| 摘要 |
A PET scanner (10) includes a ring of detector modules (16) encircling an imaging region (18). Each of the detector modules includes one or more sensor avalanche photodiodes (APDs) (34) that are biased in a breakdown region in a Geiger mode. The sensor APDs (34) output pulses in response to light from a scintillator corresponding to incident photons. A reference APD (36) also biased in a breakdown region in a Geiger mode is optically shielded from light and outputs a voltage that is measured by an analog to digital converter (44). Based on the measurement, a bias control feedback loop (42) directs a variable voltage generator (48) to adjust a bias voltage applied to the APDs (34, 36) such that a difference (86) between a voltage of a breakdown pulse (68) and a preselected logic voltage level (70) is minimized. |
