The prediction of output factors for spread-out proton Bragg peak fields in clinical practice

Kooy, Hanne M.; Rosenthal, S. S.; Engelsman, Martijn; Mazal, A.; Slopsema, R; Paganetti, Harald; Flanz, J.

doi:10.1088/0031-9155/50/24/006

Cited by 62 publications

(56 citation statements)

References 13 publications

(14 reference statements)

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“…At our institution, a theoretical model, based on the observation that the OF is the ratio of the SOBP plateau dose to the dose measured in the reference chamber IC2, is clinically used to predict the OF and for their constancy verification for any specific SOBP. 22 Output factors are measured routinely within the QA program for each option reported in Table I.…”

Section: B2 Output Factors Measurements and Simulations For Absolmentioning

confidence: 99%

Experimental validation of the TOPAS Monte Carlo system for passive scattering proton therapy

et al. 2013

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Purpose: TOPAS (TOol for PArticle Simulation) is a particle simulation code recently developed with the specific aim of making Monte Carlo simulations user-friendly for research and clinical physicists in the particle therapy community. The authors present a thorough and extensive experimental validation of Monte Carlo simulations performed with TOPAS in a variety of setups relevant for proton therapy applications. The set of validation measurements performed in this work represents an overall end-to-end testing strategy recommended for all clinical centers planning to rely on TOPAS for quality assurance or patient dose calculation and, more generally, for all the institutions using passive-scattering proton therapy systems. Methods: The authors systematically compared TOPAS simulations with measurements that are performed routinely within the quality assurance (QA) program in our institution as well as experiments specifically designed for this validation study. First, the authors compared TOPAS simulations with measurements of depth-dose curves for spread-out Bragg peak (SOBP) fields. Second, absolute dosimetry simulations were benchmarked against measured machine output factors (OFs). Third, the authors simulated and measured 2D dose profiles and analyzed the differences in terms of field flatness and symmetry and usable field size. Fourth, the authors designed a simple experiment using a half-beam shifter to assess the effects of multiple Coulomb scattering, beam divergence, and inverse square attenuation on lateral and longitudinal dose profiles measured and simulated in a water phantom. Fifth, TOPAS' capabilities to simulate time dependent beam delivery was benchmarked against dose rate functions (i.e., dose per unit time vs time) measured at different depths inside an SOBP field. Sixth, simulations of the charge deposited by protons fully stopping in two different types of multilayer Faraday cups (MLFCs) were compared with measurements to benchmark the nuclear interaction models used in the simulations. Results: SOBPs' range and modulation width were reproduced, on average, with an accuracy of +1, −2 and ±3 mm, respectively. OF simulations reproduced measured data within ±3%. Simulated 2D dose-profiles show field flatness and average field radius within ±3% of measured profiles. The field symmetry resulted, on average in ±3% agreement with commissioned profiles. TOPAS accuracy in reproducing measured dose profiles downstream the half beam shifter is better than 2%. Dose rate function simulation reproduced the measurements within ∼2% showing that the four-dimensional modeling of the passively modulation system was implement correctly and millimeter accuracy can be achieved in reproducing measured data. For MLFCs simulations, 2% agreement was found between TOPAS and both sets of experimental measurements. The overall results show that TOPAS simulations are within the clinical accepted tolerances for all QA measurements performed at our institution. Conclusions: Our Monte Carlo simulations reproduced accurat...

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Section: B2 Output Factors Measurements and Simulations For Absolmentioning

confidence: 99%

Experimental validation of the TOPAS Monte Carlo system for passive scattering proton therapy

et al. 2013

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“…8 Our reference geometry uses no range compensator as advocated by Kooy et al 3 and Fontenot et al 4 Range:…”

Section: Iib Standardized Setup For Commissioningmentioning

confidence: 99%

“…Although a standard for determining the in-patient output of a passivescattered proton field has not yet been developed, the current consensus in the proton therapy community is to perform field calibrations without the use of a range compensator. Kooy et al 3 reported on relying on the treatment planning system to calculate the effect of the range compensator and in-patient scatter, and therefore not to use field specific hardware during field calibrations. Monte Carlo data by Fontenot et al 4 supports this change.…”

Section: Iva Limitations Of the Studymentioning

confidence: 99%

“…Their model was modified by Kooy et al 2 and fitted to our historical data to allow output prediction of 80% of our clinical treatment fields with acceptable accuracy. Extension of the output model to take into account a shift in the effective source position as a function of range 3 and shifting to output calibrations without patient-specific hardware 3,4 further increased the accuracy of the model. Fields with either a large or a very small modulation were, however, typically still individually measured because of uncertainties in the modulation and/or the output.…”

Section: Introductionmentioning

confidence: 99%

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Commissioning a passive‐scattering proton therapy nozzle for accurate SOBP delivery

Engelsman

Herrup

et al. 2009

Medical Physics

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Proton radiotherapy centers that currently use passively scattered proton beams do field specific calibrations for a non-negligible fraction of treatment fields, which is time and resource consuming. Our improved understanding of the passive scattering mode of the IBA universal nozzle, especially of the current modulation function, allowed us to re-commission our treatment control system for accurate delivery of SOBPs of any range and modulation, and to predict the output for each of these fields. We moved away from individual field calibrations to a state where continued quality assurance of SOBP field delivery is ensured by limited system-wide measurements that only require one hour per week. This manuscript reports on a protocol for generation of desired SOBPs and prediction of dose output.

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“…For DMU calculations, Kooy et al 2 , 3 developed a semi‐empirical calculation method for a range modulated proton beam. It is based on the fact that the DMU depends on the ratio of the entrance dose and the reference dose.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of monitor unit calculation based on measurement and calculation with a simplified Monte Carlo method for passive beam delivery system in proton beam therapy

Hotta

Kohno

Nagafuchi

et al. 2015

J Applied Clin Med Phys

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Calibrating the dose per monitor unit (DMU) for individual patients is important to deliver the prescribed dose in radiation therapy. We have developed a DMU calculation method combining measurement data and calculation with a simplified Monte Carlo method for the double scattering system in proton beam therapy at the National Cancer Center Hospital East in Japan. The DMU calculation method determines the clinical DMU by the multiplication of three factors: a beam spreading device factor FBSD, a patient‐specific device factor FPSD, and a field‐size correction factor normalFFSfalse(Afalse). We compared the calculated and the measured DMU for 75 dose fields in clinical cases. The calculated DMUs were in agreement with measurements in ±1.1% for all of 25 fields in prostate cancer cases, and in ±3% for 94% of 50 fields in head and neck (H&N) and lung cancer cases, including irregular shape fields and small fields. Although the FBSD in the DMU calculations is dominant as expected, we found that the patient‐specific device factor and field‐size correction also contribute significantly to the calculated DMU. This DMU calculation method will be able to substitute the conventional DMU measurement for the majority of clinical cases with a reasonable calculation time required for clinical use.PACS number: 87.55.kh

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The prediction of output factors for spread-out proton Bragg peak fields in clinical practice

Cited by 62 publications

References 13 publications

Experimental validation of the TOPAS Monte Carlo system for passive scattering proton therapy

Experimental validation of the TOPAS Monte Carlo system for passive scattering proton therapy

Commissioning a passive‐scattering proton therapy nozzle for accurate SOBP delivery

Evaluation of monitor unit calculation based on measurement and calculation with a simplified Monte Carlo method for passive beam delivery system in proton beam therapy

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