Validation of Iodine-131-meta-iodobenzylguanidine cardiac scintigraphy in Parkinsonism: A preliminary study

Introduction: ¹²³I-MIBG is the most commonly used radiopharmaceutical to depict cardiac sympathetic innervation. The purpose of this study was to validate the feasibility of ¹³¹I-MIBG as an alternative myocardial sympathetic imaging probe in differential diagnosis of Parkinsonism.

Methods: We recruited 17 patients with PD, 21 patients with other parkinsonism (17 with MSA and 4 with PSP), and 6 normal controls. All participants underwent ¹³¹I-MIBG scintigraphy for both early and delayed imaging. The image quality was independently assessed by two experienced nuclear medicine specialists and graded into three categories: 1, good image quality; 2, suboptimal but sufficient for diagnosis; and 3, poor or nondiagnostic. Cardiac MIBG uptake was quantitatively measured using H/M ratio and washout rate.

Results: The image quality was good (Grade 1) in 74 and 73 of a total of 88 images by the two reviewers, respectively. No image was poor or nondiagnostic (Grade 3). Patients with PD had a significantly lower H/M ratio for both the early and the delayed images than did those with MSA or PSP and the controls (P < 0.001). For differentiating PD from other parkinsonism, the sensitivity and specificity were 95% and 94% for the early images and 100% and 94% for the delayed images, respectively. Patients with MSA or PSP has a significantly lower WR compared with those with PD. (WR = 0.15 ± 0.23 and 0.48 ± 0.17, respectively; P < 0.001).

Conclusion: ¹³¹I-MIBG scintigraphy is a feasible method to depict cardiac sympathetic activity. The diagnostic performance is comparable to that of ¹²³I-MIBG.