{
  "abstract": "Purpose: Post-mortem Diffusion Magnetic Resonance Imaging (dMRI) findings on fixation-related changes in diffusion tensor imaging (DTI) parameters remain inconsistent, partly due to lower diffusion weighting and sparse early-fixation sampling. This study investigated how post-mortem tissue condition, fixation progression, and diffusion weighting shape DTI parameters in whole human brains, including whether an ex-vivo-adjusted protocol also suits in-situ and early fixation measurements. Methods: Six neurologically healthy whole human brains (post-mortem interval (PMI) 12 - 24 h) were scanned across tissue conditions, including an in-vivo reference cohort. Five brains were scanned longitudinally through immersion fixation (0 - 150 days), yielding 175 datasets with dense early sampling. Diffusion measurements at b-values 1000 - 4000 s/mm2 assessed the influence of diffusion weighting on DTI parameters. Analyses covered multiple white- and gray-matter regions and within white matter stratification by fiber orientation dispersion ({kappa}). Results: The largest mean diffusivity (MD) shift occurred between in-vivo and in-situ, whereas fractional anisotropy (FA) changed most strongly during early fixation. During immersion fixation, MD showed reproducible monoexponential saturation, while FA was heterogeneous across brains. PMI, {kappa}, and regional anatomy explained substantial FA heterogeneity across specimens. Qualitatively, the fixationrelated changes matched across diffusion weightings, but precision across specimens was highest at b-value 4000 s/mm2. Conclusion: During fixation, MD is a robust temporal marker, whereas FA requires microstructureaware interpretation. Diffusion weighting modulates how clearly fixation effects can be resolved, but the same qualitative fixation dynamics remained detectable at in-vivo-like weighting with reduced precision.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Neuroradiology, University of Luebeck"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 8,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "N. Luethi"
    },
    {
      "name": "F. Fritz"
    },
    {
      "name": "B. Fricke"
    },
    {
      "name": "J. M. Oeschger"
    },
    {
      "name": "T. Streubel"
    },
    {
      "name": "H. Mushumba"
    },
    {
      "name": "K. Pueschel"
    },
    {
      "name": "S. Mohammadi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1m1w8sa07rw6z.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.08.31.748254",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.08.31.748254v1.full",
  "id": "1m1w8sa07rw6z",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.08.31.748254v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "neuroscience"
    ],
    [
      "openalex",
      "2741|Advanced Neuroimaging Techniques and Applications"
    ]
  ],
  "openalex": "W7208779318",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.08.31.748254v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-31",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/1m1w8sa07rw6z.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:25Z",
      "native_id": "10.64898/2026.08.31.748254",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.08.31.748254v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:neuroscience",
      "subfield": "neuroscience"
    }
  ],
  "title": "Diffusion tensor imaging of whole human brains during long-term formaldehyde fixation: Temporal evolution of diffusion parameters, post-mortem conditions, and dependence on tissue structure",
  "title_text": "Diffusion tensor imaging of whole human brains during long-term formaldehyde fixation: Temporal evolution of diffusion parameters, post-mortem conditions, and dependence on tissue structure",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:25Z",
  "url": "https://research.draconitic.com/paper/1m1w8sa07rw6z",
  "venue": "bioRxiv",
  "versions": []
}