Proton Beam Energy Research Articles

ESTIMACIÓN TEÓRICA Y COMPUTACIONAL DEL STOPPING POWER PARAELECTRONES Y PROTONES DE UN DOSÍMETRO PAGAT INFUNDIDO CONNANOPARTÍCULAS DE ORO EN RANGO ENERGÉTICO DE APLICACIONES TERAPÉUTICAS

The present work focuses on the behavior of the stopping power of a polymer gel dosimetry system, known as PAGAT,infused with high atomic number nanoparticles formed by gold, with a 1 % mass concentration. The study is carried out for different energies of electron and proton beams within ranges of therapeutic applications, first by theoretical assessment, and then by simulation with Monte Carlo codes: PENELOPE in the case of electrons, and FLUKA in the case of protons. The results obtained analytically show promising behavior for gold nanoparticle infused tissue-equivalent systems, while the simulation results show better correspondence with models that consider the net path traveled, instead of models based on the thickness of the samples as typically done in experimental determinations.

Toward real-time, volumetric dosimetry for FLASH-capable clinical synchrocyclotrons using protoacoustic imaging.

Fast low angle shot hyperfractionation (FLASH) radiotherapy (RT) holds promise for improving treatment outcomes and reducing side effects but poses challenges in radiation delivery accuracy due to its ultra-high dose rates. This necessitates the development of novel imaging and verification technologies tailored to these conditions. Our study explores the effectiveness of proton-induced acoustic imaging (PAI) in tracking the Bragg peak in three dimensions and in real time during FLASH proton irradiations, offering a method for volumetric beam imaging at both conventional and FLASH dose rates. We developed a three-dimensional (3D) PAI technique using a 256-element ultrasound detector array for FLASH dose rate proton beams. In the study, we tested protoacoustic signal with a beamline of a FLASH-capable synchrocyclotron, setting the distal 90% of the Bragg peak around 35mm away from the ultrasound array. This configuration allowed us to assess various total proton radiation doses, maintaining a consistent beam output of 21 pC/pulse. We also explored a spectrum of dose rates, from 15 Gy/s up to a FLASH rate of 48 Gy/s, by administering a set number of pulses. Furthermore, we implemented a three-dot scanning beam approach to observe the distinct movements of individual Bragg peaks using PAI. All these procedures utilized a proton beam energy of 180 MeV to achieve the maximum possible dose rate. Our findings indicate a strong linear relationship between protoacoustic signal amplitudes and delivered doses (R2=0.9997), with a consistent fit across different dose rates. The technique successfully provided 3D renderings of Bragg peaks at FLASH rates, validated through absolute Gamma index values. The protoacoustic system demonstrates effectiveness in 3D visualization and tracking of the Bragg peak during FLASH proton therapy, representing a notable advancement in proton therapy quality assurance. This method promises enhancements in protoacoustic image guidance and real-time dosimetry, paving the way for more accurate and effective treatments in ultra-high dose rate therapy environments.

Laser-driven acceleration of a 94.8 MeV uniform proton beam enhanced by a thin axial absorber rod

Laser-based proton accelerators offer promising advantages for many sensitive applications due to their compact size. However, achieving uniform beams with a narrow energy spread remains a challenge. Here, a beamline simulation is performed using the racein and codes to optimize the spectral and spatial characteristics of a laser-driven proton beam. This beamline, comprised of four magnetic quadrupoles and equipped with a thin axial absorber rod in conjunction with an energy selection aperture for narrowing the energy spread, a carbon scatterer foil for beam spot smoothing, and an angular selection aperture for beam collimation, effectively transports a selected proton beam energy within the range of 50–250 MeV. In this work, laser-accelerated protons with a wide energy spread were transported through the proposed beamline, which was optimized for 109 MeV protons. The protons emerged well-collimated with a significantly narrowed energy spread of 94.8±3.9 MeV (a reduction from the intended 109 MeV due to passage through the scatterer) and a homogenized, 11 mm diameter beam spot while maintaining a transmission efficiency above 2.2%. Published by the American Physical Society 2024

Stopping power and range estimations in proton therapy based on prompt gamma timing: motion models and automated parameter optimization

Objective. Particle therapy treatments are currently limited by uncertainties of the delivered dose. Verification techniques like Prompt-Gamma-Timing-based Stopping Power Estimation (PGT-SPE) may allow for reduction of safety margins in treatment planning. Approach. From Prompt-Gamma-Timing measurements, we reconstruct the spatiotemporal distribution of prompt gamma emissions, which is linked to the average motion of the primary particles. The stopping power is determined by fitting a model of the average particle motion. Here, we compare a previously published implementation of the particle motion model with an alternative formulation and present two formulations to automatically select the hyperparameters of our procedure. The performance was assessed using Monte-Carlo simulations of proton beams (60 MeV–219 MeV) impinging on a homogeneous PMMA phantom. Main results. The range was successfully determined within a standard deviation of 3 mm for proton beam energies from 70 MeV to 219 MeV. Stopping power estimates showed errors below 5% for beam energies above 160 MeV. At lower energies, the estimation performance degraded to unsatisfactory levels due to the short range of the protons. The new motion model improved the estimation performance by up to 5% for beam energies from 100 MeV to 150 MeV with mean errors ranging from 6% to 18%. The automated hyperparameter optimization matched the average error of previously reported manual selections, while significantly reducing the outliers. Significance. The data-driven hyperparameter optimization allowed for a reproducible and fast evaluation of our method. The updated motion model and evaluation at new beam energies bring us closer to applying PGT-SPE in more complex scenarios. Direct comparison of stopping power estimates between treatment planning and measurements during irradiation would offer a more direct verification than other secondary-particle-based techniques.

Interplay of single-particle and collective modes in the 12C(p,2p) reaction near 100 MeV

The 12C(p,2p)11B reaction at Ep=98.7 MeV proton beam energy is analyzed using a rigorous three-particle scattering formalism extended to include the internal excitation of the nuclear core or residual nucleus. The excitation proceeds via the core interaction with any of the external nucleons. We assume the 11B ground and low-lying excited states [32− (0.0 MeV), 52− (4.45 MeV), 72− (6.74 MeV)] and the excited states [12− (2.12 MeV), 32− (5.02 MeV)] to be members of K=32− and K=12− rotational bands, respectively. The dynamical core excitation results in a significant cross section for the reaction leading to the 52− (4.45 MeV) excited state of 11B that cannot be populated through the single-particle excitation mechanism. The detailed agreement between the theoretical calculations and data depends on the used optical model parametrizations and the kinematical configuration of the detected nucleons.

Simulation and experimental benchmarking of a proton pencil beam scanning nozzle model for development of MR-integrated proton therapy.

MR-integrated proton therapy is under development. It consists of the unique challenge of integrating a proton pencil beam scanning (PBS) beam line nozzle with an magnetic resonance imaging (MRI) scanner. The magnetic interaction between these two components is deemed high risk as the MR images can be degraded if there is cross-talk during beam delivery and imageacquisition. To create and benchmark a self-consistent proton PBS nozzle model for empowering the next stages of MR-integrated proton therapy development, namely exploring and de-risking complete integrated prototype system designs including magnetic shielding of the PBS nozzle. Magnetic field (COMSOL ) and radiation transport (Geant4) models of a proton PBS nozzle located at OncoRay (Dresden, Germany) were developed according to the manufacturers specifications. Geant4 simulations of the PBS process were performed by using magnetic field data generated by the COMSOL simulations. In total 315 spots were simulated which consisted of a scan pattern with 5cm spot spacings and for proton energies of 70, 100, 150, 200, and 220MeV. Analysis of the simulated deflection at the beam isocenter plane was performed to determine the self-consistency of the model. The magnetic fringe field from a sub selection of 24 of the 315 spot simulations were directly compared with high precision magnetometer measurements. These focused on the maximum scanning setting of 20cm beam deflection as generated from the second scanning magnet in the PBS for a proton beam energy of 220MeV. Locations along the beam line central axis (CAX) were measured at beam isocenter and downstream of 22, 47, 72, 97, and 122cm. Horizontal off-axis positions were measured at 22cm downstream of isocenter ( 50, 100, and 150cm from CAX). The proton PBS simulations had good spatial agreement to the theoretical values in all 315 spots examined at the beam line isocenter plane (0-2.9mm differences or within 1.5% of the local spot deflection amount). Careful analysis of the experimental measurements were able to isolate the changes in magnetic fields due solely to the scanning magnet contribution, and showed 1.9 1.2 -9.4 1.2 changes over the range of measurement locations. Direct comparison with the equivalent simulations matched within the measurement apparatus and setup uncertainty in all but one measurementpoint. For the first time a robust, accurate and self-consistent model of a proton PBS nozzle assembly has been created and successfully benchmarked for the purposes of advancing MR-integrated proton therapy research. The model will enable confidence in further simulation based work on fully integrated designs including MRI scanners and PBS nozzle magnetic shielding in order to de-risk and realize the full potential of MR-integrated proton therapy.

Liquid-lithium-cooled beryllium target as the p-to-n converter

Thermal analysis and neutron moderation simulations were carried out to assess the feasibility and performance of a proton-beam-driven neutron source where the (p,n) conversion target is a cuvette made of beryllium and cooled by flowing liquid lithium. Using a prototype model with 5 MeV proton beam energy, the simulations show that this type of target can be highly beneficial in upgrading existing facilities operating with a beryllium target, or in designing new compact neutron sources.

A study on the effects of long-term radiation exposure on superconducting magnets in MRI-Guided proton therapy

In this publication, we offer the first assessment of the long-term radiation impact on superconducting magnets utilized in MRI-guided proton therapy. We explore both uniform and non-uniform magnetic fields and create three improved therapy plans for shallow (brain), medium (liver), and deep (prostate) targets. The evaluation of radiation damage in superconducting magnets using therapy plans is carried out through the implementation of the Monte Carlo method, molecular dynamics method, and modified NRT model. The results of the three plans show that a large amount of particles do enter the superconducting magnet during the treatment, with a preponderance of photons and neutrons. For superconducting magnets in MRI systems, the closer the coil is to the target area, the greater the radiation damage, and the extent of radiation damage increases with the energy of the incident proton beam. The PKA with high energy can induce temperature fluctuations locally in the superconducting coils, but does not pose a threat to its mechanical properties. Following 20 years of continuous operation, the DPA of the internal coils is about 2.3097E-17, and the maximum dose to insulating layer is about 1.25 Gy. The results of this paper show that MRI-guided proton therapy poses no threat to the long-term operation of superconducting magnets.

Secondar neutrons induced from a medical proton accelerator in a water phantom

This study investigates the production of radiation-induced secondary neutrons resulting from the irradiation of a water phantom by a medical proton accelerator. Measurements were conducted using a 2-inch by 2-inch stilbene scintillation detector. To distinguish between neutrons and the gamma background, we applied a pulse shape discrimination technique utilizing the charge integration ratio (Qratio) method. Our analysis carries out for three proton beam energies: 76 MeV, 80 MeV, and 132 MeV. The findings demonstrate the feasibility of using a stilbene scintillator detector in conjunction with the Qratio method for the measurement and analysis of secondary neutrons, which are detectable in significant quantities.

Maxwell–Boltzmann-like neutron spectrum production for Maxwellian averaged cross sections measurements

Over the years, Maxwellian Averaged Cross Sections (MACS) have been measured by neutron activation, providing a neutron energy spectrum resembling the one found inside the stars. Recently, a new method has been proposed to produce stellar spectra at different stellar temperatures (a Maxwell–Boltzmann neutron energy distribution), employing the 7Li(p,n)7Be reaction. The method is based on the idea of shaping the proton beam energy to shape the neutron beam spectrum. This method was applied to obtain a well-reproduced Maxwell–Boltzmann neutron spectrum (MBNS) at kT=28 keV. An initial proton energy of 3170 keV and an aluminum foil as a proton energy shaper were employed. Differential angular neutron energy distributions from 0 to 90 degrees in 10∘ steps were measured to obtain the 0∘–90∘ integrated neutron spectrum over a neutron flight path of 50 cm. This manuscript reports on the measurement results, confirming the method’s capability, and suggests the approach for producing a high-quality MBNS at kT=28 keV.

Visible proton Bragg curve imaging by colour centre photoluminescence in radiation detectors based on lithium fluoride films on silica

Passive solid-state radiation detectors, based on the visible photoluminescence (PL) of radiation-induced colour centres in optically transparent lithium fluoride (LiF), polycrystalline thin films are under investigation for proton beam advanced diagnostics. After proton exposure, the latent images stored in LiF as local formations of stable F2 and F3 + aggregate defects, are directly read with a fluorescence microscope under illumination in the blue spectral range. Adopting a suitable irradiation geometry, the energy density that protons deposit in the material can be recorded as a spatial distribution of these light-emitting defects, from which a luminous replica of the proton Bragg curve can be thereafter extracted and analysed to reconstruct the proton beam energy spectrum. Their peculiar properties, such as wide dynamic range and linearity of the spectrally-integrated PL response vs. dose, make the investigation of two-dimensional LiF film radiation detectors grown on several types of substrate highly attractive. Here, the case of a LiF thin film thermally evaporated on a silica substrate, irradiated at grazing incidence with a 35 MeV proton beam, is investigated and reported for the first time. A comparison of the measured photoluminescent Bragg curve with Monte Carlo simulations demonstrates that the Bragg peak in the film is located at the very same position that would be expected in the underlying silica substrate rather than in LiF. The film packing density is shown not to have a significant effect on the peak depth, while even small nonzero grazing angle of the impinging proton beam is able to significantly modify the shape of the Bragg curve. These findings are ascribed to the effects of multiple Coulomb scattering in both the film and the substrate and are interesting for proton beam diagnostics and dosimetry.

Improving the potential of BDF@SPS to search for new physics with liquid argon time projection chambers

Beam dump experiments proposed at the SPS are perfectly suited to explore the parameter space of models with long-lived particles, thanks to the combination of a large intensity with a high proton beam energy. In this paper, we study how the exploration power may be augmented further by installing a detector based on liquid argon time projection chamber technology. In particular, we consider several signatures of new physics particles that may be uniquely searched for with such a detector, including double bang events with heavy neutral leptons, inelastic light dark matter, and millicharged particles.

Creating uniform cluster dose spread-out Bragg peaks for proton and carbon beams.

Preliminary data have shown a close association of the generalized ionization cluster size dose (in short, cluster dose) with cell survival, independent of particle type, and energy, when cluster dose is derived from an ionization detail parameter preferred for its association with cell survival. Such results suggest cluster dose has the potential to replace RBE-weighted dose in proton and ion beam radiotherapy treatment plan optimization, should a uniform cluster dose lead to comparable biological effects. However, further preclinical investigations are warranted to confirm this premise. To present an analytical approach to create uniform cluster dose spread-out Bragg peaks (SOBP) for evaluation of the potential of cluster dose to result in uniform biological effect. We modified the coefficients of the Bortfeld and Schlegel weight formula, an analytical method typically used for the creation of radiation dose SOBP in particle therapy, to produce uniform cluster dose SOBP of different widths (1-5cm) at relevant clinical proton and carbon beam energies. Optimum parameters were found by minimization of the ratio between the maximum and minimum cluster dose in the SOBP region using the Nelder-Mead method. The coefficients of the Bortfeld and Schlegel weight formula leading to uniform cluster dose SOBPs were determined for each combination of beam energy and SOBP width studied. The uniformity of the resulting cluster dose SOBPs, calculated as the relative difference between the maximum and minimum cluster dose within the SOBP, was within 0.3%-3.5% for the evaluated proton beams and 1.3%-3.4% for the evaluated carbon beams. The modifications to the analytical approach to create radiation dose SOBPs resulted in uniform cluster dose proton and carbon SOBPs over a wide range of beam energies and SOBP widths. Such SOBPs should prove valuable in preclinical investigations for the selection of nanodosimetric quantities to be used in proton and ion therapy treatment planning.

High-gradient performance of a prototype accelerator cavity for a 3 GeV proton radiography booster

This paper reports the design, fabrication, and results of the high-gradient conditioning and testing for a two-cell, π-mode, standing wave normal-conducting prototype booster cavity for the proposed 3 GeV proton linac upgrade at Los Alamos Neutron Science Center. Increasing the energy of proton beam from the existing 800 MeV to 3 GeV will improve resolution of the proton radiography by up to 10 times. The proposed energy boost can be achieved with a compact normal-conducting high-gradient radio-frequency (rf) linac section. The C-band section of the booster linac was designed with optimized-shaped copper accelerator cavities with distributed rf coupling. A short two-cell test prototype structure was designed for the frequency of 5.712 GHz, fabricated, and tested at the C-band Engineering Research Test Facility in New Mexico (CERF-NM) at Los Alamos National Laboratory. The maximum klystron power coupled into the test structure was 8.3 MW with 1 μs pulse length and 100 Hz repetition rate. The breakdown probabilities were recorded as functions of the accelerating gradient and peak surface fields. Operation of the test cavity at accelerating gradients of up to 100 MV/m was demonstrated. Published by the American Physical Society 2024

Development of focusing multi-knife-edge camera for proton beam range verification: A Monte Carlo study

Proton range uncertainties limit the ability to make full clinical use of the sharp distal falloff of the proton beam. To overcome this limitation, prompt gamma (PG) imaging system with mechanical collimation can be used in non-invasive proton beam range verification. In this study, we developed a focusing multi-knife-edge collimator to improve the counting efficiency and accuracy in detecting proton beam range. Unlike the common design of a single-knife-edge slit (SKE) collimator, the multi-knife-edge slit (MKE) collimator consists of three slits and focuses on the target detection area. To compare the performances of these two collimator designs, Monte Carlo simulation was unitized to model the cameras for measuring the PGs during proton irradiation. The simulation was performed using the GATE v9.1. The setup included a pencil beam of 100 MeV, 160 MeV, and 230 MV protons incident upon a cylindrical PMMA phantom with three different proton numbers of 107, 108, and 109. The detection PG profiles were fitted with a 3-line-segment fitting method to estimate the range of proton beams. Both cameras were aimed at the expected range depth for the corresponding proton beam energies. Experiments for range shifts were conducted by shifting the phantom between −20 mm and 20 mm along the beam axis. Results demonstrate that the MKE camera exhibits approximately twice the efficiency of the SKE camera in detecting PGs. In range shift retrieval, with the delivery of 108 protons, the MKE camera achieves submillimeter accuracy (except for incident protons at 230 MeV), while the SKE camera achieves accuracy within 2 mm. In conclusion, this study assesses the feasibility of the MKE camera and illustrates its potential application for range shift detection, contributing to precise range monitoring in proton therapy.

A new experiment on 19F(p, α)16O reaction at low energies and the spectroscopy of 20Ne at large excitation energies

In these proceedings, we present new data for the p + 19F reaction, obtained for the 19F(p, α0)16Ogs and 19F(p, απ)16O6.05 channels. The experiment was performed at the Singletron accelerator in Catania, with proton beam energies in the 1.1-1.3 and 1.6-1.7 MeV energy regions. This allowed us to provide new data for the απ channel around 1.3 MeV projectile energy and to shed light on the ambiguities existing between previous data sets in the absolute value and in the peak shape of a particular resonance, in the α0 channel, at around 1.6 MeV projectile energy.

Investigation of proton single-event transient in CMOS image sensor

With the increasingly widespread application of CMOS image sensors (CIS) in radiation environments, such as aerospace, their radiation effects have gained attention. This paper investigates single-event transient (SET) caused by the proton direct ionization on CIS, combining both experimental and simulation methods. The proton beam energy used in the experiment is 12 MeV, with a flux up to 3.5 × 108 p/(cm2 s). Due to the periodicity of the proton beam, the CIS output displays a phenomenon of alternating brightness and darkness. When the proton beam flux is low, numerous SET bright spots with different outputs are observed. To comprehensively analyze these experimental phenomena, a typical three-dimensional 4T pinned photodiode model is constructed in TCAD, and relevant SET simulation is carried out. The results indicate that incident position, incident time, and the number of incident protons significantly affect the output of SET-generated bright spots, which are key factors contributing to the different bright spots observed in the experiment.

Effects of modern aesthetic dental fillings on proton therapy

Background and purposeHigh-density dental fillings pose a non-negligible impact on head and neck cancer treatment. For proton therapy, stopping power ratio (SPR) prediction will be significantly impaired by the associated image artifacts. Dose perturbation is also inevitable, compromising the treatment plan quality. While plenty of work has been done on metal or amalgam fillings, none has touched on composite resin (CR) and glass ionomer cement (GIC) which have seen an increasing usage. Hence, this work aims to provide a detailed characterisation of SPR and dose perturbation in proton therapy caused by CR and GIC. Materials and methodsFour types of fillings were used: CR, Fuji Bulk (FB), Fuji II (FII) and Fuji IX (FIX). The latter three belong to GIC category. Measured SPR were compared with SPR predicted using single-energy computed tomography (SECT) and dual-energy computed tomography (DECT). Dose perturbation of proton beams with lower- and higher-energy levels was also quantified using Gafchromic films. ResultsThe measured SPR for CR, FB, FII and FIX were 1.68, 1.77, 1.77 and 1.76, respectively. Overall, DECT could predict SPR better than SECT. The lowest percentage error achieved by DECT was 19.7 %, demonstrating the challenge in estimating SPR, even for fillings with relatively lower densities. For both proton beam energies and all four fillings of about 4.5 mm thickness, the maximum dose perturbation was 3 %. ConclusionThis study showed that dose perturbation by CR and GIC was comparatively small. We have measured and recommended the SPR values for overriding the fillings in TPS.

Calibration assessment of the PSI proton therapy Gantry 2 scanning system after 10 years of operation

Sub-millimetre precision is a crucial criterion for beam delivery in Pencil Beam Scanning (PBS) proton therapy. Nowadays, most of the therapy systems use PBS technique where single beams with a regulated number of protons are delivered sequentially to different locations within the target. Beam energy defines the depth of the beam in the target and scanner magnets deflect the beam to the desired lateral position.The PSI Gantry 2 was among the first gantries to use the PBS technique. Available clinical proton beam energies ranging from 70 MeV to 230 MeV are achieved by de-grading a 250 MeV beam, initially provided by a super-conducting cyclotron. Beam scanning is performed just before the last bending magnet producing a nearly parallel beam at iso-centre with a well-focused beam over the full scan area of 20×12 cm2. We developed a calibration algorithm for the scanner magnets in order to achieve the desirable precision of the beam in the target. Measuring the beam position with a strip ion chamber in the gantry nozzle, we parametrized the propagation of the beam to the target calculating the beam angle at different scan positions as well as all gantry angles. During 10 years of operation we performed regular Quality Assurance (QA) tests to validate parameters obtained during the system commissioning. The QA data proved a stable system operation and no parametrization update was required so far. In this contribution, we describe the calibration pro-cess of scanning magnets with respect to beam position at the isocentre and show the stability of this implementation over the time.

Proton Beam Range and Charge Verification Using Multilayer Faraday Collector.

A daily quality assurance (QA) check in proton therapy is ensuring that the range of each proton beam energy in water is accurate to 1 mm. This is important for ensuring that the tumor is adequately irradiated while minimizing damage to surrounding healthy tissue. It is also important to verify the total charge collected against the beam model. This work proposes a time-efficient method for verifying the range and total charge of proton beams at different energies using a multilayer Faraday collector (MLFC). We used an MLFC-128-250 MeV comprising 128 layers of thin copper foils separated by thin insulating KaptonTM layers. Protons passing through the collector induce a charge on the metallic foils, which is integrated and measured by a multichannel electrometer. The charge deposition on the foils provides information about the beam range. Our results show that the proton beam range obtained using MLFC correlates closely with the range obtained from commissioning water tank measurements for all proton energies. Upon applying a range calibration factor, the maximum deviation is 0.4 g/cm2. The MLFC range showed no dependence on the number of monitor units and the source-to-surface distance. Range measurements collected over multiple weeks exhibited stability. The total charge collected agrees closely with the theoretical charge from the treatment planning system beam model for low- and mid-range energies. We have calibrated and commissioned the use of the MLFC to easily verify range and total charge of proton beams. This tool will improve the workflow efficiency of the proton QA.