A 5-Axis Calibration System for Calibrating DOI-Correcting Gamma-Ray Detectors

Abstract

Improving the resolution of pinhole single photon emission computed tomography (SPECT) depends on correcting parallax error at the edges of gamma-ray detectors. A novel way to achieve this is to use laser-induced optical barriers (LIOB) to restrict the spread of scintillation photons to a segment of the crystal that corresponds to a ray angle through the pinhole. The gains in resolution at the edge of the detector would be lost, however, without a way to use maximum likelihood (ML) position estimation to correlate detector response to the segment of the scintillation crystal where the gamma ray scintillated into visible photons. To find the response from a given segment of the crystal, a mean detector response function must be acquired from recording the mean detector responses when a known ray angle of gamma ray enters the detector. This motivates designing an building a novel calibration stage that has the ability to aim a pencil-beam of gamma rays into a detector at any position and angle that is possible with a photon traveling through the pinhole from the field of view.