<b>Myocardial Perfusion Imaging: An Approach to Find Out When to Add SPECT/CT in MIBI Scan</b>

Background: Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) is a key diagnostic tool for coronary artery disease (CAD), but its accuracy can be compromised by soft tissue attenuation artifacts, particularly from breast tissue in women and diaphragmatic fat in obese individuals. Hybrid SPECT/computed tomography (SPECT/CT) enables attenuation correction, potentially improving diagnostic accuracy, but its routine use may increase radiation exposure and resource utilization. Objective: To determine the prevalence and primary indications for adding SPECT/CT to technetium-99m sestertii (MIBI) MPI scans, and to assess the association between patient demographics, attenuation sources, and SPECT/CT utilization. Methods: This cross-sectional observational study included 70 adults undergoing one-day MIBI MPI at a tertiary cardiac hospital. Demographics, attenuation risk factors, and imaging findings were recorded. The decision to perform SPECT/CT was made by the reporting radiologist. Associations between variables were evaluated using Chi-square tests with Cramer’s V to measure effect size. Results: SPECT/CT was performed in 37.1% of patients, significantly more often in females (92.9%) than males (23.2%) (p<0.001, V=0.52). Breast attenuation accounted for 76.9% of female cases, while obesity accounted for 100% of male cases undergoing SPECT/CT (p<0.001, V=0.79). No significant association was found between attenuation source and specific perfusion defect patterns. Conclusion: SPECT/CT is most frequently added in females with breast attenuation and obese males, but imaging findings do not consistently differ by attenuation source. Targeted criteria for SPECT/CT selection may optimize diagnostic value while minimizing unnecessary exposure.