UTE imaging with simultaneous water and fat signal suppression using a time-efficient multispoke inversion recovery pulse sequence

Abstract

Purpose The long repetition time and inversion time with inversion recovery preparation ultrashort echo (UTE) often causes prohibitively long scan times. We present an optimized method for long T2 signal suppression in which several k-space spokes are acquired after each inversion preparation. Theory and Methods Using Bloch equations the sequence parameters such as TI and flip angle were optimized to suppress the long T2 fat and water signals and to maximize short T2 contrast. Volunteer imaging was performed on a healthy male volunteer. Inversion recovery preparation was performed using a Silver-Hoult adiabatic inversion pulses together with a three-dimensional (3D) UTE (3D Cones) acquisition. Results The theoretical signal curves generally agreed with the experimentally measured region of interest curves. The multispoke inversion recovery method showed good muscle and fatty bone marrow suppression, and highlighted short T2 signals such as these from the femoral and tibial cortex. Conclusion Inversion recovery 3D UTE imaging with multiple spoke acquisitions can be used to effectively suppress long T2 signals and highlight short T2 signals within clinical scan times. Theoretical modeling can be used to determine sequence parameters to optimize long T2 signal suppression and maximize short T2 signals. Experimental results on a volunteer confirmed the theoretical predictions.

Three-dimensional adiabatic inversion recovery prepared ultrashort echo time cones (3D IR-UTE-Cones) imaging of cortical bone in the hip

“…The UTE and IR-UTE sequences can potentially evaluate cortical porosity (pore water content) and organic matrix (bound water content) in the hip [27,33,[37][38][39][40][41]. Previous studies employing the UTE sequence have shown that both bound water (short T 2 ⁎ component) and pore water (long T 2 ⁎ component) in cortical bone can be quantified using a bi-component T 2 ⁎ analysis technique [18,[25][26][27][28].…”

“…Previous studies employing the UTE sequence have shown that both bound water (short T 2 ⁎ component) and pore water (long T 2 ⁎ component) in cortical bone can be quantified using a bi-component T 2 ⁎ analysis technique [18,[25][26][27][28]. Moreover, T 2 ⁎ decay time for bound water in cortical bone can be measured with the IR-UTE technique by suppressing the signal from the pore water and then using a single component analysis of the remaining signal [27,29,38]. A single component decay pattern of the cortical bone in the hip suggests that the 3D IR-UTE-Cones signal is likely from bound water.…”

“…When followed by an adiabatic inversion recovery preparation pulse, the 3D UTE-Cones sequence can be utilized to acquire signal from cortical bone with high contrast [27,28]. This is done by inverting the longitudinal magnetization of the long T 2 signal components (i.e., muscle and bone marrow fat) while saturating the signal from cortical bone [27][28][29][30][31].…”

“…This is done by inverting the longitudinal magnetization of the long T 2 signal components (i.e., muscle and bone marrow fat) while saturating the signal from cortical bone [27][28][29][30][31]. The Cones acquisition starts after an inversion time (TI) delay, which is used to null the long T 2 ⁎ components while permitting detection of recovered cortical bone signal (Fig.…”

“…The 3D IR-UTE-Cones sequence was implemented on a 3 T scanner (Signa HDx, GE Healthcare, Milwaukee, WI) [27]. The sequence has a minimal TE of 32 μs and allows anisotropic field of view and spatial resolution for fast volumetric imaging.…”