Neural pathway-guided radiosurgery: A systematic review and meta-analysis of diffusion tensor imaging applications in...

Diffusion tensor imaging (DTI) has increasingly been incorporated into stereotactic radiosurgery (SRS) to improve visualization of eloquent neural pathways and to evaluate treatment-related microstructural changes. However, its roles in tractography-guided treatment planning, dosimetric optimization, clinical outcomes, and prognostication have not been systematically characterized across intracranial SRS applications. A systematic review was conducted according to PRISMA 2020 guidelines and registered in PROSPERO (CRD420261349539). MEDLINE/PubMed, Scopus, Web of Science, and the Cochrane Library were searched, without date restriction, for studies evaluating diffusion MRI or tractography in intracranial SRS. Two reviewers independently screened studies, extracted data, and assessed risk of bias using the Newcastle-Ottawa Scale where applicable. Random-effects meta-analysis was performed when 3 or more studies reported comparable outcomes. Forty-two studies involving 1464 patients met the inclusion criteria. Twenty-one studies evaluated tractography-guided planning, and 21 evaluated DTI-derived voxel-wise or region of interest-based quantitative diffusivity parameters. The feasibility of tractography reconstruction was reported in 22 studies, with an overall failure rate of 1.2%. Meta-analysis of comparative studies suggested a lower risk of motor deficits with tractography-guided planning than with conventional planning (risk ratio 0.31, 95% CI 0.14-0.67; I² = 0%). Meta-analysis of dosimetric studies suggested reduced maximum corticospinal tract dose with tractography-guided planning (mean difference - 3.35 Gy, 95% CI - 4.83 to - 1.87; I² = 6%) without significant loss of target coverage. In trigeminal neuralgia, DTI biomarker studies indicated greater FA reduction in responders than in non-responders (mean difference - 13.70%, 95% CI - 25.09 to - 2.30; I² = 0%). DTI contributes to SRS through assisting in eloquent tract preservation during the planning stage and may offer quantitative diffusivity metrics in the evaluation of earlier treatment response. Current evidence is consistent with dosimetric and clinical advantages of tractography-guided planning and suggests prognostic value of diffusion metrics in selected indications.