Combined use of tractography and Gamma Knife radiosurgery three dimensional treatment planning Initial experience

The aim of this study is to evaluate the feasibility of image fusion between Diffusion Tensor Imaging (DTI) and pre-radiosurgery stereotactic imaging to avoid radiation induced damage to motor fibers, 8 patients were studied. Seven patients were affected by arteriovenous malformations while the eighth had a solitary metastasis. Anatomical areas involved are: thalamic-mesencephalic region (6patients) and motor cortex (2 patients). The day before radiosurgery we acquired a diffusion weighted single-shot gradient echo volumetric data set; after appropriate filtering to reduce mismatching, voxel based fractional anisotropy was calculated in order to obtain the fiber tracks. MR imaging was then performed under stereotactic conditions; registration and intersection of tracked fibers on images acquired under stereotactic conditions were performed. Superimposition of extracted fibers on the study acquired under stereotactic conditions to perform treatment planning improved calculation of the exact amount of radiations involving piramidal tracts or a specific portion of them. Because of it's non invasiveness and short time of acquisition and post-processing this technique could be easily introduced in standard stereotactic radiosurgical treatments planning.