Watanabe Ayumi, Inoue Yusuke, Asano Yuji, Kikuchi Kei, Miyatake Hiroki, Tokushige Takanobu
Department of Radiology, Kitasato University Hospital.
Department of Diagnostic Radiology, Kitasato University School of Medicine.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2017;73(4):291-297. doi: 10.6009/jjrt.2017_JSRT_73.4.291.
The specific binding ratio (SBR) was first reported by Tossici-Bolt et al. for quantitative indicators for dopamine transporter (DAT) imaging. It is defined as the ratio of the specific binding concentration of the striatum to the non-specific binding concentration of the whole brain other than the striatum. The non-specific binding concentration is calculated based on the region of interest (ROI), which is set 20 mm inside the outer contour, defined by a threshold technique. Tossici-Bolt et al. used a 50% threshold, but sometimes we couldn't define the ROI of non-specific binding concentration (reference region) and calculate SBR appropriately with a 50% threshold. Therefore, we sought a new method for determining the reference region when calculating SBR. We used data from 20 patients who had undergone DAT imaging in our hospital, to calculate the non-specific binding concentration by the following methods, the threshold to define a reference region was fixed at some specific values (the fixing method) and reference region was visually optimized by an examiner at every examination (the visual optimization method). First, we assessed the reference region of each method visually, and afterward, we quantitatively compared SBR calculated based on each method. In the visual assessment, the scores of the fixing method at 30% and visual optimization method were higher than the scores of the fixing method at other values, with or without scatter correction. In the quantitative assessment, the SBR obtained by visual optimization of the reference region, based on consensus of three radiological technologists, was used as a baseline (the standard method). The values of SBR showed good agreement between the standard method and both the fixing method at 30% and the visual optimization method, with or without scatter correction. Therefore, the fixing method at 30% and the visual optimization method were equally suitable for determining the reference region.
特异性结合率（SBR）最早由托西奇 - 博尔特等人报道，作为多巴胺转运体（DAT）成像的定量指标。它被定义为纹状体的特异性结合浓度与纹状体以外全脑的非特异性结合浓度之比。非特异性结合浓度是根据感兴趣区域（ROI）计算得出的，该区域通过阈值技术在外轮廓内20毫米处设置。托西奇 - 博尔特等人使用了50%的阈值，但有时我们无法定义非特异性结合浓度的ROI（参考区域），并且用50%的阈值无法适当地计算SBR。因此，我们寻求一种在计算SBR时确定参考区域的新方法。我们使用了在我院接受DAT成像的20名患者的数据，通过以下方法计算非特异性结合浓度：将定义参考区域的阈值固定在某些特定值（固定方法），并且在每次检查时由检查者对参考区域进行视觉优化（视觉优化方法）。首先，我们直观地评估了每种方法的参考区域，然后，我们定量比较了基于每种方法计算得出的SBR。在视觉评估中，无论有无散射校正，30%固定方法和视觉优化方法的得分均高于其他值固定方法的得分。在定量评估中，基于三名放射技师的共识通过对参考区域进行视觉优化获得的SBR值用作基线（标准方法）。无论有无散射校正，标准方法与30%固定方法和视觉优化方法得出的SBR值均显示出良好的一致性。因此，30%固定方法和视觉优化方法同样适用于确定参考区域。
