Koral K F, Rogers W L
Phys Med Biol. 1979 Sep;24(5):879-94. doi: 10.1088/0031-9155/24/5/001.
Devices for single-photon emission tomography currently take projections either in a plane over a full angular range (0--360 degrees) or in a volume with a limited angular range. The planar, pseudo-random, time-coded aperture, in conjunction with an Anger camera, is a device of the limited angular range type. It employs multiple pinholes whose transmission varies as a function of time. Previously, image reconstruction was accomplished by simple back-projection of coefficients obtained by time-correlating pinhole transmission with detector-element count rate, resulting in a low-contrast image. Using the Algebraic Reconstruction Technique (ART) a method is introduced for division of the correlation coefficients into subsets allowing the three-dimensional reconstruction to be accomplished on a minicomputer. Results from simulations and experimental phantom data show that ART improves depth resolution compared to back-projection, that under-relaxation produces better images in the case of noisy data, and that the division of the correlation coefficients into subsets has no effect on quality. The images depict the expected resolution degradation in the direction normal to the detector plane due to the limited angular range of projections but yield quantitative results whose relative values are good, even though attenuation is neglected.
单光子发射断层扫描设备目前要么在全角范围（0 - 360度）的平面上进行投影，要么在有限角范围的体积内进行投影。平面伪随机时间编码孔径与安格尔相机相结合，是一种有限角范围类型的设备。它采用多个针孔，其透射率随时间变化。以前，图像重建是通过将针孔透射率与探测器元件计数率进行时间相关得到的系数进行简单反投影来完成的，从而得到低对比度图像。使用代数重建技术（ART），引入了一种将相关系数划分为子集的方法，以便在小型计算机上完成三维重建。模拟和实验体模数据的结果表明，与反投影相比，ART提高了深度分辨率；在存在噪声数据的情况下，欠松弛产生更好的图像；并且将相关系数划分为子集对质量没有影响。图像描绘了由于投影角度范围有限而在垂直于探测器平面方向上预期的分辨率下降，但即使忽略衰减，也能产生相对值良好的定量结果。
