[en] Purpose: To evaluate the ability of MRI during intracavitary brachytherapy to visualize the tumor extension in relationship to the intracavitary applicator and to compare the actual dose distribution in the Gross Tumor Volume (GTV) as identified on the MRI with the prescribed dose in 'Manchester' point A. Methods and Materials: In 7 patients with cervical cancer stage Ib (n = 2) and IIb (n = 5), both CT and MRI were performed during intracavitary brachytherapy, using a CT-MRI compatible gynaecological applicator. The GTV was drawn on the MRI and subsequently matched in 3-D with the CT-scan using chamfer matching. Isodose distributions were calculated and displayed on the CT-scan. Dose-volume histograms of GTVs as identified on the MRI were obtained and compared with the prescribed dose in point A. Results: Although delineation of the macroscopic tumor on the MRI was possible in all 7 patients, the tumor was better visible in the 2 patients who had brachytherapy after 10 Gy external radiation than in the 5 patients who had brachytherapy after 46 Gy. The GTV varied from 8 cm³ to 44 cm³ with a mean of 22 cm³. In all 7 cases the 'treated volume' (volume encompassed by the reference isodose surface) was considerably larger than the GTV ranging from 95 cm³ to 122 cm³ with a mean of 101 cm³. However, only in 3 patients the reference isodose surface fully covered the GTV. The minimum tumor dose in these patients was 100%, 131% and 136% of the reference dose in point A. In the other 4 patients the percentage of the GTV receiving a dose equal to or higher than the reference dose was 58%, 91%, 98% and 98%. The minimum dose in the GTV in these patients was 44%, 49%, 85% and 91% of the prescribed dose respectively. Conclusion: Using a CT-MRI compatible applicator artefact-free MR images can be obtained during intracavitary brachytherapy allowing good visualization of the tumor. In many patients there is a large discrepancy between the prescribed dose in point A and the actual dose in the GTV as identified on MRI. On average the 'treated volume' is about 5 times as large as the GTV. Work to further evaluate MRI as a tool to optimize and individualize the treatment is ongoing