Physical Uncertainties in the Planning and Delivery of Light Ion Beam Treatments

Purpose: Treatment planning systems (TPSs) from different vendors can involve different implementations of Monte Carlo dose calculation (MCDC) algorithms for pencil beam scanning (PBS) proton therapy. There are currently no guidelines for validating non-water materials in TPSs. Furthermore, PBSspecific parameters can vary by 1-2 orders of magnitude among different treatment delivery systems (TDSs). This paper proposes a standardized framework on the use of commissioning data and steps to validate TDS-specific parameters and TPS-specific heterogeneity modeling to potentially reduce these uncertainties. Methods: A standardized commissioning framework was developed to commission the MCDC algorithms of RayStation 8A and Eclipse AcurosPT v13.7.20 using water and non-water materials. Measurements included Bragg peak depth-dose and lateral spot profiles and scanning field outputs for Varian ProBeam. The phase-space parameters were obtained from in-air measurements and the number of protons per MU from output measurements of 10 9 10 cm 2 square fields at a 2 cm depth. Spot profiles and various PBS field measurements at additional depths were used to validate TPS. Human tissues in TPS, Gammex phantom materials, and artificial materials were used for the TPS benchmark and validation. Results: The maximum differences of phase parameters, spot sigma, and divergence between MCDC algorithms are below 4.5 µm and 0.26 mrad in air, respectively. Comparing TPS to measurements at depths, both MC algorithms predict the spot sigma within 0.5 mm uncertainty intervals, the resolution of the measurement device. Beam Configuration in AcurosPT is found to underestimate number of protons per MU by~2.5% and requires user adjustment to match measured data, while RayStation is within 1% of measurements using Auto model. A solid water phantom was used to validate the range accuracy of non-water materials within 1% in AcurosPT. Conclusions: The proposed standardized commissioning framework can detect potential issues during PBS TPS MCDC commissioning processes, and potentially can shorten commissioning time and improve dosimetric accuracies. Secondary MCDC can be used to identify the root sources of disagreement between primary MCDC and measurement.

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“…The x‐axis of Fig. is the scaled CT numbers (CTN) calculated by eq. (3) to have 0 for air and 1000 for water.…”

Section: Resultsmentioning

confidence: 99%

“…is the scaled CT numbers (CTN) calculated by eq. (3) to have 0 for air and 1000 for water. Equation (3) is adopted from the approved TG‐202 report .…”

Section: Resultsmentioning

confidence: 99%

A standardized commissioning framework of Monte Carlo dose calculation algorithms for proton pencil beam scanning treatment planning systems

et al. 2020

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“…The monitor calibration factor has to be determined experimentally for every ion species at different energies and should be checked daily before the irradiations. Checking the monitor calibration is an important quality assurance task in particle therapy facilities [7,8]. In principle the beam monitor can be calibrated with different methods [9].…”

Section: Beam Monitor Calibrationmentioning

confidence: 99%

“…Monte Carlo simulations using the FLUKA code (version 2011.2x.5) were performed to obtain D w /D air ratios to calculate k Q correction factors according to Equation (7). Simulations were carried out for different ion species ( 1 H, 4 He, 12 C, 40 Ar, 56 Fe) at different energies (350 MeV/u, 1 GeV/u, 4 GeV/u, 10 GeV/u) for a field size of 5 × 5 cm 2 .…”

Section: Monte Carlo Simulationsmentioning

confidence: 99%

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Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

et al. 2020

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Comparison of the dosimetric accuracy of proton breast treatment plans delivered with SGRT and CBCT setups

MacFarlane

Jiang

Mundis

et al. 2021

J Applied Clin Med Phys

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To compare the dosimetric accuracy of surface-guided radiation therapy (SGRT) and cone-beam computed tomography (CBCT) setups in proton breast treatment plans.Methods: Data from 30 patients were retrospectively analyzed in this IRBapproved study. Patients were prescribed 4256-5040 cGy in 16-28 fractions.CBCT and AlignRT (SGRT; Vision RT Ltd.) were used for treatment setup during the first three fractions, then daily AlignRT and weekly CBCT thereafter. Each patient underwent a quality assurance CT (QA-CT) scan midway through the treatment course to assess anatomical and dosimetric changes. To emulate the SGRT and CBCT setups during treatment, the planning CT and QA-CT images were registered in two ways: (1) by registering the volume within the CTs covered by the CBCT field of view; and (2) by contouring and registering the surface surveyed by the AlignRT system. The original plan was copied onto these two datasets and the dose was recalculated. The clinical treatment volume (CTV): V 95% ; heart: V 25Gy , V 15Gy , and mean dose; and ipsilateral lung: V 20Gy , V 10Gy , and V 5Gy , were recorded. Multi and univariate analyses of variance were performed to assess the differences in dose metric values between the planning CT and the SGRT and CBCT setups. Results:The CTV V 95% and lung V 20Gy , V 10Gy , and V 5Gy dose metrics were all significantly (p < 0.01) lower on the QA-CT in both the CBCT and SGRT setup.The differences were not clinically significant and were, on average, 1.4-1.6% lower for CTV V 95% and 1.8%-6.0% lower for the lung dose metrics. When comparing the lung and CTV V 95% dose metrics between the CBCT and SGRT setups, no significant difference was observed. This indicates that the SGRT setup provides similar dosimetric accuracy as CBCT. Conclusion:This study supports the daily use of SGRT systems for the accurate dose delivery of proton breast treatment plans.

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Physical Uncertainties in the Planning and Delivery of Light Ion Beam Treatments

Cited by 15 publications

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A standardized commissioning framework of Monte Carlo dose calculation algorithms for proton pencil beam scanning treatment planning systems

A standardized commissioning framework of Monte Carlo dose calculation algorithms for proton pencil beam scanning treatment planning systems

Beam Monitor Calibration for Radiobiological Experiments With Scanned High Energy Heavy Ion Beams at FAIR

Comparison of the dosimetric accuracy of proton breast treatment plans delivered with SGRT and CBCT setups

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