Introduction:
Current guidelines for myocardial perfusion imaging (MPI) encourage facilities to adopt patient-centered risk mitigation strategies such as individualized radiotracer dosing and stress-first imaging. Reducing radiation exposure is also a key recommendation of multiple societies participating in the Choosing Wisely campaign. The stated goal is for over 50% of studies to be performed with <9 millisieverts (mSv) of radiation exposure. We hypothesized that adoption of a stress-first/stress-only imaging protocol would substantially reduce the median radiation dose administered in our nuclear lab.
Methods:
We switched the standard imaging protocol at the Malcom Randall VA Medical Center nuclear cardiology laboratory from rest-stress to stress-rest. To achieve this, a physician was required to review the stress images at the time they were obtained to determine if further imaging was indicated. Estimated effective radiation doses (in mSv) were calculated based on the radiotracer activity administered (in millicuries) used industry standards techniques. We compared 2 cohorts of patients: rest-stress studies consecutively done between 7/17/17 and 11/12/17 and stress-first studies consecutively done between 11/13/17 and 5/17/17. As a balancing measure, we compared the rate of normal studies between the cohorts. A normal MPI was defined as no evidence of ischemia or infarction with a preserved ejection fraction.
Results:
In the stress-first cohort, the median dose was 2.8 millisieverts (mSv) compared with 14.1 mSv in the rest-stress cohort (80.1% reduction, p<0.0001). During the observed period, we estimate that 4,780 mSv of effective dose were avoided. In the rest-stress cohort, 424 studies were performed. In the stress-first cohort, 716 tests were performed, 423 stress only studies (59.1%) and 293 stress-rest studies (40.1%). The rate of normal studies in the stress-first cohort was not different from the rest-stress cohort (stress-first: 73.5%, (526/716) versus rest-stress: 71.7%, p=0.54, odds ratio 0.92, 95% CI 0.69-1.21) In the rest-stress cohort, 3 patients (1.0%) underwent coronary angiography and 2 patients (0.7%) underwent percutaneous coronary intervention (PCI). In the stress-first cohort 8 patients (1.1%) underwent coronary angiography and 2 patient (0.3%) underwent percutaneous coronary intervention (PCI).
Conclusion:
By switching from a rest-stress to a stress-first imaging protocol, we reduced the median radiation dose in our lab by 80%. We observed no change in the proportion of normal tests, suggesting no potential for harm with this strategy.
Optimal 99mTc activity ratio in the single-day stress-rest myocardial perfusion imaging protocol: A multi-SPECT phantom study
