MicroPET II: design, development and initial performance of an improved microPET scanner for small-animal imaging
MicroPET II: design, development and initial performance of an improved microPET scanner for small-animal imaging
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DOI：
10.1088/0031-9155/48/11/303
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发表时间：
2003-06-07
影响因子：
3.5
通讯作者：
Cherry, SR
中科院分区：
文献类型：
--
作者：
Tai, YC;Chatziioannou, AF;Cherry, SR
MicroPET II是第二代动物PET扫描仪，专为小型实验室啮齿动物的高分辨率成像而设计。该系统由90个闪烁探测器模块组成，这些模块排列在三个连续的轴向环中，环直径为16.0 cm，轴向长度为4.9 cm。每个探测器模块由一个14 × 14的硅酸镥（LSO）晶体阵列组成，通过一个相干光纤束耦合到一个多通道光电倍增管（MC-PMT）。每个LSO晶体元件的横截面为0.975 mm x 0.975 mm，长度为12.5 mm。在LSO元件之间使用硫酸钡反射器材料，导致在轴向和横向方向上的检测器间距为1.15 mm。熔融光纤束由90 μ m直径的玻璃纤维制成，数值孔径为0.56。在光纤之间加入间隙式壁外吸收体以减少光串扰。在印刷电路板上实现了一个电荷分割读出电路，以从MC-PMT的64个阳极信号的输出中解码每个阵列中的196个晶体。Concorde Microsystems Inc.（田纳西州诺克斯维尔）用于信号放大、数字化、事件鉴定、重合处理和数据捕获。巧合数据被传递到主机PC，以列表模式记录事件。采集后，将数据分类到正弦图中，并使用傅立叶重组和滤波反投影算法进行重建。对该系统的基本评价已经完成。对于250-750 keV的能量窗口和10 ns的时间窗口，microPET II扫描仪在视场中心（CFOV）的绝对灵敏度为2.26%。当用直径为0.5 mm的Na-22点源测量时，系统中探测器的固有空间分辨率平均为1.21 mm半高全宽（FWHM）。重建图像分辨率范围为CFOV处的0.83 mm FWHM至径向方向上的1.47 mm FWHM、切向方向上的1.17 mm FWHM和偏离CFOV 1 cm处的轴向方向上的1.42 mm FWHM。这些值代表了与我们早期的microPET扫描仪相比的非常显著的改进（在等效操作条件下，灵敏度提高了约四倍，线性空间分辨率提高了25-35%），并且当系统完全优化时，预计将进一步改进。
MicroPET II is a second-generation animal PET scanner designed for high-resolution imaging of small laboratory rodents. The system consists of 90 scintillation detector modules arranged in three contiguous axial rings with a ring diameter of 16.0 cm and an axial length of 4.9 cm. Each detector module consists of a 14 x 14 array of lutetium oxyorthosilicate (LSO) crystals coupled to a multi-channel photomultiplier tube (MC-PMT) through a coherent optical fibre bundle. Each LSO crystal element measures 0.975 mm x 0.975 mm in cross section by 12.5 mm in length. A barium sulphate reflector material was used between LSO elements leading to a detector pitch of 1.15 mm in both axial and transverse directions. Fused optical fibre bundles were made from 90 mum diameter glass fibres with a numerical aperture of 0.56. Interstitial extramural absorber was added between the fibres to reduce optical cross talk. A charge-division readout circuit was implemented on printed circuit boards to decode the 196 crystals in each array from the outputs of the 64 anode signals of the MC-PMT. Electronics from Concorde Microsystems Inc. (Knoxville, TN) were used for signal amplification, digitization, event qualification, coincidence processing and data capture. Coincidence data were passed to a host PC that recorded events in list mode. Following acquisition, data were sorted into sinograms and reconstructed using Fourier rebinning and filtered backprojection algorithms. Basic evaluation of the system has been completed. The absolute sensitivity of the microPET II scanner was 2.26% at the centre of the field of view (CFOV) for an energy window of 250-750 keV and a timing window of 10 ns. The intrinsic spatial resolution of the detectors in the system averaged 1.21 mm full width at half maximum (FWHM) when measured with a Na-22 point source 0.5 mm in diameter. Reconstructed image resolution ranged from 0.83 mm FWHM at the CFOV to 1.47 mm FWHM in the radial direction, 1.17 mm FWHM in the tangential direction and 1.42 mm FWHM in the axial direction at 1 cm offset from the CFOV. These values represent highly significant improvements over our earlier microPET scanner (approximately fourfold sensitivity increase and 25-35% improvement in linear spatial resolution under equivalent operating conditions) and are expected to be further improved when the system is fully optimized.