Adams R, Hine G J, Zimmerman C D
J Nucl Med. 1978 May;19(5):538-44.
Deadtime performance of scintillation cameras is sensitive to such factors as scatter fraction and analyzer window width. Data from manufacturers and previous investigators do not predict counting-rate losses under clinical conditions. Scintillation cameras used with Tc-99m for quantitative nuclear cardiology should be evaluated for deadtime performance by the two-source method using a scatter phantom designed to simulate the spectrum from Tc-99m in the heart. Under these conditions, scintillation cameras were found to follow the paralyzable model; accurate estimates could be obtained for data losses and maximum useful counting rates in a clinical setting. A survey of 39 contemporary scintillation cameras yielded a range of paralyzing deadtime values of 4.3 to 10 musec, with a 20% window centered on the Tc-99m photopeak. For an average deadtime of 6 musec, counting rates should be maintained below 36,000 cps to avoid undue data losses in excess of 25%.
闪烁相机的死时间性能对散射分数和分析器窗口宽度等因素敏感。制造商和先前研究人员的数据无法预测临床条件下的计数率损失。用于定量核心脏病学的与Tc-99m一起使用的闪烁相机，应使用设计用于模拟心脏中Tc-99m光谱的散射体模，通过双源法评估其死时间性能。在这些条件下，发现闪烁相机遵循可麻痹模型；可以在临床环境中获得数据损失和最大有用计数率的准确估计值。对39台当代闪烁相机的调查得出，以Tc-99m光电峰为中心的20%窗口的麻痹死时间值范围为4.3至10微秒。对于平均死时间为6微秒的情况，计数率应保持在36,000 cps以下，以避免超过25%的过度数据损失。
