Comparison of segmentation methods for MRI measurement of cardiac function in rats

Purpose: To establish the accuracy, intra-and inter-observer variabilities of four different segmentation methods for measuring cardiac functional parameters in healthy and infarcted rat hearts.Materials and Methods: Six Wistar rats were imaged before and after myocardial infarction using an electrocardiogram and respiratory-gated spoiled gradient echo sequence. Blinded and randomized datasets were analyzed by various semi-automatic and manual segmentation methods to compare their measurement bias and variability. In addition, the accuracy of these methods was assessed by comparison with reference measurements acquired from high-resolution three-dimensional (3D) datasets of a heart phantom.Results: Relative inter-and intra-observer variability were found to be similar for all four methods. Semiautomatic segmentation methods reduced analysis time by up to 70%, while yielding similar measurement bias and variability compared with manual segmentation. Semi-automatic methods were found to underestimate the ejection fraction for healthy hearts compared with manual segmentation while overestimating them in infarcted hearts. However, semi-automatic segmentation of short axis slices agreed better with 3D reference scans of a heart phantom compared with manual segmentation.Conclusion: Semi-automatic segmentation methods are faster than manual segmentation, while offering a similar intra-and inter-observer variability. However, a potential bias has been observed between healthy and infarcted sidered when selecting the most appropriate analysis technique.