Section of Radiation Detection and Medical Imaging, Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
Phys Med Biol. 2010 Mar 7;55(5):1265-77. doi: 10.1088/0031-9155/55/5/001. Epub 2010 Feb 4.
State-of-the-art small-animal single photon emission computed tomography (SPECT) enables sub-half-mm resolution imaging of radio-labelled molecules. Due to severe photon penetration through pinhole edges, current multi-pinhole SPECT is not suitable for high-resolution imaging of photons with high energies, such as the annihilation photons emitted by positron emitting tracers (511 keV). To deal with this edge penetration, we introduce here clustered multi-pinhole SPECT (CMP): each pinhole in a cluster has a narrow opening angle to reduce photon penetration. Using simulations, CMP is compared with (i) a collimator with traditional pinholes that is currently used for sub-half-mm imaging of SPECT isotopes (U-SPECT-II), and (ii), like (i) but with collimator thickness adapted to image high-energy photons (traditional multi-pinhole SPECT, TMP). At 511 keV, U-SPECT-II is able to resolve the 0.9 mm rods of an iteratively reconstructed Jaszczak-like capillary hot rod phantom, and while TMP only leads to small improvements, CMP can resolve rods as small as 0.7 mm. Using a digital tumour phantom, we show that CMP resolves many details not assessable with standard USPECT-II and TMP collimators. Furthermore, CMP makes it possible to visualize uptake of positron emitting tracers in sub-compartments of a digital mouse striatal brain phantom. This may open up unique possibilities for analysing processes such as those underlying the function of neurotransmitter systems. Additional potential of CMP may include (i) the imaging of other high-energy single-photon emitters (e.g. I-131) and (ii) localized imaging of positron emitting tracers simultaneously with single photon emitters, with an even better resolution than coincidence PET.
最先进的小动物单光子发射计算机断层扫描（SPECT）能够实现放射性标记分子的亚半毫米分辨率成像。由于光子在针孔边缘的严重穿透，当前的多针孔 SPECT 不适合对高能光子（如正电子发射示踪剂（511keV）发出的湮没光子）进行高分辨率成像。为了解决这个边缘穿透问题，我们在这里引入了聚类多针孔 SPECT（CMP）：每个针孔在一个簇中具有较窄的开口角度以减少光子穿透。通过模拟，CMP 与（i）目前用于 SPECT 同位素的亚半毫米成像的具有传统针孔的准直器（U-SPECT-II）进行比较，以及（ii）与（i）类似，但适应于成像高能光子的准直器厚度（传统多针孔 SPECT，TMP）进行比较。在 511keV 时，U-SPECT-II 能够分辨迭代重建的 Jaszczak 样毛细管热棒体模的 0.9mm 棒，而 TMP 仅导致较小的改善，而 CMP 则可以分辨小至 0.7mm 的棒。使用数字肿瘤体模，我们表明 CMP 可以分辨出标准 U-SPECT-II 和 TMP 准直器无法评估的许多细节。此外，CMP 使得可视化正电子发射示踪剂在数字鼠纹状体脑体模的亚区室中的摄取成为可能。这可能为分析神经递质系统等功能的过程开辟独特的可能性。CMP 的额外潜力可能包括（i）对其他高能单光子发射体（例如 I-131）的成像，以及（ii）同时对正电子发射示踪剂和单光子发射体进行局部成像，其分辨率比符合线 PET 更高。
