{"doi":"10.1101/2021.02.09.21251092","title":"Longitudinal changes in brain diffusion MRI indices during and after proton beam therapy in a child with pilocytic astrocytoma: a case report","abstract":"ABSTRACT 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.","journal":"medRxiv","year":2021,"id":223249,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.953,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":798965,"name":"Nivedita Agarwal","orcid":"0000-0002-1387-9566","position":1,"is_corresponding":false},{"id":798966,"name":"Stefano Lorentini","orcid":"0000-0003-3202-2581","position":2,"is_corresponding":false},{"id":647519,"name":"Sabina Vennarini","orcid":"0000-0002-8712-8781","position":3,"is_corresponding":false},{"id":798967,"name":"Domenico Zacà","orcid":"0009-0001-6567-0684","position":4,"is_corresponding":false},{"id":799410,"name":"Anna Mussano","orcid":null,"position":5,"is_corresponding":false},{"id":311510,"name":"Ofer Pasternak","orcid":"0000-0002-7078-6446","position":6,"is_corresponding":false},{"id":798968,"name":"Jorge Jovicich","orcid":"0000-0001-9504-7503","position":7,"is_corresponding":false},{"id":798964,"name":"Lisa Novello","orcid":"0000-0003-0767-2902","position":0,"is_corresponding":true}],"reference_count":16,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:54:11.061295Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}