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SUBJECT: The aim of the study was to validate the 99mTc-Sestamibi Myokard-SPECT at quantitative analysis and to define the optimal threshold for detecting coronary artery disease in clinical routine diagnostic. The evaluation for the double-head-gamma camera system (E.CAM/Siemens) by the automatic quantitatively assessment program, which are used in the department of nuclear medicine at Philipp´s University in Marburg since 1996, was still missed for quality assurance. METHODS: The study population comprised 160 patients with suspected or known coronary artery disease who had undergone rest/stress 99mTc-Sestamibi Myokard-SPECT and coronary angiography within three month. Tomographic imaging was performed with a double-head rotating gamma camera system (E.CAM). The results of coronary angiographies, performed by internal physicians, myocardium perfusion scintigraphies and clinical inspection were registered at a database. Only patients with prior coronary revascularization were excluded. Patients who are unable to achieve a good exercise level are not excluded. The level of exercise was defined by the double-product. RESULTS: By analysis of receiver-operating-characteristic curves the best threshold was x = NM(i)–18 for a stenoses of the coronary arteries of 50%. Using this thresholds a moderate overall sensitivity and specifity of 69,4% and 72,5% for detecting CAD was found. In the detection of individual coronary artery stenoses there was no significant difference between the RIVA, RCX, RCA and overall sensitivity and specificity. Results for sensitivity and specifity in patients with an adequate exercise level were significantly better. CONCLUSIONS: In the course of the quality assurance, the new appointment of the automatic quantitatively assessment programm at the optimal threshold will be ensure the improvment of 99mTc-Sestamibi Myokard-SPECT. The present results from the clinical daily routine confirm that the sensitivity of myocardial SPECT is reduced in patients with an inadequate exercise test (double-product <25000). To improve the diagnostic efficacy of myocardial single-photon emissions computer tomography the patients should achieve a sufficient level of exercise. In patients who are unable to cope with the ergometric stress should the administration of intravenous dipyridamol perform an adequate exercise level.