Clinical Commissioning of a Pencil Beam Scanning Treatment Planning System for Proton Therapy

Saini, Jatinder; Cao, Ning; Bowen, Stephen R.; Herrera, Miguel; Nicewonger, Daniel; Wong, Tony; Bloch, C.

doi:10.14338/ijpt-16-0000.1

Cited by 50 publications

(56 citation statements)

References 13 publications

(13 reference statements)

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“…It has been shown that, especially at large depths, the Bragg peak chamber is not large enough to capture the whole laterally scattered dose . Therefore, the IDD curves have to be corrected by means of MC simulations …”

Section: Detectors For Absorbed Dose In Nonreference Conditionsmentioning

confidence: 99%

“…85,114,146,147 Therefore, the IDD curves have to be corrected by means of MC simulations. 85,109,115,148 The more recent Stingray chambers (IBA Dosimetry) mitigates this effect 149 thanks to the larger radius (6.0 cm) as compared with the Bragg peak chamber (4.08 cm), therefore it reduces the need of MC correction. The Stingray chamber can also be moved remotely and with 0.1 mm steps when mounted on the Blue Phantom2 system (IBA Dosimetry).…”

Section: F Ionization Chambersmentioning

confidence: 99%

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Dose detectors, sensors, and their applications

Giordanengo

2018

Medical Physics

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This article is intended to present the different types of particle and radiation detectors available for applications in particle therapy. Several types of detectors and sensors exist for measurements of absorbed dose in reference and nonreference conditions and the ones in use for beam monitoring. Therefore, this manuscript focuses on the following applications: (a) primary methods for dosimetry in ion beams, (b) measurements of absorbed dose in realistic patient‐specific scenarios with different dose delivery configurations, and (c) beam monitoring. Water and graphite calorimeters, Faraday cups, ionization based gas detectors are described first, followed by the description of the protocols for proton and ion dosimetry. Then films, scintillator and solid‐state detectors are reviewed. Finally, several types of ionization chambers (large, pinpoint, arrays of chambers arranged in regular 1D or 2D pattern, parallel‐plate configuration with large integral electrodes or with anode segmented in strips or pixels, multi‐wire, and the multi‐gap prototype) have been considered. New beam monitors to deal with a wide range of intensity and pulsed beams expected from new accelerators, different dose fractionation and advanced delivery techniques are presented. The existing detectors available for particle therapy have been described taking into account the different requirements for devices used in reference and nonreference conditions and the ones designed for beam monitoring.

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Section: Detectors For Absorbed Dose In Nonreference Conditionsmentioning

confidence: 99%

Section: F Ionization Chambersmentioning

confidence: 99%

Dose detectors, sensors, and their applications

Giordanengo

2018

Medical Physics

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“…For high energies, when the nuclear halo is depth dependent, this effect has been studied and characterized with Monte Carlo‐based dose calculation algorithms . With more widespread implementation of clinical Monte Carlo algorithms, and enhanced corrections for model‐based algorithms, the halo effect at depth can be modeled within 1–2% accuracy for high‐energy beams .…”

Section: Introductionmentioning

confidence: 99%

Nuclear halo measurements for accurate prediction of field size factor in a Varian ProBeam proton PBS system

Harms

Chang

Zhang

et al. 2019

J Applied Clin Med Phys

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Purpose: For pencil-beam scanning proton therapy systems, in-air non-Gaussian halo can significantly impact output at small field sizes and low energies. Since the low-intensity tail of spot profile (halo) is not necessarily modeled in treatment planning systems (TPSs), this can potentially lead to significant differences in patient dose distribution. In this work, we report such impact for a Varian ProBeam system. Methods: We use a pair magnification technique to measure two-dimensional (2D) spot profiles of protons from 70 to 242 MeV at the treatment isocenter and 30 cm upstream of the isocenter. Measurements are made with both Gafchromic film and a scintillator detector coupled to a CCD camera (IBA Lynx). Spot profiles are measured down to 0.01% of their maximum intensity. Field size factors (FSFs) are compared among calculation using measured 2D profiles, calculation using a clinical treatment planning algorithm (Raystation 8A clinical Monte Carlo), and a CC04 small-volume ion chamber. FSFs were measured for square fields of proton energies ranging from 70 to 242 MeV.Results: All film and Lynx measurements agree within 1 mm for full width at half maximum beam intensity. The measured radial spot profiles disagree with simple Gaussian approximations, which are used for modeling in the TPS. FSF measurements show the magnitude of disagreements between beam output in reality and in the TPS without modeling halo. We found that the clinical TPS overestimated output by as much as 6% for small field sizes of 2 cm at the lowest energy of 70 MeV while the film and Lynx measurements agreed within 4% and 1%, respectively, for this FSF.Conclusions: If the in-air halo for low-energy proton beams is not fully modeled by the TPS, this could potentially lead to under-dosing small, shallow treatment volumes in PBS treatment plans.

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“…These characteristics provide an opportunity for optimal target dose coverage, that is, uniformity and conformity, with reduced integral dose and sparing of surrounding healthy tissues . In Pencil Beam Scanning modality, target coverage in the plane orthogonal to the beam propagation is typically achieved by sweeping the beam by a set of scanning magnets . Coverage along the longitudinal direction is achieved by repeatedly changing the beam energy (energy stacking), covering the target layer by layer from distal to proximal depths .…”

Section: Introductionmentioning

confidence: 99%

“…2,4,5 Coverage along the longitudinal direction is achieved by repeatedly changing the beam energy (energy stacking), covering the target layer by layer from distal to proximal depths. 2,4,5 A number of factors can compromise the target dose coverage. 2 For a given prescribed range, delivering inaccurate beam range can influence the target coverage and the dose to critical structures by undershooting or overshooting of the target distal margin.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Use of commercial multilayer Faraday cup for offline daily beam range verification at the McLaren Proton Therapy Center

et al. 2019

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Purpose Daily verification of the proton beam range in proton radiation therapy is a vital part of the quality assurance (QA) program. The objective of this work is to study the use of a multilayer Faraday cup (MLFC) to perform a quick and precise daily range verification of proton beams produced by a synchrotron. Methods Proton beam depth dose measurements were performed at room iso‐center in water using PTW water tank and Bragg Peak ion chamber. The IBA Giraffe, calibrated against the water tank data, was used to measure the water equivalent thickness (WET) of the sample copper plates. The WET measurements provided the range calibration factors for the MLFC. To establish a baseline for in room measurements, range measurements for energies from 70 to 250 MeV in steps of 10 MeV were performed using the Pyramid MLFC at room iso‐center. For the daily range verification measurements, the MLFC is permanently placed at the end of the beam line, inside the accelerator vault. The daily range constancy is performed for five representative beam energies; namely 70, 100, 150, 200, and 250 MeV. Data collected over a period of more than 100 days are analyzed and presented. Results The measured WET values of the copper plates increased with increasing energy. The centroid channel number in the MLFC where the protons stop, was converted to depth in water and compared to the depth of the distal 80% (d80) obtained from the water tank measurements. The depths agreed to within 2 mm, with the maximum deviation of 1.97 mm observed for 250 MeV beam. The daily variation in the ranges measured by the MLFC was within ±0.5 mm. The total time to verify five proton beam ranges varies between 4 and 5 min. Conclusion Based on the result of our measurements, the MLFC can be used for a daily range constancy check with submillimeter accuracy. It is a quick and simple method to perform range constancy verification on a daily basis.

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Clinical Commissioning of a Pencil Beam Scanning Treatment Planning System for Proton Therapy

Cited by 50 publications

References 13 publications

Dose detectors, sensors, and their applications

Dose detectors, sensors, and their applications

Nuclear halo measurements for accurate prediction of field size factor in a Varian ProBeam proton PBS system

Technical Note: Use of commercial multilayer Faraday cup for offline daily beam range verification at the McLaren Proton Therapy Center

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