T1-weighted late gadolinium enhancement images. Left panels: Evidence of subepicardial non-ischemic myocardial fibrosis in athletes 1 and 2 (arrows), with none in healthy control. Right panels: Quantification of myocardial fibrosis by manually tracing a region of interest in health remote myocardium (blue outline). Automated computer thresholding set at 5 standard deviations above the mean signal intensity of remote myocardium detects fibrosis (red overlay). The detected extent of fibrosis for athlete 1 is 14.12%, 11.30% for athlete 2 and 0.20% for control.