Sjögreen Katarina, Ljungberg Michael, Strand Sven-Erik
Department of Radiation Physics, Jubileum Institute, University Hospital, Lund University, Sweden.
J Nucl Med. 2002 Jul;43(7):972-82.
This article presents a new method for conjugate view activity quantification for 131I-labeled monoclonal antibody distribution.
The method is based on the combined use of images from 3 modalities: whole-body (WB) scintillation camera scanning, WB transmission scanning using 57Co, and CT. All images are coaligned using a recently developed program for the registration of WB images. Corrections for attenuation, scatter, and septal penetration are performed in image space. Compensation for scatter and septal penetration is performed by deconvolution, using point-response functions determined from Monte Carlo simulations. Attenuation correction is performed by applying a patient-specific 364-keV narrow-beam attenuation map obtained by combining information from the CT and the transmission scan. A relationship is presented for the conversion of the CT numbers to mass density. The attenuation- and scatter-compensated image is converted from counts to activity using a sensitivity value that was determined for 364-keV photons in air. This activity projection image is then analyzed for the activity of volumes of interest (VOI) using 2-dimensional regions of interest (ROIs) that are determined from the CT study. The CT is first resliced into coronal slices, and a maximum-extension ROI is outlined that encloses the VOI. Compensation for background activity and overlapping organs is performed on the basis of total patient thickness in the projection line, and on precalculated organ- background thickness fractions.
Method evaluation was performed using data from both experimental measurements and Monte Carlo simulations. The use of an attenuation map derived directly from the CT study was also evaluated. For organ activity quantification, an accuracy of > or =10% was obtained. For small-diameter tumors, deviations were larger because of lack of correction for the background-dependent partial-volume effect.
Registration of CT and WB scintillation camera images was successfully applied to improve activity quantification by the conjugate view method.
本文介绍了一种用于量化¹³¹I标记单克隆抗体分布的共轭视图活性的新方法。
该方法基于三种模态图像的联合使用：全身（WB）闪烁相机扫描、使用⁵⁷Co的WB透射扫描和CT。所有图像使用最近开发的用于WB图像配准的程序进行配准。在图像空间中进行衰减、散射和隔片穿透校正。散射和隔片穿透补偿通过去卷积进行，使用从蒙特卡罗模拟确定的点响应函数。衰减校正通过应用通过组合CT和透射扫描信息获得的患者特异性364 keV窄束衰减图来执行。给出了CT值与质量密度转换的关系。使用在空气中为364 keV光子确定的灵敏度值将衰减和散射补偿图像从计数转换为活性。然后使用从CT研究确定的二维感兴趣区域（ROI）分析该活性投影图像中感兴趣体积（VOI）的活性。首先将CT重新切片为冠状切片，并勾勒出包围VOI的最大扩展ROI。基于投影线中的患者总厚度以及预先计算的器官-背景厚度分数对背景活性和重叠器官进行补偿。
使用来自实验测量和蒙特卡罗模拟的数据进行方法评估。还评估了直接从CT研究得出的衰减图的使用。对于器官活性量化，获得了≥10%的准确度。对于小直径肿瘤，由于缺乏对背景依赖性部分容积效应的校正，偏差较大。
成功应用CT和WB闪烁相机图像的配准以通过共轭视图方法改善活性量化。
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