{
  "abstract": "Background\n\nTemporal mismatches between gating signals and beam activation-beam-on and beam-off latencies-in gated particle beam therapy can compromise dose integrity. Yet standardized measurement techniques are lacking, and system-specific characterization, particularly for synchrotron-based proton systems, remains limited.Purpose\n\nTo implement a novel strategy for precise end-to-end gating latency measurements of a spot-scanned proton beam using Gafchromic film.Methods\n\nGating latencies have been measured for a Hitachi ProBeat accelerator equipped with a Varian RPM gating system. EBT4 films were positioned within a stack of acrylic blocks on a QUASAR respiratory motion platform operated with a 1.5 cm amplitude and 12 bpm sinusoidal pattern. A stainless-steel ball bearing (BB), positioned atop the film, facilitated localization. During irradiation, the BB produced a dose shadow on the film that indicated the phantom position. A proton plan consisting of a single 85.3 MeV spot was delivered to isocenter during a single gate-on/off interval initiated near the 25% phase, to maximize phantom velocity. Fifty-one measurements were made with a variety of gating intervals. Beam-on latency and delivery time produced a separation between the BB-shadow and the centroid of the Gaussian proton spot. Spot duration information was extracted from accelerator log files. BB-shadow/spot separation is modeled analytically based on phantom motion enabling the direct calculation of the total beam-on and beam-off latencies. Accelerator latency was measured directly with an oscilloscope, enabling isolation of the relative contributions of the RPM gating system.Results\n\nAn average beam-on latency of 142±27 ms is observed for the RPM+ProBeat system for the first gate of a delivery, which includes a known 69 ms beam extraction judgment time for the first proton spot in a spill from the Hitachi synchrotron. The corresponding average beam-off latency is 87±30ms . The average gate-on and gate-off latencies of the RPM system are calculated as 72±27ms and 81±30ms , respectively. The associated average contributions of the accelerator to the beam-on latencies are measured as 69.3±0.2ms (first gate in new spill) and 0.53±0.07ms (subsequent gates in existing spill) and similarly 6±4ms for beam-off latency.Conclusion\n\nA novel, high-precision method for gating-latency measurements has been implemented using film to characterize gating latencies in a spot-scanned particle beam. Commissioning and regular quality assurance methods to precisely characterize the temporal accuracy of a gating system ensure treatment accuracy and will become increasingly vital to consider for higher-frequency applications, such as cardiac gating or FLASH-capable systems.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, USA."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Z S Stottler"
    },
    {
      "affs": [
        0
      ],
      "name": "J J Kruse"
    },
    {
      "affs": [
        0
      ],
      "name": "A J Deisher"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2990emwtj4aks.bib",
  "cited_by": 0,
  "doi": "10.1002/acm2.70826",
  "fulltext_url": "https://europepmc.org/articles/PMC13686591",
  "id": "2990emwtj4aks",
  "issns": [
    "1526-9914"
  ],
  "landing_url": "https://europepmc.org/article/MED/42905951",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3108|Advanced Radiotherapy Techniques"
    ]
  ],
  "openalex": "W7223132019",
  "pdf_url": "https://europepmc.org/articles/PMC13686591?pdf=render",
  "pmcid": "PMC13686591",
  "pmid": "42905951",
  "published": "2026-10-30",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/2990emwtj4aks.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:53Z",
      "native_id": "MED:42905951",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42905951"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3108|Advanced Radiotherapy Techniques",
      "subfield": "applied-instrumentation"
    }
  ],
  "title": "End-to-end film-based characterization of gated delivery latencies in a spot-scanned synchrotron-based proton therapy system.",
  "title_text": "End-to-end film-based characterization of gated delivery latencies in a spot-scanned synchrotron-based proton therapy system.",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:19:53Z",
  "url": "https://research.draconitic.com/paper/2990emwtj4aks",
  "venue": "Journal of applied clinical medical physics",
  "versions": []
}