SiPM (silicon photomultiplier)
Solid-state semiconductor light-sensor technology that replaces conventional photomultiplier tubes (PMTs) in modern PET detectors. A SiPM is an array of small avalanche photodiodes operating in Geiger mode; the combined signal from thousands of these micro-cells detects single photons from a scintillation crystal with single-photon sensitivity and short timing resolution. SiPM PET detectors enable digital PET platforms — GE Discovery MI, Siemens Biograph Vision / Vision.X, Philips Vereos — and are the architectural feature that makes sub-300 ps Time-of-Flight practical.
Why it matters to buyers: SiPM-based PET is the current state of commercial PET hardware. SiPM detectors are magnetic-field-immune (unlike PMTs), which is the enabling architecture for simultaneous PET/MR — GE Signa PET/MR's SiPM ring is what lets PET operate inside a 3T MR bore.
Why it matters to engineers: SiPM modules have different failure modes than PMTs — solid-state drift rather than gain-drift / tube-aging. SiPM replacement is at the module level; service workflow differs from PMT-era gamma cameras and analog PET. Energy resolution and ToF timing are module-health metrics.