Remarkable reduction of exposure rate in patients with stress-only myocardial perfusion scan: Let's safe mankind from unjustified radiation exposure

Introduction: To measure radiation exposures rate in low-risk patients having stress-only and stress-rest myocardial perfusion imaging. Methods: This was a prospective study conducted from January 2012 till November 2012 upon patients with low pre-test probability for coronary artery disease (CAD). A stress MPI (stress-only if MPI is normal and no resting study) followed by a resting MPI study (same day) if stress study was positive or equivocal. Exposure rates (in milli-Roentgen/hour, mR/hr) from injected patients at 1 meter distance were measured at 10 minutes, 1 hour and at time of releasing patients in both groups. Results: Total 369 patients were included and 104 (28%) patients had stress-only and 265 (72%) had stress-resting studies. Mean administered ^99mTc-MIBI dose in Stress-only and Stress-rest groups was 8 ±1 mCi and 24 ±03 mCi respectively (p<0.05). Exposure rates(in mR/hr) within 10 min, 1 hour and at release time in Stress-only and stress-rest groups were 0.394, 0.294, 0.194and 1.540, 1.431, 1.207 respectively (p<0.05). Mean stay of patients in laboratory was 90 ±39 minute in Stress-only and 156 ±53 minute in Stress-Rest group (p <0.0001). There was a significantly widening gap between exposure rates from patients with Stress-only and stress-rest protocols as 26:74%, 21:79% and 16:84% at 10 min, 1 hour and at time of release respectively. Conclusion: We conclude that adopting a Stress-only MPI protocol in low risk patients ensures significantly lower radiation doses to patients and technologists. A worldwide paradigm shift in nuclear cardiology practice would safe mankind from unjustified radiation exposure.