Several MR methods have been proposed over the last decade to obtain quantitative estimates of the tissue blood oxygen saturation (StO2) using a quantification of the blood oxygen level dependent effect. These approaches are all based on mathematical models describing the time evolution of the MR signal in biological tissues in the presence of magnetic field inhomogeneities. Although the experimental results are very encouraging, possible biases induced by the model assumptions have not been extensively studied. In this study, a numerical approach was used to examine the influence on T2*, blood volume fraction, and StO2 estimates of possible confounding factors such as water diffusion, intravascular signal, and presence of arterial blood in the voxel. To evaluate the impact of the vessel geometry, straight cylinders and realistic data from two‐photon microscopy for microvascular geometry were compared. Our results indicate that the models are sufficiently realistic, based on a good correlation between ground truth and MR estimates of StO2. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.

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High-dose progestin therapy can be an effective conservative treatment in young patients with well-differentiated early-stage endometrial cancer. If patients wish to preserve their fertility even after they have completed childbearing, maintenance therapy with a cyclic oral contraceptive or a progestin-releasing intrauterine device may be an option to prevent recurrence.