Comparison of Image Quality, Myocardial Perfusion, and Left Ventricular Function Between Standard Imaging and Single-Injection Ultra-Low-Dose Imaging Using a High-Efficiency SPECT Camera: The MILLISIEVERT Study

Abstract

SPECT myocardial perfusion imaging (MPI) plays a central role in coronary artery disease diagnosis; but concerns exist regarding its radiation burden. Compared to standard Anger-SPECT (A-SPECT) cameras, new high-efficiency (HE) cameras with specialized collimators and solid-state cadmium-zinc-telluride detectors offer potential to maintain image quality (IQ), while reducing administered activity and thus radiation dose to patients. No previous study has compared IQ, interpretation, total perfusion deficit (TPD), or ejection fraction (EF) in patients receiving both ultra-low-dose (ULD) imaging on a HE-SPECT camera and standard low-dose (SLD) A-SPECT imaging. Methods We compared ULD-HE-SPECT to SLD-A-SPECT imaging by dividing the rest dose in 101 patients at 3 sites scheduled to undergo clinical A-SPECT MPI using a same day rest/stress Tc-99m protocol. Patients received HE-SPECT imaging following an initial ~130 MBq (3.5mCi) dose, and SLD-A-SPECT imaging following the remainder of the planned dose. Images were scored visually by 2 blinded readers for IQ and summed rest score (SRS). TPD and EF were assessed quantitatively. Results Mean activity was 134 MBq (3.62 mCi) for ULD-HE-SPECT (effective dose 1.15 mSv) and 278 MBq (7.50 mCi, 2.39 mSv) for SLD-A-SPECT. Overall IQ was superior for ULD-HE-SPECT (p<0.0001), with twice as many studies graded excellent quality. Extracardiac activity and overall perfusion assessment were similar. Between-method correlations were high for SRS (r=0.87), TPD (r=0.91), and EF (r=0.88). Conclusion ULD-HE-SPECT rest imaging correlates highly with SLD-A-SPECT. It has improved image quality, comparable extracardiac activity, and achieves radiation dose reduction to 1 mSv for a single injection.

It’s about time we think about lowering radiation dose in obese patients too

“…Other approaches rely on recent improvements in camera hardware and software such as highsensitivity cadmium zinc telluride (CZT) solid-state detectors and iterative reconstruction resolution recovery algorithms, which can allow injection of less radiotracer and/or decrease image acquisition time. 8,9 Along with specific techniques for lowering radiation dose, the many recommendations emphasize patientcentered imaging that tailors the imaging protocol specifically to each patient. [10][11][12] ASNC specifically advocated reducing radiation exposure such that [50% of a facility's MPI patients receive a total effective dose B9 mSv.…”

The tools are ready, are we?

“…The MultIcenter nucLear Low-dose Imaging at a milliSIEVERT (MILLISIEVERT) study have demonstrated that the radiation dose can be reduced to a range of 1 to 2 mSv with the same or superior image quality. 22 According to observations that increasing percentage of rest-stress studies are normal and that outcomes of normal rest-stress and stress-only studies are identical, a stress-only procedure is preferred for many patients in current guidelines. 23 Adopting the stressonly procedure with high efficiency CZT SPECT camera which gives effective dose of 1 mSv can significantly reduce the radiation exposure to the U.S. population.…”

Improving cardiac SPECT accuracy: Old robustness for a new gold standard

“…Accordingly, initial reports have clearly confirmed the excellent diagnostic accuracy of CZT cameras in detecting CAD with a global radiation burden as low as 1-2 mSv per study. 19,20 In most of these reports, evaluation of myocardial perfusion was performed visually or based on a local normal limits database, since the majority of the vendorsupplied normal limits databases for the automatic semiquantification of myocardial ischemic burden are not validated for CZT devices.…”