Development of scatter correction for quantitative SPECT imaging

该研究通过消除平面图像中的散射光子计数来重建定量的SPECT图像。提出了一种考虑平面图像局部散射分数的散射校正方法。该方法通过三个窗口获取每个像素点的计数数据：一个以光峰能量为中心的主窗口和主窗口两侧的两个子窗口。根据子窗口的数量和主窗口的宽度，估计主窗口内的散射光子为梯形区域。通过从主窗口获得的光子数中减去这些光子数，可以估计每个像素的主光子数。采用蒙特卡罗数值模拟方法对该方法进行了评价。模拟实验表明，用该方法重建的非散射光子活度分布与校正数据重建的活度分布吻合较好。然后，我们使用配备特殊硬件的市售伽马相机系统（东芝GCA-9300A）进行了幻影研究和初步临床研究。在临床研究中，我们使用了一种新的Tc-99m心肌灌注显像剂（P-53）。这些结果表明，在不增加数据采集/处理时间的情况下，在临床研究中定量测量活性是可能的。该方法也适用于常规闪烁图和多光峰放射性核素研究。

The study was carried out to reconstruct a quantitative SPECT image by eliminating the counts of scattered photons from a planar image. We have developed a new scatter correction method considering the local scatter fraction of the planar image. In this method, the count data are acquired at each pixel by using three windows: a main window centered at photopeak energy and two subwindows on both sides of the main window. The scattered photons included in the main window are estimated as a trapezoidal region shaped by the counts of the subwindows and the width of the main window. By subtracting the count of those photons from that acquired with the main window, the count of the primary photons can be estimated for each pixel. The method was evaluated by a Monte Carlo simulation using numerical phantoms. The simulation tests showed good agreement between the activity distributions reconstructed from unscattered photons and those reconstructed from corrected data by the proposed method. Then we made phantom studies and preliminary clinical studies using a commercially available gammacamera system (Toshiba GCA-9300A) equipped with special hardware. In the clinical studies we used a new Tc-99m myocardial perfusion imaging agent (P-53). These results showed that quantitative measurement of activity in clinical study is possible without adding data acquisition/processing time.The method is also applicable to conventional scintigrams and to multi-photopeak radionuclide studies.