Athertya Jiyo S, Daskareh Mahyar, Shin Soo Hyun, Wang Jiaji, Lo James, Ma Yajun
Department of Radiology, University of California San Diego, CA, USA.
Department of Radiology, University of California San Diego, CA, USA.
Neuroimage. 2025 Aug 1;316:121315. doi: 10.1016/j.neuroimage.2025.121315. Epub 2025 Jun 6.
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.
大脑中的短T成分与髓鞘结构独特相关，但由于其T值相对较短且与长T水相比质子密度较低，直接进行磁共振成像具有挑战性。本研究引入了一种新颖的3D双绝热反转恢复准备的超短回波时间（DIR-UTE）序列，用于对短T成分进行选择性全脑成像。该序列采用两个具有优化反转时间（TIs）的相同绝热反转脉冲来抑制长T信号，随后进行3D UTE采集以捕获快速衰减的信号。在3T磁共振成像扫描仪上使用体模、6名健康志愿者和5名多发性硬化症（MS）患者评估了技术可行性。在白质、灰质、MS病变以及全脑范围内测量短T质子分数（SPF），以评估髓鞘含量的差异。体模研究证实了在广泛的T值范围内对长T信号的有效抑制。在健康志愿者中，DIR-UTE选择性地捕获了短T信号，白质中估计的T*为0.21±0.01毫秒。正常白质中的SPF（5.12±0.57%）显著高于正常外观白质（4.06±0.61%，P<0.0001）和MS病变（2.76±0.78%，P<0.0001）。在灰质中也观察到了类似趋势。全脑分析还显示，与健康对照组（4.01±0.35%，P<0.0001）相比，MS患者的平均SPF较低（3.42±0.38%）。这些结果证明了DIR-UTE序列抑制长T信号并选择性成像短T成分的能力，SPF成为MS等脱髓鞘疾病的潜在生物标志物。
