Effects of system geometry and other physical factors on photon sensitivity of high-resolution positron emission tomography
Effects of system geometry and other physical factors on photon sensitivity of high-resolution positron emission tomography
复制标题
DOI：
10.1088/0031-9155/52/13/007
复制
发表时间：
2007-07-07
影响因子：
3.5
通讯作者：
Levin, C. S.
中科院分区：
文献类型：
--
作者：
Habte, F.;Foudray, A. M. K.;Levin, C. S.
我们正在研究两种新的探测器技术，它们可以直接测量511keV光子相互作用的三维坐标，用于为小动物和乳房成像设计的高分辨率正电子发射断层扫描(PET)系统。这些探测器是基于(1)与位置敏感雪崩光电二极管(PSAPD)耦合的氧硅酸(LSO)闪烁晶体阵列和(2)碲化镉锌(CZT)。探测器具有出色的测量511keV光子能量分辨率(CZT盒几何形状的15%，使用350-650keV能量窗设置)。这些模拟结果与分析估计值吻合较好。对于临床全身PET系统来说，趋势是不同的，它使用传统的LSO-PMT块探测器和更大的晶体元素。模拟预测盒式和圆柱式探测器配置的灵敏度大致相同。这是因为较大的系统直径(>；80厘米)导致临床全身PET的模块间间隙相对较小。此外，与小型动物系统相比，相对较大的块探测器(通常为>；5 x 5 cm(2)横截面积)和大晶体(>；4 x 4 x 20 mm(3))能够吸收更高比例的探测器散射光子。然而，如果盒状系统几何结构的四个探测器侧(面板)被配置为相对于彼此移动，以更好地使横轴FOV与待成像对象的实际大小相匹配，则光子灵敏度可能显著增加。模拟结果预测，对于所提出的小动物PET盒配置，光子灵敏度相对增加60%-100%，对于临床全身系统几何形状，光子灵敏度增加60%。因此，模拟结果表明，对于由矩形探测器模块构建的PET系统，将它们布置成盒子状系统几何结构可能有助于显著提高小动物和临床PET系统的光子灵敏度。
We are studying two new detector technologies that directly measure the three-dimensional coordinates of 511 keV photon interactions for high-resolution positron emission tomography ( PET) systems designed for small animal and breast imaging. These detectors are based on ( 1) lutetium oxyorthosilicate (LSO) scintillation crystal arrays coupled to position-sensitive avalanche photodiodes (PSAPD) and (2) cadmium zinc telluride (CZT). The detectors have excellent measured 511 keV photon energy resolutions ( 15% for CZT box geometry, using a 350-650 keV energy window setting. These simulation results compare well with analytical estimations. The trend is different for a clinical whole-body PET system that uses conventional LSO-PMT block detectors with larger crystal elements. Simulations predict roughly the same sensitivity for both box and cylindrical detector configurations. This results from the fact that a large system diameter (> 80 cm) results in relatively small inter-module gaps in clinical whole-body PET. In addition, the relatively large block detectors ( typically > 5 x 5 cm(2) cross-sectional area) and large crystals (> 4 x 4 x 20 mm(3)) enable a higher fraction of detector scatter photons to be absorbed compared to a small animal system. However, if the four detector sides (panels) of a box-shaped system geometry are configured to move with respect to each other, to better fit the transaxial FOV to the actual size of the object to be imaged, a significant increase in photon sensitivity is possible.Simulation results predict a 60-100% relative increase of photon sensitivity for the prposed small animal PET box configurations and >60% increase for a clinical whole-body system geometry. Thus, simulation results indicate that for a PET system built from rectangular-shaped detector modules, arranging them into a box-shaped system geometry may help us to significantly boost photon sensitivity for both small animal and clinical PET systems.