Development of an 123 I-metaiodobenzylguanidine Myocardial Three-Dimensional Quantification Method for the Diagnosis of Lewy Body Disease.

Objectives: We recently developed a new uptake index method for 123 I-metaiodobenzylguanidine (123 I-MIBG) heart uptake measurements by using planar images (radioisotope angiography and planar image) for the diagnosis of Lewy body disease (LBD), including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). However, the diagnostic accuracy of the uptake index was approximately equal to that of the heart-to-mediastinum ratio (H/M) for the discrimination of the LBD and non-LBD patients. A simple and pain-free uptake index method using 123 I-MIBG SPECT images by modifying the uptake index method may show better diagnostic accuracy than the planar uptake index method. We hypothesized that the development of a new uptake index method for the determination of 123 I-MIBG using single-photon emission computed tomography (SPECT) imaging would provide a reliable and reproducible diagnostic tool for clinical application. Regarding this, the purpose of this study was to develop a new uptake index method with a simple protocol to determine 123 I-MIBG uptake on SPECT.

Methods: The 123 I-MIBG input function was determined from the input counts of the pulmonary artery, assessed by analyzing the pulmonary artery time-activity curves. The 123 I-MIBG output function was obtained from 123 I-MIBG SPECT counts on the polar map. The uptake index was calculated through dividing the output function by the input function (SPECT uptake method). For the purpose of the study, 77 patients underwent 123 I-MIBG SPECT, with an average of 31.5 min after clinical assessment and injection of the tracer. The H/M values, as well as planar and SPECT uptake indices were calculated, and then correlated with clinical features.

Results: According to the results, values obtained for LBD were significantly lower than those for non-LBD in all analyses (P<0.01). The overlap of the H/M values between the LBD and non-LBD cases ranged from 2.06 to 2.50. Furthermore, the overlap in uptake index values between LBD and non-LBD cases in planar image analysis was 1.05-1.29. The SPECT uptake index method showed the least overlap of 1.23-1.25, with the highest value for LBD patients clearly distinguished from the lowest value for the non-LBD patients.

Conclusion: The new 123 I-MIBG SPECT quantification method, developed by the input counts of the pulmonary artery, clearly distinguished LBD from non-LBD. Therefore, this method may be appropriate for routine clinical study.