Longitudinal changes in brain diffusion MRI indices during and after proton beam therapy in a child with pilocytic astrocytoma: a case report
medRxiv(2021)
摘要
Background Proton beam therapy (PBT) is an effective pediatric brain tumor treatment. However, resulting microstructural changes within and around irradiated tumors are unknown. We retrospectively applied Diffusion-Tensor-Imaging (DTI) and Free-Water-Imaging (FWI) on diffusion-weighted Magnetic Resonance Imaging (dMRI) data to monitor microstructural changes during-PBT and after 8 months, in a pilocytic astrocytoma (PA) and normal-appearing white matter (NAWM). Methods We evaluated conventional MRI and dMRI-derived indices from six MRI sessions in a child with a hypothalamic PA: at baseline (t0), during-PBT (t1-t4), and after 8 months (t5). Tumor voxels were classified as "solid" or "fluid" based on FWI. Results While during PBT tumor volume remained stable, dMRI analyses identified two different response patterns: i) an increase in fluid content and diffusivity with anisotropy reductions in solid voxels at t1, followed by ii) smaller variations in fluid content but higher anisotropy in solid voxels at t2-t4. At follow-up (t5), tumor volume, its fluid content, and diffusivity in solid voxels increased. NAWM showed dose-dependent microstructural changes. Conclusions The use of dMRI and FWI showed complex dynamic microstructural changes in the irradiated mass during PBT and at follow-up, opening new avenues in our understanding of radiation-induced pathophysiologic mechanisms in tumor and surrounding tissues.
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关键词
proton therapy, free-water, diffusion MRI, astrocytoma
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