Kirov Ivan I, Wu William E, Soher Brian J, Davitz Matthew S, Huang Jeffrey H, Babb James S, Lazar Mariana, Fatterpekar Girish, Gonen Oded
Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, New York, USA.
Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA.
NMR Biomed. 2017 Oct;30(10). doi: 10.1002/nbm.3754. Epub 2017 Jul 5.
Total N-acetyl-aspartate + N-acetyl-aspartate-glutamate (NAA), total creatine (Cr) and total choline (Cho) proton MRS ( H-MRS) signals are often used as surrogate markers in diffuse neurological pathologies, but spatial coverage of this methodology is limited to 1%-65% of the brain. Here we wish to demonstrate that non-localized, whole-head (WH) H-MRS captures just the brain's contribution to the Cho and Cr signals, ignoring all other compartments. Towards this end, 27 young healthy adults (18 men, 9 women), 29.9 ± 8.5 years old, were recruited and underwent T -weighted MRI for tissue segmentation, non-localizing, approximately 3 min WH H-MRS (T /T /T = 5/10/940 ms) and 30 min H-MR spectroscopic imaging (MRSI) (T /T = 35/2100 ms) in a 360 cm volume of interest (VOI) at the brain's center. The VOI absolute NAA, Cr and Cho concentrations, 7.7 ± 0.5, 5.5 ± 0.4 and 1.3 ± 0.2 mM, were all within 10% of the WH: 8.6 ± 1.1, 6.0 ± 1.0 and 1.3 ± 0.2 mM. The mean NAA/Cr and NAA/Cho ratios in the WH were only slightly higher than the "brain-only" VOI: 1.5 versus 1.4 (7%) and 6.6 versus 5.9 (11%); Cho/Cr were not different. The brain/WH volume ratio was 0.31 ± 0.03 (brain ≈ 30% of WH volume). Air-tissue susceptibility-driven local magnetic field changes going from the brain outwards showed sharp gradients of more than 100 Hz/cm (1 ppm/cm), explaining the skull's Cr and Cho signal losses through resonance shifts, line broadening and destructive interference. The similarity of non-localized WH and localized VOI NAA, Cr and Cho concentrations and their ratios suggests that their signals originate predominantly from the brain. Therefore, the fast, comprehensive WH- H-MRS method may facilitate quantification of these metabolites, which are common surrogate markers in neurological disorders.
总 N - 乙酰天门冬氨酸 + N - 乙酰天门冬氨酸 - 谷氨酸（NAA）、总肌酸（Cr）和总胆碱（Cho）的质子磁共振波谱（¹H - MRS）信号常被用作弥漫性神经病理学中的替代标志物，但该方法的空间覆盖范围仅限于大脑的 1% - 65%。在此，我们希望证明非定位的全脑（WH）¹H - MRS 仅捕捉大脑对 Cho 和 Cr 信号的贡献，忽略所有其他部分。为此，招募了 27 名健康年轻成年人（18 名男性，9 名女性），年龄 29.9 ± 8.5 岁，他们接受了 T₂加权磁共振成像用于组织分割、非定位的约 3 分钟全脑¹H - MRS（T₁/T₂/T₃ = 5/10/940 ms）以及在大脑中心 360 cm³感兴趣容积（VOI）内进行的 30 分钟¹H - 磁共振波谱成像（MRSI）（T₁/T₂ = 35/2100 ms）。VOI 中 NAA、Cr 和 Cho 的绝对浓度分别为 7.7 ± 0.5、5.5 ± 0.4 和 1.3 ± 0.2 mM，均在全脑浓度的 10%以内：全脑浓度分别为 8.6 ± 1.1、6.0 ± 1.0 和 1.3 ± 0.2 mM。全脑中 NAA/Cr 和 NAA/Cho 的平均比值仅略高于“仅大脑”VOI 的比值：分别为 1.5 对 1.4（7%）和 6.6 对 5.9（11%）；Cho/Cr 无差异。大脑/全脑体积比为 0.31 ± 0.03（大脑约占全脑体积的 30%）。从大脑向外的空气 - 组织磁化率驱动的局部磁场变化显示出超过 100 Hz/cm（1 ppm/cm）的陡峭梯度，这解释了颅骨通过共振偏移、线宽展宽和相消干涉导致的 Cr 和 Cho 信号损失。非定位全脑和定位 VOI 的 NAA、Cr 和 Cho 浓度及其比值的相似性表明它们的信号主要源自大脑。因此，快速、全面的全脑¹H - MRS 方法可能有助于对这些代谢物进行定量，这些代谢物是神经疾病中常见的替代标志物。
