7T 磁共振波谱成像在多发性硬化中的应用：空间分辨率如何影响脑病变代谢变化的检测能力？
7 T Magnetic Resonance Spectroscopic Imaging in Multiple Sclerosis: How Does Spatial Resolution Affect the Detectability of Metabolic Changes in Brain Lesions?
机构信息
Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Russell H. Morgan Department of Radiology and Radiological Science, The John Hopkins University School of Medicine, Baltimore, MD.
出版信息
Invest Radiol. 2019 Apr;54(4):247-254. doi: 10.1097/RLI.0000000000000531.
OBJECTIVES
The aim of this study was to assess the utility of increased spatial resolution of magnetic resonance spectroscopic imaging (MRSI) at 7 T for the detection of neurochemical changes in multiple sclerosis (MS)-related brain lesions.
MATERIALS AND METHODS
This prospective, institutional review board-approved study was performed in 20 relapsing-remitting MS patients (9 women/11 men; mean age ± standard deviation, 30.8 ± 7.7 years) after receiving written informed consent. Metabolic patterns in MS lesions were compared at 3 different spatial resolutions of free induction decay MRSI with implemented parallel imaging acceleration: 2.2 × 2.2 × 8 mm; 3.4 × 3.4 × 8 mm; and 6.8 × 6.8 × 8 mm voxel volumes, that is, matrix sizes of 100 × 100, 64 × 64, and 32 × 32, respectively. The quality of data was assessed by signal-to-noise ratio and Cramér-Rao lower bounds. Statistical analysis was performed using Wilcoxon signed-rank tests with correction for multiple testing.
RESULTS
Seventy-seven T2-hyperintense MS lesions were investigated (median volume, 155.7 mm; range, 10.8-747.0 mm). The mean metabolic ratios in lesions differed significantly between the 3 MRSI resolutions (ie, 100 × 100 vs 64 × 64, 100 × 100 vs 32 × 32, and 64 × 64 vs 32 × 32; P < 0.001). With the ultra-high resolution (100 × 100), we obtained 40% to 80% higher mean metabolic ratios and 100% to 150% increase in maximum metabolic ratios in the MS lesions compared with the lowest resolution (32 × 32), while maintaining good spectral quality (signal-to-noise ratio >12, Cramér-Rao lower bounds <20%) and measurement time of 6 minutes. There were 83% of MS lesions that showed increased myo-inositol/N-acetylaspartate with the 100 × 100 resolution, but only 66% were distinguishable with the 64 × 64 resolution and 35% with the 32 × 32 resolution.
CONCLUSIONS
Ultra-high-resolution MRSI (~2 × 2 × 8 mm voxel volume) can detect metabolic alterations in MS, which cannot be recognized by conventional MRSI resolutions, within clinically acceptable time.
目的
本研究旨在评估磁共振波谱成像（MRSI）在 7T 下空间分辨率增加对多发性硬化症（MS）相关脑病变中神经化学变化的检测能力。
材料与方法
这项前瞻性的机构审查委员会批准的研究纳入了 20 例接受书面知情同意的复发缓解型 MS 患者（9 名女性/11 名男性；平均年龄±标准差，30.8±7.7 岁）。在不同的空间分辨率下，对 MRSI 中的代谢模式进行比较，采用自由感应衰减 MRSI 与实施的并行成像加速相结合：2.2×2.2×8mm；3.4×3.4×8mm；6.8×6.8×8mm 体素体积，即矩阵大小分别为 100×100、64×64 和 32×32。通过信噪比和克拉默-劳下限评估数据质量。采用校正多重检验的 Wilcoxon 符号秩检验进行统计分析。
结果
共检测到 77 个 T2 高信号 MS 病变（中位数体积为 155.7mm；范围 10.8-747.0mm）。3 种 MRSI 分辨率之间的病变代谢比值差异有统计学意义（即 100×100 与 64×64、100×100 与 32×32、64×64 与 32×32；P＜0.001）。与最低分辨率（32×32）相比，超高分辨率（100×100）获得的 MS 病变的平均代谢比值提高了 40%至 80%，最大代谢比值增加了 100%至 150%，而保持了良好的光谱质量（信噪比＞12，克拉默-劳下限＜20%）和 6 分钟的测量时间。83%的 MS 病变在 100×100 分辨率下显示肌醇/N-乙酰天冬氨酸升高，但在 64×64 分辨率下仅 66%的病变可分辨，在 32×32 分辨率下仅 35%的病变可分辨。
结论
超高分辨率 MRSI（~2×2×8mm 体素体积）可在临床可接受的时间内检测到 MS 中的代谢改变，而常规 MRSI 分辨率无法识别这些改变。
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