Beam Dose Research Articles

Estimations of fluorine-18 production yields from 13-MeV proton bombardment of enriched water target

Fluorine-18 (18F) is a positron emitter frequently used in Positron Emission Tomography (PET) to assist in the staging of primary tumors, Recent research suggests that the positron emitting radionuclide can also be applied for pneumonia imaging caused by Covid-19 infection. In this work, a 13-MeV proton beam was theoretically bombarded to 99.5% enriched water (H2 18O) target to produce 18F radionuclide via (p, n) nuclear reaction. The CalcuYield code was used in the predictions of the F-18 production yields. Using the CalcuYield code, the 18F radioactivity yields were calculated at the end of bombardment (EOB) at various proton beam currents, irradiation time and proton beam doses. Based on the CalcuYield calculated results, the maximum EOB yield of 18F at 13 MeV proton energy was 60.073 mCi/µAh. At a proton dose of 60 µAh, the EOB yield could be achieved as high as 3784.393 mCi, which could be used to diagnose more than 500 patients. The calculations also found that for the same proton dose, increasing proton beam current would result in greater 18F radioactivity yield than increasing irradiation time. In addition, radionuclide impurities which could predictably be present in the target were mostly due to nuclear reactions between proton beam and havar window. The predicted radionuclide impurities include 96Tc, 55Fe, 59Ni, 56Co, 52Mn, 186Re and 58Cu which were due to (p, n) nuclear reactions. The total radionuclide impurity yield was found to be 0.793 mCi/µAh. Among the other impurities, 58Cu was expected to have the highest radioactivity yield at all irradiation parameters. These predicted results could be used as a reference for future 18F radionuclide production should a 13-MeV proton beam is employed.

Rotation during reaction

Catalysis Determining changes in heterogeneous catalysts under reaction conditions can provide insight into mechanisms. Under reaction conditions, not only can metal nanoparticles change shape but their interaction with the oxide support could also be affected. Yuan et al. used aberration-corrected environmental transmission electron microscopy to study gold nanoparticles on titanium surfaces at low electron beam doses. During carbon monoxide (CO) oxidation at total pressures of a few millibars and 500°C, they observed that gold nanoparticles rotated by about 10° but returned to their original position when CO was removed. Density function theory calculations indicated that rotation was induced by changes in the coverage of adsorbed molecular oxygen at the interface. Science , this issue p. [517][1] [1]: /lookup/doi/10.1126/science.abe3558

Radioprotective effect of melatonin against radiotherapy-induced cerebral cortex and cerebellum damage in rat

Purpose The present study aims to investigate the radioprotective effect of melatonin (MEL) against early period brain damage caused by different dose rate beams in the experimental rat model. Materials and methods Forty-eight Sprague Dawley rats were randomly divided into six groups; the control, only melatonin, low dose rate-radiotherapy (LDR-RT), high dose rate-radiotherapy (HDR-RT) groups and (LDR-RT) + MEL and (HDR-RT) + MEL radiotherapy plus melatonin groups. Each rat administered melatonin was given a dose of 10 mg/kg through intraperitoneal injection, 15 minutes before radiation exposure. The head and neck region of each rat in only radiotherapy and radiotherapy plus melatonin groups was irradiated with a single dose of 16 Gy in LDR-RT and HDR-RT beams. Rats in all groups were examined for histopathology and biochemistry analysis 10 days after radiotherapy. Results Comparing the findings for LDR-RT and HDR-RT only radiotherapy groups and the control group, there was a statistically significant difference in histopathological and biochemical parameters, however, melatonin administered in radiotherapy plus melatonin groups contributed improving these parameters (p < .05). There was no statistically significant difference between LDR-RT and HDR-RT beams (p > .05). Conclusions It was concluded that melatonin applied before LDR-RT and HDR-RT radiotherapy protected early period radiotherapy-induced brain damage. The effects of clinically low and high dose beams on the cerebral cortex and cerebellum were investigated histopathologically for the first time. HDR beams can be safely applied in brain radiotherapy. However, more experimental rat and clinical studies are needed to explain the radiobiological uncertainties about the clinic dose rate on different cancerous and healthy tissues.

Atomic imaging of the motion and transformation of Pt3Ni nanoparticles in liquids

In this work, we used liquid cell TEM to observe the motion and transformation pathways of Pt3Ni nanoparticles in solution by systematically changing the electron beam dose rate.

Electron-Beam Irradiation Induced Regulation of Surface Defects in Lead Halide Perovskite Thin Films.

Organic-inorganic hybrid perovskites (OIHPs) have been intensively studied due to their fascinating optoelectronic performance. Electron microscopy and related characterization techniques are powerful to figure out their structure-property relationships at the nanoscale. However, electron beam irradiation usually causes damage to these beam-sensitive materials and thus deteriorates the associated devices. Taking a widely used CH3NH3PbI3 film as an example, here, we carry out a comprehensive study on how electron beam irradiation affects its properties. Interestingly, our results reveal that photoluminescence (PL) intensity of the film can be significantly improved along with blue-shift of emission peak at a specific electron beam dose interval. This improvement stems from the reduction of trap density at the CH3NH3PbI3 surface. The knock-on effect helps expose a fresh surface assisted by the surface defect-induced lowering of displacement threshold energy. Meanwhile, the radiolysis process consistently degrades the crystal structure and weaken the PL emission with the increase of electron beam dose. Consequently, the final PL emission comes from a balance between knock-on and radiolysis effects. Taking advantage of the defect regulation, we successfully demonstrate a patterned CH3NH3PbI3 film with controllable PL emission and a photodetector with enhanced photocurrent. This work will trigger the application of electron beam irradiation as a powerful tool for perovskite materials processing in micro-LEDs and other optoelectronic applications.

Transverse profile forming for high energy electron beams using 3D-printed plastic samples

The work presents application of previously proposed approach for transverse profile forming of high energy electron beams with plastic samples made using 3D printing technology. The collimator made of PLA (polylactide) plastic is designed and produced in a frame of this work. The results of transverse profile forming for 6 MeV electron beam of clinical linear accelerator Elekta Synergy using designed collimator is presented. Obtained results comparison with data from XiO dosimetry planning system shows good agreement of calculated and experimentally formed by plastic collimator electron beam dose fields.

LaAlO3:Pr3+ as photon radiotherapy dosimeter

The intention of radiotherapy is to control and cure tumor while avoiding late effects caused by radiation. High energy photon beam dose can be determined by different modalities. In this paper, dosimetric properties of praseodymium doped lanthanum aluminate exited by X-ray beams are reported. LaAlO3:Pr3+ powders samples were prepared using modified Pechinis’s method. The formations of the obtained samples were confirmed by an X-ray diffraction patterns. TL glow curve and dosimetric characteristics of LaAlO3:Pr3+ powder samples were investigated under X-ray irradiation effects. All TL measurements were made using an automated Harshaw TL reader 5500. TL glow curves were obtained using a constant heating rate 10 °C/s from room temperature up to 350°C in a nitrogen atmosphere. The dose response and minimum detectable dose (MDD) values of the samples were determined. Dosimetric characteristics of the samples were carefully analyzed. Experimental results of TL dosimetric characteristics of the powder samples appear to have potential application for high energy photon beam dose measurements.

Comparison of Starch Characteristics from Pigmented and Non‐Pigmented Sorghum Cultivars before and after Electron Beam Irradiation

AbstractStarch is extracted from the seeds of a pigmented (Phule Rohini) and a non‐pigmented (Phule Maldandi) Indian sorghum cultivar using same wet milling method for both cultivars. This study is focused on investigation of the effect of the pigment on starch characteristics. Isolated starches differing in color are irradiated with an electron beam dose of 5 kGy and compared by measuring physicochemical, structural, pasting, and digestibility properties. Amylose content increases after irradiation and the increase is greater in the case of Phule Maldandi starch. The pigmented starch shows higher carboxyl content after irradiation which may be due to higher amylopectin content. Granular morphology remains constant after irradiation. Irradiation causes a decrease in swelling power and an increase in pasting viscosity of both starches. Color content of red sorghum starch is not changed significantly after irradiation. The increase in pasting viscosity and solubility of non‐pigmented starch is more drastic in nonpigmented starch than in pigmented starch after irradiation. Resistant starch decreases after irradiation which indicates opening up of granular structure or hydrolytic action of irradiation. Pigmented starch can have potential applications in custard powder and bakery products.

PFOA and PFOS breakdown in experimental sand, laboratory-grade water, investigation-derived groundwater and wastewater effluent samples at 50 kGy electron beam dose

In recent years, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been recognized as widespread persistent organic pollutants and identified as a great concern to public health. Electron beam (eBeam) technology is a form of ionizing radiation that had been previously successful in mediating the breakdown of PFOA and PFOS. These studies report complete breakdown of PFOA and partial breakdown of PFOS in samples with high pH, nitrate content, alkalinity, and anoxic conditions when exposed to eBeam technology at a dose of 50 kilograys (kGy). In lab-spiked water and sand, the concentrations of PFOA were reduced by 87% and 86% respectively. PFOS was reduced by 16% in lab-spiked water and 28% in lab-spiked sand. In spiked IDW groundwater exposed to 50 kGy, PFOA and PFOS were reduced by 98% and 41% respectively. Groundwater samples were collected from a monitoring well at Randolph AFB in San Antonio, TX, USA. Similarly, PFOA was reduced by 94% and PFOS by 41% in spiked post-UV wastewater effluent collected at the Texas A&M water treatment plant in College Station, TX, USA. Although the aforementioned conditions facilitated the complete breakdown of PFOA, more optimization and higher doses will be needed to achieve the same in PFOS.

Effect of Electron Beam Irradiation on Viability of Sarcocystis spp. in Beef

Background: Sarcocystosis is one of the most distributed parasitic diseases over the world, caused by Sarcocystis spp. In this study, we assessed the effect of electron beam irradiation on the viability of Sarcocystis spp. in beef. Methods: Experimental beef groups were irradiated by four different electron beam doses of 1, 2, 3, and 4 kGy, at intervals of 0 and 24 h after irradiation, then the samples were transferred inside a sterile microtube containing RNAlater solution and stored at -20 °C till next steps. RNA extractions and cDNA synthesis were done using the related kit in order to detect the presence of the 18S ribosomal RNA region. Relative quantification was carried out using SYBR Green Real time Polymerase Chain Reaction. The statistical analysis was done using SPSS 16.0 by Tukey’s and Kruskal-Wallis tests. Results: Irradiation at zero time was not effective on viability of Sarcocystis, but at 24 h, irradiation doses of 3 (p=0.003) and 4 kGy (p=0.008) caused a significant reduction in Sarcocystis viability. Irradiation doses of 1 and 2 kGy had no significant (p&gt;0.05) effect on Sarcocystis viability reduction. Also, no significant differences (p&gt;0.05) were observed between irradiation doses of 3 and 4 kGy. Conclusion: Electron beam radiation at dose of 3 kGy was effective as the optimal dose for the elimination of Sarcocystis spp. in beef.

A novel approach to seamless simulations of compact hadron therapy systems for self-consistent evaluation of dosimetric and radiation protection quantities

Hadron therapy installations are evolving towards more compact systems that require higher-quality beams for advanced treatment modalities such as proton flash and arc therapy. Therefore the accurate modelling of present and next-generation systems poses new challenges where the simulations require both magnetic beam transport and particle-matter interactions. We present a novel approach to building simulations of beam delivery systems at a level suitable for clinical applications while seamlessly providing the computation of quantities relevant for beam dose deposition, radiation protection assessment, and shielding activation determination. A realistic model of the Ion Beam Applications (IBA) Proteus® One system is developed using Beam Delivery Simulation (BDSIM), based on Geant4, that uniquely allows simulation using a single model. Its validation against measured data is discussed in detail. The first results of self-consistent simulations for beam delivery and equivalent ambient dose are presented. The results show that our approach successfully models the complex interactions between the beam transport and its interactions with the system for relevant clinical scenarios at an acceptable computational cost.

Tumor Immune Microenvironment in Response to Radiotherapy vs BCG in a Murine Model of Bladder Cancer

The role of radiotherapy combined with immunotherapy in patients with non-muscle invasive bladder cancer (NMIBC) is currently being investigated. Radiation induced DNA damage triggering immunogenic tumor cell death and consequent immune responses in bladder tumor microenvironment is not fully understood. We compared local immune response following radiotherapy with BCG-induced immune response using a BBN murine model of urothelial carcinoma (UC). Female C57BL/6 control(no tumor, n=15) or BBN exposed mice(tumor, n=13) received radiotherapy(single external beam dose,15 Gy,n=10), intravesical BCG instillation (3 × 100μL of 1 × 10 8 CFU,n=9) or saline treatment (n=9). Tumor involvement was assessed by pathologic grading of bladder tissue and immune responses quantified using Nanostring Myeloid Innate Immunity Panel. Infiltrating Tcells were evaluated by CD4, CD8 and FOXP3 immunohistochemistry (IHC) and tissue macrophages quantified as M1 or M2 phenotype based on CD86 and CD206 IHC. No tumors were seen in BBN+BCG bladder tissues compared to BBN+saline or BBN+radiotherapy. Intravesical BCG instillation in BBN mice elevated cytosolic DNA sensing pathway as seen by increased mRNA levels of tmem173 (STING) that was consistent with elevated levels of downstream cytokines tnfa, infg, il6 and chemokine cxcl10 . mRNA expression of 3’exonuclease trex1 , that degrades 3′ ends of nicked DNA during immunogenic cell death, was elevated in BBN+BCG as well as BBN+radiation samples. BBN+BCG samples had increased CD8/FOXP3 and CD4/FOXP3 ratios assessed by IHC and increased M1 macrophage shift validated by mRNA expression and IHC. BCG instillation caused a robust proinflammatory immune response compared to radiation in murine UC possibly via STING-dependent induction of proinflammatory cytokines and chemokines concomitant with shift toward M1 macrophage polarization and increased Teff/Treg ratios. Elevated trex1 may degrade DNA damage as a direct response to radiation thereby inhibiting STING activation and cytokine response in radiated samples. These findings highlight the need to uncover mechanisms of radiation induced immune response in NMIBC to optimize utilization of immunotherapy with radiotherapy.

Radiotherapy enhances uptake and efficacy of 90Y-cetuximab: A preclinical trial

Background and purposeSystemic molecular radiotherapy utilizes internal irradiation by radionuclide-labeled tumor-targeting agents with the potential to destroy (micro-)metastases. However, doses that are applicable in solid tumors do not reach the levels nessecary for tumor control. Thus, the combination of molecular and external radiotherapy is a promising treatment strategy, as enhanced tumor doses can be delivered with and without minor overlapping toxicities. Here, we combined a 90Y-labeled anti-EGFR antibody (Cetuximab) with clinically relevant fractionated radiotherapy in a preclinical trial using head and neck squamous cell carcinoma xenograft tumors. Materials and methodsTo model 90Y-Cetuximab uptake for treatment schedule optimization, FaDu-bearing mice were injected with near-infrared-labeled-Cetuximab at different time points during radiotherapy with differing doses. Cetuximab uptake was longitudinally followed by in vivo-optical imaging. Tumor control probability experiments with fractionated radiotherapy (30 fx, 6 weeks, 8 dose groups/ arm) in combination with 90Y-Cetuximab were performed to test the curative potential. ResultsImaging of near-infrared-labeled-Cetuximab uptake revealed that low to moderate external beam doses can enhance antibody uptake. Using the optimized schedule, combination of molecular and external radiotherapy using 90Y-Cetuximab at a dose that did not result in permanent tumor inactivation in previous experiments, led to substantially increased tumor control compared to radiotherapy alone. ConclusionOur results indicate that combination of radiolabeled therapeutics with clinically relevant fractionated radiotherapy has a remarkable potential to improve curative treatment outcome. Application of some radiation dose prior to injection may improve drug uptake and enable patient stratification and treatment personalization via a corresponding PET-tracer during therapy.

Carbon Ion Therapy Inhibits Esophageal Squamous Cell Carcinoma Metastasis by Upregulating STAT3 Through the JAK2/STAT3 Signaling Pathway.

Radiation therapy is an important component of the comprehensive treatment of esophageal cancer. However, conventional radiation resistance is one of the main reasons for treatment failure. The superiority of heavy ion radiation in physics and biology has been increasingly highlighted in radiation therapy research. The Janus Kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) pathway plays an important role in the occurrence, development and metastasis of esophageal squamous cell carcinoma (ESCC) and is related to the development of resistance to ionizing radiation in ESCC. Therefore, the aim of the present study was to investigate the relationship between carbon ion inhibition of the proliferation and metastasis of esophageal carcinoma cells and the JAK2/STAT3 signaling pathway. The results demonstrated that carbon ion beams significantly reduced cell viability and stimulated apoptosis in human ESCC cells in a dose-dependent manner. In addition, carbon ion beams induced G2/M phase cell cycle arrest in ESCC cells and inhibited tumor metastasis in a dose-dependent manner. Additionally, poorly differentiated KYSE150 cells were more sensitive to the same carbon ion beam dose than moderately differentiated ECA109 cells. Carbon ion beam exposure regulated the relative expression of metastasis-related molecules at the transcriptional and translational levels in ESCC cells. Carbon ion beams also regulated CDH1 and MMP2 downstream of the STAT3 pathway and inhibited ESCC cell metastasis, which activated the STAT3 signaling pathway. This study confirmed the inhibition of cell proliferation and the metastatic effect of carbon ion beam therapy in ESCC cells.

Theoretical lateral and axial sensitivity limits and choices of molecular reporters for Cherenkov-excited luminescence in tissue during x-ray beam scanning.

.Purpose: Unlike fluorescence imaging utilizing an external excitation source, Cherenkov emissions and Cherenkov-excited luminescence occur within a medium when irradiated with high-energy x-rays. Methods to improve the understanding of the lateral spread and axial depth distribution of these emissions are needed as an initial step to improve the overall system resolution.Methods: Monte Carlo simulations were developed to investigate the lateral spread of thin sheets of high-energy sources and compared to experimental measurements of similar sources in water. Additional simulations of a multilayer skin model were used to investigate the limits of detection using both 6- and 18-MV x-ray sources with fluorescence excitation for inclusion depths up to 1 cm.Results: Simulations comparing the lateral spread of high-energy sources show approximately higher optical yield from electrons than photons, although electrons showed a larger penumbra in both the simulations and experimental measurements. Cherenkov excitation has a roughly inverse wavelength squared dependence in intensity but is largely redshifted in excitation through any distance of tissue. The calculated emission spectra in tissue were convolved with a database of luminescent compounds to produce a computational ranking of potential Cherenkov-excited luminescence molecular contrast agents.Conclusions: Models of thin x-ray and electron sources were compared with experimental measurements, showing similar trends in energy and source type. Surface detection of Cherenkov-excited luminescence appears to be limited by the mean free path of the luminescence emission, where for the given simulation only 2% of the inclusion emissions reached the surface from a depth of 7 mm in a multilayer tissue model.

Enhanced response of radioresistant carcinoma cell line to heterogeneous dose distribution of grid; the role of high-dose bystander effect

Purpose The classical dogma that restricted the radiation effect to the directly irradiated cells has been challenged by the bystander effect. This off-target phenomenon which was manifested in adjacent cells via signaling of fully exposed cells might be involved in high-dose Grid therapy as well. Here, an in-vitro study was performed to examine the possible extent of carcinoma cells response to the inhomogeneous dose distribution of Grid irradiation in the context of the bystander effect. Materials and methods Bystander effect was investigated in human carcinoma cell lines of HeLa and HN5 adjacent to those received high-dose Grid irradiation using ‘medium transfer’ and ‘cell-to-cell contact’ strategies. Based on the Grid peak-to-valley dose profile, medium transfer was exerted from 10 Gy uniformly exposed donors to 1.5 Gy uniformly irradiated recipients. Cell-contact bystander was evaluated after nonuniform dose distribution of 10 Gy Grid irradiation using cloning cylinders. GammaH2AX foci, micronucleus and clonogenic assays besides gene expression analysis were performed. Results Various parameters (ɑ/β, D37, D50) extracted from survival curve which fitted to the Linear Quadratic model, verified more radioresistance of HN5. Survival fraction at 2 Gy (SF2) indicated as 0.42 ± 0.06 in HeLa and 0.5 ± 0.03 in HN5. The level of survival decrease, DNA damages and micronucleus of cells located in the Grid shielded areas (1.5 Gy cell-to-cell contact bystander cells) were significantly more than the values obtained from cells which were irradiated by merely uniform dose of 1.5 Gy. The gH2AX foci and micronuclei frequencies were enhanced in cell-contact bystander approximately more than 1.8 times. Relative expression of DNA damage repair pathway genes (Xrcc6 and H2afx) in bystander cells increased significantly. The most cell survival reduction (11.6 times) was revealed in the Grid bystander cells of radioresistant cell line (HN5). No statistically significant difference between 10 Gy uniform beam and Grid non-uniform beam was observed. Conclusions Various endpoints confirmed an augmented response of cells in the valley dose region of the Grid block significantly (compared with the cells irradiated by identical dose of uniform beam), suggesting the role of high-dose bystander effect which was more pronounced in resistant carcinoma cell lines. These findings could provide a partial explanation for the Grid beneficial response seen in a number of pre-clinical and clinical studies.

On-line beam monitoring and dose profile measurements of a [formula omitted]Pb beam of 150 GeV/n with a liquid-filled ionization chamber array

In this study, the possibility of on-line monitoring of an ultra-high-energy (UHE) beam of 150 GeV/n lead (208Pb) ions using a liquid-filled ionization chamber array (OCTAVIUS 1000SRS, PTW Freiburg, Germany) is evaluated. The applicability of the array has been tested for the investigated beam, where adequate adjustments of the array have been made for measurements under very low fluxes of 102 to 104 ions / cm2/s. The results have been compared to measurements obtained using the standard beam line detectors, such as a scintillator and a delay wire chamber (DWC). Since these detectors were situated further upstream from the experimental position, measurements with these devices may not be representative of the beam characteristics at setup due to the interactions of the primary beam particles within these detectors and the subsequent transport of these particles between these detectors and the setup. The main advantage of the application of the liquid-filled array is its portability so that it can be placed directly at the position of the experimental setup to capture the beam characteristics. A comparison between the measured beam profile and independent film measurements has demonstrated its reliability for analysing the beam characteristics. In this context, the 2D array has been implemented to measure on-line not only the 2D beam profile but also the total imparting particle fluence of the UHE lead beam by using the measured dose and considering the calibration of the detector.

A Simple Approach for Experimental Characterization and Validation of Proton Pencil Beam Profiles

A precise characterization of therapeutic proton pencil beams is essential for commissioning of any treatment planning system (TPS). The dose profile characterization includes measurement of the beam lateral dose profile in the beam core and far from the beam core, in the so called low-dose envelope, and requires a sophisticated detection system with a few orders of magnitude dynamic range. We propose to use a single-quantum sensitive Minipix Timepix detector, along with an in-house designed holder to perform measurements of the pencil beam dose profile in air and in water. We validated the manufacturer calibration of the Minipix Timepix detector in proton beams of various energies and compared the deposited energy spectra to Monte Carlo (MC) simulations. The precision of the lateral dose profile measurements has been systematically validated against Krakow proton facility commissioning data and dose profile simulations performed with MC codes Gate/Geant4 and Fred. We obtained an excellent agreement between Minipix Timepix measurements and simulations demonstrating the feasibility of the system for a simple characterization and validation of proton pencil beams. The proposed approach can be implemented at any proton therapy facility to acquire experimental data needed to commission and validate analytical and MC based TPS.

FLASH Proton Irradiation Using a Synchrocyclotron: Proof of Concept

Recent studies have shown that radiotherapy at ultra-high dose rates (>40 Gy/s, FLASH vs. 0.5 Gy/s, Conventional) has a potential advantage in sparing healthy tissues compared to that at conventional dose rates. The purpose of this work is to demonstrate the feasibility of proton beam delivery in FLASH mode using a clinical synchrocyclotron. A unique feature associated with a synchrocyclotron system is that it provides a platform for further investigation with the intention to clarify whether instantaneous dose rate vs. average dose rate is the main driver of the FLASH-irradiation protective effect in proton therapy. A clinical synchrocyclotron was engineered for ultra-high dose rate beam delivery. The pulse structure of the protons was varied between 1 μs to 20 μs to deliver in conventional and ultra-high dose rates. A boron carbide block was used to reduce the 230 MeV energy of the protons to 70 MeV corresponding to 4 cm range in water. A brass aperture was used for beam shaping in longitudinal plane. A Faraday cup was utilized to measure the number of protons per pulse at various dose rates. A plane-parallel ionization chamber with sensitive volume of 1cm in diameter was used to measure the dose rate and integral depth dose. Radiochromic film dosimetry was performed for verification of the ion chamber measurements. Monte Carlo simulation was performed in TOPAS to calculate the IDD and dose-rate for comparison with the experimental measurements. Average dose rate of 100 Gy/s at the entrance and 216 Gy/s at the Bragg peak was measured. The field size measured with radiochromic film had 1.2 cm full-width at half-maximum (FWHM). A reasonable agreement was observed among the ion chamber, film measurements and the MC simulation calculations. Feasibility of proton FLASH irradiation with a synchrocyclotron was demonstrated to achieve average dose rate between 100 Gy/s and 216 Gy/s along the depth dose curve.

Development and validation of an analytical model allowing accurate predictions of gamma and electron beam dose distributions in a water medical phantom.

The aim of this work was to study photon and electron dose distributions in a phantom filled with water using the Monte Carlo Geant4 tool for electron energies ranging from 1 to 21MeV and for photon energies ranging from 1.25MeV to 25MeV, corresponding to conventional radiotherapy Linac energies. The results of the Geant4 calculations were validated based on the relevant experimental data previously published. The results obtained were fitted and analytical models of dose distributions were developed for gamma radiation and electrons. For each of these models, one-dimensional (including dose depth profiles as a function of the depth inside the phantom) and two-dimensional (including the dose distribution as a function of depth and lateral position inside the phantom) dose distributions have been considered. Results are presented for photons and electrons of various energies. The coefficient of determination [Formula: see text] illustrates an excellent match between the developed analytical model and the Geant4 results. It is demonstrated that the analytical models developed in the present study can be applied in various fields such as those used for calibration applications and radiation therapy. It is concluded that the analytical models developed allow for quick, easy and reliable clinical dose estimates and offer promising alternatives to the standard tools and methods used in radiotherapy for treatment planning.