Quality control for SPECT systems

A comprehensive set of acceptance tests is the basis for an effective quality control program. Acceptance tests indicate whether the scintillation camera meets published specifications but should also include evaluation of certain parameters not specified by the vendor but that can seriously affect image quality. Once a camera is "accepted," initial quality control tests serve as a benchmark for future measurements. Tomographic systems must be subjected to the same basic quality control program as planar cameras. Flood field images must be acquired and evaluated daily; spatial resolution must be tested once each week. Less frequently, parameters such as multiple-window spatial registration, collimator uniformity, system sensitivity, and camera "dead time" should be evaluated. Single photon emission computed tomographic systems require additional tests to ensure optimum performance. Center-of-rotation calibration and verification of detector registration are needed to avoid losses of spatial resolution. Flood corrections based on high-count images eliminate residual detector nonuniformiaties and correct for subtle collimator defects. Pixel size must be calibrated to avoid errors in attenuation correction and distortion when cardiac and brain reorientation software is used. Completed clinical studies must be checked for unacceptable patient movement and incomplete views. A quality control program may be time-consuming, but, from the standpoint of maximum benefit to patients and confidence in clinical interpretations, there is no alternative.