raises density and patient dose.
- Label images with patient name or ID, date, view, and side marker. Poor labeling can make a study unusable.
- Ultrasound is operator-dependent; use acoustic gel, clip hair, and choose a transducer frequency appropriate to depth. Keep original images; annotate copies only.
Worked example
A radiograph is made at 300 mA and 0.02 seconds. mAs = 300 × 0.02 = 6 mAs. If the image is underexposed because the patient is thicker than expected, the technician should adjust technique according to the chart rather than simply repeating the same exposure.
Traps that cost marks
Taking only one view; failing to collimate; using a hand to restrain a patient during exposure; and forgetting the side marker.