A model for the lateral penumbra in water of a 200‐MeV proton beam devoted to clinical applications

Oozeer, Raish; Mazal, A.; Rosenwald, Jean-Claude; Belshi, R.; Nauraye, C.; Ferrand, R.; Biensan, S.

doi:10.1118/1.597967

Cited by 26 publications

(17 citation statements)

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“…The fact that the source‐to‐isocenter distance (220 cm) is much smaller in the PBS nozzle than in the passive beamline used in previous studies requires a new collimator design in order to account for the greater beam divergence and any impact on the penumbra size or homogeneity of lateral dose distributions. Indeed, a smaller lateral penumbra can be obtained by using divergent collimators when they are designed to fit the beam divergence as a function of the virtual source‐axis and collimator‐axis distances . In order to take these effects into account, a divergent collimator in which the slit tilt follows the beam divergence was considered.…”

Section: Methodsmentioning

confidence: 99%

“…Indeed, a smaller lateral penumbra can be obtained by using divergent collimators when they are designed to fit the beam divergence as a function of the virtual source-axis and collimator-axis distances. 33,34 In order to take these effects into account, a divergent collimator in which the slit tilt follows the beam divergence was considered. A 6.5-cm-thick brass multislit collimator with five slits with a width of 2 cm 9 400 lm and a center-to-center distance of 4 mm was finally manufactured and tested at our institution.…”

Section: B Collimator Designmentioning

confidence: 99%

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Implementation of planar proton minibeam radiation therapy using a pencil beam scanning system: A proof of concept study

et al. 2018

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Purpose Proton minibeam radiation therapy (pMBRT) is an innovative approach that combines the advantages of minibeam radiation therapy with the more precise ballistics of protons to further reduce the side effects of radiation. One of the main challenges of this approach is the generation of very narrow proton pencil beams with an adequate dose‐rate to treat patients within a reasonable treatment time (several minutes) in existing clinical facilities. The aim of this study was to demonstrate the feasibility of implementing pMBRT by combining the pencil beam scanning (PBS) technique with the use of multislit collimators. This proof of concept study of pMBRT with a clinical system is intended to guide upcoming biological experiments. Methods Monte Carlo simulations (TOPAS v3.1.p2) were used to design a suitable multislit collimator to implement planar pMBRT for conventional pencil beam scanning settings. Dose distributions (depth‐dose curves, lateral profiles, Peak‐to‐Valley Dose Ratio (PVDR) and dose‐rates) for different proton beam energies were assessed by means of Monte Carlo simulations and experimental measurements in a water tank using commercial ionization chambers and a new p‐type silicon diode, the IBA RAZOR. An analytical intensity‐modulated dose calculation algorithm designed to optimize the weight of individual Bragg peaks composing the field was also developed and validated. Results Proton minibeams were then obtained using a brass multislit collimator with five slits measuring 2 cm × 400 μm in width with a center‐to‐center distance of 4 mm. The measured and calculated dose distributions (depth‐dose curves and lateral profiles) showed a good agreement. Spread‐out Bragg peaks (SOBP) and homogeneous dose distributions around the target were obtained by means of intensity modulation of Bragg peaks, while maintaining spatial fractionation at shallow depths. Mean dose‐rates of 0.12 and 0.09 Gy/s were obtained for one iso‐energy layer and a SOBP conditions in the presence of multislit collimator. Conclusions This study demonstrates the feasibility of implementing pMBRT on a PBS system. It also confirms the reliability of RAZOR detector for pMBRT dosimetry. This newly developed experimental methodology will support the design of future preclinical research with pMBRT.

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Section: Methodsmentioning

confidence: 99%

Section: B Collimator Designmentioning

confidence: 99%

Implementation of planar proton minibeam radiation therapy using a pencil beam scanning system: A proof of concept study

et al. 2018

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“…The slope of this dose decrease is characterized by the transverse penumbra given by the distance to decrease between two specified dose values. In the case of lateral spreading by scattering, this distance is determined primarily by the distance between the aperture and the patient while, for scanned beams, it is primarily determined by the size of the scanned beam spot, focused at the target . In the latter case, the beam spot is normally in the shape of a Gaussian, and the conformity of the irradiated field will be related to the overall size of that beam …”

Section: Current State: Beam Delivery Systemsmentioning

confidence: 99%

New horizons in particle therapy systems

Farr¹,

Flanz

Gerbershagen

et al. 2018

Medical Physics

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Particle therapy is rapidly expanding and claiming its position as the treatment modality of choice in teletherapy. However, the rate of expansion continues to be restricted by the size and cost of the associated particle therapy systems and their operation. Additional technical limitations such as dose delivery rate, treatment process efficiency, and achievement of superior dose conformity potentially hinder the complete fulfillment of the promise of particle therapy. These topics are explored in this review considering the current state of particle therapy systems and what improvements are required to overcome the current challenges. Beam production systems (accelerators), beam transport systems including gantries and beam delivery systems are addressed explicitly in these regards.

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“…A sharp lateral penumbra is particularly important for the treatment sites that have organs at risk (OARs) abutting the target volume. Several groups [1][2][3][4][5] have performed the measurements and Monte Carlo simulation investigating the dependency of lateral penumbra of proton beams on different beam conditions and geometrical configurations, and it was found that lateral penumbra increases with an increase in range (or energy), depth, and air gap between the aperture/range compensator and phantom.…”

Section: Introductionmentioning

confidence: 99%

Impact of heterogeneities on lateral penumbra in uniform scanning proton therapy

Rana

Singh

2013

Int J Cancer Ther Oncol

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Purpose: In the treatment planning of uniform scanning proton therapy, an aperture block is designed for each beam with a margin, which typically includes the lateral penumbra measured in water (homogenous) medium. However, during real proton therapy treatment, protons may pass through tissues of different densities within the patient's body before they are stopped. The main aim of this study was to investigate the dependency of lateral penumbra on low-and high-density heterogeneities placed in the plateau and spread-out Bragg peak (SOBP) regions. Method: The measurements were performed by placing radiographic films at the isocenter (center of SOBP), and each proton beam was delivered with 150 monitor units using standard beam conditions of the institution. Results and Conclusion: The preliminary results from this study showed that the lateral penumbra of uniform scanning proton beams was less sensitive to the inhomogeneities introduced in the protons beam path. The low-density heterogeneity in the plateau region had more impact on the lateral penumbra when compared to the low-density in the SOBP region. In contrast, the placement of high-density heterogeneity (whether in the plateau or SOBP region) produced a very minimal difference. The overall difference in lateral penumbra among different phantoms was within ±1 mm.

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A model for the lateral penumbra in water of a 200‐MeV proton beam devoted to clinical applications

Cited by 26 publications

References 1 publication

Implementation of planar proton minibeam radiation therapy using a pencil beam scanning system: A proof of concept study

Implementation of planar proton minibeam radiation therapy using a pencil beam scanning system: A proof of concept study

New horizons in particle therapy systems

Impact of heterogeneities on lateral penumbra in uniform scanning proton therapy

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