{
  "id": "2505.06223",
  "version": "v1",
  "published": "2025-05-09T17:57:30.000Z",
  "updated": "2025-05-09T17:57:30.000Z",
  "title": "A Proton Treatment Planning Method for Combining FLASH and Spatially Fractionated Radiation Therapy to Enhance Normal Tissue Protection",
  "authors": [
    "Weijie Zhang",
    "Xue Hong",
    "Ya-Nan Zhu",
    "Yuting Lin",
    "Gregory Gan",
    "Ronald C Chen",
    "Hao Gao"
  ],
  "categories": [
    "physics.med-ph"
  ],
  "abstract": "Background: FLASH radiation therapy (FLASH-RT) uses ultra-high dose rates to induce the FLASH effect, enhancing normal tissue sparing. In proton Bragg peak FLASH-RT, this effect is confined to high-dose regions near the target at deep tissue levels. In contrast, Spatially Fractionated Radiation Therapy (SFRT) creates alternating high- and low-dose regions with high peak-to-valley dose ratios (PVDR), sparing tissues at shallow-to-intermediate depths. Purpose: This study investigates a novel proton modality (SFRT-FLASH) that synergizes FLASH-RT and SFRT to enhance normal tissue protection across all depths. Methods: Two SFRT techniques are integrated with FLASH-RT: proton GRID therapy (pGRID) with conventional beam sizes and proton minibeam radiation therapy (pMBRT) with submillimeter beams. These are implemented as pGRID-FLASH (SB-FLASH) and minibeam-FLASH (MB-FLASH), respectively. The pGRID technique uses a scissor-beam (SB) method to achieve uniform target coverage. To meet FLASH dose (5 Gy) and dose-rate (40 Gy/s) thresholds, a single-field uniform-dose-per-fraction strategy is used. Dose and dose-rate constraints are jointly optimized, including a CTV1cm structure (a 1 cm ring around the CTV) for each field. Results: Across four clinical cases, MB-FLASH and SB-FLASH plans were benchmarked against conventional (CONV), FLASH-RT (FLASH), pMBRT (MB), and pGRID (SB) plans. SFRT-FLASH achieved high FLASH effect coverage (~60-80% in CTV1cm) while preserving PVDR (~2.5-7) at shallow-to-intermediate depths. Conclusions: We present a proton treatment planning approach that combines the FLASH effect at depth with high PVDR near the surface, enhancing normal tissue protection and advancing proton therapy.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2025-05-09T17:57:30.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "enhance normal tissue protection",
      "spatially fractionated radiation therapy",
      "proton treatment planning method",
      "high flash effect coverage"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}