Dynamic planar scintigraphy for the rapid kinetic measurement of myocardial 123 I-MIBG turnover can identify Lewy body disease

Background Using two static scans for 123 I-meta-iodobenzyl-guanidine ( 123 I-MIBG) myocardial scintigraphy ignores the dynamic response from vesicular trapping in nerve terminals. Moreover, the long pause between scans is impractical for patients with Lewy body diseases (LBDs). Here, we optimized indices that capture norepinephrine kinetics, tested their diagnostic performance, and determined the differences in 123 I-MIBG performance among disease groups. Methods We developed a new 30-min protocol for 123 I-MIBG dynamic planar imaging for suspected LBD patients. Pharmacokinetic modelling of time-activity curves (TACs) was used to calculate three new indices: unidirectional uptake of 123 I-MIBG to vesicular trapping (iUp), rate of myocardial 123 I-MIBG loss (iLoss), and non-specific fractional distribution of 123 I-MIBG in the interstitial space. We compared the performance of the new and existing indices with regard to discrimination of patients with or without LBDs. Subgroup analysis was performed to examine differences in 123 I-MIBG turnover between patients in a dementia with Lewy bodies (DLB) group and two Parkinson’s disease (PD) groups, one with and the other without REM sleep behaviour disorder (RBD). Results iLoss was highly discriminative, particularly for patients with low myocardial 123 I-MIBG trapping, and the new indices outperformed existing ones. ROC analysis revealed that the AUC of iLoss (0.903) was significantly higher than that of early HMR (0.863), while comparable to that of delayed HMR (0.892). The RBD-positive PD group and the DLB group had higher turnover rates than the RBD-negative PD group, indicating a potential association between prognosis and iLoss. Conclusion 123 I-MIBG turnover can be quantified in 30 min using a three-parameter model based on 123 I-MIBG TACs. The discriminatory performance of the new model-based indices might help explain the neurotoxicity or neurodegeneration that occurs in LBD patients.