Fundamental and clinical evaluation of attenuation correcting using TCT on SPECT

传统上使用具有外部辐射源的透射计算机断层扫描（TCT）进行衰减校正（AC）。CT最近被用于AC而不是TCT。我们通过体模和临床研究评估了TCT（TCT方法）和CT（CT方法）对衰减校正的有用性。在CT方法中，我们还评估了融合图像（AC图像与CT）的临床实用性。在TCT方法中，我们使用了配备非对称扇束准直器（GCA 7200，Toshiba）的2头伽马相机系统和配备扇束准直器（Prism 3000，Picker）的3头伽马相机。我们在同一个房间引入了无机架伽马相机（SkyLight，ADAC）和多探测器行CT（Lightspeed ultra，GE）作为CT/SPECT组合系统。在CT方法中，我们使用了该系统。在使用拟人体模的体模研究中，两种方法都显示出Tl-201在心肌中分布均匀性的改善。在Tl-201心肌断层显像中，未校正（NC）和AC图像在RCA区域的特异性与在LCX区域的特异性和准确性之间存在显著性差异。在LAD区域，AC图像和NC图像之间的敏感性和特异性存在变化，融合图像在84%（50/57）的癌症患者中获得了临床有用性。TCT融合图像可用于T1 -201心肌SPECT显像的衰减校正，对临床分期、复发、良恶性、病理性和生理性病变的鉴别诊断有一定的参考价值。用CT方法制作的融合图像对肿瘤的核研究是有用的。

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.