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Radhe Mohan - One of the best experts on this subject based on the ideXlab platform.
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report of the aapm tg 256 on the relative biological effectiveness of Proton Beams in radiation therapy
Medical Physics, 2019Co-Authors: H Paganetti, Radhe Mohan, David R Grosshans, David J Carlson, Eleanor A Blakely, A Carabefernandez, Lei Dong, Kathryn D Held, Vitali Moiseenko, Andrzej NiemierkoAbstract:: The biological effectiveness of Proton Beams relative to photon Beams in radiation therapy has been taken to be 1.1 throughout the history of Proton therapy. While potentially appropriate as an average value, actual relative biological effectiveness (RBE) values may differ. This Task Group report outlines the basic concepts of RBE as well as the biophysical interpretation and mathematical concepts. The current knowledge on RBE variations is reviewed and discussed in the context of the current clinical use of RBE and the clinical relevance of RBE variations (with respect to physical as well as biological parameters). The following task group aims were designed to guide the current clinical practice: Assess whether the current clinical practice of using a constant RBE for Protons should be revised or maintained. Identifying sites and treatment strategies where variable RBE might be utilized for a clinical benefit. Assess the potential clinical consequences of delivering biologically weighted Proton doses based on variable RBE and/or LET models implemented in treatment planning systems. Recommend experiments needed to improve our current understanding of the relationships among in vitro, in vivo, and clinical RBE, and the research required to develop models. Develop recommendations to minimize the effects of uncertainties associated with Proton RBE for well-defined tumor types and critical structures.
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A model for relative biological effectiveness of therapeutic Proton Beams based on a global fit of cell survival data
Scientific Reports, 2017Co-Authors: Ramin Abolfath, Mark Newpower, Lawrence Bronk, Christopher R. Peeler, David Grosshans, Radhe MohanAbstract:We introduce an approach for global fitting of the recently published high-throughput and high accuracy clonogenic cell-survival data for therapeutic scanned Proton Beams. Our fitting procedure accounts for the correlation between the cell-survival, the absorbed (physical) dose and the Proton linear energy transfer (LET). The fitting polynomials and constraints have been constructed upon generalization of the microdosimetric kinetic model (gMKM) adapted to account for the low energy and high lineal-energy spectrum of the beam where the current radiobiological models may underestimate the reported relative biological effectiveness (RBE). The parameters ( α , β ) of the linear-quadratic (LQ) model calculated by the presented method reveal a smooth transition from low to high LETs which is an advantage of the current method over methods previously employed to fit the same clonogenic data. Finally, the presented approach provides insight into underlying microscopic mechanisms which, with future study, may help to elucidate radiobiological responses along the Bragg curve and resolve discrepancies between experimental data and current RBE models.
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experimental characterization of the low dose envelope of spot scanning Proton Beams
Physics in Medicine and Biology, 2010Co-Authors: Gabriel O Sawakuchi, Radhe Mohan, Ronald X Zhu, Falk Poenisch, Michael Gillin, Kazumichi Suzuki, G Ciangaru, Uwe Titt, A Anand, Narayan SahooAbstract:In scanned Proton beam radiotherapy, multiple pencil Beams are used to deliver the total dose to the target volume. Because the number of such Beams can be very large, an accurate dosimetric characterization of every single pencil beam is important to provide adequate input data for the configuration of the treatment planning system. In this work, we present a method to measure the low-dose envelope of single pencil Beams, known to play a meaningful role in the dose computation for scanned Proton Beams. We measured the low-dose Proton beam envelope, which extends several centimeters outwards from the center of each single pencil beam, by acquiring lateral dose profile data, down to relative dose levels that were a factor of 10(4) lower than the central axis dose. The overall effect of the low-dose envelope on the total dose delivered by multiple pencil Beams was determined by measuring the dose output as a function of field size. We determined that the low-dose envelope can be influential even for fields as large as 20 cm x 20 cm.
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exploration of the potential of liquid scintillators for real time 3d dosimetry of intensity modulated Proton Beams
Medical Physics, 2009Co-Authors: S Beddar, L Archambault, Narayan Sahoo, Falk Poenisch, Michael Gillin, George T Y Chen, Radhe MohanAbstract:In this study, the authors investigated the feasibility of using a 3D liquid scintillator (LS) detector system for the verification and characterization of Proton Beams in real time for intensity and energy-modulated Proton therapy. A plastic tank filled with liquid scintillator was irradiated with pristine Proton Bragg peaks. Scintillation light produced during the irradiation was measured with a CCD camera. Acquisition rates of 20 and 10 frames per second (fps) were used to image consecutive frame sequences. These measurements were then compared to ion chamber measurements and Monte Carlo simulations. The light distribution measured from the images acquired at rates of 20 and 10 fps have standard deviations of 1.1% and 0.7%, respectively, in the plateau region of the Bragg curve. Differences were seen between the raw LS signal and the ion chamber due to the quenching effects of the LS and due to the optical properties of the imaging system. The authors showed that this effect can be accounted for and corrected by Monte Carlo simulations. The liquid scintillator detector system has a good potential for performing fast Proton beam verification and characterization.
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stray radiation dose and second cancer risk for a pediatric patient receiving craniospinal irradiation with Proton Beams
Physics in Medicine and Biology, 2009Co-Authors: Phillip J Taddei, Dragan Mirkovic, Annelise Giebeler, David G Kornguth, Jason D Fontenot, Radhe Mohan, Wayne D NewhauserAbstract:Proton beam radiotherapy unavoidably exposes healthy tissue to stray radiation emanating from the treatment unit and secondary radiation produced within the patient. These exposures provide no known benefit and may increase a patient's risk of developing a radiogenic cancer. The aims of this study were to calculate doses to major organs and tissues and to estimate second cancer risk from stray radiation following craniospinal irradiation (CSI) with Proton therapy. This was accomplished using detailed Monte Carlo simulations of a passive-scattering Proton treatment unit and a voxelized phantom to represent the patient. Equivalent doses, effective dose and corresponding risk for developing a fatal second cancer were calculated for a 10-year-old boy who received Proton therapy. The Proton treatment comprised CSI at 30.6 Gy plus a boost of 23.4 Gy to the clinical target volume. The predicted effective dose from stray radiation was 418 mSv, of which 344 mSv was from neutrons originating outside the patient; the remaining 74 mSv was caused by neutrons originating within the patient. This effective dose corresponds to an attributable lifetime risk of a fatal second cancer of 3.4%. The equivalent doses that predominated the effective dose from stray radiation were in the lungs, stomach and colon. These results establish a baseline estimate of the stray radiation dose and corresponding risk for a pediatric patient undergoing Proton CSI and support the suitability of passively-scattered Proton Beams for the treatment of central nervous system tumors in pediatric patients.
J Fuchs - One of the best experts on this subject based on the ideXlab platform.
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buffered high charge spectrally peaked Proton Beams in the relativistic transparency regime
New Journal of Physics, 2016Co-Authors: N P Dover, J Fuchs, D C Carroll, C A J Palmer, M J V Streeter, H Ahmed, B Albertazzi, M Borghesi, R HeathcoteAbstract:Spectrally-peaked Proton Beams of high charge (E-p approximate to 8 MeV, Delta E approximate to 4 MeV, N approximate to 50 nC) have been observed from the interaction of an intense laser (> 10(19) W cm(-2)) with ultrathin CH foils, as measured by spectrally-resolved full beam profiles. These Beams are reproducibly generated for foil thicknesses 5-100 nm, and exhibit narrowing divergence with decreasing target thickness down to approximate to 8 degrees for 5 nm. Simulations demonstrate that the narrow energy spread feature is a result of buffered acceleration of Protons. The radiation pressure at the front of the target results in asymmetric sheath fields which permeate throughout the target, causing preferential forward acceleration. Due to their higher charge-to-mass ratio, the Protons outrun a carbon plasma driven in the relativistic transparency regime.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies $g10\text{ }\text{ }\mathrm{MeV}$, the transverse and longitudinal emittance are, respectively, $l0.004\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ and $l{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{eV}\text{ }\mathrm{s}$, i.e., at least 100-fold and may be as much as ${10}^{4}$-fold better than conventional accelerator Beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be $l15\text{ }\ensuremath{\mu}\mathrm{m}$ (FWHM) for Proton energies $g10\text{ }\text{ }\mathrm{MeV}$.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, 10 MeV.
T E Cowan - One of the best experts on this subject based on the ideXlab platform.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies $g10\text{ }\text{ }\mathrm{MeV}$, the transverse and longitudinal emittance are, respectively, $l0.004\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ and $l{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{eV}\text{ }\mathrm{s}$, i.e., at least 100-fold and may be as much as ${10}^{4}$-fold better than conventional accelerator Beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be $l15\text{ }\ensuremath{\mu}\mathrm{m}$ (FWHM) for Proton energies $g10\text{ }\text{ }\mathrm{MeV}$.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, 10 MeV.
J Seco - One of the best experts on this subject based on the ideXlab platform.
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mo ab bra 07 prompt gamma ray spectroscopy for range verification of clinical Proton Beams
Medical Physics, 2015Co-Authors: J Verburg, Thomas Bortfeld, J SecoAbstract:Purpose: We developed a pre-clinical prototype system for range verification of Proton pencil-beam scanning fields. The system was evaluated using phantom treatment plans delivered with a clinical dose rate. Methods: The absolute range of Proton pencil-Beams was verified through an optimization procedure, which matches energy- and time-resolved prompt gamma-ray measurements with models, based on cross sections for discrete prompt gamma-ray line excitations. Phantom experiments were performed with a pre-clinical prototype detector, using treatment plans delivered with a clinical pencil-beam scanning system. The detector consisted of an actively shielded lanthanum(III) bromide scintillator. Tungsten was used to collimate the gamma-rays. To support high event rates, the detector readout featured custom amplifiers and an active voltage divider for the photomultiplier. The detector signals were acquired by fast analog-to-digital converters and processed using digital algorithms. The data acquisition was also synchronized with the pencil-beam scanning and dosimetry systems. Results: We successfully acquired prompt gamma-ray spectra during the delivery of Proton pencil-Beams with a clinical beam current of 2 nA at the exit of the treatment head. The number of events in the primary detector ranged from 1 x 10⁶ to 2 x 10⁶ per second. In phantom experiments, non-uniform range errors were introduced by placing strips of plastic in the beam path. The magnitudes and positions of these range errors were correctly detected in two-dimensional range maps that were generated from the measurements. With our small scale prototype, a 1.0 mm standard deviation on the absolute range required about 5 x 10⁸ Protons per delivered pencil-beam. Conclusions: Prompt gamma-ray spectroscopy to verify the absolute range of Proton Beams was demonstrated under clinical pencil-beam delivery conditions. A 1 mm to 2 mm range verification accuracy for a field delivering 1 Gy, appears feasible with a full scale system. This work was supported by the Federal Share of program income earned on C06-CA059267, Proton Therapy Research and Treatment Center.
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range verification of passively scattered Proton Beams using prompt gamma ray detection
Physics in Medicine and Biology, 2015Co-Authors: J Verburg, M Testa, J SecoAbstract:We performed an experimental study to verify the range of passively scattered Proton Beams by detecting prompt gamma-rays emitted from Proton-nuclear interactions. A method is proposed using a single scintillation detector positioned near the distal end of the irradiated target. Lead shielding was used to attenuate gamma-rays emitted along most of the entrance path of the beam. By synchronizing the prompt gamma-ray detector to the rotation of the range modulation wheel, the relation between the gamma emission from the distal part of the target and the range of the incident Proton beam was determined. In experiments with a water phantom and an anthropomorphic head phantom, this relation was found to be sensitive to range shifts that were introduced. The wide opening angle of the detector enabled a sufficient signal-to-background ratio to be achieved in the presence of neutron-induced background from the scattering and collimating devices. Uniform range shifts were detected with a standard deviation of 0.1 mm to 0.2 mm at a dose level of 30 cGy to 50 cGy (RBE). The detectable magnitude of a range shift limited to a part of the treatment field area was approximately proportional to the ratio between the field area and the area affected by the range shift. We conclude that it is feasible to detect changes in the range of passively scattered Proton Beams using a relatively simple prompt gamma-ray detection system. The method can be employed for in vivo verification of the consistency of the delivered range in fractionated treatments.
P Audebert - One of the best experts on this subject based on the ideXlab platform.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies $g10\text{ }\text{ }\mathrm{MeV}$, the transverse and longitudinal emittance are, respectively, $l0.004\text{ }\text{ }\mathrm{mm}\text{ }\mathrm{mrad}$ and $l{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{eV}\text{ }\mathrm{s}$, i.e., at least 100-fold and may be as much as ${10}^{4}$-fold better than conventional accelerator Beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be $l15\text{ }\ensuremath{\mu}\mathrm{m}$ (FWHM) for Proton energies $g10\text{ }\text{ }\mathrm{MeV}$.
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ultralow emittance multi mev Proton Beams from a laser virtual cathode plasma accelerator
Physical Review Letters, 2004Co-Authors: T E Cowan, J Fuchs, H Ruhl, A J Kemp, P AudebertAbstract:The laminarity of high-current multi-MeV Proton Beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For Proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, 10 MeV.
