ARRT LXMO Practice Questions (2026) — Free Sample Questions with Answers

Answer: C

Gloves and gown only, removed before leaving the room: Gloves and gown are contact precautions; they do not stop inhalation of droplet nuclei that carry M. tuberculosis.

A surgical mask, plus gloves if contact with secretions is likely: A surgical mask is used for droplet precautions; airborne organisms pass around and through it.

A fit-tested N95 or higher-level respirator: Correct. Airborne precautions require a fit-tested N95 (or higher) respirator and a negative-pressure room for diseases such as tuberculosis, measles and varicella.

A face shield only, cleaned with disinfectant after the exam: A face shield guards against splashes but does not filter airborne particles.

Airborne (TB, measles, varicella): N95 respirator + negative-pressure room. Droplet (influenza, pertussis): surgical mask. Contact (MRSA, C. difficile): gown and gloves.

Answer: C

Skin erythema after a long, high-dose exposure: Erythema is a deterministic tissue reaction: it occurs only above a threshold and gets more severe as dose increases.

Radiation-induced cataract of the lens: Cataracts are deterministic; they need a threshold dose and severity increases with dose.

Radiation-induced cancer appearing years later: Correct. Stochastic effects (cancer, genetic effects) have no assumed threshold; dose raises the probability, not the severity.

Temporary sterility after a high gonadal dose: Sterility is a deterministic effect that occurs only above a threshold dose.

Stochastic = chance (probability rises with dose, no threshold, e.g., cancer). Deterministic = threshold and severity (e.g., erythema, cataract, sterility).

Answer: B

0.4 mGy/h: Halving the rate would assume intensity falls in direct proportion to distance, not with the square of distance.

0.2 mGy/h: Correct. I2 = I1 × (d1/d2)² = 0.8 × (1/2)² = 0.8 × 0.25 = 0.2 mGy/h.

0.1 mGy/h: This divides by 8, as if intensity fell with the cube of distance.

3.2 mGy/h: This multiplies by 4; intensity decreases, not increases, as distance grows.

Double the distance → one-fourth the exposure. Distance is the most effective way for the operator to cut exposure.

Answer: A

76 kVp at 6 mAs: Correct. 66 × 1.15 ≈ 76 kVp; a 15% kVp increase roughly doubles receptor exposure, so mAs is halved from 12 to 6.

76 kVp at 12 mAs: Raising kVp 15% without reducing mAs would about double receptor exposure and patient dose.

76 kVp at 24 mAs: Doubling mAs along with a 15% kVp increase would quadruple receptor exposure.

56 kVp at 6 mAs: Lowering both kVp and mAs would cut receptor exposure to about a quarter, causing a noisy image.

15% rule: +15% kVp ≈ 2× receptor exposure, so halve the mAs. Higher kVp with lower mAs lowers patient dose.

Answer: C

Lateral sinuses with the patient upright: The lateral shows all sinus groups superimposed side to side; it is not the best view of the maxillary sinuses.

PA axial (Caldwell) with 15° caudad CR: The Caldwell best shows the frontal and anterior ethmoid sinuses; the petrous ridges overlie the maxillary sinuses.

Parietoacanthial (Waters), OML at 37° to the IR: Correct. With the chin raised so the OML makes 37° with the IR (MML perpendicular), the petrous ridges fall below the maxillary sinuses.

Submentovertical with the IOML parallel to the IR: The SMV best shows the sphenoid sinuses and skull base.

Sinus series: Waters = maxillary; Caldwell = frontal and ethmoid; SMV = sphenoid; lateral = all. Do sinuses upright to show air-fluid levels.

Answer: D

PA wrist with radial deviation: Radial deviation opens the medial (ulnar-side) carpals and makes the scaphoid more foreshortened.

Lateral wrist with the hand in true lateral: In the lateral the carpals overlap heavily, so the scaphoid is not shown clearly.

PA axial wrist in tangential carpal canal view: The tangential (carpal canal) view shows the hamate hook and pisiform, not the scaphoid waist.

PA wrist with ulnar deviation: Correct. Ulnar deviation (often with 10–15° proximal CR angle) lengthens the scaphoid and opens the spaces around it.

Snuffbox pain after a FOOSH injury = suspected scaphoid fracture → PA with ulnar deviation.