Clinthorne Neal, Cochran Eric, Chesi Enrico, Grkovski Milan, Grošičar Borut, Honscheid Klaus, Huh Sam S, Kagan Harris, Lacasta Carlos, Brzezinski Karol, Linhart Vladimir, Mikuž Marko, Smith D Shane, Stankova Vera, Studen Andrej, Weilhammer Peter, Žontar Dejan
Nuclear Medicine and Molecular Imaging, University of Michigan, Ann Arbor, MI 48109-5610 USA.
Department of Physics, Ohio State University, Columbus, OH USA.
Phys Procedia. 2012;37:1488-1496. doi: 10.1016/j.phpro.2012.03.747. Epub 2012 Oct 2.
To assist ongoing investigations of the limits of the tradeoff between spatial resolution and noise in PET imaging, several PET instruments based on silicon-pad detectors have been developed. The latest is a segment of a dual-ring device to demonstrate that excellent reconstructed image resolution can be achieved with a scanner that uses high-resolution detectors placed close to the object of interest or surrounding a small field-of-view in combination with detectors having modest resolution at larger radius. The outer ring of our demonstrator comprises conventional BGO block detectors scavenged from a clinical PET scanner and located at a 500mm radius around a 50mm diameter field-of-view. The inner detector-in contrast to the high-Z scintillator typically used in PET-is based on silicon-pad detectors located at 70mm nominal radius. Each silicon detector has 512 1.4mm x 1.4mm x 1mm detector elements in a 16 x 32 array and is read out using VATA GP7 ASICs (Gamma Medica-Ideas, Northridge, CA). Even though virtually all interactions of 511 keV annihilation photons in silicon are Compton-scatter, both high spatial resolution and reasonable sensitivity appears possible. The system has demonstrated resolution of ~0.7mm FWHM with Na-22 for coincidences having the highest intrinsic resolution (silicon-silicon) and 5-6mm FWHM for the lowest resolution BGO-BGO coincidences. Spatial resolution for images reconstructed from the mixed silicon-BGO coincidences is ~1.5mm FWHM demonstrating the "magnifying-glass" concept.
为了助力正在进行的关于正电子发射断层扫描（PET）成像中空间分辨率与噪声之间权衡极限的研究，已经开发了几种基于硅垫探测器的PET仪器。最新的是一种双环设备的一部分，用于证明使用靠近感兴趣对象放置的高分辨率探测器或围绕小视野的探测器，并结合在较大半径处具有适度分辨率的探测器的扫描仪，可以实现出色的重建图像分辨率。我们演示器的外环由从临床PET扫描仪中回收的传统BGO块状探测器组成，位于直径50mm视野周围半径500mm处。与PET中通常使用的高原子序数闪烁体不同，内部探测器基于位于标称半径70mm处的硅垫探测器。每个硅探测器在16×32阵列中有512个1.4mm×1.4mm×1mm的探测器元件，并使用VATA GP7专用集成电路（Gamma Medica-Ideas，加利福尼亚州北岭）进行读出。尽管在硅中511keV湮灭光子的几乎所有相互作用都是康普顿散射，但似乎有可能实现高空间分辨率和合理的灵敏度。该系统已证明，对于具有最高固有分辨率（硅-硅）的符合事件，使用Na-22时的分辨率约为0.7mm半高宽，对于最低分辨率的BGO-BGO符合事件，分辨率为5-6mm半高宽。从混合硅-BGO符合事件重建的图像的空间分辨率约为1.5mm半高宽，证明了“放大镜”概念。
