The Spatial Frequency Response of Orthogonal Strip Detectors

The spatial frequency aliasing properties of orthogonal strip electrode, position sensing germanium detectors have been investigated both analytically and experimentally. The study demonstrates that alising is a property of strip electrode detectors but not necessarily a property of strip electrode cameras. Aliasing in gamma cameras can be eliminated using the collimator and spatial channel electronics as anti-aliasing spatial frequency filters. The system resolution of a strip electrode gamma camera is determined by the collimator resolution and the intrinsic detector resolution. The collimator resolution is a function of the source depth while the intrinsic detector resolution is a function of the strip width spacing and the spatial channel readout electronics. The elimination of aliasing limits the overall spatial resolution of a camera to 1.7 to 2.3 times the strip width spacing depending on readout technique. It should be noted that this is not the intrinsic detector resolution but rather the camera resolution at the source depth for which the collimator is designed. The spatial resolution at depth for first generation clinical germanium cameras is anticipated to be from 1.7 mm to 4.6 mm.