Imaging sequence for joint myocardial T mapping and fat/water separation.

Purpose: To develop and evaluate an imaging sequence to simultaneously quantify the epicardial fat volume and myocardial T relaxation time.

Methods: We introduced a novel simultaneous myocardial T mapping and fat/water separation sequence (joint T -fat/water separation). Dixon reconstruction is performed on a dual-echo data set to generate water/fat images. T maps are computed using the water images, whereas the epicardial fat volume is calculated from the fat images. A phantom experiment using vials with different T /T values and a bottle of oil was performed. Additional phantom experiment using vials of mixed fat/water was performed to show the potential of this sequence to mitigate the effect of intravoxel fat on estimated T maps. In vivo evaluation was performed in 17 subjects. Epicardial fat volume, native myocardial T measurements and precision were compared among slice-interleaved T mapping, Dixon, and the proposed sequence.

Results: In the first phantom, the proposed sequence separated oil from water vials and there were no differences in T of the fat-free vials (P = .1). In the second phantom, the T error decreased from 22%, 36%, 57%, and 73% to 8%, 9%, 16%, and 26%, respectively. In vivo there was no difference between myocardial T values (1067 ± 17 ms versus 1077 ± 24 ms, P = .6). The epicardial fat volume was similar for both sequences (54.3 ± 33 cm versus 52.4 ± 32 cm , P = .8).

Conclusion: The proposed sequence provides simultaneous quantification of native myocardial T and epicardial fat volume. This will eliminate the need for an additional sequence in the cardiac imaging protocol if both measurements are clinically indicated.