Improved quantitative myocardial T 2 mapping: Impact of the fitting model

Purpose To develop an improved T 2 prepared (T 2 prep) balanced steady‐state free‐precession (bSSFP) sequence and signal relaxation curve fitting method for myocardial T 2 mapping. Methods Myocardial T 2 mapping is commonly performed by acquisition of multiple T 2 prep bSSFP images and estimating the voxel‐wise T 2 values using a two‐parameter fit for relaxation. However, a two‐parameter fit model does not take into account the effect of imaging pulses in a bSSFP sequence or other imperfections in T 2 prep RF pulses, which may decrease the robustness of T 2 mapping. Therefore, we propose a novel T 2 mapping sequence that incorporates an additional image acquired with saturation preparation, simulating a very long T 2 prep echo time. This enables the robust estimation of T 2 maps using a 3‐parameter fit model, which captures the effect of imaging pulses and other imperfections. Phantom imaging is performed to compare the T 2 maps generated using the proposed 3‐parameter model with the conventional two‐parameter model, as well as a spin echo reference. In vivo imaging is performed on eight healthy subjects to compare the different fitting models. Results Phantom and in vivo data show that the T 2 values generated by the proposed 3‐parameter model fitting do not change with different choices of the T 2 prep echo times, and are not statistically different than the reference values for the phantom ( P  = 0.10 with three T 2 prep echoes). The two‐parameter model exhibits dependence on the choice of T 2 prep echo times and are significantly different than the reference values ( P  = 0.01 with three T 2 prep echoes). Conclusion The proposed imaging sequence in combination with a three‐parameter model allows accurate measurement of myocardial T 2 values, which is independent of number and duration of T 2 prep echo times. Magn Reson Med 74:93–105, 2015. © 2014 Wiley Periodicals, Inc.