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

Answer: D

Inject FDG now and extend the uptake time to 120 minutes instead: Incorrect. A longer uptake time does not overcome high glucose competing with FDG for transport.

Give the patient's insulin dose, then inject FDG right away: Incorrect. Insulin shortly before FDG pushes tracer into muscle and fat, degrading the images.

Inject FDG at twice the usual activity to make up for it: Incorrect. Raising activity adds dose but does not fix poor tumor-to-background contrast.

Consult the physician and reschedule once glucose is controlled: Correct. Glucose competes with FDG; most protocols reschedule or consult when glucose is above about 150–200 mg/dL.

High blood glucose lowers tumor FDG uptake; check glucose before injection and follow the protocol threshold (often 200 mg/dL).

Answer: B

10 mR/h: Incorrect. This assumes exposure drops in direct proportion to distance, not with its square.

2.5 mR/h: Correct. I2 = I1 × (d1/d2)² = 40 × (0.5/2)² = 40 × 1/16 = 2.5 mR/h.

5 mR/h: Incorrect. This uses a factor of 8 instead of squaring the fourfold distance (16).

0.6 mR/h: Incorrect. This over-reduces the exposure, as if the distance had increased about eightfold.

Inverse square law: I1/I2 = (d2/d1)². Doubling distance cuts exposure to 1/4; quadrupling it cuts exposure to 1/16.

Answer: A

Flood field nonuniformity that is magnified by reconstruction: Correct. Small uniformity defects are reprojected at every angle and form rings in reconstructed slices, so SPECT needs tighter uniformity.

Using a 20% energy window instead of a 15% window: Incorrect. Window width affects scatter and sensitivity, not ring patterns.

Acquiring 128 projections instead of 64 projections: Incorrect. More projections reduce streaking and do not cause rings.

Choosing a low-pass filter with too low a cutoff: Incorrect. A low cutoff over-smooths the image but does not create rings.

SPECT rings = nonuniformity; center-of-rotation error = blurring and loss of resolution (point sources become 'tuning fork' shapes).

Answer: D

Give sincalide and measure gallbladder ejection fraction: Incorrect. Sincalide contracts the gallbladder; it is used to measure GBEF or before the study after long fasting, not when the gallbladder is not seen.

End the study and report a normal hepatobiliary scan: Incorrect. Non-visualization at 60 minutes is not normal; it needs morphine or delayed imaging.

Give a second, larger dose of mebrofenin and repeat: Incorrect. Redosing does not answer whether the cystic duct is open.

Give IV morphine and image for about 30 more minutes: Correct. Morphine (about 0.04 mg/kg) contracts the sphincter of Oddi, sending bile into an open cystic duct; non-filling then supports acute cholecystitis.

No gallbladder at 60 min with bowel seen: morphine augmentation plus 30 min of imaging (or delayed imaging); persistent non-filling = cystic duct obstruction.

Answer: D

Proceed, since caffeine affects only exercise stress: Incorrect. Caffeine blocks the adenosine receptors that regadenoson acts on.

Proceed and give aminophylline before regadenoson: Incorrect. Aminophylline is also an adenosine antagonist and would block the stress effect further.

Switch to a double dose of regadenoson: Incorrect. Regadenoson is a fixed 0.4-mg dose; doubling it is not an approved fix for caffeine.

Reschedule or consult about another stress method: Correct. Methylxanthines should be held (usually at least 12 hours); recent caffeine can blunt hyperemia and cause false-negative results.

Vasodilator stress (adenosine, regadenoson, dipyridamole): no caffeine or methylxanthines for about 12 hours; aminophylline reverses side effects.

Answer: B

0.40 mL: Incorrect. This ignores decay and uses the 0800 concentration (20 ÷ 50).

0.80 mL: Correct. 50 × 0.501 = 25.0 mCi/mL at 1400; 20 ÷ 25.0 = 0.80 mL.

1.60 mL: Incorrect. This applies two half-lives of decay, but only one has passed between 0800 and 1400.

0.20 mL: Incorrect. This multiplies by the decay factor instead of dividing, as if activity had increased.

Decay-correct the concentration first (A = A0 × e^(−0.693t/T½)), then volume = dose desired ÷ current concentration.