Double inversion recovery MRI with fat suppression at 7 tesla: Initial experience

Background and Purpose Double Inversion Recovery Magnetic Resonance Imaging (DIR) consists of two adiabatic non-selective inversion pulses applied before a Turbo Spin Echo (TSE) sequence, in order to suppress the signal from two tissues with different longitudinal relaxation times T ₁ simultaneously. In the brain, DIR is used to selectively image the gray matter (GM) by nulling the signal from white matter (WM) and cerebrospinal fluid (CSF). The main limitation of the technique remains the intrinsic low SNR due to the specific preparation of the longitudinal magnetization. The recent availability of high field magnets operating at 7 T for human imaging offers the advantage of higher SNR. This study shows the feasibility of brain Double Inversion Recovery Magnetic Resonance Imaging (DIR-MRI) at 7 T in vivo in healthy volunteers. METHODS The MRI experiments were performed on phantoms at 7 T and on four healthy volunteers at 7 and 3 T. For fat suppression, a chemical shift selective Fat Inversion Recovery (csFatIR) technique was used and compared to the standard fat saturation (FatSat). RESULTS The csFatIR method resulted to be significantly more efficient than the Fatsat at 7 T and slightly more efficient at 3 T, enabling a clear delineation of GM. CONCLUSIONS DIR is feasible at 7 T despite the problems associated with B ₁ in-homogeneity.