{
  "abstract": "PurposeTo quantify the dosimetric effect of residual intrafraction motion during gated MR-guided prostate stereotactic body radiotherapy with simultaneous integrated boost to the dominant intraprostatic lesion, and to derive and evaluate target-specific, population-based margins designed to mitigate motion-induced coverage loss.\n\nMaterials and MethodsThirty patients were treated on a 1.5-T MR-Linac with 36.25, 40, and 45 Gy prescribed to the planning target volume, clinical target volume (CTV), and gross tumor volume (GTV), in 5 fractions. Across 150 fractions, segment-level dose matrices synchronized with time-resolved target displacements were combined to reconstruct per-fraction and cumulative dose. Directional prescription-isodose deviations were used to derive internal target volume margins, which were evaluated through offline replanning, gating-envelope analysis, and dose reconstruction.\n\nResultsMedian 95th-percentile motion ranges were 0.5, 1.4, and 2.9 mm in the left-right, anterior-posterior, and superior-inferior directions; these exceeded 3 mm in 0.7%, 13.2%, and 47.7% of fractions, respectively. The median treatment time was 13.2 min (IQR, 12.0-15.1 min) with a median gating duty cycle of 93.2% (80.6%-97.8%). Per-fraction median GTV deviations were -1.2% (-2.4% to -0.1%) for D95 and -5.6% (-15.3% to -0.2%) for V45Gy; corresponding CTV deviations were -0.5% (-1.1% to -0.1%) and -2.1% (-4.1% to -0.4%). Cohort-derived margins of 2/2/1/2/1/2 mm for the GTV and 1/1/1/2/1/2 mm for the CTV in the left/right/anterior/posterior/superior/inferior directions achieved sufficient coverage in approximately 94% of fractions in each direction. Gated delivery using the proposed margins improved coverage but may reduce duty cycle by an average of 6.9 {+/-} 4.7 %.\n\nConclusionResidual intrafraction motion produced directionally asymmetric coverage loss, with the largest effect on the boosted GTV. Motion-inclusive dose reconstruction enabled derivation of practical asymmetric margins that improved robustness while identifying the tradeoff between target coverage and delivery efficiency.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 20,
  "authors": [
    {
      "name": "K. H. Tam"
    },
    {
      "name": "S. Jogi"
    },
    {
      "name": "A. Sobremonte"
    },
    {
      "name": "J. D. Ohrt"
    },
    {
      "name": "D. J. Rhee"
    },
    {
      "name": "J. Yang"
    },
    {
      "name": "Y. Ding"
    },
    {
      "name": "K. K. Brock"
    },
    {
      "name": "P. A. Balter"
    },
    {
      "name": "C. J. Hassanzadeh"
    },
    {
      "name": "M. K. Rooney"
    },
    {
      "name": "S. Choi"
    },
    {
      "name": "R. J.-h. Park"
    },
    {
      "name": "C. Tang"
    },
    {
      "name": "K. R. Patel"
    },
    {
      "name": "S. J. Frank"
    },
    {
      "name": "P. T. Tran"
    },
    {
      "name": "D. E. Hyer"
    },
    {
      "name": "N. Tyagi"
    },
    {
      "affs": [
        0
      ],
      "name": "E. D. Subashi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/am0yex3s3zdbd.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.09.11.26362864",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.09.11.26362864v1.full",
  "id": "am0yex3s3zdbd",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.09.11.26362864v1",
  "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": [
    [
      "medrxiv",
      "oncology"
    ],
    [
      "openalex",
      "3108|Advanced Radiotherapy Techniques"
    ]
  ],
  "openalex": "W7213143509",
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.09.11.26362864v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-11",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/am0yex3s3zdbd.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:31Z",
      "native_id": "10.64898/2026.09.11.26362864",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.09.11.26362864v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:oncology",
      "subfield": "oncology"
    }
  ],
  "title": "Dosimetric Impact of Residual Intrafraction Motion in Gated MR-Guided Prostate SBRT With Focal Dose Intensification",
  "title_text": "Dosimetric Impact of Residual Intrafraction Motion in Gated MR-Guided Prostate SBRT With Focal Dose Intensification",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:31Z",
  "url": "https://research.draconitic.com/paper/am0yex3s3zdbd",
  "venue": "medRxiv",
  "versions": []
}