Applied Clinical Study on Hyperpolarized Noble Gas MRI/MRS using Pathologic Model Animal

对国产偏光装置进行了改造，使之能提供连续的Xe气体偏振到3-5%。在麻醉和自主呼吸条件下，对小鼠施加偏振Xe气体，并对肺和脑进行MRI和MRS测量。主要结果如下：1.在小鼠肺Xe-129MRS实验中，发现Xe自旋从肺组织溶解状态向肺泡气体状态的反向扩散影响了洗涤曲线的斜率。通过使溶解的自旋饱和来消除这种影响，测量了冲刷曲线的真实斜率。2.将影响冲刷曲线斜率的因素分为三个项，分别给出了脉冲角、通气量和表观松弛时间。3.对小鼠脑组织的洗脱曲线进行了精确化分析，得到了脑组织的真松弛时间。4.以VILI(呼吸机诱导肺损伤)小鼠为模型，分析了肺洗脱曲线的斜率。与健康小鼠相比，VILI小鼠的斜率被发现延迟，这表明病理肺的换气缓慢。

Home-built polarizing apparatus has been modified to supply continuous flow of Xe gas polarized to 3-5%. The polarized Xe gas was applied to mice under anesthesia and spontaneous respiration, and MRI and MRS measurements were performed with lung and brain. The results are summarized as follows :1.In the Xe-129 MRS experiments with mice lungs, diffusion of Xe spins backward from the dissolved state in lung tissue to alveolar gas state was found to affect the slope in washout curve. The true slope of the washout curve was measured by removing this effect by saturating the dissolved spins.2.The factors affecting the slope of the washout curve was separated into three terms, which afforded pulse angle, ventilation volume, and apparent relaxation time. The separation of the true relaxation term and the perfusion term is now underway.3.Precise analysis of the washout curve in mouse brain was performed and the value of true relaxation time in brain tissue was obtained.4.The slope in the lung washout curve was analyzed with the VILI(Ventilator Induced Lung Injury) mice. The slope was found to be retarded with the VILI mice compared with the healthy ones, suggesting slow ventilation in the pathologic lungs.