Fundamental and clinical evaluation of attenuation correcting using TCT on SPECT

传统上采用外辐射源透射计算机断层扫描（TCT）进行衰减校正。最近使用CT代替TCT进行交流。我们通过幻影和临床研究评估了TCT （TCT方法）和CT （CT方法）在衰减校正中的有效性。在CT方法中，我们还评估了融合图像（AC图像与CT）的临床应用价值。在TCT方法中，我们使用了配备非对称扇形光束准直器的2头伽马相机系统（东芝GCA 7200）和配备扇形光束准直器的3头伽马相机（Prism 3000, Picker）。我们在同一房间引入了一台无龙门伽马相机（天窗，ADAC）和多探测器行CT（光速超，GE）作为CT/SPECT组合系统。在CT方法中，我们使用该系统。在拟人模型的幻体研究中，两种方法均改善了心肌中Tl-201分布的均匀性。通过散点校正提高缺损心肌与正常心肌的对比。在Tl-201心肌SPECT中，RCA区域的非校正（NC）和AC图像与LCX区域的特异性和准确性存在显著差异。在LAD区域，AC图像和NC图像在敏感性和特异性上有不同的变化。84%（50/57）的癌症患者获得了融合图像的临床有用性。融合图像在诊断分期和复发，区分恶性和良性，以及区分病理性和生理性积累方面获得了有用的信息。TCT方法可用于Tl-201心肌SPECT的衰减校正。CT融合成像对肿瘤患者的核研究具有重要意义。

Transmission computed tomography (TCT) with external radiation source was conventionally used for attenuation correction (AC). CT is recently used for AC instead of TCT. We evaluated the usefulness of TCT (TCT method) and CT (CT method) for the attenuation correction by a phantom and clinical study. In CT method, we also assessed the clinical usefulness of fused image (AC image with CT).In TCT method, we used a 2-head gamma camera system equipped with asymmetric fan-beam collimator (GCA 7200, Toshiba) and the 3-head gamma camera equipped with fan-beam collimator (Prism 3000, Picker). We introduced a gantry-free gamma camera (SkyLight, ADAC) and multi-detector row CT (Lightspeed ultra, GE) in a same room as a CT/SPECT combined system. In CT method, we used this system.In phantom study using a anthropomorphic phantom, both methods showed improvement in the uniformity of the distribution of Tl-201 in the myocardium. The contrast between the defect and normal myocardium was improved by the scatter correction.In Tl-201 myocardial SPECT, there was the significant difference in specificity between non-corrected (NC) and AC images in the RCA territory and those in specificity and accuracy in the LCX territory. In the LAD territory, there were variable changes in sensitivity and specificity observed on between the AC images and the NC images.Clinical usefulness of fused images was obtained in 84% (50/57) of cancer patients. Useful information on fused images was obtained in the diagnosis of staging and recurrence, differentiation of malignant from benign, and differentiation of pathological from physiological accumulation.TCT method is useful for the attenuation correction on Tl-201 myocardial SPECT. Fused image made by CT method is useful for the nuclear studies of patients with cancer.