Along-tract analysis of DTI parameters reveals a link to neuropsychological impairment in patients with diffuse gliomas.

Introduction: Diffuse gliomas(DG) grade 2-3 show extensive infiltration through white matter(WM) tracts. Diffusion tensor tractography(DTI) with along-tract analysis(ATA) has been used to assess the microstructural integrity of WM pathways. We aimed to use ATA analysis to compare DTI parameters in DG and correlate them with clinical features.

Methods: Fourteen patients with IDH-mutated DG grade 2-3 were included. Tumour volumes were manually segmented on 3D-FLAIR images, spatially normalized to MNI space. DTI was acquired using a single-shot echo-planar sequence on a 3T with 48 sampling directions. DTI data was reconstructed within MNI space using q-space diffeomorphic reconstruction(QSDR) in DSI studio. Five bilateral sets of WM pathways were reconstructed based on the HCP-1065 template. All WM pathways were stretched to the same length of 100 indices and FA, RD, AD, MD and QA were sampled for each index. An overlay of tumor 3D reconstruction was used to detect contact with WM pathways. Contralateral and not-affected WM pathways were considered normal and included as normal data. WM pathways were compared individually and per index to the normal data using a z-test. Preoperative neuropsychological assessment was performed in all the subjects and correlated to ATA.

Results: WM abnormalities were detected in infiltrated pathways at the z-test. Tumour volume (Tv), the tumour infiltration per voxel(TIv) and tumour extension(Te) along the pathway were displayed with topographical details. Abnormal AD, RD, MD and FA correlated with Tv, TIv and Te (p <.001). Preoperative neuropsychological impairment was correlated with higher AD (p .04), lower QA (p .005), higher TIv (p .01) and Te (p .03).

Conclusion : ATA analysis is a sensitive and reliable method to detect the extension of WM infiltration in DG. Quantitative and qualitative DTI abnormalities were correlated with preoperative neuropsychological impairment. ATA may be valuable for preoperative assessment, surgical planning, or tailored radiotherapy treatment.