Energy Photon Beams Research Articles

An alternative way to decipher the nature of the doubly charmed tetraquark Tcc(3875)+: Its antiparticle Tc̄c̄(3875)− photoproduction off nuclei near threshold

In this paper, we study the inclusive photoproduction of [Formula: see text] mesons (which are the antiparticles of the doubly charmed tetraquarks [Formula: see text] discovered recently by the LHCb Collaboration) from nuclei in the near-threshold energy region within the nuclear spectral function approach by considering incoherent direct ([Formula: see text]) photon–nucleon [Formula: see text] creation processes as well as five possible different scenarios for their internal structure with the main goal of clarifying the possibility to decipher this structure (and, hence, that of [Formula: see text]) in photoproduction via integral and differential observables. We calculate the absolute and relative excitation functions for [Formula: see text] production off [Formula: see text]C and [Formula: see text]W target nuclei at near-threshold photon beam energies of 30–38 GeV, the absolute differential cross-sections for their production off these target nuclei at laboratory polar angles of 0°–10° as well as the A and momentum dependences of the relative (transparency ratios) cross-sections for [Formula: see text] production at photon energy of 35[Formula: see text]GeV within the adopted scenarios for the [Formula: see text] meson intrinsic structure. We demonstrate that the absolute and relative observables considered show a certain sensitivity to these scenarios. Therefore, the measurement of such observables in future experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the US and China in the near-threshold energy region might shed light on the [Formula: see text] internal structure.

Performance evaluation of an inorganic optical fibre dosimeter for use in external beam radiotherapy with pulsed beams

Objective. Optical fibre dosimeters (OFDs) offer great promise for real-timein vivodose measurement in radiation-based treatment modalities such as radiotherapy and brachytherapy. This is attributed to their many useful qualities such as high spatial resolution and sensitivity. However, there are several requirements that an optical fibre dosimeter must meet to be acceptable for dose measurement in a specified treatment modality. In this work, the dosimetric performance of a novel optical fibre dosimeter for use in external beam radiotherapy is presented.Approach. The dosimeter was characterised for photon beam energies between 6-15 MV using a Varian TrueBeam Linac at dose rates between 100-2400 MU/min and assessed based on its repeatability, dose dependence, dose rate dependence, energy dependence and dose-per-pulse dependence.Main Results. The results demonstrated excellent short-term repeatability of 0.3%, good linearity in response (R2>0.9997), and minor dose rate dependence between 0.53%-2.49% for all beam qualities investigated. As the scintillator of the OFD is non-water equivalent, Monte-Carlo-TOPAS simulations were used to calculate the absorbed dose energy dependence. A dose-per-pulse dependence was also investigated and compared with dosimetry measurements made with an ionisation chamber and simulated from the treatment planning system. An over-response of 20%was found at the lowest investigated dose-per-pulse, and an under-response of 34%was found at the highest investigated dose-per-pulse. This is believed to be due to an intrinsic energy dependence making this type of OFD unsuitable for external beam radiotherapy dosimetry.Significance. The OFD evaluated in this work was primarily designed for high-dose-rate brachytherapy whereas this study includes the first measurements made in external beam radiotherapy and highlights the challenges of transferability of the dosimeter to a different radiation source.

Long-term performance monitoring of a-Si 1200 electronic portal imaging device for dosimetric applications.

Recently, dosimetri applications of the electronic portal imaging device (EPID) in radiotherapy have gained popularity. Confidence in the robust and reliable dosimetric performance of EPID detectors is essential for their clinical use. This study aimed to evaluate the dosimetric performance of the a-Si 1200 EPID and assess the long-term stability of its response. Weekly measurements were performed on two clinically used TrueBeam linear accelerators (linacs) equipped with a-Si 1200 EPID detectors over a 2-year period. They included dark and flood calibration fields, and EPID response to an open field corrected for the long-term machine output drift measured with the secondary absolute dosimeters: an ion chamber and an ion chamber array. All measurements were performed using five photon beam energies and two imaging modes: continuous and dosimetry. The measurements were analyzed for constancy and the presence of long-term trends. Comparisons were made between the two linacs for each beam energy. Pixel sensitivity matrices (PSM) were determined semi-annually and analyzed for long-term constancy for both treatment machines. The long-term variation of the dark and flood field signals, integrated across the EPID plane, over the entire observation period did not exceed 0.17% and 0.79%, respectively. The output-corrected EPID response showed long-term variation from 0.28% to 0.36%, depending on beam energy, while the short-term variation was 0.04%-0.07% for EPID and 0.02%-0.06% for secondary dosimeters. The long-term variation of secondary dosimeters was 0.2%-0.3%. PSMs were found to be stable to within 1% for 97.8% of pixels and 2% for 100% of pixels. Techniques to monitor and assess the long-term performance of the a-Si 1200 EPID as a dosimeter were developed and implemented using two TrueBeam linacs. The long-term variation of the EPID response was within clinical tolerance indicated in AAPM TG-142 report, and the detector was shown to be stable and reproducible for routine clinical dosimetry.

The proton charge radius from dimuon photoproduction off the proton

We investigate the feasibility of measuring the proton charge radius through dimuon photoproduction off a proton target. Our findings indicate that the Bethe-Heitler mechanism, which dominates at small momentum transfers, allows for an extraction of the proton electromagnetic form factors in the extremely low Q2 region below 10−3 GeV2 in the spacelike region, when the incident photon beam energy exceeds several hundred MeV. The optimal kinematical region and a sensitivity study of the proton charge radius from dimuon photoproduction are presented. Such a measurement is expected to provide an alternative to the elastic muon-proton scattering measurements such as MUSE at PSI and AMBER at CERN.

Estimation of the lateral variation of photon beam energy spectra using the percentage depth dose reconstruction method

In photon-collapsed cone convolution (pCCC) algorithm of the Monaco treatment planning system (TPS), the central-axis energy spectrum is assumed constant throughout the entire irradiation area. To consider lateral variations, an off-axis softening factor is applied to attenuation coefficients during the total energy released per unit mass calculation. We evaluated this method through comparison studies of percentage depth doses (PDDs) and off-axis ratios (OARs) calculated by Monaco and measured for a 6 MV photon beam at various off-axis angles and depths. Significant differences were observed, with relative differences exceeding ± 1%. Therefore, this method may not accurately represent lateral variations of energy spectra. We propose directly implementing energy spectra on both central-axis and off-axis to improve dose calculation accuracy for large field. To this end, we introduce reconstruction of PDDs from monoenergetic depth doses (MDDs) along off-axis angles, thereby estimating energy spectra as functions of radial distance. This method derives energy spectra quickly without significantly increasing the beam modeling time. MDDs were computed through Monte Carlo simulations (DOSRZnrc). The variances between reconstructed and measured PDDs were minimized using the generalized-reduced-gradient method to optimize energy spectra. Reconstructed PDDs along off-axis angles of 0°, 1.15°, 2.29°, 3.43°, 4.57°, 5.71°, 6.84°, 7.97°, 9.09°, 10.2° to estimate energy spectra at radial distances of 0–18 cm in 2 cm increments and OARs calculated using estimated energy spectra at 5, 10, and 20 cm depths, well agreed with measurement (relative differences within ± 0.5%). In conclusion, our proposed method accurately estimates lateral energy spectrum variation, thereby improving dose calculation accuracy of pCCC algorithm.

Comparison of two different VMAT radiotherapy TPSs for pancreatic cancer using flattening filter free photon beam energy

BackgroundPancreatic cancer is a devastating disease with a poor prognosis, and radiation therapy plays a crucial role in its treatment and management. Conventional radiation therapy (RT) techniques have limitations in delivering adequate doses to the tumor while sparing surrounding normal tissues. However, modern RT techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT) have led to the development of novel approaches that can reduce toxicity. The incorporation of advanced imaging modalities, like four-dimensional computed tomography (4D-CT) and magnetic resonance imaging (MRI), enables enhancement of tumor control and improves conformality and treatment outcomes. Additionally, using flattening filter-free (FFF) beams can further enhance treatment efficiency and efficacy. PurposeThis study aims to compare two different VMAT techniques using two different treatment planning systems (TPSs), Monaco and Eclipse, in the treatment of pancreatic cancer II stage infiltrating duct carcinoma patients using an FFF photon beam. Materials and methods20 pancreatic cancer II stage infiltrating duct carcinoma patients were retrospectively analyzed, and each patient's plans were designed using the two TPSs. The dose distribution of the target using 6 MV FFF for TrueBeam-Varian and organs at risk (OARs) were compared. The monitor unit (MU), treatment time, conformity (CI), and homogeneity (HI) indices were also evaluated. ResultsFor pancreatic cancer patients, the mean dose of the planning target volume (PTV) in the Monaco plan was lower than the Eclipse plan. The plan evaluation parameters in Monaco and Eclipse were similar without significant differences (p-value = 0.152). The Monaco plan was better than the Eclipse plan regarding mean dose and V15Gy of the kidneys; the spinal cord was lowest in the Monaco plan, and the maximum dose and V45Gy of the spinal cord were 592.1 cGy and 1.37% lower than the Eclipse plan, respectively. ConclusionThe VMAT Monaco plan is a favorable TPS for pancreatic cancer patients, providing improved sparing of critical organs while maintaining adequate target coverage.

Gold nanoparticle effect on dose and DNA damage enhancement in the vicinity of gold nanoparticles

This study uses Monte Carlo simulations to examine the dose enhancement effect of gold nanoparticles (AuNPs) in radiation therapy and its effects on DNA damage. Using the GATE- 9.0 and Geant4-DNA packages, Monte Carlo simulations were used to simulate a mathematical phantom and determine the energy deposition in the vicinity of AuNP. The simulations were conducted for various photon beam energies (50, 100, 250, and 6000 keV) with and without the presence of different-size AuNPs (10, 30, 50 and 100 nm). The dose enhancement factor (DER) was evaluated using Geant4-DNA to examine the effects AuNP sizes and photon beam energies on DNA damage. A multi-scale Monte Carlo simulation was conducted to evaluate enhanced DNA damage owing to nanoparticles in the proximity of cancer cells. The Monte Carlo simulations indicated that AuNPs boost the dose delivery, resulting in enhanced energy deposition and subsequent DNA damage. The DER analysis revealed a significant increase in the dose deposition within DNA, leading to single or double-strand breaks. Geant4-DNA simulations revealed information on the dosage enhancement factor for various AuNP sizes and photon beam intensities, enabling a deeper comprehension of the underlying mechanics. The outcomes of this study emphasize the potential of AuNPs as effective radiosensitizers in radiation therapy and contribute to the growing body of research on the use of nanotechnology in enhancing cancer treatment outcomes. Further investigations and experimental validations are necessary to optimize the usage of AuNPs for improved radiation therapy.

Modification of algorithm for accurate estimation of Hp(3) based on response of head TLD badge calibrated using ISO cylindrical phantom.

In India, the prevailing approach to eye lens dosimetry is the placement of an existing dosemeter on the forehead region after slight modification serves as a dedicated Eye Lens Dosemeter. A methodology for estimating the eye lens dose in terms of the Hp(3) has been previously explored employing an algorithm based on the response characteristics of this dosemeter using ISO slab phantom. It was observed that the performance of the dosemeter in terms of Hp(3) using previous algorithm showed under response at higher angles of incidence and photon beams of energy < 200keV. Further, study was conducted to modify the algorithm following the latest ISO recommendations. This involved generation of data from the response of existing dosemeter on a cylindrical phantom. The results of this study revealed better performance of the newly established algorithm in estimating eye lens dose in terms of Hp(3) when compared to the earlier algorithm.

The investigation of dose rate and photon beam energy dependence of optimized PASSAG polymer gel dosimeter using magnetic resonance imaging.

It seems that dose rate (DR) and photon beam energy (PBE) may influence the sensitivity and response of polymer gel dosimeters. In the current project, the sensitivity and response dependence of optimized PASSAG gel dosimeter (OPGD) on DR and PBE were assessed. We fabricated the OPGD and the gel samples were irradiated with various DRs and PBEs. Then, the sensitivity and response (R2) of OPGD were obtained by MRI at various doses and post-irradiation times. Our analysis showed that the sensitivity and response of OPGD are not affected by the evaluated DRs and PBEs. It was also found that the dose resolution values of OPGD ranged from 9 to 33 cGy and 12 to 34 cGy for the evaluated DRs and PBEs, respectively. Additionally, the data demonstrated that the sensitivity and response dependence of OPGD on DR and PBE do not vary over various times after the irradiation. The findings of this research project revealed that the sensitivity and response dependence of OPGD are independent of DR and PBE.

Feasibility assessment of polycrystalline CsPbI3 relative dosimeters in photon and electron beam radiotherapy

Volumetric modulated arc therapy represents the latest technology in radiotherapy. It involves continuous modification of the multi-leaf collimator spatial distribution, dose rate, and gantry rotational speed, necessitating a dosimeter with high spatial resolution and exceptional sensitivity per unit volume. In particular, cesium-based inorganic perovskites have been studied for various applications, spanning from photoconductor solar cells to radiation detectors. These perovskites are renowned for their outstanding attributes, including thermal stability, inorganic stability, and light absorption capacity. Despite such advantageous characteristics, CsPbI3 materials have only been investigated in radiodiagnostics, with limited exploration in radiotherapy. To address this gap, this study verified the viability of CsPbI3 materials, note for their outstanding radiation detection efficiency, as dosimeters capable of measuring the radiation detection performance for radiotherapy devices. The reproducibility, linearity, and percent depth dose (PDD) were evaluated under the application of photon and electron beams in linear accelerators. The reproducibility assessment revealed impressive results, with the relative standard deviation registering at 0.53%, 0.32%, and 0.38% under electron beam energies of 6, 9, and 12 MeV and 0.45%, and 0.89% under photon beam energies of 6 and 15 MV. Moreover, the linearity test revealed an R 2 value of 0.9999, indicating high linearity, at 6, 9, and 12 MeV and at 6 and 15 MV. The PDD graphs drawn for the CsPbI3 dosimeter fabricated in this study showed that the D max points were consistent. The novel CsPbI3 dosimeter demonstrated a level of detection performance that satisfied all criteria; reproducibility, linearity, and PDD. The results collectively indicated that the CsPbI3 dosimeter can be used for dosimeters in radiotherapy devices.

Development of a semi empirical calculation approach for the determination of percentage depth dose in water for higher energy photon beams using a medical linear accelerator

The development of a calculation approach to determine the Percentage Depth Dose (PDD) by manual calculation for medical linear accelerator of 6 MV and 15 MV photon beam energy. The equation to determine PDD can be divided into two components i.e., the primary component and the scatter component. To calculate the primary component, the linear attenuation coefficient needs to be calculated. The measurement of charge was taken at various depths and for different field sizes using 6 MV and 15 MV photon beams. To determine the linear attenuation coefficient, a graph of ln (MR) where, MR represents corrected meter reading was plotted against depth in cm. By plotting another graph of linear attenuation coefficient against field size, to determine the effective linear attenuation coefficient. The scattered component KS was graphically plotted against depth in cm and derived an equation for scatter component. The calculated PDD for 6 MV was found to be within 1 % difference and for 15 MV percentage difference within 3 %. It was found that numerically developed PDD values table for higher energy photon beam becomes valid and it can be utilized for the manual dose calculation.

Incidence of Radiotherapy Induced Cardiac Implantable Electronic Devices Malfunction: Australian-Based Observation Study.

To assess the incidence rate of cardiac implantable electronic devices (CIED) malfunction with radiotherapy (RT) and identify factors resulting in CIED malfunction. The working hypothesis is that CIED malfunction is associated with higher photon beam energy, treatment anatomical location, device type and dose to device. This retrospective review involved 441 patients with CIED treated with RT. Clinical information, RT (prescription, dose to device, beam energy, anatomical regions treated etc.) and CIED details (type, manufacturer, and device malfunction) were collected from electronic medical records. A total of 344 patients (78%) had a permanent pacemaker (PPM), 44 patients (10%) had implantable cardioverter defibrillator (ICD), 44 patients (10%) had CRT-defibrillator (CRT-D) and 9 (2%) had cardiac resynchronization therapy-pacing (CRT-P). The median prescribed dose was 36 Gy (IQR 1.8-80 Gy). 17 out of 441 patients (3.9%) experienced an CIED malfunction event. This group had a higher prescribed median dose of 42.5 Gy (IQR 20-77 Gy) and beam energy of 14 MV (12-18 MV). None of the malfunctions resulted in clinical symptoms. Median dose to CIED was 0.28 Gy (IQR 0-3.3). No patents received dose to device ≥2 Gy. Using logistic regression, the predictors of CIED malfunction were photon beam energy use ≥10 MV (OR 5.73; 95% CI, 1.58-10.76), anatomical location of RT above the diaphragm (OR 5.2, 95% CI, 1.82-15.2), and having an ICD (OR 4.6, 95% CI, 0.75-10.2). We have demonstrated that photon beam energies ≥10 MV, RT to above the diaphragm and ICD devices are significantly associated with CIED malfunction. The recorded CIED malfunctions in this study were minor malfunctions which did not result in any clinical symptoms. Stringent adherence to the local institution's CIED treatment guidelines, utilization of safety measures and careful choice of beam energy are recommended to minimize risk of symptomatic CIED malfunctions.

Comparison of the Direct Power Consumption for Different Linac Treatment Parameters in External Beam Radiation Therapy

The negative impact of climate change on the environment has led to increasing concern around the world. Relatively little is known about the contribution of radiation oncology systems to carbon emissions. This study measures the energy utilization of Linac-based EBRT for different treatment parameters and techniques, which was then converted to power use (kWh) and ultimately a carbon footprint of various photon treatment approaches. A Varian TrueBeam was evaluated. The direct power consumption was measured using a Fluke 1736 Power Logger, recorded in one-second intervals for one week. Different photon and electron beam energies, dose rates, treatment techniques (3D, IMRT, gated), and imaging types (kV, MV) were evaluated. Clinical treatment plans were reviewed, and average treatment times used to determine kWh. IRB approval was obtained. The Greenhouse Gas Equivalencies Calculator was used to determine kg of CO2. Power draw for 6 MV, 10 MV, and 18 MV at a rep rate of 600 MU/min was 31.6, 32.0, and 27.5 kW, respectively. The power draw for end of range dose rates for 6 MV (60, 600), 6 FFF (400, 1400), 10 FFF (400, 2400), and 6 MeV (100, 1000) were (22.2, 31.6 kW), (23.7, 31.6 kW), (19.6, 32.1 kW), and (22.6, 23.6 kW), respectively. 6 MV open 2D fields, modulated IMRT fields, and gated/beam hold fields had similar power draw at 31.6, 31.7, and 31.9 kW, respectively. Portal MV imaging with 2.5 MV beam was 32.5 kW, while CBCT and kV/kV imaging was ∼11 kW and not distinguishable from baseline power fluctuations. A total of 191 delivered treatment plans were reviewed. Electron plans (n = 8) treatment time was on average 29 sec (16 sec STDEV) per fraction and 635 sec (185 sec STDEV) per course, 2D/3D plans (n = 63) were 77 sec (32 sec STDEV) and 1004 sec (1002 sec STDEV), and IMRT plans (n = 120) were 182 sec (60 sec STDEV) and 5351 sec (2401 sec STDEV), respectively. The kWh per treatment for electron, 2D/3D, and IMRT plans were 0.19, 0.68, and 1.6 kWh, respectively. The CO2 equivalent for electrons, 2D/3D, and IMRT techniques are 0.08, 0.29, and 0.7 kg. There was some variability in the power draw for different energies and different dose rates but was relatively stable around 32 kW. Power consumption for clinical therapy is a result of kW power draw multiplied by duration of beam delivery, which for our patients varied significantly as a function of technique and number of fractions delivered. Reduction in radiation oncology carbon footprint will likely be driven more by number of fractions and type of treatment technique, and length of patient commute, rather than beam energy and dose rate selection.

Measurement of the helicity asymmetry {mathbb {E}} for the vec {gamma }vec {p} rightarrow p pi ^0 reaction in the resonance region

The double-spin-polarization observable {mathbb {E}} for vec {gamma }vec {p}rightarrow ppi ^0 has been measured with the CEBAF Large Acceptance Spectrometer (CLAS) at photon beam energies E_gamma from 0.367 to 2.173~textrm{GeV} (corresponding to center-of-mass energies from 1.240 to 2.200~textrm{GeV}) for pion center-of-mass angles, cos theta _{pi ^0}^{c.m.}, between - 0.86 and 0.82. These new CLAS measurements cover a broader energy range and have smaller uncertainties compared to previous CBELSA data and provide an important independent check on systematics. These measurements are compared to predictions as well as new global fits from The George Washington University, Mainz, and Bonn-Gatchina groups. Their inclusion in multipole analyses will allow us to refine our understanding of the single-pion production contribution to the Gerasimov-Drell-Hearn sum rule and improve the determination of resonance properties, which will be presented in a future publication.

DNA Damage of Iron-Gold Nanoparticle Heterojunction Irradiated by kV Photon Beams: A Monte Carlo Study

This study aims to evaluate the dependence of DNA damage on the proportion of iron and gold in iron-gold nanoparticle heterojunctions using Monte Carlo simulations. The simulation setup included a spherical nanoparticle with varying percentages of iron and gold, irradiated by photon beams of different energies (50–150 keV). The Geant4-DNA Monte Carlo code was utilized for the accurate tracking of radiation transport. The results reveal that DNA damage increases with a higher percentage of gold volume in the heterojunction, primarily due to photoelectric enhancement. Furthermore, a lower photon beam energy of 50 keV induces greater DNA damage compared to energies of 100 keV and 150 keV. The findings suggest that for effective cancer cell eradication through DNA damage, the gold volume should be equal to or greater than 50% in the iron-gold nanoparticle heterojunction. In conclusion, the findings from this study will shed light on the potential of iron-gold nanoparticle heterojunctions in enhancing radiotherapy outcomes. The investigation of DNA damage resulting from the combination of contrast agents and radiosensitizers is crucial for advancing cancer research and treatment. The knowledge gained from this research will aid in the development of personalized and effective radiotherapy approaches, ultimately improving patient outcomes in cancer treatment.

Transmission probability filter optimization for Agility MLC in Monaco treatment planning system.

In the Monte Carlo-based treatment planning system (TPS) Monaco, transmission probability filters (TPF) are utilized to describe the transmission through the multi leaf collimator (MLC). By having knowledge of the TPF parameters for various photon beam energies, adjusting the MLC transmission parameters becomes easier, enhancing the accuracy of the Monte Carlo algorithm in achieving a dose distribution that closely aligns with the irradiated dose at the Versa HD linear accelerator (linac). The objective of this study was to determine the TPF parameters for 6MV, 10MV, 6MV flattening filter free (FFF) and 10MV FFF for a Versa HD linac equipped with Agility MLC. The TPF parameters were adjusted using point dose measurements and vendor-provided fields specifically designed to fine-tune the MLC. After adjusting the TPF parameters, a gamma passing rate (GPR) analysis was conducted on 25 treatment plans to ensure that the Monte Carlo model, with the updated TPF parameters, accurately matched the actual linac delivery. The TPF values ranged from 0.0018 to 0.0032 for leaf transmission and 1.15 to 1.25 for Leaf Tip leakage across the different energies. The average GPR ranged from 97.8% for 10MV FFF to 98.5% for 6MV photon energies. Additionally, the TPF parameters for 6MV obtained in this study were consistent with previously published TPF values for 6MV photon energy. Hence, it was concluded that optimizing the TPF does not need to be performed for every individual Versa HD linac with Agility MLC. Instead, the published parameters can be applied to other Versa HD linacs to enhance clinical accuracy. In conclusion, this study determined the TPF parameters for 6MV and previously unpublished photon energies 10MV, 6MV FFF and 10MV FFF. These parameters can be easily transferred to other facilities, resulting in improved agreement between the dose distribution from the TPS and the linac.

Dosimetric properties of PASSAG polymer gel dosimeter in electron beam radiotherapy using magnetic resonance imaging.

Several physical factors such as photon beam energy, electron beam energy, and dose rate may affect the dosimetric properties of polymer gel dosimeters. The photon beam energy and dose rate dependence of PASSAG gel dosimeter were previously evaluated. This study aims to assess the dosimetric properties of the optimized PASSAG gel samples in various electron beam energies. The optimized PASSAG gel samples are first fabricated and irradiated to various electron energies (5, 7, 10 and 12 MeV). Then, the response (R2) and sensitivity of gel samples are analyzed by magnetic resonance imaging technique at a dose range of 0 to 10 Gy, scanning room temperature range of 15 to 22 °C, and post-irradiation time range of 1 to 30 days. The R2-dose response and sensitivity of gel samples do not change under the evaluated electron beam energies (the differences are less than 5%). Furthermore, a dose resolution range of 11 to 38 cGy is obtained for the gel samples irradiated to different electron beam energies. Moreover, the findings show that the R2-dose response and sensitivity dependence of gel samples on electron beam energy varies over different scanning room temperatures and post-irradiation times. The dosimetric assessment of the optimized PASSAG gel samples provides the promising data for this dosimeter during electron beam radiotherapy.

Comparison of h-BN material with metal implants in radiotherapy applications: Characterization and dose distribution measurements in LINAC

Patients with metal implants having high atomic numbers (Zeff) can be encountered in radiotherapy applications. These heterogeneous structures cause dose perturbations at the bone-tissue interface. These perturbations are undesired due to the lack of accurate dose calculation and contouring process through a higher image quality. In this study, the effect of 6–18 MV photon irradiation on hexagonal boron nitride (h-BN) in comparison with titanium and stainless-steel implants was proposed as an implant material due to its biocompatibility and low Zeff. First, h-BN material was characterized and its mass attenuation coefficient was determined. Then, the percent depth doses (PDD) were obtained for the implant materials. Next, the dose distributions were evaluated with both TPS using CT images and TLDs. A dose perturbation was not observed at the interface for h-BN material different from the metal implants as seen from the PDD distributions. The change in PDD varied between 1 and 3% for h-BN with respect to RW3 slab phantom, which was 4–7 times lower than that of metal implants, depending on the material thickness. No metal artifact was seen at h-BN implants compared to metal implants. Homogenous dose distribution was also seen from the isodose lines on the CT images, while dose perturbations were more pronounced in metal implants. In addition, a more severe dose reduction at the metal implant/bone tissue interface was observed at 6 MV photon beam energy compared to 18 MV. In contrast, no dose change was observed for the h-BN material at each photon beam energy. Hence, an accurate dose calculation can be done for h-BN as a result of these advantages. The results showed that, due to its biocompatible property, h-BN material can be evaluated as an implant material in radiotherapy applications if its mechanical properties were further improved.

Depth Dose Enhancement in Orthovoltage Nanoparticle-Enhanced Radiotherapy: A Monte Carlo Phantom Study.

This study was to examine the depth dose enhancement in orthovoltage nanoparticle-enhanced radiotherapy for skin treatment by investigating the impact of various photon beam energies, nanoparticle materials, and nanoparticle concentrations. A water phantom was utilized, and different nanoparticle materials (gold, platinum, iodine, silver, iron oxide) were added to determine the depth doses through Monte Carlo simulation. The clinical 105 kVp and 220 kVp photon beams were used to compute the depth doses of the phantom at different nanoparticle concentrations (ranging from 3 mg/mL to 40 mg/mL). The dose enhancement ratio (DER), which represents the ratio of the dose with nanoparticles to the dose without nanoparticles at the same depth in the phantom, was calculated to determine the dose enhancement. The study found that gold nanoparticles outperformed the other nanoparticle materials, with a maximum DER value of 3.77 at a concentration of 40 mg/mL. Iron oxide nanoparticles exhibited the lowest DER value, equal to 1, when compared to other nanoparticles. Additionally, the DER value increased with higher nanoparticle concentrations and lower photon beam energy. It is concluded in this study that gold nanoparticles are the most effective in enhancing the depth dose in orthovoltage nanoparticle-enhanced skin therapy. Furthermore, the results suggest that increasing nanoparticle concentration and decreasing photon beam energy lead to increased dose enhancement.

MEPhI’s option of lab scale Compton source

A development and construction of comparatively cheap and compact (several meters scale) X-ray sources is possible with the help of inverse Compton backscattering of laser photons on an electron bunch. Such sources can be used in the field of materials science (new materials, diagnostics of nanostructures at the atomic level), research of nano- and biosystems, medicine and pharmacology (new drugs R&amp;D), physics and chemistry of fast-flowing processes (burning, explosion). It is suggested that compact storage synchrotron will operate with normal conducting S-band top-up linac. Linac will provides bunches with tunable energy in the range of 20– 60 MeV to generate the photon flux with tunable energy [1, 2]. The use of a storage ring provides the following advantages: comparatively high average intensity of the generated photon flux, high brightness, photon beam energy tuning in a wide range, high degree of monochromaticity and coherence of the generated photons. There are current results of the design of a compact storage ring for generating the photons in the energy range of 5-45 keV and investigations of the development of relativistic picosecond electron beam dynamics instabilities in the report.