Original Article
High-efficiency SPECT MPI: Comparison of automated quantification, visual interpretation, and coronary angiography

https://doi.org/10.1007/s12350-013-9735-xGet rights and content

Abstract

Background

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

Methods

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

Results

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

Conclusions

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.

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

References (30)

Cited by (0)

View full text