Infographics / Nuclear Medicine

Collimator resolution vs sensitivity tradeoff

Two gamma-camera collimator geometries compared. Left: narrow, long holes give a small acceptance angle, so only near-vertical photons reach the crystal — a narrow blur (better spatial resolution) but few photons (lower sensitivity). Right: wide, short holes give a large acceptance angle, so many photons pass but over a wide blur — worse resolution but higher sensitivity. A lower panel shows the same collimator with the source moved further away, where the blur widens, so resolution degrades with distance. Relations: geometric resolution Rcoll is proportional to d(L+z)/L and sensitivity is proportional to d to the fourth over L squared, where d is hole diameter, L is hole length and z is source-to-collimator distance.