Owenius Rikard, Zanette Michelle, Cella Patrick
Department of Surgical Sciences, Radiology, Uppsala University, Uppsala, Sweden; and.
GE Healthcare, Life Sciences, Imaging R&D, Marlborough, Massachusetts.
J Nucl Med Technol. 2017 Dec;45(4):297-303. doi: 10.2967/jnmt.117.196055. Epub 2017 Oct 17.
A heart-to-mediastinum (H/M) ratio of 1.6 or greater on planar I-iobenguane (I-MIBG) images identifies heart failure patients at low risk of experiencing an adverse cardiac event. This phase-4 study used standardized phantoms to assess the intercamera, intracamera, and interhead variability in H/M ratio determinations from planar cardiac I-MIBG imaging using commercially available, dual-head γ-cameras. A fillable thorax phantom was developed to simulate the typical uptake of I-MIBG. The phantom had a nominal H/M ratio of 1.6 on the reference camera. Commercial cameras used in the study were dual-head and capable of 90° configuration for cardiac imaging. The target sample size was 8 units (examples) per camera model. Two imaging technologists independently analyzed planar images of simulated I-MIBG uptake from the thorax phantom. H/M was the ratio of the average counts per pixel of the heart and mediastinum regions of interest. The primary endpoint, intercamera variability in H/M ratio from head 1, was determined for each camera model via comparison with the H/M ratio on the reference camera. Only cameras with at least 8 units tested ( ≥ 8) were included in the primary analysis. Intracamera and interhead variability in the H/M ratio were also evaluated. Nine camera models were studied. The mean H/M ratio ranged from 1.342 to 1.677. The primary analysis (6 camera models) using a mixed-model, repeated-measures analysis showed no significant difference in H/M ratio between any camera model and the reference camera. Intracamera variability (head 1) in the H/M ratio among camera models with 8 units or more was high, with SDs ranging from 0.0455 to 0.1193. Interhead variability was low (SDs of the interhead difference, 0.017-0.074). Commonly used γ-cameras produced H/M ratios from simulated I-MIBG phantom images that were not significantly different from those on the reference camera. This finding indicates that the results of previous clinical trials of I-MIBG, involving many different clinical sites and camera models, are valid. The assessment of the performance of a given camera unit using an I planar phantom before H/M results from I-MIBG imaging are used for classifying risk in heart failure patients is encouraged.
平面碘苄胍（I-MIBG）图像上心纵隔（H/M）比值≥1.6可识别发生不良心脏事件风险较低的心力衰竭患者。这项4期研究使用标准化体模，评估使用市售双头γ相机进行平面心脏I-MIBG成像测定H/M比值时的相机间、相机内和探头间变异性。研发了一种可填充的胸部体模，以模拟I-MIBG的典型摄取情况。该体模在参考相机上的标称H/M比值为1.6。研究中使用的商用相机为双头相机，能够配置成90°进行心脏成像。目标样本量为每个相机型号8个单位（样本）。两名成像技术人员独立分析胸部体模模拟I-MIBG摄取的平面图像。H/M为心脏和纵隔感兴趣区域每像素平均计数的比值。通过与参考相机上的H/M比值比较，确定每个相机型号的主要终点，即探头1的H/M比值的相机间变异性。仅将测试单位数至少为8个（≥8）的相机纳入主要分析。还评估了H/M比值的相机内和探头间变异性。研究了9种相机型号。平均H/M比值范围为1.342至1.677。使用混合模型重复测量分析的主要分析（6种相机型号）显示，任何相机型号与参考相机之间的H/M比值均无显著差异。8个单位及以上相机型号的H/M比值的相机内变异性（探头1）较高，标准差范围为0.0455至0.1193。探头间变异性较低（探头间差异的标准差为0.017 - 0.074）。常用γ相机从模拟I-MIBG体模图像得出的H/M比值与参考相机上的H/M比值无显著差异。这一发现表明，之前涉及许多不同临床地点和相机型号的I-MIBG临床试验结果是有效的。鼓励在将I-MIBG成像的H/M结果用于心力衰竭患者风险分类之前，使用I平面体模评估给定相机设备的性能。
