Radiation Dose and Prognosis of Ultra-Low-Dose Stress-First Myocardial Perfusion SPECT in Patients with Chest Pain Using a High-Efficiency Camera

Abstract

Although SPECT myocardial perfusion imaging (MPI) provides valuable information about patients with chest pain, there is growing concern regarding its radiation burden and lengthy duration. New high-efficiency (HE) cameras and stress-first protocols both offer the potential to markedly reduce radiation. No previous study has assessed outcomes and radiation doses of patients undergoing MPI on an HE-SPECT camera using an ultra-low-dose stress-first protocol. Methods: One hundred patients presenting to the emergency department with chest pain who were candidates for stress-first MPI underwent injection of approximately 185 MBq (5 mCi) of 99m Tctetrofosmin at peak stress, followed by supine and prone imaging on an HE-SPECT camera. Same-day rest imaging was performed on patients with any abnormality on imaging after stress. Radiation effective dose was calculated from administered and residual activities. Patients were contacted 3 mo after discharge, and electronic records were accessed to evaluate the need for reevaluation for chest pain, additional imaging, or cardiac events. Results: Stress-only imaging was performed in 69 patients, for whom radiation effective dose averaged 0.99 mSv and study duration, 117 min. Radiation dose averaged 2.22 mSv over all patients. At 3 mo, 96 patients were free of major adverse cardiac events, repeat hospital chest pain evaluation, and repeat imaging or stress testing. One year after MPI and hospital discharge, all patients were living and without acute coronary syndrome. Conclusion: HE-SPECT stress-only imaging can be performed in more than two thirds of chest pain patients without a high pretest probability of a stress perfusion defect, with excellent prognosis, a radiation dose averaging 1 mSv, and a test duration of less than 2 h.

What do we know? What do we need to know?

“…Einstein et al followed 69 patients with a normal stress-only SPECT referred from the Emergency Department for the evaluation of acute chest pain. 18 Imaging was done on a CZT camera with Tc99m tetrofosmin with very low radiation exposure to the patient (0.99 mSv). There were no major adverse cardiac events at one year of follow-up.…”

Using advanced technology to reduce the dose of SPECT MPI radiation

“…For example, the addition of attenuation correction to SPECT allows more patients to be tested with stress-only protocols and solid state detector systems allow higher resolution with lower radiation dose and acquisition times compared with standard Anger cameras. [2][3][4] In this issue of the Journal, Lyon et al demonstrate that with a particular commercial solution, IQ-SPECT, one can acquire images with the same diagnostic content in half the time and half the dose as with a standard LEEP collimator. 5 The IQ-SPECT solution incorporates a newly designed collimator, a cardio-centric orbit, and optimized computer software to achieve this improvement in counts and resolution over standard systems.…”

Which SPECT for today, which SPECT for tomorrow?

“…The rapidity of image acquisition can be traded (e.g., in younger patients) for reduced administered activity; 1 mSv studies are achievable and faster than ''normal'' imaging. 5,12 Full rest-stress studies are possible with 4.2-6.3 mSv and rapid imaging. 17 In reality, it is not only the administered activity from a single test which is of importance, but also the cumulative dose from multiple, repeat studies performed over decades to follow a chronic, noncurable disease.…”

“…Their solid-state detectors and novel cardiocentric collimation first and foremost results in higher count sensitivity which dramatically shortens acquisition time and/or markedly lowers radiation dose (both to the patients and employees). [3][4][5] They are also less bulky, offer better image quality, and provide improved spatial. Additionally, the new technology opens up the possibility of new ''disruptive'' advances in SPECT as well.…”