Validation of the SIMIND simulation code using the myocardial phantom HL.

[Introduction] Monte Carlo simulation codes simulating medical imaging nuclear detectors (SIMIND) are notable tools used to model nuclear medicine experiments.This study aimed to confirm the usability of SIMIND as an alternative method for nuclear medicine experiments with a cardiac phantom HL, simulating human body structures, by comparing the actual experiment data. [Methods] A cardiac phantom HL that simulates myocardial scintigraphy using ¹²³I-meta-iodobenzylguanidine was developed, and single-photon emission computed tomography/computed tomography imaging was performed using Discovery NM/CT 670 scanner. Aside from the main-energy window(159 keV ± 10%), additional windows were set on the low(137.5 keV ± 4% ) and high(180.5 keV ± 3%)-energy sides. The simulations were performed under the same conditions as the actual experiments. Regions of interest (ROIs) were set in each organ part of the experiments and simulated data, and a polar map for the myocardial part was developed. The mean, maximum (max), and minimum (min) counts within each ROI, as well as the relative errors of each segment in the polar map, were calculated to evaluate the accuracy of the simulation. [Results] Overall, the results were favorable with relative errors of <10% except in some areas based on the data from the main-energy window and postreconstruction. On the other hand, relative errors of ＞10% were found in both the low and high subenergy windows. The smallest error occurred when assessing using mean values within the ROIs. The relative error was high at the cardiac base in the polar map evaluation; however, it remained <10% from the mid to apical heart sections. [Conclusion] SIMIND is considered an alternative method for nuclear medicine experiments using a myocardial phantom HL that closely resembles human body structures. However, caution is warranted as accuracy may decrease under specific conditions.