Non-complete Recovery of White Matter Diffusion Metrics at One Year Post-Radiotherapy: Implications for Radiation-Induced Necrosis Risk

Motivation: Radiotherapy for nasopharynx carcinoma (NPC) can lead to various white matter (WM) abnormalities. Goal(s): Explores the connection between WM injuries and temporal lobe necrosis (TLN) and optimizing radiotherapy (RT) regimens for NPC. Approach: Multi-shell diffusion MRI (MS-dMRI) quantification using automated fiber-tract quantification (AFQ). Diffusion metrics alterations analysis using rANOVA. TLN risk factors identification using Cox regression models. Optimal RT regiments development using normal tissue complication probability (NTCP) models. Results: Most TL WM tract segments showed a "decrease/increase without complete recovery" pattern. MD_UF.L.1, NDI_CH.L.1, and NDI_ILF.R.1 were identified as TLN risk predictors. Tolerance dose for D10cc.L, D20cc.L and D10cc.R were revealed for optimal regiments. Impact: Our findings highlight the importance of "decrease/increase without complete recovery" pattern in TL WM tract segment impairments in TLN development. Identifying high-risk WM tract segments and their tolerance doses can aid in optimizing radiotherapy regimens for NPC.