Statistical guideline of threshold determination for cardiac spiral wave center detection using phase variance analysis

Abstract

Spiral wave (SW) plays a key role in generation and termination of fatal tachyarrhythmia. In our previous study, we proposed a novel objective tracking method of SW center trajectories by using phase variance (PV) analysis. This method evaluates local variance of phase values around each point to detect the position of SW center as the peak of PV map. PV analysis improved the detection accuracy of meandering SW centers and complex multiple SW centers significantly. However, the algorithm still includes some hyperparameters, the window size for the evaluation of phase variance and the binarization threshold for the peak detection. Thus, some guideline for proper determination of those parameters has been required. In this study, we hypothesized that the appropriate binarization threshold depends on the window size, and it can be determined as the level of PV value with specific p-value on Rayleigh’s test. We compared the detection results with various window sizes (3, 6, 9, 12 pixels) and various thresholds (from 0.4 to 0.9). Optical mapping measurement data with single SW center and four SW centers were evaluated. As a result, proper numbers of SW centers were detected with the thresholds corresponding to the p-value of 0.05, even with the smallest window size (3 pixels). From these results, it was indicated that the suggested method based on Rayleigh’s test is valuable for proper determination of PV analysis parameters.