Institute of Biomedical Engineering, Department of Engineering Sciences, University of Oxford, Oxford, UK.
Magn Reson Med. 2022 Oct;88(4):1867-1885. doi: 10.1002/mrm.29315. Epub 2022 Jun 9.
Inducing hyperoxia in tissues is common practice in several areas of research, including oxygen-enhanced MRI (OE-MRI), which attempts to use the resulting signal changes to detect regions of tumor hypoxia or pulmonary disease. The linear relationship between PO and R1 has been reproduced in phantom solutions and body fluids such as vitreous fluid; however, in tissue and blood experiments, factors such as changes in deoxyhemoglobin levels can also affect the ΔR1.
This manuscript proposes a three-compartment model for estimating the hyperoxia-induced changes in R1 of tissues depending on B0, SO , blood volume, hematocrit, oxygen extraction fraction, and changes in blood and tissue PO . The model contains two blood compartments (arterial and venous) and a tissue compartment. This model has been designed to be easy for researchers to tailor to their tissue of interest by substituting their preferred model for tissue oxygen diffusion and consumption. A specific application of the model is demonstrated by calculating the resulting ΔR1 expected in healthy, hypoxic and necrotic tumor tissues. In addition, the effect of sex-based hematocrit differences on ΔR1 is assessed.
The ΔR1 values predicted by the model are consistent with reported literature OE-MRI results: with larger positive changes in the vascular periphery than hypoxic and necrotic regions. The observed sex-based differences in ΔR1 agree with findings by Kindvall et al. suggesting that differences in hematocrit levels may sometimes be a confounding factor in ΔR1.
This model can be used to estimate the expected tissue ΔR1 in oxygen-enhanced MRI experiments.
在多个研究领域，包括氧增强磁共振成像（OE-MRI），诱导组织中的高氧是常见做法，OE-MRI 试图利用由此产生的信号变化来检测肿瘤缺氧或肺部疾病区域。PO 和 R1 之间的线性关系已经在体模溶液和玻璃体等体液中得到重现；然而，在组织和血液实验中，脱氧血红蛋白水平的变化等因素也会影响ΔR1。
本文提出了一个三腔室模型，用于根据 B0、SO 、血容量、血细胞比容、氧提取分数以及血液和组织 PO 的变化来估计组织中高氧诱导的 R1 变化。该模型包含两个血液腔室（动脉和静脉）和一个组织腔室。该模型旨在便于研究人员根据自己感兴趣的组织，用他们首选的组织氧扩散和消耗模型来调整模型。通过计算健康、缺氧和坏死肿瘤组织中预期的 R1ΔR1，展示了模型的具体应用。此外，还评估了性别相关的血细胞比容差异对ΔR1 的影响。
模型预测的 R1ΔR1 值与报告的 OE-MRI 文献结果一致：血管周围的变化幅度较大，呈正性，而缺氧和坏死区域则较小。观察到的 R1ΔR1 性别差异与 Kindvall 等人的发现一致，表明血细胞比容水平的差异有时可能是 R1ΔR1 的一个混杂因素。
该模型可用于估计氧增强 MRI 实验中预期的组织 R1ΔR1 值。
