King M A, Hademenos G J, Glick S J
Department of Nuclear Medicine, University of Massachusetts Medical School, Worcester 01655.
J Nucl Med. 1992 Apr;33(4):605-12.
The imaging of scattered photons degrades contrast and is a major source of error in the quantitation of activity. It was hypothesized that, if the photopeak was divided into two nonoverlapping energy windows, a regression relation could be obtained between the ratio of counts within these windows and the scatter fraction for counts within the total region. This idea was tested by acquiring dual photopeak window acquisitions of a 99mTc point source in an elliptical attenuator, and at the same locations in air. From these, a regression between the scatter fraction and window ratio was determined. When this regression was applied to estimate the scatter distribution for acquisitions in both uniform and nonuniform elliptical attenuators, the residual scatter fraction was reduced approximately ten-fold and the estimated scatter line spread functions matched very closely the tails of the total line spread functions. In SPECT acquisitions, dual-photopeak window scatter correction was observed to significantly increase the contrast of "cold" spheres, improve the accuracy of estimating activity at the center of "hot" spheres, and return the three-dimensional modulation transfer function for point sources in an elliptical attenuator to near their in-air shape.
散射光子的成像会降低对比度，并且是活度定量分析中误差的主要来源。据推测，如果将光电峰划分为两个不重叠的能量窗，那么在这些窗内的计数比与整个区域内计数的散射分数之间可以获得一种回归关系。通过在椭圆形衰减器中以及在空气中相同位置采集99m锝点源的双光电峰窗采集数据来验证这一想法。据此确定了散射分数与窗比之间的回归关系。当将此回归用于估计在均匀和非均匀椭圆形衰减器中采集数据的散射分布时，残余散射分数降低了约10倍，并且估计的散射线扩展函数与总线扩展函数的尾部非常紧密地匹配。在单光子发射计算机断层显像（SPECT）采集中，观察到双光电峰窗散射校正可显著提高“冷”球形体的对比度，提高估计“热”球形体中心活度的准确性，并使椭圆形衰减器中点源的三维调制传递函数恢复到接近其在空气中的形状。
