Photon Radiation Research Articles

Radical, ion, and photon’s effects on defect generation at SiO2/Si interface during plasma etching

Defect generation and recovery at the SiO2/Si interface are experimentally studied during SiO2 etching and annealing. The SiO2 etching over the underlaying Si is performed with CF4 plasma, where the remaining SiO2 layer thickness is varied to clarify the effects of radicals, ions, and photons on the defect generation. The defects are generated initially by photon irradiation, and then generated by ion bombardment/penetration, as the remaining layer becomes thin. Around the endpoint, defects are also generated by radical reactions and in-diffusion. The photon-mediated defects are fully recovered by annealing, whereas the ion and radical-mediated defects are not sufficiently recovered; residual defects are created.

Systematic Review and Meta-Analysis of Particle Beam Therapy versus Photon Radiotherapy for Skull Base Chordoma: TRP-Chordoma 2024.

[Objective] The aim of this study was to compare the efficacy of particle beam therapy (PT) with photon radiotherapy (RT) for treatment of skull base chordoma. [Methods] A systematic review was conducted for skull base chordoma treated with PT or photon RT reported from 1990 to 2022. Data were extracted for overall survival (OS) and progression-free survival (PFS), late adverse events, age, gender, gross total resection (GTR) rates, tumor volume, total irradiation dose, and treatment modality. Random-effects meta-regression analysis with the treatment modality as an explanatory variable was performed for each outcome to compare the modalities. [Results] A meta-analysis of 30 selected articles found 3- and 5-year OS rates for PT vs. photon RT or combined photon RT/proton beam therapy (PBT) of 90.8% (95% CI: 87.4-93.3%) vs. 89.5% (95% CI: 83.0-93.6%), p = 0.6543; 80.0% (95% CI: 75.7-83.6%) vs. 89.5% (95% CI: 83.0-93.6%), p = 0.6787. The 5-year PFS rates for PT vs. photon RT or photon RT/PBT were 67.8% (95% CI: 56.5-76.7%) vs. 40.2% (95% CI: 31.6-48.7%), p = 0.0004. A random-effects model revealed that the treatment modality (PT vs. photon RT or photon RT/PBT) was not a significant factor for 3-year OS (p = 0.42) and 5-year OS (p = 0.11), but was a significant factor for 5-year PFS (p < 0.0001). The rates of brain necrosis were 8-50% after PT and 0-4% after photon RT or photon RT/PBT. [Conclusion] This study shows that PT results in higher PFS compared to photon RT for skull base chordoma, but that there is a tendency for a higher incidence of brain necrosis with PT. Publication and analysis of further studies is needed to validate these findings.

Optimizing optoelectronic properties and energy harvesting potential of Co-doped LaFeO3: A DFT-based investigation

In response to the growing demand for advanced optoelectronic materials, this comprehensive investigation explores the effects of Co substitution on LaFeO3 using density functional theory. The study provides novel insights into the mechanical and optical properties of the doped structures. Structural stability is assessed through structural optimization, elastic stability tests, and enthalpy of formation calculations. The doped compounds exhibit significant improvements in electronic and optical properties, including enhanced thermal conductivity and reflectivity. Band structure analysis reveals metallic attributes and the Moss-Burstein effect, while magnetic property assessments indicate a decrease in magnetic moment due to Fe-Co degeneracy resulting from higher Co content. Mechanical analysis of elastic moduli B, G, and Y demonstrates enhanced durability and strength with metal-like conductivity, attributed to reduced anharmonicity. The study also highlights increased bond flexibility, suggesting potential applications in flexible electronics and UV light reflectors for effective shielding against photon radiation.

Pencil Beam Scanning Proton Therapy as Single Vocal Cord Irradiation for Early-Stage Glottic Cancer

PurposeSingle vocal cord irradiation (SVCI) is a promising technique to maintain excellent oncologic control and potentially improve upon toxicities for treatment of early-stage glottic squamous cell carcinomas. We sought to investigate whether pencil beam scanning (PBS) proton therapy could improve upon the already favorable dose gradients demonstrated with volumetric modulated arc therapy (VMAT) SVCI. Patients and MethodsA 64-year-old gentleman was treated in our department with 6X-flattening filter-free VMAT SVCI to 58.08 Gy in 16 fractions for a T1a well-differentiated squamous cell carcinoma of the left true vocal cord and tolerated it well with good local control. Comparative PBS plans were created in Raystation for the Varian ProBeam with clinical target volume (CTVs) generated to mimic the prescription target volume extent of the VMAT planning target volumes when accounting for PBS plan robustness (±3 mm translational shifts, 3.5% density perturbation). A 3-field single-field optimization plan was selected as dosimetrically preferable. Dosimetric variables were compared. ResultsSeveral organs at risk doses improved with PBS, including the maximum and mean dose to ipsilateral carotids, maximum and mean dose to contralateral carotid, maximum dose to the spinal cord, maximum and mean dose to inferior constrictor/cricopharyngeus, maximum and mean dose to the uninvolved vocal cord, and mean dose to the thyroid gland. There are tradeoffs in skin dose depending on location relative to the target—with the highest and lowest isodoses extending more into the skin with the VMAT plan but with the moderate isodose lines covering a wider area with the PBS plan, but we deemed it tolerable regardless. ConclusionSVCI is a promising strategy for maintaining the oncologic effectiveness of whole-larynx photon radiation while potentially improving upon the historic toxicity profile. The favorable dose distribution with PBS with respect to organs at risk dosimetry for PBS may allow for further improvements upon VMAT SVCI strategies. Clinical implementation of PBS SVCI may be considered.

Carbon-ion radiotherapy alone vs. standard dose photon radiation with carbon-ion radiotherapy boost for high-grade gliomas: a retrospective study

BackgroundThis study aimed to compare the survival outcome and side effects in patients with primary high-grade glioma (HGG) who received carbon ion radiotherapy (CIRT) alone or as a boost strategy after photon radiation (photon + CIRTboost).Patients and methodsThirty-four (34) patients with histologically confirmed HGG and received CIRT alone or Photon + CIRTboost, with concurrent temozolomide between 2020.03–2023.08 in Wuwei Cancer Hospital & Institute, China were retrospectively reviewed. Overall survival (OS), progression-free survival (PFS), and acute and late toxicities were analyzed and compared.ResultsEight WHO grade 3 and 26 grade 4 patients were included in the analysis. The median PFS in the CIRT alone and Photon + CIRTboost groups were 15 and 19 months respectively for all HGG cases, and 15 and 17.5 months respectively for grade 4 cases. The median OS in the CIRT alone and Photon + CIRTboost groups were 28 and 31 months respectively for all HGG cases, and 21 and 19 months respectively for grade 4 cases. No significant difference in these survival outcomes was observed between the CIRT alone and Photon + CIRTboost groups. Only grade 1 acute toxicities were observed in CIRT alone and Photon + CIRTboost groups. CIRT alone group had a significantly lower ratio of acute toxicities compared to Photon + CIRTboost (3/18 vs. 9/16, p = 0.03). No significant difference in late toxicities was observed.ConclusionBoth CIRT alone and Photon + CIRTboost with concurrent temozolomide are safe, without significant differences in PFS and OS in HGG patients. It is meaningful to explore whether dose escalation of CIRTboost might improve survival outcomes of HGG patients in future randomized trials.

Synthetic CT generation for pelvic cases based on deep learning in multi-center datasets

Background and purposeTo investigate the feasibility of synthesizing computed tomography (CT) images from magnetic resonance (MR) images in multi-center datasets using generative adversarial networks (GANs) for rectal cancer MR-only radiotherapy.Materials and methodsConventional T2-weighted MR and CT images were acquired from 90 rectal cancer patients at Peking University People’s Hospital and 19 patients in public datasets. This study proposed a new model combining contrastive learning loss and consistency regularization loss to enhance the generalization of model for multi-center pelvic MRI-to-CT synthesis. The CT-to-sCT image similarity was evaluated by computing the mean absolute error (MAE), peak signal-to-noise ratio (SNRpeak), structural similarity index (SSIM) and Generalization Performance (GP). The dosimetric accuracy of synthetic CT was verified against CT-based dose distributions for the photon plan. Relative dose differences in the planning target volume and organs at risk were computed.ResultsOur model presented excellent generalization with a GP of 0.911 on unseen datasets and outperformed the plain CycleGAN, where MAE decreased from 47.129 to 42.344, SNRpeak improved from 25.167 to 26.979, SSIM increased from 0.978 to 0.992. The dosimetric analysis demonstrated that most of the relative differences in dose and volume histogram (DVH) indicators between synthetic CT and real CT were less than 1%.ConclusionThe proposed model can generate accurate synthetic CT in multi-center datasets from T2w-MR images. Most dosimetric differences were within clinically acceptable criteria for photon radiotherapy, demonstrating the feasibility of an MRI-only workflow for patients with rectal cancer.

Subclinical dose irradiation triggers human breast cancer migration via mitochondrial reactive oxygen species

BackgroundDespite technological advances in radiotherapy, cancer cells at the tumor margin and in diffusive infiltrates can receive subcytotoxic doses of photons. Even if only a minority of cancer cells are concerned, phenotypic consequences could be important considering that mitochondrial DNA (mtDNA) is a primary target of radiation and that damage to mtDNA can persist. In turn, mitochondrial dysfunction associated with enhanced mitochondrial ROS (mtROS) production could promote cancer cell migration out of the irradiation field in a natural attempt to escape therapy. In this study, using MCF7 and MDA-MB-231 human breast cancer cells as models, we aimed to elucidate the molecular mechanisms supporting a mitochondrial contribution to cancer cell migration induced by subclinical doses of irradiation (< 2 Gy).MethodsMitochondrial dysfunction was tested using mtDNA multiplex PCR, oximetry, and ROS-sensitive fluorescent reporters. Migration was tested in transwells 48 h after irradiation in the presence or absence of inhibitors targeting specific ROS or downstream effectors. Among tested inhibitors, we designed a mitochondria-targeted version of human catalase (mtCAT) to selectively inactivate mitochondrial H2O2.ResultsPhoton irradiation at subclinical doses (0.5 Gy for MCF7 and 0.125 Gy for MDA-MB-231 cells) sequentially affected mtDNA levels and/or integrity, increased mtROS production, increased MAP2K1/MEK1 gene expression, activated ROS-sensitive transcription factors NF-κB and AP1 and stimulated breast cancer cell migration. Targeting mtROS pharmacologically by MitoQ or genetically by mtCAT expression mitigated migration induced by a subclinical dose of irradiation.ConclusionSubclinical doses of photon irradiation promote human breast cancer migration, which can be countered by selectively targeting mtROS.

High-performance PEEK composite materials research on 3D printing for neutron and photon radiation shielding

With the rapid advancement of nuclear energy technology, addressing technical challenges in the field of radiation shielding, particularly achieving lightweight and efficient shielding against neutron and multiple radiation types, remains a formidable task. To address the aforementioned issues, this study investigates the 3D printing performance of polyether ether ketone (PEEK) composite materials for shielding against both neutron and photon multibeam radiation. High-content 3D printing filament is developed, with simultaneous shielding capabilities against neutron and photon radiation. This research successfully accomplishes the high-density 3D printing of PEEK shielding composites with increased concentrations of boron carbide(B4C), tungsten(W), and both materials. The experimental results indicate that 3D printed specimens of B4C/W/PEEK, a neutron and photon shielding composite material, exhibit excellent mechanical properties. Importantly, the radiation shielding composite 3D function parts achieves effective shielding against muitibeam radiation and weight reduction compared to traditional radiation shielding materials.

Evaluation and applicability of radiation detectors for quantitative assessment of radiation exposure in a 16-MeV electron UHDR linac

Background and purposeThe investigation of the FLASH effect requires experimental accelerators capable of delivering ultra-high dose rate (UHDR) beams. Rapid widespread use of this technology could be achieved by modifying clinical electron linacs, originally designed to deliver megavoltage photon radiation up to a few Gy per minute to the isocenter, to deliver electron beams at 40 Gy/s and beyond. Only limited experience has been reported on the radiation safety of UHDR electron beams. This work aims to evaluate the performance and applicability of radiation detectors to quantitatively assess the radiation exposure in this context. MethodsA Varian TrueBeam linac has been modified to deliver 16-MeV electron UHDR with dose rates up to 3⋅105 Gy/s (instantaneous) and 256 Gy/s (average) at the isocenter and used to investigate the detectors performances. A short-term survey was performed at the first UHDR beam-on with passive and active detectors. Then, a long-term survey was conducted with passive detectors during the first three months of operation of the UHDR linac. Moreover, linearity of detector response, activation of the linac components and secondary radiation inside the bunker were evaluated. ResultsSelected active survey metres were shown to have a linear response for the detection of the ambient radiation outside the bunker when performing pulsed UHDR irradiations. The most critical locations outside the bunker were identified at the bunker door and at the control room. The results showed that the operation of the linac with a workload limit of 1000 Gy/week at the isocenter would allow respecting a limit of 0.02 mSv/week to the personnel. The activation of the linac head with 16-MeV electron beam was more than ten times greater with conventional beams compared to UHDR. The secondary radiation inside the bunker was also reduced by −27% when employing UHDR beams. ConclusionsThis work provides a comprehensive evaluation of the suitability of active and passive detectors to perform a radiation safety assessment for a 16-MeV electron UHDR linac. The conditions under which commonly available survey metres for photons (FLUKE 451P) and neutrons (Ludlum Model 3007) can safely be employed in controlled areas outside the bunker were investigated. Moreover, we showed that if a radiation vault is safe for 16-MeV electron beams at conventional dose rates, this applies also to UHDR when fixing the linac weekly workload to a given amount of dose at the isocenter.

The possibility of using the DKS-AT1123 dosimeter for radiation monitoring of medical electron accelerators with the energy of more than 10 MeV

In the Russian Federation, there is a constant increase in the number of radiation medical installations with electron accelerators. Over the past 4 years, their number has increased 2.5 times. These installations contain pulsed electron accelerators that generate pulsed bremsstrahlung radiation with a maximum energy from 6 to 21 MeV. Currently, there are no devices designed for dosimetry of the pulsed photon radiation with energy of more than 10 MeV in the state register of measuring instruments of the Russian Federation. The most widely used radiation monitoring device for pulsed electron accelerators is the DKS-AT1123 X-ray and gamma radiation dosimeter designed for dosimetry of pulsed bremsstrahlung radiation with an energy of up to 10 MeV. The purpose of this work is to evaluate the possibility of using this device for dosimetry of pulsed bremsstrahlung radiation with a maximum energy of up to 20 MeV. The authors calculated the energy spectra of bremsstrahlung radiation for a point source with a maximum energy of 20 MeV behind flat concrete screens with a thickness of 1 m, 2 m and 3 m by the Monte Carlo method using the GEANT4 calculation program. The energy dependence of the registration efficiency of the DKS-AT1123 dosimeter was extrapolated to the energy range of 10–50 MeV in the kerma-approximation without taking into account the energy transfer by secondary electrons. It was assumed that it corresponds to the energy dependence of the total mass attenuation coefficient for the absorbed energy of gamma quanta in water. Using conversion coefficients for converting the fluence of monoenergetic photons into the effective dose rate at an anterior-posterior radiation incidence on the human body, real dose rates were calculated, and using the energy dependence of the dosimeter readings, the predicted results of measuring the unit dose rate with the DKS-AT1123 dosimeter behind a concrete protection with a thickness of 1, 2 and 3 m were obtained. It is shown that the maximum expected underestimation of the measurement results will not exceed 40% and practically does not depend on the thickness of the concrete shield in the thickness range from 1 to 3 m. To account for this underestimation, it is necessary to use the value of additional measurement error due to the energy dependence of the sensitivity of this device for the photon radiation energy of more than 10 MeV, equal to 70%. This makes it possible to use the measurement results obtained using this dosimeter to adequately characterize the state of radiation safety during operation of pulsed electron accelerators with a maximum energy of up to 20 MeV. It is possible to use a correction factor to the measurement results equal to 1.63 ±0.04 to compensate for this underestimation. The proposed approach can be used to create a methodology for using this dosimeter for radiation monitoring of medical electron accelerators with the energy of up to 20 MeV, if there are correction factors for radiation protection configurations and radiation energies encountered in practice.

Transcriptomic response of prostate cancer cells to carbon ion and photon irradiation with focus on androgen receptor and TP53 signaling

BackgroundRadiotherapy is essential in the treatment of prostate cancer. An alternative to conventional photon radiotherapy is the application of carbon ions, which provide a superior intratumoral dose distribution and less induced damage to adjacent healthy tissue. A common characteristic of prostate cancer cells is their dependence on androgens which is exploited therapeutically by androgen deprivation therapy in the advanced prostate cancer stage. Here, we aimed to analyze the transcriptomic response of prostate cancer cells to irradiation by photons in comparison to carbon ions, focusing on DNA damage, DNA repair and androgen receptor signaling.MethodsProstate cancer cell lines LNCaP (functional TP53 and androgen receptor signaling) and DU145 (dysfunctional TP53 and androgen receptor signaling) were irradiated by photons or carbon ions and the subsequent DNA damage was assessed by immuno-cytofluorescence. Furthermore, the cells were treated with an androgen-receptor agonist. The effects of irradiation and androgen treatment on the gene regulation and the transcriptome were investigated by RT-qPCR and RNA sequencing, followed by bioinformatic analysis.ResultsFollowing photon or carbon ion irradiation, both LNCaP and DU145 cells showed a dose-dependent amount of visible DNA damage that decreased over time, indicating occurring DNA repair. In terms of gene regulation, mRNAs involved in the TP53-dependent DNA damage response were significantly upregulated by photons and carbon ions in LNCaP but not in DU145 cells, which generally showed low levels of gene regulation after irradiation. Both LNCaP and DU145 cells responded to photons and carbon ions by downregulation of genes involved in DNA repair and cell cycle, partially resembling the transcriptome response to the applied androgen receptor agonist. Neither photons nor carbon ions significantly affected canonical androgen receptor-dependent gene regulation. Furthermore, certain genes that were specifically regulated by either photon or carbon ion irradiation were identified.ConclusionPhoton and carbon ion irradiation showed a significant congruence in terms of induced signaling pathways and transcriptomic responses. These responses were strongly impacted by the TP53 status. Nevertheless, irradiation mode-dependent distinct gene regulations with undefined implication for radiotherapy outcome were revealed. Androgen receptor signaling and irradiations shared regulation of certain genes with respect to DNA-repair and cell-cycle.

Motion-induced dose perturbations in photon radiotherapy and proton therapy measured by deformable liver-shaped 3D dosimeters in an anthropomorphic phantom

Background and purposeThe impact of intrafractional motion and deformations on clinical radiotherapy delivery has so far only been investigated by simulations as well as point and planar dose measurements. The aim of this study was to combine anthropomorphic 3D dosimetry with a deformable abdominal phantom to measure the influence of intra-fractional motion and gating in photon radiotherapy and evaluate the applicability in proton therapy. Material and methodsAn abdominal phantom was modified to hold a deformable anthropomorphic 3D dosimeter shaped as a human liver. A liver-specific photon radiotherapy and a proton pencil beam scanning therapy plan were delivered to the phantom without motion as well as with 12 mm sinusoidal motion while using either no respiratory gating or respiratory gating. ResultsUsing the stationary irradiation as reference the local 3 %/2 mm 3D gamma index pass rate of the motion experiments in the planning target volume (PTV) was above 97 % (photon) and 78 % (proton) with gating whereas it was below 74 % (photon) and 45 % (proton) without gating. ConclusionsFor the first time a high-resolution deformable anthropomorphic 3D dosimeter embedded in a deformable abdominal phantom was applied for experimental validation of both photon and proton treatments of targets exhibiting respiratory motion. It was experimentally shown that gating improves dose coverage and the geometrical accuracy for both photon radiotherapy and proton therapy.

Nonlinear electrodynamics for the vacuum of Dirac materials: Photon magnetic properties and radiation pressures

We investigate the magnetic properties of photons propagating through Dirac materials in a magnetic field, considering both vacuum and medium contributions. Photon propagation properties are obtained through a second-order expansion of nonlinear Euler-Heisenberg electrodynamics at finite density and temperature considering Dirac material parameters (Dirac fine structure constant, band gap, and Fermi velocity). Total magnetization (including electron and photon contributions) and photon-effective magnetic moment are computed. Observables such as photon energy density, radiation pressure, and Poynting vector are obtained by an average of components of the energy-momentum tensor. All quantities are expressed in terms of Lagrangian derivatives. Those related to the vacuum are valid for any value of the external magnetic field, and both the weak- and strong-field limits are recovered. We discuss some ideas of experiments that may contribute to testing in Dirac materials the phenomenology of the strong magnetic field in the quantum electrodynamic (QED) vacuum and how nonlinear corrections on the magnetization, radiation pressure, and birefringence are amplified up to 103 times QED corrections. Published by the American Physical Society 2024

Evaluation of magnetic resonance imaging derived synthetic computed tomography for proton therapy planning in prostate cancer

Background and purposeMagnetic resonance imaging (MRI)-only workflow is used in photon radiotherapy (RT) today, but not yet for protons. To bring MRI-only proton RT into clinical use, proton dose calculation on MRI-derived synthetic CT (sCT) must be validated. We evaluated proton dose calculation accuracy of prostate cancer proton plans using a commercially available sCT generator already validated for photon planning. Materials and methodsThe retrospective planning study included 10 prostate cancer patients who underwent MRI and planning CT (pCT) before RT. sCT were generated from the MRI with MRI Planner v2.3, and compared to pCT using structural mean absolute error (MAE). The pCT was used to create one-arc volumetric modulated arc therapy (VMAT) photon plan and two-field intensity modulated proton therapy (IMPT) proton plan. Each plan was recalculated on the sCT and compared to pCT doses. Dose volume histogram parameters, gamma analyses and range differences were evaluated. ResultsMedian MAE for the body contour was 71 HU. Dose differences between pCT and sCT were small and similar for VMAT and IMPT plans. Median (range) gamma pass rates were lower for IMPT plans with 95.8 (89.3–98.7) % compared to VMAT plans with 99.4 (91.2–99.6) %. The proton range difference was 1.0 (interquartile range –0.1 – 0.2) mm deeper for sCT compared to the reference. ConclusionMRI-only IMPT planning for prostate cancer seems feasible in a clinical setting for the evaluated beam arrangement and sCT generator. More patients and evaluation of other beam arrangements are needed for a more general conclusion.

Photon emission and radiation reaction effects in surface plasma waves in ultra-high intensities

Manipulating and harnessing plasmonic phenomena in the ultra-relativistic regime reveal promising prospects for the use of surface plasma waves (SPW) to create high-energy particle and radiation sources in the next generation of multi-petawatt lasers. Indeed, relativistic high-charge electron bunches can be produced by SPW excited by ultra-high intensity femtosecond lasers impinging on a periodically modulated solid-density target. In this regime, there is good evidence that SPW excitation survives and that the produced electron bunches experience strong acceleration, thus emitting large amounts of electromagnetic radiation. Therefore, extending the study to ultra-high laser intensities (I&amp;gt;1021 W/cm2), the use of a resonant grating for SPW generation represents an interesting alternative to light sources, as the energy lost by electrons due to radiation emission is transferred to high-energy γ photons. In addition, we show that using a laser with wavefront rotation coupled with a tailored blazed grating improves photon emission in the ultra-relativistic regime of interaction.

Carbon Ion Beam Radiation Therapy as Part of a Trimodal Therapy for Non-small Cell Superior Sulcus Tumors: The INKA Study

Purpose/ObjectiveSuperior sulcus tumors are frequently treated with neoadjuvant chemoradiotherapy (nCRT) followed by surgery in a trimodal approach. The INKA study evaluated the replacement of photon irradiation by carbon ion radiotherapy (C12-RT) in this regimen. Material/methodsThe prospective INKA-study included patients with locally advanced non-small cell superior sulcus tumors (<cN3 cM0). Patients received 2 cycles of cisplatin and vinorelbine as per local standard. During the second cycle, 39Gy(RBE) of hypofractionated C12-RT in 13 fractions were applied. Surgery following an FDG-PET/CT restaging was performed 2 weeks later. The primary endpoint was feasibility and safety measured by the incidence of CTCAE (v4.0) grade 3/4 toxicity and/or discontinuation due to any reason. Secondary endpoints included the morphological (RECIST 1.0), metabolic (PERCIST 1.0) and histopathological response after nCRT as well as Quality of Life measurement (QLQ-C30/LC13). ResultsBetween 2015 and 2020, 14 patients were included and received nCRT. No grade 3/4 toxicity occurred with no discontinuation due to toxicity. Before surgery, 8 patients (57%) showed a partial response on CT scan. Thirteen patients showed a metabolic response (mCR=1, mPR=12). Three patients were judged as inoperable after nCRT (21%). In patients with resection, a pathological CR was seen in 2 patients (19%) and near-complete remission (<10% vital tumor cells) in 6 patients (55%). Pain score was more than halved compared to baseline (mean: 69.2±26.2 vs. 30.6 ± 29.1; p=0.005) after completion of nCRT and before surgery. ConclusionThe INKA trial is the first study to evaluate nCRT with C12-RT and showed excellent response, low toxicity and rapid pain relief.

Methodology for Measuring the Dose Rate of Pulsed Bremsstrahlung Radiation using Gamma Radiation Dosimeters with Geiger-Muller Counter

Introduction. Industrial monitoring of pulsed bremsstrahlung radiation is associated with a number of challenges. Russia produces only three dosimeters that can be used for measuring pulsed bremsstrahlung radiation with a pulse duration of less than 10 gs. These dosimeters, in addition to being rather expensive, have a number of significant restrictions on the energy range (10 MeV) and the minimum pulse duration (10 ns). The DKG-RM1621 dosimeter with a Geiger-Muller counter can be used for dosimetry of photon radiation with energies up to 20 MeV. However, this device is not intended for dosimetry of pulsed radiation.Aim. Development of a methodology for conducting radiation monitoring of pulsed bremsstrahlung radiation sources using dosimeters with Geiger-Muller counters.Materials and methods. In 2021, measurements of the dose rate of pulsed bremsstrahlung radiation with a maximum energy of 3.0 MeV at pulse repetition rates of 50, 100, 150, 200, 250, 300, and 400 Hz were carried out using DKS- AT1123 (as a reference) and MKS-AT117M dosimeters with a Geiger-Muller counter.Results. A technique was developed for correcting the results of measuring the dose rate of pulsed bremsstrahlung radiation by a dosimeter equipped with a Geiger-Muller counter, which allows the dose rate of pulsed bremsstrahlung radiation to be measured with an additional error of less than 15 % in a practically significant range of dose rates. For the MKS- AT117M dosimeter at a pulse repetition rate of 400 Hz, this value was 320 gSv/h, which is sufficient for most practical tasks in radiation monitoring.Conclusion. The feasibility and possibility of successful application of dosimeters with Geiger-Muller counters for dosimetry of pulsed bremsstrahlung radiation using the proposed measurement technique with a limitation on the maximum measured dose rate is shown.

Development and performance testing of a chamber for absorbed dose in water absolute measurement for 125I brachytherapy seeds

The application of more and more low-energy, low-dose-rate photon radiation seeds in brachytherapy. According to the TG43 report and TG43-U1 report issued by the American Association of Physicists in Medicine, both apparent activity and air kerma strength are physical characterization parameters of brachytherapy seed strength,which are needed to convert into water absorbed dose at the depth of 1 cm. At present, the method of obtaining the water absorbed dose is to convert the air kerma strength, the uncertainty of results exceeds 5% (k = 1), which could reduce the cure rate of the treatment. In order to address this issue ,the China Institute of Atomic Energy has designed a device that can directly replicate the water absorbed dose of 125I brachytherapy seeds,which is an extrapolation chamber embedded with water equivalent material. In order to evaluate the performance of the extrapolation chamber, a series of experiments were carried out, including partial pressure test, leakage current, saturation curve, response linearity, collection area and zero point position. The test results show that the performance parameters of the extrapolation chamber meet the relevant requirements.

Motion Management and Image-Guided Technique in Photon Radiation Therapy: A Review of an Advanced Technology

Motion Management and Image-Guided Technique in Photon Radiation Therapy: A Review of an Advanced Technology

Impact of setup and geometric uncertainties on the robustness of free-breathing photon radiotherapy of small lung tumors

Purpose:Respiratory motion and patient setup error both contribute to the dosimetric uncertainty in radiotherapy of lung tumors. Managing these uncertainties for free-breathing treatments is usually done by margin-based approaches or robust optimization. However, breathing motion can be irregular and concerns have been raised for the robustness of the treatment plans. We have previously reported the dosimetric effects of the respiratory motion, without setup uncertainties, in lung tumor photon radiotherapy using free-breathing images. In this study, we include setup uncertainty. Methods:Tumor positions from cine-CT images acquired in free-breathing were combined with per-fraction patient shifts to simulate treatment scenarios. A total of 14 patients with 300 tumor positions were used to evaluate treatment plans based on 4DCT. Four planning methods aiming at delivering 54 Gy as median tumor dose in three fractions were compared. The planning methods were denoted robust 4D (RB4), isodose to the PTV with a central higher dose (ISD), the ISD method normalized to the intended median tumor dose (IRN) and homogeneous fluence to the PTV (FLU). Results:For all planning methods 95% of the intended dose was achieved with at least 90% probability with RB4 and FLU having equal CTV D50% values at this probability. FLU gave the most consistent results in terms of CTV D50% spread and dose homogeneity. Conclusions:Despite the simulated patient shifts and tumor motions being larger than observed in the 4DCTs the dosimetric impact was suggested to be small. RB4 or FLU are recommended for the planning of free-breathing treatments.