Harms W et al from Germany studied the fusion of CT and MRI images from sixteen patients who were treated by interstitial (n=12) and endocavitary (n=4) brachytherapy for recurrent cervix, head and neck, sarcoma and vulva carcinoma. They compared conventional 3D-brachytherapy planning based on CT-information alone to brachytherapy planning based on fused CT and MRI data. They measured the accuracy of image fusion using predefined corresponding landmarks in the CT and MRI data. They found that an automated algorithm was robust and reliable (mean registration error 1.8 mm, range 0.8-4.1 mm, SD 0.9 mm); tumor visualization was difficult using CT alone; and brachytherapy treatment planning based on fused CT and MRI data enabled better definition of target volume and critical structures as compared to treatment planning based on CT alone.