Ultra-high resolution SPECT with a semiconductor detector and a diverging collimator

在室温下工作的CdTe等半导体探测器的发展促进了新的SPECT系统的发展。这些半导体探测器具有高能量分辨率。此外，它们被用作像素化检测器，因此固有分辨率可以等于用于测量的像素的大小。探测器像素小至0.5mm，因此重建的SPECT图像的空间分辨率可以小于3mm FWHM。为了阐明超高分辨率SPECT系统的可行性，我们进行了一些模拟和评价图像的质量。在这些模拟中，我们使用了一个发散准直器，以扩大视野的检测器和比较的像素化的SPECT系统与传统的SPECT系统与闪烁探测器和平行孔准直器在相同的灵敏度和降低的灵敏度下的重建图像的质量。结果表明，像素化半导体探测器的空间分辨率的提高，即使在低灵敏度的条件下，由于像素的小尺寸产生高质量的图像。基于上述结果，我们建立了一个原型半导体SPECT系统与发散准直器。在这个系统中，我们用几百个薄钨片制作了发散准直器。利用该超高分辨率系统，我们建立了热棒体模和冷棒体模的重建系统，热棒体模的空间分辨率为1.0mm，冷棒体模的空间分辨率为1.6mm。仿真和实验结果表明，采用半导体探测器和平行孔准直器或小孔发散准直器的超高分辨率SPECT系统是可行的。

The development of semiconductor detectors such as CdTe, which works at room temperature, has facilitated the development of a new SPECT system. These semiconductor detectors have a high energy resolution. Moreover, they are used as pixellated detectors, and so the intrinsic resolution can be equal to the size of the pixel used for measurement. The detector pixel is as small as 0.5mm, and so the spatial resolution of a reconstructed SPECT image can be less than 3mm FWHM. To clarify the feasibility of an ultra-high resolution SPECT system, we conducted some simulations and evaluated the quality of images. In these simulations we used a diverging collimator to enlarge the field of view of the detector and compared the quality of the reconstructed images of a pixellated SPECT system with a conventional SPECT system with a scintillation detector and parallel-hole collimator under the same sensitivity and reduced sensitivity. The results showed that the improvement of the spatial resolution in the pixellated semiconductor detector yielded high quality images even under the low sensitivity condition due to the small size of the pixels. With the above results we built a prototype semiconductor SPECT system with a diverging collimator. In this system we made the diverging collimator by using several hundreds of thin tungsten plates. With this proposed ultra-high resolution system we established the reconstruction of rod phantoms(hot rod phantom and cold rod phantom) with the spatial resolution of 1.0mm for the hot rods and 1.6mm for the cold rods. The obtained results with the simulation and experiment showed that the ultra-high resolution SPECT system was available with the semiconductor detector and a parallel-hole collimator or a diverging collimator with holes of a small size.