Simultaneous fat saturation and magnetization transfer contrast imaging with steady‐state incoherent sequences

Abstract

Purpose This work combines an n-dimensional (nD) fat sat(uration) RF pulse with steady-state incoherent (SSI) pulse sequences, e.g., spoiled Gradient echo sequence, to simultaneously produce B0 insensitive fat suppression and magnetization transfer (MT) contrast. This pulse is then referred to as ”fat sat and MT contrast pulse” (FSMT-pulse). Theory We discuss the features of the FSMT-pulse and the MT sensitivities of the SSI sequences when combining with fat sat. Moreover, we also introduce an adapted RF spoiling scheme for SSI sequences with fat sat. Methods Simulations and phantom experiments were conducted to demonstrate the adapted RF spoiling. Fat suppression and MT effects are shown in 3T phantom experiments and in-vivo experiments, including brain imaging, cartilage imaging and angiography. Results To ensure that the sequence reaches steady state, the adapted RF spoiling is required for fat-sat SSI sequences. FSMT-pulse works robustly with field inhomogeneity and also produces MT contrasts. Conclusion SSI sequences with FSMT-pulse and adapted RF spoiling can robustly produce fat suppressed and MT contrast images in the presence of field inhomogeneity.

The physical mechanism of “inhomogeneous” magnetization transfer MRI

“…(15) showing that it is applicable to any dipolar-coupled lineshape. [4,[38][39][40]. A 63 mg sample of curly, black human hair was obtained 10-20 cm from the scalp.…”

Joint Design of Excitation k-Space Trajectory and RF Pulse for Small-Tip 3D Tailored Excitation in MRI

“…Spatially tailored RF excitation has a range of applications in MRI, including B1 shimming [1]–[6], reduced FOV excitation [7]–[13], susceptibility artifact correction [14]–[18], and fat suppression [19], [20]. The task of designing time-varying RF and gradient waveforms for a desired target excitation pattern poses a non-linear, non-convex, constrained optimization problem with relatively large problem size that is difficult to solve directly.…”

Chemical Shift magnetization transfer magnetic resonance imaging

“…For in vivo applications, it may be necessary to consider evaluation of only those voxels above a threshold water fraction level to avoid inaccuracies and associated misinterpretation. Third, recent studies have demonstrated the potential to use fat saturation pulses less sensitive to B 0 and B 1 heterogeneity to produce fat-suppressed MT contrast images (37,38). Additional future studies will be valuable for rigorous comparison of these fat-suppression-based MT methods to our proposed CSMT approaches for quantitative MTR measurements.…”