Parajuli Raj Kumar, Sano Hiromi, Ueno Megumi, Gao Shan, Suzuki Saaya, Sumiyoshi Akira, Osada Kensuke, Obata Takayuki, Aoki Ichio, Matsumoto Ken-Ichiro
Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology (QST), Chiba, Japan.
Sydney Imaging Core Research Facility, The University of Sydney, Sydney, New South Wales, Australia.
NMR Biomed. 2025 Sep;38(9):e70104. doi: 10.1002/nbm.70104.
A noninvasive method to estimate oxygenation and oxygen (O) consumption rates in mouse brain tissue based on T-weighted tissue oxygen level-dependent (TOLD) MRI was developed. The aim of the present study was to estimate the kinetics of O in tissue in order to facilitate the planning of radiation therapy. The relationship between the proton T relaxation rate and O concentrations was examined in water and corn oil samples, which are models of the aqueous and lipidic phases of cell components. T maps of the mouse brain were obtained under breathing high oxygen concentration gas, carbogen (95% O + 5% CO), or 100% O, and shifts in the concentration of O from the physiological state in the brain were then estimated. Pseudo-TOLD signals in blood samples, hemoglobin, and myoglobin aqueous solutions under oxygenation were measured to examine the effects of heme iron on T. O metabolism in mouse brains was evaluated by the enhancement/diminishment rates of the TOLD signal when the breathing gas was switched from air to carbogen or 100% O and when it was switched back to air. Carbogen or 100% O inhalation increased cortical O levels by 0.28 or 0.26 mmol/L, respectively. By analyzing the time course profile of the TOLD signal, the oxygenation rate, oxygenation level, and O consumption rate were successfully estimated. TOLD MRI has potential as a useful tool to estimate the quantitative indices of oxygenation and O consumption rates in brain tissue.
开发了一种基于T加权组织氧水平依赖（TOLD）磁共振成像（MRI）来估计小鼠脑组织氧合和氧（O）消耗率的非侵入性方法。本研究的目的是估计组织中O的动力学，以便于放射治疗的规划。在水和玉米油样品中研究了质子T弛豫率与O浓度之间的关系，水和玉米油样品分别是细胞成分水相和脂质相的模型。在小鼠呼吸高氧浓度气体、卡波金（95%O₂+5%CO₂）或100%O₂的情况下获得小鼠脑的T图，然后估计脑中O浓度相对于生理状态的变化。测量了氧合状态下血样、血红蛋白和肌红蛋白水溶液中的伪TOLD信号，以研究血红素铁对T的影响。当呼吸气体从空气切换到卡波金或100%O₂以及再切换回空气时，通过TOLD信号的增强/减弱率评估小鼠脑中的O代谢。吸入卡波金或100%O₂分别使皮质O水平升高0.28或0.26 mmol/L。通过分析TOLD信号的时间进程曲线，成功估计了氧合率、氧合水平和O消耗率。TOLD MRI有潜力作为一种有用的工具来估计脑组织中氧合和O消耗率的定量指标。
