Webb S, Binnie D M, Flower M A, Ott R J
Joint Department of Physics, Institute of Cancer Research, Sutton, Surrey, UK.
Phys Med Biol. 1992 May;37(5):1095-108. doi: 10.1088/0031-9155/37/5/006.
Planar imaging with a gamma camera is currently limited by the performance of the collimator. Spatial resolution and sensitivity trade off against each other; it is not possible with conventional parallel-hole collimation to have high geometric sensitivity and at the same time excellent spatial resolution unless field-of-view is sacrificed by using fan- or cone-beam collimators. We propose a rotating slit-collimator which collects one-dimensional projections from which the planar image may be reconstructed by the theory of computed tomography. The performance of such a collimator is modelled by Monte Carlo methods and images are reconstructed by a convolution and backprojection technique. The performance is compared with that of a conventional parallel-hole collimator and it is shown that higher spatial resolution with increased sensitivity is possible with the slit-collimator. For a point source a spatial resolution of some 6 mm at a distance of 100 mm from the collimator with a x7 sensitivity compared with a parallel-hole collimator was achieved. Applications to bone scintigraphy are modelled and an improved performance in hot-spot imaging is demonstrated. The expected performance in cold-spot imaging is analytically investigated. The slit-collimator is not expected to improve cold-spot imaging. Practical design considerations are discussed.
γ相机的平面成像目前受限于准直器的性能。空间分辨率和灵敏度相互制约；采用传统的平行孔准直时，除非使用扇形或锥形准直器牺牲视野，否则不可能同时具备高几何灵敏度和出色的空间分辨率。我们提出一种旋转狭缝准直器，它收集一维投影，可依据计算机断层扫描理论重建平面图像。这种准直器的性能通过蒙特卡罗方法建模，图像采用卷积和反投影技术重建。将其性能与传统平行孔准直器的性能进行比较，结果表明狭缝准直器能够实现更高的空间分辨率并提高灵敏度。对于点源，在距准直器100毫米处实现了约6毫米的空间分辨率，与平行孔准直器相比灵敏度提高了7倍。对骨闪烁显像的应用进行了建模，并展示了在热点成像方面的改进性能。对冷点成像的预期性能进行了分析研究。狭缝准直器预计不会改善冷点成像。文中还讨论了实际设计考量。
