A gamma camera detects gamma photons using a scintillation crystal, photomultiplier tubes, and position estimation electronics. The accuracy of image formation depends on precise functioning of each component.

One of the most important tests is uniformity testing, usually performed daily. A uniform flood source is imaged to ensure the detector responds evenly across its surface. Non-uniformities may indicate crystal defects, photomultiplier drift, or electronic instability.

Energy window calibration (peaking) ensures that the energy window is centred on the photopeak of the radionuclide being used. If misaligned, excess scatter photons may be included or true photopeak photons excluded, degrading contrast and quantitative accuracy.

Spatial resolution testing evaluates the system’s ability to distinguish small structures. Bar phantoms or line sources are used to confirm expected resolving capability.

Sensitivity testing assesses the count rate per unit activity. Reduced sensitivity may indicate collimator damage or detector inefficiency.

For SPECT systems, centre of rotation (COR) testing is critical. Mechanical or electronic misalignment during rotation can cause reconstruction artefacts, including blurring or ring artefacts.

These QC tests ensure that the measured distribution of counts accurately represents the true distribution of radiotracer within the patient.