Diffusion-tensor imaging tractography of the corticospinal tract for evaluation of motor fiber tract radiation exposure in gamma knife® radiosurgery treatment planning.

Aims: To assess the feasibility of diffusion-tensor imaging (DTI) fiber tractography of the corticospinal tract (CST) performed with 3 T MRI as a tool for Gamma Knife® radiosurgery (GKS) treatment planning. Methods: 15 patients with brain arteriovenous malformationsor intra-axial lesions undergoing radiosurgery were studied at 3 T to obtain DTI and at 1 T to obtain stereotactic three-dimensional (3D) imaging. 3D corticospinal tractography was fused on 3D T1-weighted stereotactic volumetric study. After superimposition of the radiosurgical isodose line on the registered images, the maximum dose to the CST and the volumes of the CST receiving ≥20 and ≥25 Gy were calculated.Results: DTI clearly visualized fibers of CST in 13 out of 15 patients. The mean maximum dose to the reconstructed CST was 21.5 Gy. The mean volume of the CST receiving ≥20 Gy was 95 mm3. The mean volume of the CST receiving ≥25 Gy was 32 mm3. In 4 cases, data integration of tractography was used during treatment planning. Conclusion: Integration of tractography within GKS planning is feasible within a routine clinical setting. Data obtained could be used to develop models predicting the development of complications and to optimize radiosurgical treatment planning.