Original ArticleHigh-efficiency SPECT MPI: Comparison of automated quantification, visual interpretation, and coronary angiography
Introduction
Recently introduced high-efficiency cadmium zinc telluride (CZT) camera systems with novel collimation methods have helped overcome historical limitations of myocardial perfusion imaging (MPI) by significantly shortening image acquisition times and reducing administered activity.1 In parallel, methods for automated, quantification of MPI studies have been developed to modernize and improve the reliability and reproducibility of MPI.2 These techniques have been studied in recent years demonstrating reproducibility,3 favorable comparison to visual interpretation,2,4 good correlation with coronary angiography,5, 6, 7, 8 and the ability to predict cardiac events.9
The two commercially available CZT SPECT cameras, D-SPECT (Spectrum Dynamics, Caesarea, Israel) and Discovery NM 530c (GE Healthcare, Haifa, Israel),10 have been validated by comparison to conventional SPECT using standard radiopharmaceutical activity11, 12, 13, 14, 15, 16, 17 as well as lower administered activity.18, 19, 20 There have now been four published studies correlating conventional administered activity CZT SPECT MPI to invasive coronary angiography,5,16,21,22 and two studies addressing the accuracy of low administered activity CZT SPECT MPI.23,24 One of these compared automated computer analysis to coronary angiography with good results and is the only implementation of automated quantification applied to CZT SPECT (D-SPECT camera) to date.5 However, to date no study has examined the automated quantification of data from the GE Discovery camera, which has a unique collimation and reconstruction system based on a multipinhole design.
The objective of this study was to evaluate the applicability of the automated perfusion analysis based on normal limits to this new type of device and examine the agreement of automated assessment of CZT SPECT MPI with standard visual interpretation and invasive coronary angiography in an unselected clinical population. Furthermore, we sought to evaluate the value of combined supine-prone automated and visual analysis for this new device.4,6
Section snippets
Study Design
In a study protocol approved by our institutional IRB, we retrospectively evaluated all patients who presented to the Mount Sinai Non-Invasive Cardiology Laboratory over a 1-year period (June 2009 to May 2010) for a clinically indicated Tc-99m sestamibi SPECT MPI stress test using a CZT camera (GE Discovery NM 530c).1,13 Patients who then underwent an invasive coronary angiogram within 2 months after the MPI were identified. Patients with a history of coronary artery bypass grafting (CABG)
Demographics
A total of 4,291 patients presented to the Mount Sinai Non-Invasive Stress Laboratory for a stress test over this 1-year period with 3,111 undergoing stress MPI on the CZT camera (Figure 1). A total of 160 patients without a history of CABG surgery subsequently underwent invasive coronary angiography within a 2-month period of their Tc-99m MPI study, and 59 of them had no known history of CAD and normal left ventricular function.
The characteristics of all the patients from the time period and
Discussion
This investigation found that automated and visual CZT SPECT MPI quantification provides similar overall diagnostic accuracy based on ROC AUC when compared to coronary angiography. This is the first time that the two methods of quantification have been compared to each other with coronary angiography as the gold standard. The agreement between the automated and visual assessments was high with correlation coefficients of 0.76-0.81. Sensitivity which ranged from 64% to 93% was higher with visual
Limitations
The study is limited by the single site clinical experience and relatively small sample size. Coronary angiograms were performed for clinical indications on select patients and not uniformly on all patients. While performing angiograms on all patients undergoing MPI may have been possible in the past, the use of stress MPI as a clinical “gatekeeper” to the catheterization laboratory means that most patients referred for angiography have abnormal myocardial perfusion. This “referral bias” which
Conclusion
Automated and visual CZT SPECT MPI quantification provide similar overall diagnostic accuracy when compared to coronary angiography. Automated quantification has the potential to support clinical reads by “checking” their results. Furthermore, combined supine-prone stress imaging is needed for best diagnostic accuracy given its ability to greatly increase specificity.
Acknowledgements
This research was supported in part by Grant R0HL089765-05 from the National Heart, Lung, and Blood Institute/National Institutes of Health (NHLBI/NIH). Cedars-Sinai Medical Center receives royalties for the licensure of quantitative perfusion software, a portion of which is distributed to one of the authors (PS) of this manuscript.
Addendum
The patients analyzed in this study were also included in an earlier study which correlated CZT SPECT MPI to coronary angiography irrespective of tracer (Tc-99m or
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