Tc-99m attenuation coefficients in water-filled phantoms determined with gamma cameras.
Tc-99m attenuation coefficients in water-filled phantoms determined with gamma cameras.
复制标题
使用伽马相机确定的充满水的模型中的 Tc-99m 衰减系数。
DOI：
10.1118/1.595623
复制
发表时间：
1984
期刊：
影响因子：
3.8
通讯作者：
Coleman,RE
中科院分区：
文献类型：
--
作者：
Harris,CC;Greer,KL;Jaszczak,RJ;FloydJr,CE;Fearnow,EC;Coleman,RE
使用伽马相机的定量成像需要对源光子的衰减进行补偿。一些补偿方法利用恒定或平均估计衰减系数μ。对于水或组织中的140.5-keV光子，通常使用0.15 cm− 1的μ值。然而，该值忽略了在伽马相机成像中的能量窗口内检测到的散射光子。在均匀圆柱源的Tc-99 m单光子发射计算机断层扫描的衰减补偿中，使用μ = 0.12 cm− 1的值与使用μ=0.15 cm−1相比，结果有所改善。在这项研究中，使用伽马相机和多通道脉冲高度分析仪来确定光子在水中的有效μ值作为能量窗口的函数。使用两个圆柱形充水体模（圆形和椭圆形），点源Tc-99垫深度达18 cm。能量数据集成在Tweak的上半部分，超过10%，20%和30%的窗口集中在Tweak上。衰减曲线对于所有的峰值窗口都是指数型的，μ值对于20%以下的所有窗口为0.12±0.014 cm− 1，对于30%的窗口为0.1 cm− 1。这项研究表明，μ值为0.11-0.12 cm− 1，实际上适合用于需要平均值的衰减补偿。
Quantitative imaging with gamma cameras requires compensation for attenuation of source photons. Some methods of compensation make use of a constant or average estimated attenuation coefficient μ. A value for μ of 0.15 cm−1for 140.5‐keV photons in water or tissue is commonly used. This value, however, neglects scattered photons which are detected within the energy window in gamma camera imaging. Values for μ of 0.12 cm−1used in attenuation compensation of Tc‐99msingle‐photon emission computed tomography scans of uniform cylindrical sources have been shown to give improved results compared with use of μ=0.15 cm−1. In this study, gamma cameras and a multichannel pulse‐height analyzer were used to determine effective values of μ for photons in water as a function of energy window. Two cylindrical water‐filled phantoms, circular and elliptical, were used with a point source of Tc‐99mat depths up to 18 cm. Energy data were integrated over the top half of the photopeak, and over 10%, 20%, and 30% windows centered on the photopeak. Attenuation curves were exponential for all photopeak windows with values of μ of 0.12±0.014 cm−1for all windows up to 20% and 0.1 cm−1for a 30% window. This study suggests that a value of μ of 0.11–0.12 cm−1is, in fact, appropriate for use in attenuation compensations where an average is required.