Monte-Carlo dosimetry for intraoperative radiotherapy using a low energy x-ray source

Bouzid, Dounia; Bert, Julien; Dupré, Pierre‐François; Benhalouche, Saadia; Pradier, Olivier; Boussion, Nicolas; Visvikis, Dimitris

doi:10.3109/0284186x.2015.1016623

Cited by 27 publications

(23 citation statements)

References 23 publications

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“…This is further exacerbated by the above noted rapid variation in target dose with depth; for example, a 3.5 times reduction in dose within 1 cm thick shell surrounding a 4 cm diameter breast applicator. Therefore, Bouzid et al have recommended CT-based treatment planning with Monte Carlo dose calculations for improved prescription and assessment of delivered IORT dose ( 30 ). With CT based planning, any concerns related to a lack of target coverage and/or OAR sparing can be addressed by the planner.…”

Section: Discussionmentioning

confidence: 99%

Intraoperative Radiotherapy With INTRABEAM: Technical and Dosimetric Considerations

et al. 2018

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PurposeWe evaluate dose characteristics and clinical applications of treatment accessories used in intraoperative radiotherapy (IORT) and make site-specific recommendations for their optimal use.Methods and materialsDose measurements were performed for a low energy (50 kV) X-ray INTRABEAM source. For spherical, flat, surface, and needle applicators, the following dosimetric parameters were measured: depth-dose (DD) profiles, surface dose (Ds), output factors (OF), and target dose homogeneity (DH). Optical density versus exposure calibration films were employed to obtain 2-dimensional dose distributions in planes parallel and perpendicular to beam direction. Film results were verified via repeat dose measurements with a parallel-plate ionization chamber in a custom water tank. The impact of applicator design on dose distributions was evaluated.ResultsSpherical applicators are commonly used for treating the inner-surface of breast lumpectomy cavity. Flat and surface applicators provide uniform planar dose for head and neck, abdomen, and pelvis targets. Needle applicators are designed for kypho-IORT of spinal metastasis. Typically, larger applicators produce a more homogeneous target dose region with lower surface dose, but require longer treatment times. For 4-cm diameter spherical, flat, and surface applicators, dose rates (DR) at their respective prescription points were found to be: 0.8, 0.3, and 2.2 Gy/min, respectively. The DR for a needle applicator was 7.04 Gy/min at 5 mm distance from the applicator surface. Overall, film results were in excellent agreement with ion-chamber data.ConclusionIORT may be delivered with a variety of site-specific applicators. Appropriate applicator use is paramount for safe, effective, and efficient IORT delivery. Results of this study should help clinicians assure optimized target dose coverage and reduced normal tissue exposure.

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Section: Discussionmentioning

confidence: 99%

Intraoperative Radiotherapy With INTRABEAM: Technical and Dosimetric Considerations

et al. 2018

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“…The initial model of INTRABEAM ® was taken from Bouzid et al [18]. It consists of a mathematical description of the XRS.…”

Section: Gate (Geant4 Application For Tomography Emission) Is a Montementioning

confidence: 99%

Monte Carlo evaluation of the effect of inhomogeneities on dose calculation for low energy photons intra-operative radiation therapy in pelvic area

et al. 2015

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“…Detailed Monte Carlo simulations of a miniature 50 keV accelerator used to treat brain tumours were performed by Yanch and Harte with ITS 3.0 (Yanch and Harte 1996). More specifically, Bouzid et al developed a Geant4/GATE code suitable to INTRABEAM® treatment issues (Bouzid et al 2015) while Ebert and Carruthers used EGSnrc to model the INTRABEAM® source (Ebert and Carruthers 2003). High accuracy is reached with full Monte Carlo (MC) simulations, however it is still a time-consuming technique and it is not suitable for real-time planning in the Operating Room (OR).…”

Section: Introductionmentioning

confidence: 99%

Fast optimized Monte Carlo phase-space generation and dose prediction for low energy x-ray intra-operative radiation therapy

et al. 2019

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Low energy X-ray Intra-Operative Radiation Therapy (IORT) is used mostly for breast cancer treatment with spherical applicators. X-ray IORT treatment delivered during surgery (ex: INTRABEAM®, Carl Zeiss) can benefit from accurate and fast dose prediction in a patient 3D volume. However, full Monte Carlo (MC) simulations are time-consuming and no commercial treatment planning system was available for this treatment delivery technique. Therefore, the aim of this work is to develop a dose computation tool based on MC phase space information, which computes fast and accurate dose distributions for spherical and needle INTRABEAM® applicators. First, a database of monoenergetic phasespace (PHSP) files and depth dose profiles (DDPs) in water for each applicator is generated at factory and stored for on-site use. During commissioning of a given INTRABEAM® unit, the proposed Fast and Optimized Phase-Space (FOPS) generation process creates a phasespace at the exit of the applicator considered, by fitting the energy spectrum of the source to a combination of the monoenergetic precomputed phase-spaces, by means of a genetic algorithm, with simple experimental data of depth dose profiles in water provided by the user. An in-house hybrid MC algorithm which takes into account condensed history simulations of photoelectric, Rayleigh and Compton interactions for X-rays up to 1 MeV computes the dose from the optimized phase-space file. The whole process has been validated against radiochromic films in water as well as reference MC simulations performed with penEasy in heterogeneous phantoms. From the pre-computed monoenergetic PHSP files and DDPs, building the PHSP file optimized to a particular depth-dose curve in water only takes a few minutes in a single core (i7@2.5 GHz), for all the applicators considered in this work, and this needs to be done only when the X-ray source is replaced. Once the phase-space file is ready, the hybrid Monte Carlo code is able to compute dose distributions within 10 minutes. For all the applicators, more than 95% of voxels from dose distributions computed with the FOPS+hybrid code agreed within 7%-0.5 mm with both reference MC simulations and measurements. The method proposed has been fully validated and it is now implemented into radiance (GMV SA, Spain), the first commercial IORT Treatment Planning System (TPS).

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Monte-Carlo dosimetry for intraoperative radiotherapy using a low energy x-ray source

Cited by 27 publications

References 23 publications

Intraoperative Radiotherapy With INTRABEAM: Technical and Dosimetric Considerations

Intraoperative Radiotherapy With INTRABEAM: Technical and Dosimetric Considerations

Monte Carlo evaluation of the effect of inhomogeneities on dose calculation for low energy photons intra-operative radiation therapy in pelvic area

Fast optimized Monte Carlo phase-space generation and dose prediction for low energy x-ray intra-operative radiation therapy

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