As part of a pioneering national initiative led by Lanzhou University to develop domestic Actinium-225 ( \({}^{225}Ac\) )-targeted therapy equipment and algorithms, this work introduces a preliminary high-resolution three-dimensional SPECT image reconstruction method for \({}^{225}Ac\) therapy, employing the Ordered Subsets Expectation Maximization (OSEM) algorithm. SPECT imaging of \({}^{225}Ac\) presents significant challenges due to low signal intensity, attenuation effects, and scattering, which can compromise image quality and hinder precise treatment planning. To address these issues within the context of localized medical technology development, we adopt a three-dimensional reconstruction approach that utilizes the OSEM algorithm to iteratively enhance image quality while minimizing noise and artifacts. The influence of collimator geometry on the point spread function is discussed within the framework of the system configuration. Numerical simulations based on a mouse model are conducted to validate the adopted method, with two test cases designed to evaluate the OSEM algorithm’s performance under varying simulation conditions. The results demonstrate that this OSEM-based approach significantly improves the resolution and quality of \({}^{225}Ac\) SPECT images, laying a promising foundation for optimizing domestic \({}^{225}Ac\) therapy applications. This preliminary work highlights the potential of advanced SPECT imaging techniques to enhance therapeutic precision in resource-constrained settings and outlines future research directions for refining reconstruction algorithms and broadening their clinical applicability.
