F-19 MRI oximetry: simulation of perfluorocarbon distribution impact

In ¹⁹F MRI oximetry, a method used to image tumour hypoxia, perfluorocarbons serve as oxygenation markers. The goal of this study is to evaluate the impact of perfluorocarbon distribution and concentration in ¹⁹F MRI oximetry through a computer simulation. The simulation studies the correspondence between ¹⁹F measured (pO ^FNMR₂) and actual tissue oxygen tension (pO₂) for several tissue perfluorocarbon distributions. For this, a Krogh tissue model is implemented which incorporates the presence of perfluorocarbons in blood and tissue. That is, in tissue the perfluorocarbons are distributed homogeneously according to Gaussian diffusion profiles, or the perfluorocarbons are concentrated in the capillary wall. Using these distributions, the oxygen tension in the simulation volume is calculated. The simulated mean oxygen tension is then compared with pO^FNMR₂, the ¹⁹F MRI-based measure of pO₂ and with pO⁰₂, pO ₂ in the absence of perfluorocarbons. The agreement between pO ^FNMR₂ and actual pO₂ is influenced by vascular density and perfluorocarbon distribution. The presence of perfluorocarbons generally gives rise to a pO₂ increase in tissue. This effect is enhanced when perfluorocarbons are also present in blood. Only the homogeneous perfluorocarbon distribution in tissue with no perfluorocarbons in blood guarantees small deviations of pO^FNMR₂ from pO ₂. Hence, perfluorocarbon distribution in tissue and blood has a serious impact on the reliability of ¹⁹F MRI-based measures of oxygen tension. In addition, the presence of perfluorocarbons influences the actual oxygen tension. This finding may be of great importance for further development of ¹⁹F MRI oximetry.