Brain Short T2 Component Imaging using Double Adiabatic Inversion Recovery Prepared Ultrashort Echo Time (DIR-UTE) Sequence.

Journal: NeuroImage
Published:
Abstract

Short T2 components in the brain are uniquely associated with myelin structure, but direct MR imaging is challenging due to their relatively short T2 values and low proton density compared to long T2 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 T2 components. The sequence employs two identical adiabatic inversion pulses with optimized inversion times (TIs) to suppress long T2 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 T2 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 T2 signals over a wide range of T1 values. In healthy volunteers, DIR-UTE selectively captured short T2 signals, with an estimated T2* 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 T2 signals and selectively image short T2 components, with SPF emerging as a potential biomarker for demyelinating diseases like MS.

Authors
Jiyo Athertya, Mahyar Daskareh, Soo Shin, Jiaji Wang, James Lo, Yajun Ma
Relevant Conditions

Multiple Sclerosis (MS)