Nuclear Cardiology, Yale-New Haven Hospital, New Haven, Connecticut.
Department of Internal Medicine (Cardiology), Yale University, New Haven, Connecticut.
J Nucl Med. 2018 Apr;59(4):652-658. doi: 10.2967/jnumed.117.197152. Epub 2017 Sep 15.
Assessment of cardiac I-meta iodobenzylguanidine (I-mIBG) uptake relies on the heart-to-mediastinum ratio (HMR) derived from planar images. We have developed novel semiautomated quantitative methodologies for assessing HMR from SPECT images using a dedicated cardiac multipinhole SPECT/CT system and determined the lower limit of normal (LLN) SPECT-derived HMR and the correlation to planar-derived HMR. Twenty-one healthy volunteers were injected with I-mIBG and imaged using 2 different cameras. Planar images were acquired using a conventional SPECT camera equipped with parallel hole collimators, and hybrid SPECT/CT images were acquired using a dedicated cardiac SPECT system with 19 pinhole collimators interfaced with 64-slice CT. Planar HMR was calculated as per standard guidelines (manual traditional method) and elliptic region-of-interest (Elip-ROI) and region-growing (RG-ROI) techniques. SPECT HMR was quantified using a new method that incorporates various cardiac and mediastinal segmentation schemes in which upper and lower limits of the heart were determined from CT and the left ventricular ROI, and mean counts were calculated using Elip-ROI and RG-ROI techniques. Mean counts in mediastinal ROI were computed from a fixed volume in 3 different regions: upper mediastinum (UM), lower mediastinum (LM), and contralateral lung (CL). HMRs were processed by 2 observers, and reproducibility was assessed by intraclass correlation coefficient and Bland-Altman analysis. Planar HMR calculated using the RG-ROI method showed highest intra- and interobserver levels of agreement compared with Elip-ROI and manual traditional methods. SPECT HMR calculated on the basis of UM, LM, and CL background regions showed excellent intra- and interobserver agreement. SPECT HMR with UM resulted in highest correlation ( = 0.91) with planar HMR compared with that with LM ( = 0.74) and CL ( = 0.73). The LLN of SPECT HMR with UM and that of planar HMR was calculated as 5.5 and 1.6, respectively. The normal values of SPECT-derived HMR and planar-derived HMR were correlated linearly. We reconfirmed the previous planar HMR threshold and determined SPECT LLN HMR for SPECT. Planar HMR can be estimated from SPECT HMR via a simple linear regression equation, allowing use of the new cardiac-dedicated SPECT camera for I-mIBG imaging.
心脏 I-间碘苄胍（I-mIBG）摄取的评估依赖于平面图像得出的心脏与纵隔比值（HMR）。我们使用专用的心脏多针孔 SPECT/CT 系统开发了新的半自动化定量方法，用于从 SPECT 图像评估 HMR，并确定 SPECT 衍生的 HMR 的下限正常（LLN）和与平面衍生的 HMR 的相关性。 21 名健康志愿者注射 I-mIBG 后，使用 2 种不同的相机进行成像。平面图像使用配备平行孔准直器的传统 SPECT 相机采集，混合 SPECT/CT 图像使用专用的心脏 SPECT 系统采集，该系统配备 19 个针孔准直器并与 64 层 CT 接口。按照标准指南（手动传统方法）计算平面 HMR，并使用椭圆感兴趣区（Elip-ROI）和区域生长（RG-ROI）技术。使用一种新方法定量 SPECT HMR，该方法结合了各种心脏和纵隔分割方案，其中从 CT 和左心室 ROI 确定心脏的上下限，并使用 Elip-ROI 和 RG-ROI 技术计算平均计数。从中计算纵隔 ROI 中的平均计数 3 个不同区域的固定体积：上纵隔（UM）、下纵隔（LM）和对侧肺（CL）。由 2 位观察者处理 HMR，并通过组内相关系数和 Bland-Altman 分析评估可重复性。与 Elip-ROI 和手动传统方法相比，使用 RG-ROI 方法计算的平面 HMR 显示出最高的观察者内和观察者间一致性水平。基于 UM、LM 和 CL 背景区域计算的 SPECT HMR 显示出极好的观察者内和观察者间一致性。与 LM（=0.74）和 CL（=0.73）相比，UM 计算的 SPECT HMR 与平面 HMR 的相关性最高（=0.91）。UM 计算的 SPECT HMR 的 LLN 和平面 HMR 的分别计算为 5.5 和 1.6。SPECT 衍生的 HMR 和平面衍生的 HMR 的正常值呈线性相关。 我们重新确认了以前的平面 HMR 阈值，并确定了 SPECT 的 SPECT LLN HMR。可以通过简单的线性回归方程从 SPECT HMR 估计平面 HMR，从而允许使用新的专用心脏 SPECT 相机进行 I-mIBG 成像。
