MAGN FIELD &TISSUE DEPENDENCIES OF HUMAN BRAIN LONGITUDINAL 1H2O RELAX IN VIVO

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 在0.2T、1.0T、1.5T、4.0T和7.0T的磁场强度（B 0）下，测量了3名健康人的脑水质子（1H 2 O）纵向弛豫时间常数（T1）。采用改良的Look-Righting技术，以1.5 mm的平面内分辨率和绝热反转后32个时间点对5 mm的心室中部轴向切片进行采样。结果证实，对于大多数脑组织，T1值在0.2T和7 T之间增加了3倍以上，并且在此范围内，白色物质（WM）、内部GM和血液1H 2 O的T1（s）= 0.583（B 0）0.382、T1（s）=0.857（B 0）0.376和T1（s）=1.35（B 0）0.340拟合良好。脑室脑脊液（CSF）1H 2 O T1值不随B 0变化，受试者和磁场的平均值（标准差（SD））为4.3（+/-0.2）s。在每个领域的组织1/T1值与大分子质量分数，并在较小程度上组织铁含量。1H 2 O T1值的场依赖性增加超过了典型MRI造影剂（CR）弛豫率的众所周知的降低，模拟预测这会导致CR浓度检测阈值随磁场增加而降低。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Brain water proton (1H2O) longitudinal relaxation time constants (T1) were obtained from three healthy individuals at magnetic field strengths (B0) of 0.2 Tesla (T), 1.0T, 1.5T, 4.0T, and 7.0T. A 5-mm midventricular axial slice was sampled using a modified Look-Locker technique with 1.5 mm in-plane resolution, and 32 time points post-adiabatic inversion. The results confirmed that for most brain tissues, T1 values increased by more than a factor of 3 between 0.2T and 7T, and over this range were well fitted by T1 (s)=0.583(B0)0.382, T1(s)=0.857(B0)0.376, and T1(s)=1.35(B0)0.340 for white matter (WM), internal GM, and blood 1H2O, respectively. The ventricular cerebrospinal fluid (CSF) 1H2O T1 value did not change with B0, and its average value (standard deviation (SD)) across subjects and magnetic fields was 4.3 (+/-0.2) s. The tissue 1/T1 values at each field were well correlated with the macromolecular mass fraction, and to a lesser extent tissue iron content. The field-dependent increases in 1H2O T1 values more than offset the well-known decrease in typical MRI contrast reagent (CR) relaxivity, and simulations predict that this leads to lower CR concentration detection thresholds with increased magnetic field.