Inoue Y, Ohtake T, Oritate T, Nishikawa J, Yoshikawa K, Sasaki Y
Department of Radiology, Institute of Medical Science, University of Tokyo, Japan.
Radiat Med. 1998 Mar-Apr;16(2):149-52.
Quantitative studies with a single-crystal gamma camera often require correction for deadtime count loss. We evaluated the deadtime characteristics of a gamma camera using point sources. Point sources with various radioactivities were measured, and the relation between radioactivity and count rate was assessed. Two sources with different activities were imaged apart or adjacent to each other, and the effect of the geometrical distribution on counting efficiency was investigated. Count loss was increased at a high radioactivity level, and was well corrected using a nonparalyzable model and a deadtime of 4.99 microsec. It was not affected by the distance between the two sources, and occurred equally for the two sources imaged together. The count loss in imaging two sources was successfully corrected by multiplying the obtained image by a correction factor based on the count rate in the whole field-of-view. These results support the reliability of the analytic technique for deadtime correction.
使用单晶γ相机进行的定量研究通常需要对死时间计数损失进行校正。我们使用点源评估了γ相机的死时间特性。测量了具有不同放射性的点源，并评估了放射性与计数率之间的关系。对两个具有不同活度的源进行成像，它们彼此分开或相邻，研究了几何分布对计数效率的影响。在高放射性水平下计数损失增加，使用非平行模型和4.99微秒的死时间可以很好地校正。它不受两个源之间距离的影响，并且对于一起成像的两个源来说计数损失是相同的。通过将获得的图像乘以基于整个视野中计数率的校正因子，成功校正了对两个源成像时的计数损失。这些结果支持了死时间校正分析技术的可靠性。
