Converging / Diverging Collimators

Product description

Converging collimator geometry

In a converging collimator, all holes aim toward a common focal point located in front of the collimator face. Gamma photons from a small source region are accepted across a large detector area, producing a magnified image with improved spatial resolution and improved sensitivity compared to parallel hole collimation of the same resolution. The magnification factor depends on the source-to-collimator distance relative to the focal length. Objects closer to the collimator are magnified more than distant objects, and the field of view decreases with distance. This variable magnification can cause image distortion for thick or extended sources but provides excellent imaging of small, well-defined organs.

Diverging collimator geometry

Diverging collimators are geometrically opposite to converging designs. Holes aim toward a focal point behind the collimator, spreading the acceptance pattern outward. This produces image minification, making the projected image smaller than the source, but expands the field of view beyond the physical detector dimensions. Diverging collimators were historically used to image large body regions (such as lungs or abdomen) on small gamma camera detectors. With modern large-format rectangular detectors, this application has largely disappeared. However, diverging geometries remain relevant in specialized configurations and hybrid collimator designs.