Abstract : GUIDELINES ON QUALITY CONTROL FOR NUCLEAR MEDICINE INSTRUMENTATION Dr M Lyra, Dr R Klett, Dr W B T
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Abstract : GUIDELINES ON QUALITY CONTROL FOR NUCLEAR MEDICINE INSTRUMENTATION Dr M Lyra, Dr R Klett, Dr W B Tindale In diagnostic nuclear medicine, the quality assurance objective is the provision of high quality, reproducible data which provides the required clinical information with the smallest radiation burden to the patient. Quality assurance programmes must ensure the most effective use of available equipment and must ensure that processes are in place to minimise clinical risk. Our guidelines focus on the quality control (QC) procedures used in nuclear medicine with a special focus on new, sophisticated, digital technologies. Routinely, quality control procedures are required to ensure that nuclear medicine equipment is functioning correctly. These quality control tests are intended to detect problems of the systems before they impact on clinical patient studies. They are not intended to provide a full evaluation of equipment performance. Further tests may be required to trace the cause of the problem and to ensure that the equipment is performing properly after service or adjustment. The first part of our presentation describes the aims and rationale of the recommended quality control procedures. In particular, it attempts to provide background information on the reasons for performing particular procedures and the types of problems detected. It defines measurement parameters and their influence on the resulting images or measurements. An understanding of the potential impact of system performance aberrations is a prerequisite for implementing an effective quality control program. Secondly, reference will be made to general procedures for carrying out the recommended quality control tests. These can be used as a basis for developing detailed protocols for individual makes and models of equipment. Recommendations are provided on the frequency of the quality control tests. As the frequency of tests depends on the equipment, criteria are provided for selecting appropriate test frequencies. It is imperative that quality control procedures are carried out in a consistent manner (for example, same collimator, orientation, activity, energy window width etc) and the quality control settings and results are recorded to enable meaningful comparisons to be made over time. Proper record keeping greatly facilitates detection of gradual deterioration of performance over an extended period of time, by analyzing the results for degradation and initiating corrective action when necessary. A baseline set of quality control results should be recorded, after installation and acceptance testing, to serve as a reference for the life of the equipment. Several parameters associated with a scanner system are critical to good quality image formation and in many cases are interdependent. A summarized reference of the quality control tests that must be performed follows: 1. Calibration procedures for planar gamma camera a. Gamma ray spectra and pulse height analysis b. Energy Resolution c. System sensitivity d. Uniformity (intrinsic, extrinsic) e. Collimator performance f. Linearity-Spatial Resolution 2. SPECT gamma camera quality control a. Center of rotation b. High count field uniformity requirements c. Energy correction and spatial coordinates; d. Pixel calibration e. Reconstruction of phantom studies 3. Multi-detector gamma camera a. Detector alignment b. SPECT /511keV coincidence calibration 4. PET system quality control a. Daily blank scan, Normalization scan b. Photon detection/discrimination c. Resolution requirements d. Scatter reaction, Count loss, Randoms measurement e. Sensitivity, Deadtime loss f. Random count correction accuracy g. Well counter (absolute activity) calibration h. Glucometer QA by high & low standards 5. Hybrid PET/CT system a. System alignment calibration b. CT system QA (scanning parameters-mA, kVp, helical scanning). Practices are encouraged to call on the advice of experienced nuclear medicine physicists to draw up detailed QC protocols for their specific equipment based on the guidelines presented here. Advances in medicine occur at a rapid rate. The date of a guideline should always be considered in determining its current applicability. - Slides
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