Brain short T component imaging using double adiabatic inversion recovery prepared ultrashort Echo time (DIR-UTE) sequence.

Short T components in the brain are uniquely associated with myelin structure, but direct MR imaging is challenging due to their relatively short T values and low proton density compared to long T water. This study introduces a novel 3D double adiabatic inversion recovery-prepared ultrashort echo time (DIR-UTE) sequence for selective whole-brain imaging of short T components. The sequence employs two identical adiabatic inversion pulses with optimized inversion times (TIs) to suppress long T signals, followed by a 3D UTE acquisition to capture rapidly decaying signals. Technical feasibility was evaluated using phantoms, six healthy volunteers, and five patients with multiple sclerosis (MS) on a 3T MRI scanner. Short T proton fraction (SPF) was measured in white matter, gray matter, MS lesions, and across the whole brain to assess differences in myelin content. Phantom studies confirmed effective suppression of long T signals over a wide range of T values. In healthy volunteers, DIR-UTE selectively captured short T signals, with an estimated T* of 0.21±0.01 ms in white matter. SPF in normal white matter (5.12±0.57 %) was significantly higher than in normal-appearing white matter (4.06±0.61 %, P < 0.0001) and MS lesions (2.76±0.78 %, P < 0.0001). Similar trends were observed in gray matter. Whole-brain analysis also showed lower average SPF in MS patients (3.42±0.38 %) compared to healthy controls (4.01±0.35 %, P < 0.0001). These results demonstrate the DIR-UTE sequence's ability to suppress long T signals and selectively image short T components, with SPF emerging as a potential biomarker for demyelinating diseases like MS.