ARRT Radiography Flashcards

What is the primary purpose of using automatic exposure control (AEC) in radiography?

Answer: To terminate exposure when sufficient radiation reaches the detector

AEC detects radiation reaching the detector and terminates the exposure once a preset charge is reached, ensuring consistent image density.

A radiograph of the lumbar spine appears too light (underexposed). Which single change will most effectively increase radiographic density?

Answer: Increase mAs by 50%

mAs directly controls the quantity of x-ray photons produced; increasing mAs proportionally increases image density.

Which projection of the sacroiliac joints places both joints equidistant from the image receptor?

Answer: Posterior oblique (30° rotation)

A 30° posterior oblique (LPO or RPO) rotation places one sacroiliac joint parallel to the image receptor for optimal visualization.

Under ALARA principles, which of the following is a primary method to reduce patient dose in fluoroscopy?

Answer: Using pulsed fluoroscopy

Pulsed fluoroscopy delivers x-rays in brief pulses rather than continuously, significantly reducing patient and operator dose.

Which artifact appears as thin, sharp lines parallel to the long axis of the grid, caused by damage to grid strips?

Answer: Grid lines

Damaged or improperly aligned grid strips cause grid lines to appear as parallel white lines on the radiographic image.

The anatomical structure located at the level of T4-T5 that serves as a landmark for chest radiography is the:

Answer: Aortic arch (aortic knuckle)

The aortic arch (aortic knuckle) is found at the T4-T5 level and is a key landmark on the PA chest radiograph.

Which federal regulation requires that the x-ray beam be collimated to no larger than the size of the image receptor?

Answer: 21 CFR 1020.30–1020.33 (CDRH)

21 CFR Part 1020 (administered by the FDA/CDRH) sets federal performance standards for diagnostic x-ray equipment including beam limitation.