Validation of a New T2*Algorithm and Its Uncertainty Value for Cardiac and Liver Iron Load Determination from MRI Magnitude Images

Purpose: To validate an automatic algorithm for offline T2* measurements, providing robust, vendor-independent T2*, and uncertainty estimates for iron load quantification in the heart and liver using clinically available imaging sequences. Methods: A T2* region of interest (ROI)-based algorithm was developed for robustness in an offline setting. Phantom imaging was performed on a 1.5 Tesla system, with clinically available multiecho gradient-recalled-echo (GRE) sequences for cardiac and liver imaging. A T2* single-echo GRE sequence was used as reference. Simulations were performed to assess accuracy and precision from 2000 measurements. Inter-and intraobserver variability was obtained in a patient study (n = 23). Results: Simulations: Accuracy, in terms of the mean differences between the proposed method and true T2* ranged from 0-0.73 ms. Precision, in terms of confidence intervals of repeated measurements, was 0.06-4.74 ms showing agreement between the proposed uncertainty estimate and simulations. Phantom study: Bias and variability were 0.26 +/- 4.23 ms (cardiac sequence) and -0.23 +/- 1.69 ms (liver sequence). Patient study: Intraobserver variability was similar for experienced and inexperienced observers (0.03 +/- 1.44 ms versus 0.16 +/- 2.33 ms). Interobserver variability was 1.0 +/- 63.77 ms for the heart and -0.52 +/- 2.75 ms for the liver. Conclusion: The proposed algorithm was shown to provide robust T2* measurements and uncertainty estimates over the range of clinically relevant T2* values.