Onishi Hideo, Motomura Nobutoku, Takahashi Masaaki, Yanagisawa Masamichi, Ogawa Koichi
Program in Health and Welfare, Graduate School of Comprehensive Scientific Research, Prefectural University of Hiroshima, Hiroshima, Japan.
J Nucl Med Technol. 2010 Mar;38(1):42-8. doi: 10.2967/jnmt.108.061192. Epub 2010 Feb 16.
Degradation of SPECT images results from various physical factors. The primary aim of this study was the development of a digital phantom for use in the characterization of factors that contribute to image degradation in clinical SPECT studies.
A 3-dimensional mathematic cylinder (3D-MAC) phantom was devised and developed. The phantom (200 mm in diameter and 200 mm long) comprised 3 imbedded stacks of five 30-mm-long cylinders (diameters, 4, 10, 20, 40, and 60 mm). In simulations, the 3 stacks and the background were assigned radioisotope concentrations and attenuation coefficients. SPECT projection datasets that included Compton scattering effects, photoelectric effects, and gamma-camera models were generated using the electron gamma-shower Monte Carlo simulation program. Collimator parameters, detector resolution, total photons acquired, number of projections acquired, and radius of rotation were varied in simulations. The projection data were formatted in Digital Imaging and Communications in Medicine (DICOM) and imported to and reconstructed using commercial reconstruction software on clinical SPECT workstations.
Using the 3D-MAC phantom, we validated that contrast depended on size of region of interest (ROI) and was overestimated when the ROI was small. The low-energy general-purpose collimator caused a greater partial-volume effect than did the low-energy high-resolution collimator, and contrast in the cold region was higher using the filtered backprojection algorithm than using the ordered-subset expectation maximization algorithm in the SPECT images. We used imported DICOM projection data and reconstructed these data using vendor software; in addition, we validated reconstructed images.
The devised and developed 3D-MAC SPECT phantom is useful for the characterization of various physical factors, contrasts, partial-volume effects, reconstruction algorithms, and such, that contribute to image degradation in clinical SPECT studies.
单光子发射计算机断层扫描（SPECT）图像的退化源于多种物理因素。本研究的主要目的是开发一种数字体模，用于表征临床SPECT研究中导致图像退化的因素。
设计并开发了一种三维数学圆柱体（3D-MAC）体模。该体模（直径200毫米，长200毫米）由3组嵌入的5个30毫米长的圆柱体（直径分别为4、10、20、40和60毫米）组成。在模拟中，为3组圆柱体和背景分配了放射性同位素浓度和衰减系数。使用电子伽马射线蒙特卡罗模拟程序生成了包含康普顿散射效应、光电效应和伽马相机模型的SPECT投影数据集。在模拟中改变了准直器参数、探测器分辨率、采集的总光子数、采集的投影数和旋转半径。投影数据按照医学数字成像和通信（DICOM）格式进行格式化，并导入临床SPECT工作站，使用商业重建软件进行重建。
使用3D-MAC体模，我们验证了对比度取决于感兴趣区域（ROI）的大小，当ROI较小时对比度被高估。低能通用准直器比低能高分辨率准直器产生更大的部分容积效应，并且在SPECT图像中，使用滤波反投影算法时冷区的对比度高于使用有序子集期望最大化算法时的对比度。我们使用导入的DICOM投影数据并使用供应商软件对这些数据进行重建；此外，我们验证了重建图像。
所设计和开发的3D-MAC SPECT体模可用于表征临床SPECT研究中导致图像退化的各种物理因素、对比度、部分容积效应、重建算法等。
