The impact of attenuation correction and prone positioning on stress-only imaging in cardiac SPECT: An observational study

Background: Current guidelines recommend stress-only single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) in select patients to reduce time, cost, and radiation. However, stress-only imaging remains underutilized. Objectives: We assessed techniques to increase the adoption of stress-only SPECT MPI, specifically evaluating whether prone positioning and CT-based attenuation correction (AC) reduce the need for additional rest imaging. Methods: Consecutive patients with normal stress SPECT MPI scans were included. The need for additional rest imaging was assessed according to the use of prone positioning and AC. Radiotracer dose was calculated per the institution's protocol and compared between groups. Survival analysis compared the safety of stress-only protocols to stress-rest protocols. Results: Between 2018 and 2024, 14,274 patients with no stress perfusion defects were included. The use of stress-only imaging increased from 43.6% among patients with neither AC nor prone to 63.4% with AC and 65.7% with prone to 76 % with both techniques. Using multivariable logistic regression, the simultaneous use of prone and AC techniques significantly increased stress-only imaging (OR: 5.0, 95% CI: 4.38-5.72). This was more pronounced among females, obese patients, patients >65 years, and patients with an EF ≥ 55%. Radiotracer dose dropped by 35.6% when both AC and prone were used. Patients with normal stress-only SPECT scans had similar prognoses to those with normal SPECT scans using both stress and rest images, regardless of AC or prone imaging use. Conclusion: Combined use of AC and prone reduces the need for rest imaging by nearly half and lowers radiotracer doses by a third. Benefits are more pronounced in women, the elderly, patients with obesity, non-diabetics, and those with preserved ejection fraction.