The distribution and kinetics of 123I-MIBG in normal human hearts

123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy was performed in twelve normal human subjects, and the distribution and clearance of MIBG were estimated. In PLANAR studies, heart to mediastinum (H/M) and lung to mediastinum activity ratio (L/M) were 2.68±0.45 and 1.82±0.23 in initial images, and 2.75±0.44 and 1.55±0.13 in delayed images. The clearance of MIBG in the lung was more rapid than that in the heart, 41.6±4.1 vs. 29.8±3.2(%), therefore MIBG cardiac profiles were more clarified in delayed images. In SPECT studies, the regional relative uptake (RRU) in anterior, septal, inferior and lateral walls were 100.0±0, 93.9±6.9, 85.0±10.0 and 104.9±8.3(%) in initial images, and 100.0±0, 96.8±9.6, 79.4±8.3 and 99.1±7.9(%) in delayed images, respectively. The RRU in inferior wall was significantly lower than that in the other walls. The regional clearance rate (RCR) in these four walls were 25.1±4.6, 22.5±8.2, 29.7±8.3, 29.3±3.4(%), respectively. The RCR in inferior and lateral walls was significantly larger than that in anterior and septal walls. The RRU in basal, mid and apical portions was 100.0±0, 104.5±3.3, 98.9±12.1(%) in initial images, and 100.0±0, 103.9±4.5, 96.8±15.2(%) in delayed images, respectively. The RRU in mid portion was significantly higher than that in basal portion. The RCR in these three portions were 26.5±5.9, 27.0±4.6, 28.3±6.2(%), respectively, and no significant difference was seen. Mean clearance rate of the whole left ventricle was 26.9±4.1(%) by Bull's eye method. In this study, we obtained the normal values of the distribution and clearance of MIBG. Those were concluded to be heterogeneous even in normal human hearts, and it indicated that we should pay attention to this heterogeneity. (author)