| 摘要 |
When detecting photons in a computed tomography (CT) detector, a sensor (10, 38) includes a photodiode that is switchable between liner and Geiger operation modes to increase sensing range. When signal to noise ratio (SNR) is high, a large bias voltage is applied to the photodiode (12) to charge it beyond its breakdown voltage, which makes it sensitive to single photons and causes it to operate in Geiger mode. When a photon is received at the photodiode (12), a readout transistor (18) senses the voltage drop across the photodiode (12) to detect the photon. Alternatively, when SNR is low, a low bias voltage is applied to the photodiode (12) to cause it to operate in linear mode.
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