Introduction: Analysis using cardiac iodine-123 metaiodobenzylguanidine (MIBG) scintigraphy with regions of interest (ROIs) is useful for assessing myocardial sympathetic activity. However, manual placement of the cardiac ROI is sometimes difficult because myocardial MIBG uptake is reduced in patients with heart failure. A new method was developed to reconstruct the semiautomated cardiac ROI in a sympathetic denervated heart.
Materials and methods: Using dynamic planar data, a summed image was generated and the matrix size was changed. Then, the radial count profiles originating from the center of the left ventricle were generated to extract the myocardial count profiles. An asymmetric Gaussian distribution was fitted to each profile and the epicardial border was defined by the threshold method. This program was tested in 50 patients, and its reproducibility was validated when compared with the manual tracing method.
Results: The semiautomated method yielded a better quality image compared with the standard image with higher counts. Cardiac ROIs were generated successfully in each patient within normal limits. The intraobserver and interobserver agreements were excellent (P<0.0001 each). This approach showed a significantly higher consistency in measuring the heart-to-mediastinum ratio as compared with the manual tracing method (P<0.05).
Conclusion: The semiautomated method is useful in generating cardiac ROIs with high reproducibility in myocardial MIBG imaging.