Cardiac Phantom for Improved Small-Animal SPECT Myocardial Blood Flow Quantification

To assess myocardial blood flow (MBF) in mice, and subsequently coronary microvascular function, we have previously developed a non-invasive, in-vivo, dynamic cardiac imaging protocol using the U-SPECT+ system. This work investigates microSPECT quantitative capabilities of cardiac imaging by utilizing a multi-part cardiac phantom and applying a known kinetic model to static data, allowing for assessment of kinetic modeling accuracy. The phantom was designed with four main components: two left-ventricular myocardium sections and two left-ventricular blood pool sections, sized for end-systole and end-diastole. Each section of the phantom was imaged separately while acquiring list-mode data. A Gaussian-based kinetic model was developed and applied to list-mode data to estimate both the myocardium and blood pool activity concentrations over time. The generated dynamic list-mode data were then combined, such that the myocardium and blood pool segments are contained in a single image, and reconstructed. Regions of interest were drawn in the resulting images, and kinetic modeling parameter estimation was performed. Given an input K
₁
of 0.5 min
^-1
, the resulting fit estimated K
₁
of 0.514 and 0.517 min
^-1
for end-diastole and end-systole, respectively. We have designed and imaged a phantom that allows for estimation of the of accuracy of kinetic modeling of small-animal cardiac SPECT and performed an initial evaluation. Future work will employ multiple reconstruction noise ensembles to analyze the robustness of our fitting method and to evaluate the effects of noise. Additionally, these results will be used to optimize reconstruction parameters.