INTERSTITIAL RADIOTHERAPY FOR BRAIN TUMORS USING THREE-DIMENSIONAL MRI

Between 1990 and 1994, 7 patients with brain tumors were treated by interstitial brachytherapy at the Ryukyus University Hospital. We used 198Au grains that were attached to a plastic tube, either spaced or contiguously according to localization of the tumor relative to the radioactive sources. This technique is demonstrated by presenting a typical case. Pretreatment three-dimensional (3D) MR images were obtained using spoiled gradient-recalled acquisition in the steady state (spoiled GRASS). After data acquisition, respective slices along and perpendicular to the interstitial applicator were reconstructed. Determination of optimal grains placement was based on information from the provisional dose distributions made by the radiation treatment planning system. 3D MRI can detect tumor extent more clearly than is possible with CT images and reformat data in any orientation. Furthermore, compared with our previous technique, the use of 3D MRI results in easier management. Although there is a problem of geometric distortion in MR images, 3D MRI may be useful in the planning of interstitial radiotherapy for brain tumors.