Usefulness of rapid low-dose/high-dose 1-day ^99mTc-sestamibi ECG-gated myocardial perfusion single-photon emission computed tomography

Background: The clinical usefulness of a rapid rest low-dose/stress high-dose (dose ratio =1:5) ^99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT) protocol for the detection of coronary artery disease was evaluated. Methods and Results: In 89 patients, rest images were obtained immediately after the injection of ^99mTc-sestamibi (256.1±28.4 MBq) followed by drinking water (400 ml). Exercise or vasodilator stress test was performed immediately after the completion of rest imaging with the injection of ^99mTc-sestamibi (1312.3±167.6 MBq). Prior to the post-stress imaging, patients were asked again to drink water (400 ml) in order to eliminate subdiaphragmatic tracer activity. The myocardial count ratio (stress/rest) of ^99mTc-sestamibi was calculated. Image quality was scored using a 4-point scale system (4= excellent, 3= good, 2= poor, 1= unacceptable). Coronary angiography was performed in 56 patients within 1 month of the SPECT scan. All patients successfully performed the protocol and total examination time was 108±7 min. The myocardial count ratio of ^99mTc-sestamibi was always greater than 6. The image quality was satisfactory both at rest (3.4±0.9) and after stress (3.9±0.2). The sensitivity and specificity to detect coronary artery stenosis >50% was 84% and 97%, respectively. Conclusions: This rapid one-day ^99mTc-sestamibi protocol provides adequate image quality and diagnostic accuracy for detecting coronary artery disease.