UTE results in collagen solutions. (a) Collagen solution calibration plot, demonstrating a linear relationship between the UTE collagen signal fraction and the collagen concentration. m = slope, b = y-intercept, R2 = correlation coefficient, sr = standard deviation about the regression. (b) T2* decay of the 50 % collagen solution, fitted using a bi-exponential T2* model with oscillation. T2*long denotes the long T2* of MnCl2 (mimicking cardiac muscle). Although not all long TEs were fitted, the focus was in the characterization of the short TEs ≤ 2 ms, where the T2* model is accurate.