QUALlTY CONTROL OF THE SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY IMAGING

Abstract

Gamma scintillation cameras are very complex devices with physical, mechanical and electronic components. Malfunction or leakage of any of these can be catastrophic in system performance and may not be recognized from the review of clinical images. Quality control tests performed on both systems gave an idea about their performance status and the variability of results on different occasions proved how valuable quality control tests are. SPECT demands much higher field of uniformity over the face of the detector than does conventional planar imaging. Field non-uniformities that would be invisible can render a SPECT study uninterpretible. Daily variation of uniformity tests are due to detector changes (specially the photo-multiplier tubes). Automatic tuning of a SPECT system prevents drifts in the photomultiplier gains. It proved to be efficient as long as there is no major factor. Although a software uniformity scanning program is ideal, the pinpoint densitometer gave an idea on the uniformity of the intrinsic flood image. The head of the densitometer was made .to travel across the film in three levels and gave good comparison between the two systems.