The dosimetric advantage of proton and carbon-ion therapy — the Bragg peak — is also its greatest vulnerability. Unlike photon beams, particle therapy delivers near-zero dose beyond the Bragg peak. A setup error of just 2–3 mm can shift the Bragg peak entirely outside the target and into an adjacent organ at risk.
Fiducial-based image guidance is not merely helpful in particle therapy — it is the mechanism by which the biological advantage of particles is preserved fraction after fraction. Gold Anchor has been validated in real-time gated proton delivery and carbon-ion IGRT in publications from 2022 to 2024.
Why setup accuracy is more critical in particle therapy
Proton Fluence Data
A 2022 Frontiers in Oncology study used CMOS pixel sensors to directly measure the proton fluence perturbation caused by different fiducial marker types at clinical energies. Gold Anchor's folding design and lower effective volume result in significantly less proton beam shadowing than solid cylindrical gold markers.
Critically, Gold Anchor also provides superior kV and MRI visibility compared with lower-Z alternatives such as carbon fiducials — making it the best combination of visibility and minimal perturbation available.
Frontiers in Oncology 2022 — full paper →Relative proton fluence perturbation (%) — lower is better
Illustrative data based on published proton fluence perturbation measurements. Exact values vary by beam energy and marker position relative to beam axis. Source: Frontiers in Oncology (2022).
Platform Compatibility
Published Research
Real-time gated proton delivery with Gold Anchor fiducials — full commissioning and QA protocol validated
Real-time gated proton therapy with a reduced source to imager distance: Commissioning and quality assurance
Physica Medica · 2024
Fiducial markers significantly reduced both inter-fractional setup error and intra-fractional motion uncertainty in carbon-ion treatment
Inter-fractional error and intra-fractional motion comparisons with vs without fiducial markers during carbon-ion radiotherapy
Radiological Physics and Technology · 2024
Proton beam perturbation by Gold Anchor markers measured as minimal at clinical energies across all assessed imaging modalities
Experimental comparison of fiducial markers used in proton therapy: imaging modalities and proton fluence perturbations measured with CMOS pixel sensors
Frontiers in Oncology · 2022
Gold Anchor fiducials used in a prospective randomized controlled proton therapy trial — image guidance protocol validated
Proton therapy planning and image-guidance strategies within a randomized controlled trial for high-risk prostate cancer
Clinical and Translational Radiation Oncology · 2023
Saxsons Group supplies Gold Anchor markers across India with technical support for proton and carbon-ion IGRT workflows.
Gold Anchor™
Other Radiation Oncology posts and pages in the Gold Anchor family.
For Radiation Oncologist
Conventional coil and cylindrical fiducials migrate up to 19–47 %. Can a 0.32 % migration rate change how prostate SBRT is planned?
Read this Radiation OncologistWhen the target moves with every breath, what does it take to get from 5.3 mm soft-tissue alignment error down to 1.5 mm?
Read this Radiation OncologistRoughly one in five standard coil markers migrate in lung parenchyma. What changes with a fold-anchor design and a thinner needle?
Read this Radiation OncologistA single-page overview of where the published evidence sits for prostate, liver, lung and particle therapy.
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