Which device has a spatial resolution of 0.1 lp/mm?

• A. MRI and CT
• B. Gamma camera
• C. Ultrasonography
• D. Fluoroscopy

Answer: (B)

Spatial resolution is about how finely two nearby points can be distinguished in an image, quantified as line pairs per millimeter (lp/mm). Higher lp/mm means sharper detail; lower lp/mm means blurrier images.

A gamma camera images gamma rays from a radiotracer but relies on a collimator to determine where photons originate. The collimator design (hole size, length, spacing) introduces significant blur, so the spatial resolution ends up around a relatively low value—about 0.1 lp/mm in typical practice. That relatively coarse resolution reflects the trade-off for detecting faint gamma emissions across the body.

Other modalities used for anatomical imaging usually achieve much finer detail: MRI and CT provide sub-millimeter to millimeter-scale resolution; ultrasound can resolve small structures with high detail depending on frequency; fluoroscopy offers good real-time imaging with better resolution than a gamma camera in many cases. Therefore, the device with a spatial resolution around 0.1 lp/mm is the gamma camera.