Quantitative OEF Determination by Separate T2 and T2* Mapping

measurement of oxygenation is of great interest, because tumor oxygenation is an indicator of aggressiveness and affinity to metastazation [1]. Moreover, the chance of success of a radiation therapy or chemo therapy depends on the oxygen partial pressure of the tumorous tissue [2]. That is the reason why hypoxia is a large obstacle to tumor therapy [3]. In this study, a model of static dephasing magnetization [4] can be used to measure the oxygen extraction fraction (OEF) by using a gradient echo sampled spin echo (GESSE) sequence. This model has already been tested with promising results [5,6]. A disadvantage of this technique is, that the reversible relaxation rate R2’, the irreversible relaxation rate R2 and the deoxygenated blood volume λ are determined simultaneously with one fit. This results in an uncertainty of the fitted parameters. Here, the parameters R2 and R2* are determined independently by separate measurements, resulting in much more stable fit parameters. Quantitative OEF Determination by Separate T2 and T2* Mapping