Contribution of magnetique resonance imaging (MRI) in dosimetry of gynaecological brachytherapy, a study of 32 patients

In gynaecological brachytherapy, one major obstacle is the difficulty of specifying volume and dose. The purpose of this study was to evaluate the contribution of magnetic resonance imaging (MRI) in dosimetry. 32 patients were studied. We have shown an excellent quality of tumour imaging with applicator inserted. No distortion phenomenon was observed in T2 images. MRI provided a precise determination of the anatomic relationships between tumours extension, sources and critical organs. The comparison of 60 Gy RIS and MRI tumour volume (29 patients) showed in 12 patients an underdosage of 5 to 60% of the tumour volume; 7 of them underwent a secondary surgery, 6 had a persistent tumour and 3 experienced a local recurrence. No residual tumour was found and no recurrence occurred in the 17 other patients. The percentage of tumour volume underdosed was the sole factor predictive of residual tumor and recurrence.