Lodge M A, Binnie D M, Flower M A, Webb S
Joint Department of Physics, Institute of Cancer Research, Surrey, UK.
Phys Med Biol. 1995 Mar;40(3):427-48. doi: 10.1088/0031-9155/40/3/007.
A collimator consisting of a series of parallel slats has been constructed and used in conjunction with a conventional gamma camera to collect one-dimensional projections of the radioisotope distribution being imaged. With the camera remaining stationary, the collimator was made to rotate continuously over the face of the detector and the projections acquired were used to reconstruct a planar image by the theory of computed tomography. The propagation of noise on image reconstruction was largely offset by the increased geometric efficiency that resulted from the enlarged solid angle of acceptance afforded by the slat collimator. For a uniform disc of activity the signal to noise ratio (SNR) at a point in an image reconstructed by convolution and backprojection is shown to be given by [formula:see text] and Q1(xi) is the one-dimensional filter function in Fourier space. Improved noise behaviour was observed for images acquired with the slat collimator compared to those acquired with a low-energy high-resolution (LEHR) collimator for small distributions of activity. Spatial resolution with the slat collimator was approximately equal to that obtained with an LEHR collimator and improved contrast was observed in images of small hot regions.
已构建了一种由一系列平行板条组成的准直器，并将其与传统伽马相机配合使用，以收集正在成像的放射性同位素分布的一维投影。相机保持静止，准直器在探测器表面连续旋转，采集到的投影用于通过计算机断层扫描理论重建平面图像。图像重建过程中噪声的传播在很大程度上被板条准直器提供的更大接收立体角所带来的几何效率提高所抵消。对于均匀的放射性圆盘，通过卷积和反投影重建的图像中某一点的信噪比（SNR）由[公式：见原文]给出，并且Q1(xi)是傅里叶空间中的一维滤波函数。与使用低能高分辨率（LEHR）准直器采集的图像相比，使用板条准直器采集的图像在小放射性分布情况下观察到了更好的噪声特性。板条准直器的空间分辨率与使用LEHR准直器获得的分辨率大致相当，并且在小热点区域的图像中观察到了对比度的提高。
