The most widely used instrument in nuclear medicine for the evaluation of the function or diagnosis of pathologies is a gamma camera. It is used for bio-distribution imaging by performing dynamic and static studies of biological tissues. The functional information from gamma camera is overlapped with the information of anatomy and internal structures obtained through X-ray and CT installed on the same equipment. Single Photon Emission Computed Tomography (SPECT) images obtained from gamma camera provide improved disease localization.The performance of cameras may vary due to characteristics of the detector crystal. Gamma camera detectors are commonly made of hygroscopic NaI crystal or Cadmium-Zinc-Telluride (CZT). Poor ambience or environment may have an influence on the performance characteristics of gamma camera. Diagnostic imaging quality and optimized radiation doses of radiopharmaceuticals to patients are ensured through a quality assurance program and monitoring of equipment performance. Routine quality control, calibration and performance testing of gamma cameras are necessary in order to consistently acquire good quality images without artifacts. The QA of gamma camera consists of a number of tests proposed by international organizations such as IAEA and AAPM. Acceptance testing of gamma camera provides baseline data for the performance evaluation and ensures that the instrument meets the end-user requirements for the manufacturer in relation to safety, damages, or deficiencies, compromising clinical studies. Planar and rotational uniformity test, spatial resolution test, and center of rotation test are important tests for dual head SPECT gamma cameras. A complete list of gamma camera acceptance tests is given in references. The uniformity of the gamma camera refers to its ability to produce a uniform image when detector is irradiated with uniform flux of radiations. Flood field uniformity may be quantified as the degree of uniformity exhibited by the detector itself (intrinsic uniformity) or by the detector with collimator mounted (extrinsic uniformity). It may be quantified in terms of the maximum variation in count density over the entire field of view (integral uniformity) or in terms of the maximum rate of change of count density over a specified distance (differential uniformity). The factors affecting intrinsic uniformity are gamma source activity, acquired counts for the flood image, image matrix size, and source volume. The use of software is becoming common for quality control of images from a gamma camera. In a study, NMQC software from IAEA was used to perform image analysis of ten non-uniform QC images from a gamma camera.

With Regards,
Sara Giselle
Associate Managing Editor
Journal of Medical Physics and Applied Scinces