CRES Practice Questions (2026) — Free Sample Questions with Answers

Answer: B

PA chest, because air-filled lungs need little penetration: Incorrect. Chest radiography commonly uses high kVp (about 110–125) to penetrate the mediastinum and reduce rib contrast.

Mammography, because breast soft tissues differ only slightly in density: Correct. Mammography uses about 25–35 kVp so photoelectric absorption differences between glandular, fatty and calcified tissue are maximized.

Lateral lumbar spine, because bone is thin in that projection: Incorrect. The lateral lumbar spine is one of the thickest projections and requires relatively high kVp.

AP abdomen, because bowel gas already adds plenty of natural subject contrast: Incorrect. Abdominal radiography typically uses about 75–85 kVp, well above mammography values.

Thin, low-contrast soft tissue (breast) uses low kVp to exploit photoelectric absorption; thick or high-contrast anatomy (chest, spine) uses higher kVp.

Answer: C

56 A: Incorrect. This divides by 3 × 480 instead of √3 × 480, treating the phases as if each carried full line voltage independently.

167 A: Incorrect. This uses the single-phase formula I = P ÷ V (80,000 ÷ 480) and ignores the √3 factor.

96 A: Correct. For balanced 3-phase loads, I = P ÷ (√3 × V × PF) = 80,000 ÷ (1.732 × 480) ≈ 96 A.

289 A: Incorrect. This multiplies by √3 instead of dividing (80,000 × 1.732 ÷ 480).

Three-phase power: P = √3 × V(line) × I(line) × PF, so I = P ÷ (1.732 × V × PF).

Answer: B

A faulty network cable between the DR console and the wall data jack: Incorrect. A successful ping proves the physical link and IP routing are working.

A mismatch in the AE title or port, or the DR is not configured on PACS: Correct. When IP connectivity works but the DICOM association fails, the problem is at the application layer: AE titles, port number, PACS node configuration or a firewall blocking the DICOM port.

A failed flat-panel detector that cannot acquire any images: Incorrect. C-ECHO tests communication only; detector failure would not cause a DICOM verification failure.

A duplicate IP address on the network that blocks all traffic to the console: Incorrect. A duplicate IP would usually make ping unreliable or fail, which is not the case here.

Ping tests the network layer; C-ECHO tests the DICOM association. Ping OK + echo fail = check AE title, port, remote node entry and firewall rules.

Answer: B

8,000 HU: Incorrect. This is kVp × mA × s with no rectification factor, which applies only to single-phase generators.

11,280 HU: Correct. HU = kVp × mA × s × 1.41 = 80 × 200 × 0.5 × 1.41 = 11,280 HU.

5,674 HU: Incorrect. This divides by 1.41 rather than multiplying.

22,560 HU: Incorrect. This doubles the correct value, for example by using 1.0 s instead of 0.5 s.

Heat units = kVp × mA × s × factor (1.0 single-phase; about 1.35 three-phase six-pulse; 1.41 twelve-pulse/high-frequency). Joules ≈ 0.7 × HU for single-phase.

Answer: C

Replace the AEC ion chamber assembly and then recalibrate the generator: Incorrect. The AEC tested within specification, so replacing hardware will not fix the problem.

Lower the AEC density setting by two steps for every exam performed in that room: Incorrect. A global density change would underexpose other exams that are using the correct chambers.

Report it as a technique (user) issue and arrange training on chamber selection: Correct. Using the center chamber for a PA chest makes the AEC expose for the dense mediastinum, overexposing the lungs; the fix is selecting the lateral (lung) chambers.

Replace the DR detector because its sensitivity has drifted beyond limits: Incorrect. Detector drift would affect all exams, and the pattern links clearly to chamber choice.

Before replacing parts, confirm whether the device meets specification; a pattern tied to a user setting points to user error and training, documented in the CMMS.

Answer: C

The magnet poses no risk because no scan is currently in progress: Incorrect. The static field of a superconducting magnet stays on whether or not a scan is running.

Turning off the room lights disables the static field: Incorrect. Room power and lighting have no effect on a superconducting magnet's field.

The field is always on; bring only MR Safe or Conditional items: Correct. Superconducting magnets remain at field continuously; staff must be screened and bring only MR Safe or appropriately MR Conditional tools and equipment.

Steel tools are safe if held firmly with both hands: Incorrect. Ferromagnetic objects can be pulled into the bore with great force regardless of grip, causing serious injury.

Assume the MRI magnet is always on: screen yourself, follow ACR zone controls, and use MR Safe/MR Conditional equipment only.