Xiaoming Yin1,2, Saurabh Shah3, Peter Kellman4, Andrew C. Larson1,5
1Department of Radiology, Northwestern University, Chicago, IL, USA; 2Department of Electrical Engineering and Computer Science, Northwestern University, Evanston , IL, USA; 3Siemens Medical Solutions,, Chicago, IL, USA; 4Laboratory of Cardiac Energetics, NIH, Bethesda, MD, USA; 5Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, USA
R2* is typically estimated via mono-exponential fitting of signal decay within a series of GRE images combined by root sum-of-square (RSS) approach. However, RSS approaches rectify and bias noise in later TEs, resulting in systematic fitting errors. Our work investigated the accuracy of low SNR R2* measurements. By combining a truncation model with array coil combination methods, we found that SNR-based truncation can be an effective method to reduce measurement error. Given that the SNR threshold providing minimum error in the truncation process may be unknown to us, the optimal B1-weighted combined method is the optimal choice for R2* measurement.