Assessment of the efficacy of early phase parameters by (123)I-MIBG dynamic imaging for distinguishing Lewy body-related diseases from Parkinson's syndrome.

Objective: The aim of this study was to assess the efficacy of early phase washout rate (early WR) and area under the time-activity curve (AUTAC) by (123)I-metaiodobenzylguanidine (MIBG) dynamic chest imaging for distinguishing Lewy body-related diseases (LBRD) from Parkinson's syndrome (PS) and reducing examination time.

Methods: Sixty-two patients with suspected LBRD who underwent (123)I-MIBG dynamic imaging in early phase were retrospectively selected. The early WR and AUTAC were calculated from (123)I-MIBG dynamic data of the heart. We evaluated the relationships between proposed and conventional parameters by using Spearman's rank correlation coefficient. Differences in parameters between LBRD and PS groups were tested for statistical significance using the Mann-Whitney U test. The diagnostic performance of all parameters for distinguishing LBRD from PS was assessed in terms of receiver operating characteristic (ROC) analysis. Additionally, combination diagnostic performance and concordance rate between early phase parameters and late H/M ratio by kappa statistics were also assessed.

Results: The early WR and AUTAC showed a positive and negative correlation with conventional parameters. Both the early WR and AUTAC of LBRD group were significantly distinguishable from those of the PS group (p < 0.001). Area under the ROC curve of the early WR (0.98) was greater than that of AUTAC (0.91). The diagnostic performance of combination of the early phase parameters was 93 % sensitivity and 100 % specificity. Moreover, the early phase parameters showed excellent agreement with late H/M ratio (k = 0.93).

Conclusions: The early WR and AUTAC showed high performance for distinguishing LBRD from PS, and the combination diagnosis with early H/M ratio and early WR contribute to improve the diagnostic performance. Thus, these parameters would be useful for reducing the examination time of myocardial (123)I-MIBG scintigraphy to diagnose LBRD.