ARRT Cheat Sheet 2026

The 30 highest-yield ARRT facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. For an AP axial (Towne) projection of the skull, the central ray is directed at what angle caudally when using the OML? → 30°
2. Why should metformin be held after contrast media administration in patients with diabetes? → Risk of lactic acidosis if renal function is impaired
3. A timer accuracy test reveals that the actual exposure time is 20% longer than the set time. This most likely indicates: → A malfunctioning timer circuit requiring calibration
4. Which interaction between X-ray photons and matter is the primary source of occupational scatter radiation in diagnostic imaging? → Compton scatter
5. Which projection is best suited to demonstrate a spondylolisthesis of the lumbar spine? → Lateral projection
6. What is the recommended minimum waiting period after a severe contrast reaction before re-administering contrast, if clinically necessary? → No standard waiting period — premedication protocol is the key precaution
7. What is the effective dose limit for a declared pregnant radiation worker during the entire gestation period? → 5 mSv
8. Quantum mottle (noise) in digital radiography is primarily caused by which factor? → Too few X-ray photons reaching the detector
9. Which radiation quantity measures the energy deposited per unit mass of tissue? → Absorbed dose (Gray)
10. For a true AP (Grashey method) of the glenohumeral joint, the patient is rotated how many degrees toward the affected side? → 35–45°
11. The acetabulum is best demonstrated with which projection? → Judet method (anterior and posterior obliques)
12. For a radiograph of the zygomatic arch using the oblique inferosuperior projection, the CR is directed at what angle? → 15° medially
13. Which type of ionizing radiation has the greatest linear energy transfer (LET)? → Alpha particles
14. In a lateral projection of the paranasal sinuses, the central ray should be directed to a point: → Midway between the outer canthus and the EAM.
15. Nephrogenic systemic fibrosis (NSF) is a rare complication associated with which contrast agent in patients with severe renal failure? → Gadolinium-based contrast
16. Radioactive equilibrium in which the daughter's activity equals the parent's activity is called: → Secular equilibrium
17. Which oblique body position places the LEFT zygapophyseal joints of the lumbar spine closest to the IR? → Left posterior oblique (LPO)
18. Primary radiation barriers in a radiographic room must protect against: → The primary (useful) beam
19. During a barium swallow examination, which position best demonstrates a posterior esophageal impression or defect? → RAO projection
20. In a three-phase, twelve-pulse generator, voltage ripple is approximately: → 3-4%
21. Which of the following best defines the concept of 'workload' (W) in shielding calculations for a radiographic room? → Weekly total of mA-minutes at a reference kVp
22. How does increasing kVp affect the scatter radiation reaching the image receptor? → Increases scatter production, reducing image contrast
23. In digital radiography, which exposure indicator value signifies optimal exposure on most current CR/DR systems? → EI of 300 (system-dependent target near 300)
24. Mallet finger results from an avulsion injury to which structure? → Extensor tendon at the base of the distal phalanx
25. During fluoroscopy, the image intensifier converts x-ray photons into a visible image through which sequence? → X-ray → cesium iodide input phosphor light → photocathode electrons → output phosphor
26. Which centering point is used for the AP projection of the sacroiliac joints? → 2 inches superior to the pubic symphysis and 2 inches lateral to midline
27. During which phase of the cell cycle are cells MOST radiosensitive? → M phase (mitosis)
28. The inverse square law states that radiation intensity is: → Inversely proportional to the square of the distance
29. An AP oblique projection of the shoulder (Grashey method) is performed primarily to demonstrate which of the following? → An open glenohumeral joint space.
30. Which positioning error causes grid cutoff on a cross-table lateral projection? → Angling the tube across the grid lines