正子電腦斷層造影(PET)可提供放射性藥物在活體中的濃度分佈與定量資訊,目前已被廣泛應用於功能性檢查與腫瘤偵測上。三維正子電腦斷層造影可以達到更高的系統靈敏度,目前逐漸取代傳統的二維正子電腦斷層造影,但是因為其缺乏septa,無可避免的會使散射符合事件隨著真實符合事件(coincident events)的增加而增加。相關的研究發現,散射符合事件的貢獻可能佔所有事件的50%以上,因此對於PET影像定量分析與藥物動力模型之研究,如何精確矯正散射影響益形重要。目前已有許多不同類型的散射矯正方法相繼被提出,並且成功應用於三維正子電腦斷層造影上。本文回顧介紹主要的散射矯正方法,包括:內插密合法、能窗基底法、旋積減贅法、模式基底法、重建基底法,以及我們近年研發的射束阻檔裝置法。
Positron emission tomography (PET) offers the possibility of quantitative assessment of tracer concentration in vivo. Fully 3D PET can achieve higher system sensitivity of coincidence events than the 2D mode, but the absence of inter-slice septa inevitably leads to increased scattered events. The scattered events can contribute as much as 50% of the total detected events. Therefore, accurate correction for the scatter component is necessary for meaningful quantitative image analysis and tracer kinetic modeling. A number of scatter correction methods have been proposed and successfully implemented for 3D PET. In this article, we comprehensively reviewed five scatter correction approaches, including curve fitting method, energy-based method, convolution subtraction method, model-based method, reconstruction-based method, and our newly developed beam stopper approach.