PET imaging relies on detecting pairs of 511 keV annihilation photons in coincidence. The system must correctly identify simultaneous photon pairs and assign them to accurate lines of response.

Several QC components ensure this process remains stable.

Daily QC commonly includes a system check that verifies detector function, timing alignment, and basic electronics stability. Modern PET systems often perform automated self-checks before scanning.

A blank scan or normalization scan evaluates uniform detector response across the ring. In PET, detector elements must have consistent sensitivity. Differences in crystal efficiency or photodetector gain can lead to ring artefacts if uncorrected. Normalization factors are applied to compensate for small detector-to-detector variations.

Calibration checks verify that measured activity concentrations correspond to true activity. This is crucial for quantitative imaging and SUV calculation. Cross-calibration between the PET scanner and the dose calibrator ensures consistency in activity measurement.

Timing calibration is particularly important in PET because coincidence detection depends on precise timing windows. Misalignment can reduce sensitivity and increase random coincidences.

Periodic testing also assesses spatial resolution, sensitivity, count rate performance, and image quality using standard phantoms.

Because PET images are reconstructed from coincidence events rather than single-photon detection, QC focuses heavily on detector uniformity, timing precision, and quantitative calibration.