ARRT Radiography Flashcards

The specific absorption of x-ray photons by the photoelectric effect is MOST likely to occur when:

Answer: Photon energy is slightly greater than the binding energy of the electron

Photoelectric absorption is most probable when the incident photon energy just exceeds the binding energy of the inner-shell electron.

Which modality uses gradient magnetic fields superimposed on the static magnetic field to spatially encode the MR signal?

Answer: Gradient coils

Gradient coils create small, controlled variations in the magnetic field used for slice selection, frequency encoding, and phase encoding in MRI.

The Bucky factor (grid factor) represents:

Answer: How much more mAs is required when using a grid compared to non-grid technique

The Bucky factor indicates the exposure increase needed when adding a grid; a factor of 4 means 4× more mAs is required.

For the AP axial projection of the coccyx, the central ray is angled:

Answer: 30° caudad

A 10–30° caudad angle is directed to 2 inches superior to the pubic symphysis to project the coccyx free of superimposition.

Which of the following is a late (deterministic) effect of high-dose radiation exposure?

Answer: Cataracts of the lens

Cataracts are a deterministic (non-stochastic) effect with a threshold dose; they occur at high exposures to the ocular lens.

The Society of Motion Picture and Television Engineers (SMPTE) test pattern is used in radiology to evaluate:

Answer: Display monitor performance and quality

The SMPTE test pattern is a standardized chart used to assess display monitor luminance, contrast, resolution, and artifact performance.

A patient has a history of iodine contrast allergy. The most appropriate pre-medication regimen typically includes:

Answer: Prednisone 50 mg at 13 hours, 7 hours, and 1 hour before contrast, plus diphenhydramine

The standard corticosteroid premedication protocol uses prednisone (50 mg PO) at 13, 7, and 1 hour before contrast, often with diphenhydramine 1 hour before.