Original Article
Fully automated wall motion and thickening scoring system for myocardial perfusion SPECT: Method development and validation in large population

https://doi.org/10.1007/s12350-011-9502-9Get rights and content

Background

Objective assessment of wall motion (M) and thickening (T) will aid in diagnosis of coronary artery disease (CAD) from myocardial perfusion SPECT (MPS). We aimed to develop and validate an improved fully automated M/T segmental scoring system for MPS.

Methods

100 normal gated stress/rest Tc-99m sestamibi MPS scans from patients with low-likelihood (LLk) of CAD were used to derive the regional normal M/T ranges. A new automatic algorithm incorporated regional dependence on the global contractility in polar map coordinates by linear regression analysis and automatically derived 17-segment M (scale 0-5) and T (scale 0-3) scores. We validated this new method in 630 consecutive Tc-99m stress MPS studies in patients with suspected CAD and available correlating angiography, and an additional 241 LLk studies. Two independent observers with 12 and 30 years of experience in nuclear cardiology, blinded to clinical and angiographic data, scored M /T in 17-segments for all 971 studies.

Results

Computation time was <1 s per case. In the angiography group, there was a high correlation between the summed scores (averaged for two observers) and automatic scores with r = 0.91 (slope = 1.02, offset = 0.2; P < .0001) for M and r = 0.88 (slope = 1.06, offset = 0.28 for T; P < .0001). Weighted kappa was 0.63 for M and 0.57 for T, with expected agreement of 89% (M) and 91% (T) in individual segments (n = 10710). Weighted kappa between two experts was 0.45 for M and 0.52 for T. The normalcy rate in LLk cases was 96% for automated M and 99% for T (summed score <3). Detection of the angiographically significant disease by automated M or T scoring was better than or equivalent to individual expert observer scoring, and better than the previous automated system.

Conclusions

Fully automated scoring of MPS regional ventricular function can be performed rapidly, is highly correlated with expert visual scoring, can outperform individual experienced observers in the detection of CAD by wall thickening from MPS, and avoids inter-observer variability.

Introduction

Myocardial perfusion SPECT (MPS) provides valuable information about both perfusion and function of the left ventricle (LV). We have previously developed optimized methods for automated perfusion scoring, which have high performance in detection of coronary artery disease (CAD).1 Accurate regional assessment of contractile function is also of great importance since it could further enhance the detection of CAD2 and provide additional prognostic information.3 Automated assessment of regional three-dimensional left ventricular function can provide highly reproducible objective and rapid assessment of regional parameters. In contrast, visual segmental scoring is laborious and is associated with significant inter- and intra-operator variability. We aimed to develop and validate an improved fully automated motion (M) and thickening (T) segmental (AHA 17-segment) scoring system for MPS, which is based on analysis of normal values in patients with low-likelihood (LLk) of disease and quantitative deviations from normal thresholds without training the system by subjective expert observer scoring in abnormal patients.4 Such a method allows us to compare the automated performance to the expert scoring in a large population and potentially demonstrates advantages over visual scoring. Furthermore, by this approach we remove the subjective aspect associated with training the system with a particular visual perception of functional abnormalities.

Section snippets

Patients

In brief, the subjects were consecutively selected from the patients who were referred to the Nuclear Medicine Department, Sacred Heart Medical Center, Eugene, OR, USA from March 1, 2003, to December 31, 2006, for rest and stress electrocardiography (ECG) gated MPS. The LLk studies were obtained from patients who performed an adequate treadmill stress test, did not have correlating coronary angiography available, but had <5% likelihood of CAD using the Diamond and Forrester criteria based on

Results

Computation time was <1 s per case on the 64-bit PC computer with Intel Xeon X5450 processor operating at 3 GHz. The process was fully automated and performed in batch mode for all 971 cases simultaneously with automatic dump of the results to the Microsoft Excel spreadsheet. The processing time of the entire cohort was approximately 20 minutes.

Discussion

In this study, we have presented the design and validation of the improved scoring system for regional left ventricular motion and thickening derived from MPS. In particular, we have designed a new method for the establishment of lower normal limits for the motion and thickening based on the relationship between the global left ventricular EF with regional segmental values. We found both the regional and the global heterogeneity of the normal limits, and applied linear regression analysis to

Conclusion

We demonstrated that improved fully automated scoring of MPS regional ventricular function is highly correlated with expert visual scoring, and can outperform an experienced observer in the detection of significant CAD by wall thickening. 17-segment visual motion and thickening scoring from MPS is associated with significant inter-observer variability, and we therefore recommend automated scoring of these features.

Acknowledgments

This research was supported in part by grant R0HL089765-05 from the National Heart, Lung, and Blood Institute/National Institutes of Health (NHLBI/NIH). We would like to acknowledge Jim Gerlach and Mark Hyun for quality control of all the data. We would like to thank Arpine Oganyan for editing and proof-reading the text.

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This research was supported in part by Grant R0HL089765-01 from the National Heart, Lung, and Blood Institute/National Institutes of Health (NHLBI/NIH).

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