{"doi":"10.1002/mrm.29262","title":"Rat Brain Global Ischemia–Induced Diffusion Changes Revisited: Biophysical Modeling of the Water and <scp>NAA MR</scp> “Diffusion Signal”","abstract":"Purpose To assess changes in intracellular diffusion as a mechanism for the reduction in water ADC that accompanies brain injury. Using NAA as a marker of neuronal cytoplasmic diffusion, NAA diffusion was measured before and after global ischemia (immediately postmortem) in the female Sprague–Dawley rat. Methods Diffusion‐weighted PRESS spectra, with diffusion encoding in a single direction, were acquired from large voxels of rat brain gray matter in vivo and postischemia employing either pairs of pulsed half‐sine–shaped gradients (in vivo and postischemia, b max = 19 ms/μm 2 ) or sinusoidal oscillating gradients (in vivo only) with frequencies of 99.2–250 Hz. A 2D randomly oriented cylinder (neurite) model gave estimates of longitudinal and transverse diffusivities ( D L and D T , respectively). In this model, D L represents the “free” diffusivity of NAA, whereas D T reflects highly restricted diffusion. Using oscillating gradients, the frequency dependence of D T [ D T (ω)] gave estimates of the cylinder (axon/dendrite) radius. Results A 10% decrease in D L,NAA followed global ischemia, dropping from 0.391 ± 0.012 μm 2 /ms to 0.350 ± 0.009 μm 2 /ms. Modeling D T,NAA (ω) provided an estimate of the neurite radius of 1.0 ± 0.6 μm. Conclusion Whereas the increase in apparent intraneuronal viscosity suggested by changes in D L,NAA may contribute to the overall reduction in water ADC associated with brain injury, it is not sufficient to be the sole explanation. Estimates of neurite radius based on D T (ω) were consistent with literature values.","journal":"Magnetic Resonance in Medicine","year":2022,"id":292921,"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":2,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.8983,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":977768,"name":"A. L. Sukstanskiı̆","orcid":null,"position":1,"is_corresponding":false},{"id":178314,"name":"G. Larry Bretthorst","orcid":null,"position":2,"is_corresponding":false},{"id":307370,"name":"Jeffrey J. Neil","orcid":"0000-0002-8069-8175","position":3,"is_corresponding":false},{"id":760778,"name":"Joseph J. H. Ackerman","orcid":"0000-0002-6514-9282","position":4,"is_corresponding":false},{"id":977385,"name":"William M. Spees","orcid":"0000-0002-9735-3106","position":0,"is_corresponding":true}],"reference_count":73,"raw_metadata":null,"created_at":"2026-07-19T00:30:50.076284Z","pmid":"35452137","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":[]}