Proton Irradiation Research Articles

Performance of a BeO-based dosimetry system for proton and electron beam dose measurements

This study aims to evaluate the performance of the BeO-based myOSLchip system (RadPro International GmbH, Remscheid, Germany) for dosimetry of proton and electron radiotherapy beams. Although beryllium oxide (BeO) has been recognised as a promising material for luminescence dosimetry in radiotherapy, this research extends beyond material properties and examines the entire BeO-based dosimetry system, including the detector, holder, and readout components.Packages of myOSLchip detectors were irradiated either in a (70−230) MeV proton beam or in a 16 MeV electron beam. The readouts were carried out using the portable myOSLchip reader. In the electron beam, tests on the precision, dose response up to 100 Gy and dose-rate effects of the system were carried out. In the proton beam, the system was tested for its dose response (up to 10 Gy), fading, and linear energy transfer (LET) response.For proton irradiations, the myOSLchip BeO OSLDs exhibited stability within 2 % over 135 days, as well as a linear dose response in the tested range, (0.1−10) Gy. The efficiency showed a reduction for proton beams with LET values (for water) above 0.6 keV/μm, with up to 40 % loss in efficiency at 4 keV/μm. For the electron irradiations, they showed a linear dose–response up to 20 Gy and dose-rate independence, with a constant response at least up to 2.99×105 Gy s−1. Using individual chip sensitivity correction, the precision for a single chip was around 3.5% (standard deviation of the data of all chips) and for a package comprising four chips was 1.7% (standard deviation of the mean of the four chips).These findings suggest the myOSLchip system’s potential as a reliable alternative to existing dosimetry systems in clinical applications.

Studies of GAGG:Ce scintillators for space missions dedicated to Terrestrial Gamma-Ray Flashes and Gamma-Ray Bursts observation

Fast Gamma ray Spectrometer (FGS) is an on-going detector development for the observation of transient gamma ray events such as Terrestrial Gamma ray Flashes (TGFs) produced in Earth’s thunderstorms and Gamma Ray Bursts (GRBs) produced in the far Universe. In this work, we compare different Cerium-doped Gadolinium Aluminium Gallium Garnet (GAGG:Ce) scintillators, associated with Silicon Photo-Multipliers (SiPMs), quantifying their performances at atmospheric pressure and under vacuum, with different surface finitions. We also study their afterglow following proton irradiation, similar to what will be observed in space environment. Our measurements with GAGG:Ce scintillators after proton irradiation confirm that GAGG:Ce can be used in space.

LET-based approximation of the microdosimetric kinetic model for proton radiotherapy.

Phenomenological relative biological effectiveness (RBE) models for proton therapy, based on the dose-averaged linear energy transfer (LET), have been developed to address the apparent RBE increase towards the end of the proton range. The results of these phenomenological models substantially differ due to varying empirical assumptions and fitting functions. In contrast, more theory-based approaches are used in carbon ion radiotherapy, such as the microdosimetric kinetic model (MKM). However, implementing microdosimetry-based models in LET-based proton therapy treatment planning systems poses challenges. This work presents a LET-based version of the MKM that is practical for clinical use in proton radiotherapy. At first, we derived an approximation of the Mayo Clinic Florida (MCF) MKM for relatively-sparsely ionizing radiation such as protons. The mathematical formalism of the proposed model is equivalent to the original MKM, but it maintains some key features of the MCF MKM, such as the determination of model parameters from measurable cell characteristics. Subsequently, we carried out Monte Carlo calculations with PHITS in different simulated scenarios to establish a heuristic correlation between microdosimetric quantities and the dose averaged LET of protons. A simple allometric function was found able to describe the relationship between the dose-averaged LET of protons and the dose-mean lineal energy, which includes the contributions of secondary particles. The LET-based MKM was used to model the in vitro clonogenic survival RBE of five human and rodent cell lines (A549, AG01522, CHO, T98G, and U87) exposed to pristine and spread-out Bragg peak (SOBP) proton beams. The results of the LET-based MKM agree well with the biological data in a comparable or better way with respect to the other models included in the study. A sensitivity analysis on the model results was also performed. The LET-based MKM integrates the predictive theoretical framework of the MCF MKM with a straightforward mathematical description of the RBE based on the dose-averaged LET, a physical quantity readily available in modern treatment planning systems for proton therapy.

399 - Comparison of image-guidance in proton and photon radiation therapy: Preliminary clinical experience

399 - Comparison of image-guidance in proton and photon radiation therapy: Preliminary clinical experience

Comparing robust proton versus online adaptive photon radiotherapy for short-course treatment of rectal cancer

Background and purposeImage-guided proton beam therapy (IG-PBT) and cone-beam CT (CBCT)-based online adaptive photon radiotherapy (oART) have potentials to restrict radiation toxicity. They are both hypothesised to reduce therapy limiting bowel toxicity in the multimodality treatment of locally advanced rectal cancer (LARC). This study aimed to quantify the difference in relevant dose-volume metrics for these modalities. Material and MethodsSix-degrees-of-freedom IG-PBT and oART short-course radiotherapy (SCRT) were simulated for 18 LARC patients. Relative biological effectiveness (RBE) was 1.1 for IG-PBT. Delivered dose was evaluated using post-CBCTs. Target coverage was considered robust if average dose to 99 % of the clinical target volume was ≥ 95 % of the prescription. Organ at risk (OAR) doses were compared using dose-volume histograms and severe bowel toxicity estimated using dose–response modelling. ResultsTarget coverage was robust in all patients for oART and all but one patient for IG-PBT. For the main OARs, IG-PBT increased the volume exposed to ≥ 15 Gy (RBE), but reduced volumes exposed to lower doses. Both low- and high-dose exposure to bowel loops were significantly different between the modalities (median (interquartile range) IG-PBT-V8.9Gy(RBE) = 92 cm3 (51–156), oART-V8.9Gy(RBE) = 166 cm3 (107–234), p < 0.001; IG-PBT-V23Gy(RBE) = 62 cm3 (25–106), oART-V23Gy(RBE) = 38 cm3 (18–75), p < 0.001), translating into similar total grade ≥ 3 bowel toxicity risk. ConclusionIG-PBT and oART delivered comparable and satisfying target coverage in SCRT for LARC with similar estimated risk of severe bowel toxicity. Volumes of OAR exposed to 15 Gy (RBE) or more were reduced by oART, while IG-PBT reduced the volumes receiving doses below this level.

Intensity-modulated proton radiotherapy spares musculoskeletal structures in regional nodal irradiation for breast cancer: a dosimetric comparison.

Regional nodal irradiation (RNI) for breast cancer delivers radiation in proximity to the shoulder and torso, and radiation exposure may contribute to long-term upper extremity and postural morbidity. To date, no studies have assessed the differential dosimetric impact of proton versus photon radiation on shoulder and torso anatomy. This study examined clinically relevant musculoskeletal (MSK) structures and assessed the dose delivered with each modality. Ten MSK structures were contoured on IMPT (intensity-modulated proton therapy) and VMAT (volumetric modulated arc therapy) plans for 30 patients receiving RNI. Relevant dose metrics were compared for each of the structures. Intensity-modulated proton therapy dose was calculated using the relative biological effective value of 1.1. Hypo-fractionated plans were scaled to the equivalent dose in 2 Gy fractions (EQD2) using an alpha/beta ratio of four. Wilcoxon signed rank sum tests compared doses. Select three-dimensional and optimised VMAT plans were also informally compared. Each of the 10 structures received a statistically significantly lower dose with the use of IMPT compared with VMAT. Differences were greatest for posterior structures, including the trapezius, latissimus dorsi and glenohumeral joint. Mean absolute differences were as great as 23 Gy (supraspinatus D5cc) and up to 30-fold dose reductions were observed (deltoid D50cc). An average 3.7-fold relative dose reduction existed across all structures. Measures of low/intermediate dose (V15Gy and D50cc) showed the largest differences. Intensity-modulated proton therapy results in statistically lower radiation exposure to relevant shoulder and torso anatomy compared to photon radiation for patients requiring RNI. Prospective study is needed to correlate functional outcomes with radiation dose.

Precise and Accurate Short-term Forecasting of Solar Energetic Particle Events with Multivariate Time-series Classifiers

Solar energetic particle (SEP) events are one of the most crucial aspects of space weather that require continuous monitoring and forecasting using robust methods. We demonstrate a proof of concept of using a data-driven supervised classification framework on a multivariate time-series data set covering solar cycles 22, 23, and 24. We implement ensemble modeling that merges the results from three proton channels (E ≥ 10 MeV, 50 MeV, and 100 MeV) and the long-band X-ray flux (1–8 Å) channel from the Geostationary Operational Environmental Satellite missions. Our task is binary classification, such that the aim of the model is to distinguish strong SEP events from nonevents. Here, strong SEP events are those crossing the Space Weather Prediction Center’s “S1” threshold of solar radiation storm and proton fluxes below that threshold are weak SEP events. In addition, we consider periods of nonoccurrence of SEPs following a flare with magnitudes ≥C6.0 to maintain a natural imbalance of sample distribution. In our data set, there are 244 strong SEP events comprising the positive class. There are 189 weak events and 2460 “SEP-quiet” periods for the negative class. We experiment with summary statistic, one-nearest neighbor, and supervised time-series forest (STSF) classifiers and compare their performance to validate our methods for prediction windows from 5 minutes up to 60 minutes. We find the STSF model to perform better under all circumstances. For an optimal classification threshold of ≈0.3 and a 60 minutes prediction window, we obtain a true skill statistic TSS = 0.850, Heidke skill score HSS = 0.878, and Gilbert skill score GSS = 0.783.

Development of an algorithm for proton dose calculation in magnetic fields.

The advantages of proton therapy can be further enhanced with online magnetic resonance imaging (MRI) guidance. One of the challenges in the realization of MRI-guided proton therapy (MRPT) is accurately calculating the radiation dose in the presence of magnetic fields. This study aims to develop an efficient and accurate proton dose calculation algorithm adapted to the presence of magnetic fields. An analytical-numerical radiation dose calculation algorithm, Proton and Ion Dose Engine (PRIDE), was developed. The algorithm combines the pencil beam algorithm (PBA) with a novel iterative voxel-based ray-tracing algorithm. The new ray-tracing method uses fewer assumptions and ensures broader applicability for proton beam trajectory prediction in magnetic fields, and has been compared to Wolf's method and Schellhammer's method. The accuracy of PRIDE algorithm was validated on three phantoms and two practical plans (one single-field water plan and one prostate tumor plan) in different magnetic field strengths up to 3.0 T. The validation was performed by comparing the results against the Monte Carlo (MC) simulations, using the global gamma index criteria of 2%/2mm and 3%/3mm with a 10% threshold. PRIDE showed good agreement with MC in homogeneous and slab heterogeneous phantom, achieving gamma passing rates (%GPs) above 99% for 2%/2mm criteria when magnetic field strength is not greater than 1.5 T. Although the agreement decreased for scenarios involving high proton energy (240 MeV) and strong magnetic field (3.0 T), the 2%/2mm %GPs still remained above 98%. In lateral heterogeneous phantom, the accuracy of PRIDE decreased due to the PBA's limitation. For the two practical plans in different magnetic fields, %GPs exceeded 98% and 99% for 2%/2mm and 3%/3mm criteria, respectively. PRIDE can perform efficient and accurate proton dose calculation in magnetic fields up to 3.0 T, and is expected to work as a useful tool for proton dose calculation in MRPT.

Proton Radiation Therapy for Head and Neck Cancers.

Head and neck (HnN) cancers are among the most common cancers in the world. Proton therapy (PT) is one of the latest advancements in the treatment modalities of cancers. Proton therapy is specifically used to treat HnN cancer patients due to its less toxic effects on the surrounding critical structures. Keeping in view the opportunities for further advancements, there is a lot of literature covering PT in HnN cancer patients. However, few compiled studies are not enough to compare the toxicities, overall survival (OS), local control (LC), and quality of life (QoL) of PT with that of intensity-modulated radiation therapy (IMRT). The objective of this review is to compile and summarize the literature available on the toxicities, OS, LC, and QoL in HnN cancer patients post PT. We have gathered and summarized the literature found under the keyword "proton therapy for head and neck cancers". Proton therapy is a preferable option over IMRT because it isolates tumors of the HnN, reduces exposure of healthy cells to radiation, and allows accurate tumor scanning using the pencil beam technique. In view of this article, we can say that PT is a preferable mode of radiotherapy for HnN cancer patients in view of its accuracy and lower incidents of acute and late toxicities.

Impact of Proton Irradiation Depending on Breast Cancer Subtype in Patient-Derived Cell Lines

Research on different types of ionizing radiation’s effects has been ongoing for years, revealing its efficacy in damaging cancer cells. Solid tumors comprise diverse cell types, each being able to respond differently to radiation. This study evaluated the radiobiological response of established (MDA-MB-231 (Triple negative breast cancer, TNBC), MCF-7 (Luminal A)) and patient-derived malignant cell lines, cancer-associated fibroblasts, and skin fibroblasts following proton IRR. All cell line types were irradiated with the proton dose of 2, 4, and 6 Gy. The radiobiological response was assessed using clonogenic assay, γH2AX, and p53 staining. It was noticeable that breast cancer lines of different molecular subtypes displayed no significant variations in their response to proton IRR. In terms of cancer-associated fibroblasts extracted from the tumor tissue, the line derived from a TNBC subtype tumor demonstrated higher resistance to ionizing radiation compared to lines isolated from luminal A tumors. Fibroblasts extracted from patients’ skin responded identically to all doses of proton radiation. This study emphasizes that tumor response is not exclusively determined by the elimination of breast cancer cells, but also takes into account tumor microenvironmental variables and skin reactions.

Silicate-lunar regolith composite: A vacuum self-hardened and comprehensively durable extraterrestrial construction material

Extraterrestrial exploration, represented by Lunar base construction, has been promoted worldwide as a multi-disciplinary, cutting-edge and strategic issue. Herein we proposed a novel extraterrestrial construction material composed of Lunar/Martian regolith simulants and only 4 wt% of silicate adhesive. This silicate-regolith composite can be directly self-hardened in vacuum within 4.5 h without any curing to achieve 29 MPa of hardening strength. Meanwhile, it shows comprehensive durability with stable microstructures and >70 % of residual strength against long-term vacuum exposure, huge temperature difference and intense γ-ray and proton radiations. Its in-situ solidification and durability originate from vacuum dehydration, where silica clusters in solution spontaneously cohere into a solid network with strong connections of silica tetrahedra and bound water. A moderate silicate modulus around 2.5 and appropriate modifications can disperse finer silica clusters to increase oligomer silica units in solution and enhance hardening strength. Compared with lunar geopolymer and other existing extraterrestrial construction materials, this vacuum self-hardening composite allows a cryogenic preparation even below −40 ℃ using diverse regolith with a wide range of compositions and sizes, proposing a facile, durable and versatile solution towards in-situ extraterrestrial constructions.

Cardiac Conduction System as an OAR in Radiation Therapy: Doses to SA/AV Nodes and Their Reduction

PurposeDespite advancements in radiation techniques, concerns persist regarding the adverse effects of radiation therapy, particularly cardiotoxicity or radiation-induced heart disease. Recently, arrhythmogenic toxicity has come to the forefront—the impact of radiation therapy on the cardiac conduction system. Our objective was to conduct a dosimetric study and subsequently investigate the feasibility of optimizing the sinoatrial (SA) and atrioventricular (AV) nodes as organs at risk (OARs) in proton radiation therapy for non–small cell lung cancer with N3 disease. Patients and MethodsThirty-two non–small cell lung cancer patients with N3 disease undergoing proton radiation therapy were included. Sinoatrial and AV nodes, along with standard OARs, were delineated. Dosimetric analysis and optimization were performed using intensity-modulated proton therapy. ResultsPatients surpassing a predefined SA node dose threshold underwent dose optimization. Proton radiation therapy with pencil beam scanning demonstrated a significant reduction in SA and AV node doses without compromising target volume coverage or significant shift in the dose to other monitored OARs. ConclusionDose reduction to the SA and AV nodes for pencil beam scanning is a relatively simple task, and the reduction can be very substantial. Larger cohort studies and diverse radiotherapeutic modalities are needed for further validation and refinement of dose constraints.

The connection between the accumulation of structural defects caused by proton irradiation and the destruction of the near-surface layer of Li4SiO4 – Li2TiO3 ceramics

The key problem of using lithium-containing ceramics as materials of breeders for the propagation of tritium in thermonuclear reactors is phase stability, as well as the preservation of strength and thermophysical parameters of ceramics during their operation, which is accompanied by the accumulation of fission products in the near-surface layers, alongside mechanical influences from the outside. Moreover, in contrast to other types of ceramics, the presence of lithium in the composition of the samples under study leads to limitations in the use of classical analysis methods (scanning electron microscopy, energy dispersive analysis or optical spectroscopy) of structural changes caused by the accumulation of radiation damage, which requires the use of more complex methods for the assessment of the defect concentration in the structure, as well as establishing their relationship with the deterioration of strength and thermophysical parameters, playing a key role in determining the stability mechanisms and further exploitation of ceramics for tritium production. In this regard, the aim of the study is to determine the kinetics of changes in the near-surface layer of two-phase Li4SiO4 – Li2TiO3 ceramics associated with the accumulation of structural distortions caused by irradiation, as well as their relationship with strain embrittlement and disorder. During the studies, it was found that the accumulation of implanted hydrogen in the near-surface layer under high-dose irradiation initiates deformation distortion processes, the intensity of which depends on the ratio of components in the ceramics, according to which the optimal compositions of two-phase ceramics are ratios of components from 0.3 to 0.6. Determination of the type of defects in the composition of the damaged layer, as well as their concentration, was carried out using the electron spin resonance (ESP) method. During the studies, it was found that at low irradiation fluences, the dominant role in the accumulation of structural defects is played by vacancy defects associated with E′-centers, the formation of which is associated with structural distortions, while as the fluence grows, the structure is dominated by deformation disordering caused by the accumulation of Ti3+ defects and HC2 centers (SiO43-), the concentrations of which have a clear dependence on the phase composition of the ceramics.

Internalizing Symptoms and Their Impact on Patient-Reported Health-Related Quality of Life and Fatigue among Patients with Craniopharyngioma During Proton Radiation Therapy.

The aim of this study was to describe fatigue, health-related quality of life (HRQOL) and brain tumor-associated symptoms after surgical resection and during proton radiotherapy, using latent class analysis (LCA), and to determine if there is class membership change among pediatric patients with craniopharyngioma. For all patients (n = 92), demographic and disease-related/clinical variables were attained, and patient reported outcomes were collected prior to proton therapy, at week three, and at the completion of proton therapy. The mean scores for fatigue, HRQOL, and brain tumor symptoms were compared over time and profiles were identified. Factors that influenced profile status and transition probability were examined. Fatigue, HRQOL, and brain tumor symptoms improved over time during proton therapy; however, a subset remained in the lower profile, profile 1, associated with increased internalizing behaviors, compared to profile 2. Future study should explore the bidirectional relationship of sleep, worry and anxiety in the context of ongoing radiotherapy.

Linear energy transfer dependent variation in viability and proliferation along the Bragg peak curve in sarcoma and normal tissue cells

Objective.The energy deposition of photons and protons differs. It depends on the position in the proton Bragg peak (BP) and the linear energy transfer (LET) leading to a variable relative biological effectiveness (RBE). Here, we investigate LET dependent alterations on metabolic viability and proliferation of sarcoma and endothelium cell lines following proton irradiation in comparison to photon exposure.Approach.Using a multi-step range shifter, each column of a 96-well plate was positioned in a different depth along four BP curves with increasing intensities. The high-throughput experimental setup covers dose, LET, and RBE changes seen in a treatment field. Photon irradiation was performed to calculate the RBE along the BP curve. Two biological information out of one experiment were extracted allowing a correlation between metabolic viability and proliferation of the cells.Main results.The metabolic viability and cellular proliferation were column-wise altered showing a depth-dose profile. Endothelium cell viability recovers within 96 h post BP irradiation while sarcoma cell viability remains reduced. Highest RBE values were observed at the BP distal fall-off regarding proliferation of the sarcoma and endothelial cells.Significance.The high-throughput experimental setup introduced here (I) covers dose, LET, and RBE changes seen in a treatment field, (II) measures short-term effects within 48 h to 96 h post irradiation, and (III) can additionally be transferred to various cell types without time consuming experimental adaptations. Traditionally, RBE values are calculated from clonogenic cell survival. Measured RBE profiles strongly depend on physical characteristics such as dose and LET and biological characteristics for example cell type and time point. Metabolic viability and proliferation proofed to be in a similar effect range compared to clonogenic survival results. Based on limited data of combined irradiation with doxorubicin, future experiments will test combined treatment with systemic therapies applied in clinics e.g. cyclin-dependent inhibitors.

Synergistic Effects of Surface States and Deep Energy Level Traps on InGaAs p-i-n Diodes under Proton Irradiation

Synergistic Effects of Surface States and Deep Energy Level Traps on InGaAs p-i-n Diodes under Proton Irradiation

Acceptability of a Serious Game About Proton Radiotherapy Designed for Children Aged 5 to 14 Years and Its Potential Impact on Perceived Anxiety: Feasibility and Randomized Controlled Pilot Trial.

Children who are going to undergo radiotherapy have displayed fear and anxiety. Therefore, a web-based serious game was developed as a psychological preparation to investigate if it could affect anxiety levels. In an earlier stage, children with experience of radiotherapy had been part of the developmental process. The study aimed to investigate the feasibility in terms of reach, usability, and acceptability of a serious game about proton radiotherapy and to pilot that it did not increase anxiety levels in children aged 5 to 14 years undergoing radiotherapy. The design was a randomized controlled pilot trial with predefined feasibility criteria. In total, 28 children were assessed for eligibility, and 23 met the inclusion criteria. They were consecutively randomized into 1 of 2 study arms. One child was excluded after randomization. If randomized into arm 1, the children received the intervention before treatment started. Children in arm 2 were treated as controls. Questionnaires with fixed answers were used to assess anxiety levels (an adapted version of the State-Trait Anxiety Inventory for Children) and experiences of gameplay (an adapted version of Player Experience of Need Satisfaction [PENS]). The children were asked to answer questionnaires at 5 different measurement occasions during their radiotherapy treatment. In arm 1, age ranged from 5 to 13 (mean 8.4, SD 2.4) years. In arm 2, age ranged from 5 to 11 (mean 7.6, SD 2.3) years. The sample consisted of 15 girls and 7 boys. The feasibility criterion that the children should play the game for 20 minutes or more was not met. Mean playtime for children in arm 1 was 32.1 (SD 23.8) minutes, where 18 children had played for at least 15 minutes. The criterion that 70% (n=16) or more of the participants should return all of the questionnaires was not met; however, more than 73% (n=16) returned the PENS questionnaires. The State-Trait Anxiety Inventory for Children was returned by 73% (n=16) on day 0, 77% (n=17) on day 1, 82% (n=18) on day 3, 82% (n=18) on day 6, and 86% (n=19) on day 15. All feasibility criteria set for the study were not met, suggesting that adaptions need to be made if a future study is to be undertaken. Further, the analysis revealed that there was no indication that playing increased the children's self-reported anxiety. The PENS questionnaire adapted for children showed promising results regarding player satisfaction when using the serious game. When studying children with severe conditions and young age, 5 measurement occasions seemed to be too many. Measuring both player satisfaction or experience and knowledge transfer would be preferable in future studies.

Effect of Proton Irradiation on Thin-Film YBa2Cu3O7-δ Superconductor.

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa2Cu3O7-δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6×1016 p/cm2. Upon irradiation, Tc was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above Tc. This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between Tc and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov-Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress Tc.

Five-Year Prostate-Specific Membrane Antigen Positron Emission Tomography-Based Outcomes of Spot-Scanning Proton Radiation Therapy for Localized Prostate Cancer: A Single Institution Experience

PURPOSE: We report 5-year oncologic outcomes of a prospective series of patients with prostate cancer treated with spot-scanning proton therapy (SSPT).METHODS AND MATERIALS: A prospective registry identified patients with prostate cancer treated with SSPT between January 2016 and December 2018. Five-year overall survival (OS), local control (LC), biochemical failure (BF), regional and distant failures, and adverse events (AEs) were assessed. Biochemical failure was defined as rise in PSA ≥ 2.0 ng/mL above nadir PSA. Baseline-adjusted toxicities were assigned using CTCAE v5.0.RESULTS: With a median follow up of 4.4 years, 284 prostate cancer patients were treated with SSPT. Median total radiation dose was 79.2 Gy over 44 fractions, 70 Gy over 28 fractions, and 38 Gy over 5 fractions for conventional fractionation (CF), hypofractionation (HF), and stereotactic body radiation therapy (SBRT), respectively. Biochemical failure rate for all patients was 6.7%. Five-year LC rates for CF, HF, and SBRT were 100%, 100%, and 97.3%, respectively (p = 0.07). Regional recurrences occurred in 12 (4.2%) patients: 8 treated with CF, 2 with HF, and 2 with SBRT (p = 0.62). Distant failures occurred in 12 patients (4.2%): 5 treated with CF, 7 with HF, and none with SBRT (p = 0.05). Five-year OS for patients treated with CF, HF, and SBRT SSPT were 88.1%, 86.1%, and 97.2%, respectively (p = 0.1). Acute and chronic grade 2+ GI AEs occurred in 8 (2.8%) and 51 (18.0%) patients, respectively. Acute and chronic grade 3+ GI AEs occurred in 3 (1.1%) and 4 (1.4%) patients, respectively. Acute and chronic grade 2+ GU-related AEs were observed in 71 (25%) and 63 (22.2%) patients, respectively. Acute and chronic grade 3+ GU toxicity were observed in 3 (1.1%) and 6 (2.1%) patients, respectively.CONCLUSIONS: SSPT provides high local control rates and excellent oncologic outcomes across different fractionation schedules with low long-term AE rates.

Accelerated formation of M2C carbides by proton irradiation inhibits molten salt corrosion in Ni-based alloy

The effect of displacement damage on the corrosion behavior in a molten FLiBe salt environment was investigated. The element distribution and microstructure around the grain boundaries (GBs) after corrosion were characterized. The results show a decrease in corrosion thickness with increasing irradiation dose and the presence of intergranular corrosion. Nanoscales M2C carbides were observed to be distributed, with a denser and thicker distribution in samples with higher irradiation doses. Their distribution depth is related to the Cr depletion region, inhibiting Cr diffusion toward the GBs and surface. Furthermore, the nucleation mechanism of M2C carbides along the GBs and in irradiated regions was revealed, attributed to the combined effects of thermal influences, element preferential dissolution due to corrosion, and irradiation-induced segregation.