Determination of the Heart-to-Mediastinum Ratio of ¹²³I-MIBG Uptake Using Dual-Isotope (¹²³I-MIBG/^99mTc-Tetrofosmin) Multipinhole Cadmium-Zinc-Telluride SPECT in Patients with Heart Failure

Abstract

The aim of this retrospective study was to compare the heart-to-mediastinum ratio (HMR) of ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) uptake obtained using a multipinhole cadmium-zinc-telluride (CZT) camera with that obtained using conventional planar imaging. <b>Methods:</b> Forty consecutive heart failure patients underwent planar acquisition 4 h after ¹²³I-MIBG injection (191 ± 41 [mean ± SD] MBq). To localize the heart using the CZT camera, ^99mTc-tetrofosmin (358 ± 177 MBq) was administered and dual-isotope acquisition was performed. The HMRs were calculated with conventional planar imaging (HMR_planar), with anterior reprojection images using the CZT camera (HMR_reproj), and with transaxial reconstructed images using the CZT camera (HMR_transaxial). In a phantom study, we estimated a linear model fitting the CZT camera data to the planar data, and we applied it to provide corrected CZT camera-determined HMRs in patients (cHMR_reproj and cHMR_transaxial). <b>Results:</b> Thirty-four men and 6 women (71 ± 9 y old) with ischemic (22 patients) and nonischemic (18 patients) heart failure completed the study. For 22 of the 40 patients (55%), the New York Heart Association classification was class II and the ejection fraction was 35% ± 9%. HMR_reproj (1.12 ± 0.19) and HMR_transaxial (1.35 ± 0.34) were lower than HMR_planar (1.44 ± 0.14) (<i>P</i> < 0.0001 and <i>P</i> < 0.01, respectively). cHMR_reproj (1.54 ± 0.09) and cHMR_transaxial (1.45 ± 0.14) were significantly different (<i>P</i> < 0.0001). Lin concordance correlation and Bland-Altman analysis demonstrated an almost perfect concordance and a high agreement between HMR_planar and cHMR_transaxial (<i>P</i> was not significant) but not between HMR_planar and cHMR_reproj (<i>P</i> < 0.0001). <b>Conclusion:</b> This study demonstrated that determination of the late HMR of cardiac ¹²³I-MIBG uptake using dual-isotope (¹²³I and ^99mTc) acquisition on a multipinhole CZT camera was feasible in patients with heart failure. However, this determination should be performed using transaxial reconstructed images and linear correction based on phantom data acquisitions.