External Radiation Research Articles

Josephson dynamics and Shapiro steps at high transmissions: current bias regime.

We investigate Josephson dynamics of highly transparent superconducting nanojunctions at subgap voltages and temperatures. In this limit, intrinsic dissipation in such junctions turns out to be sub-Ohmic, which yields a linear dependence of the average voltage on the bias current I slightly exceeding the critical one Ic. We demonstrate a strong impact of intrinsic sub-Ohmic dissipation on integer Shapiro steps appearing on the I-V curve in the presence of external microwave radiation.

Risk of central nervous system tumour incidence in a cohort of workers chronically exposed to ionising radiation.

The aim of the present study was to assess the risk of primary central nervous system (CNS) tumour incidence in a cohort of 22,377 Mayak Production Association workers chronically exposed to ionising radiation. There were 96 primary CNS tumours, including 42 cases of glioma and 44 cases of meningioma, registered during the whole follow-up period (1948-2018). The study demonstrated that the risk of primary CNS tumour incidence was associated with sex, attained age, calendar period, tall body height, age at the beginning of exposure, and facility type. There was no association found between risk of CNS tumour incidence and body mass index, smoking (males) and alcohol consumption status. The study did not find an effect of the total external gamma radiation dose absorbed in the brain on risk of CNS tumour incidence irrespective of whether an adjustment for the total external neutron dose absorbed in the brain was included or not. Excess relative risk per 1Gy of external gamma brain dose was 0.05 (95% confidence interval (CI) -0.30; 0.70) for all CNS tumours, -0.18 (95% CI -; 0.44) for gliomas, and 0.38 (95% CI -0.32; 2.08) for meningiomas without adjustment for total neutron brain dose. There was no effect modification by sex, attained age, age at hire or facility.

Time Factor in External Radiotherapy: Radiobiological Mechanisms and Clinical Applications

Time Factor in External Radiotherapy: Radiobiological Mechanisms and Clinical Applications

Non-coplanar lung SABR treatments delivered with a gantry-mounted x-ray tube

Objective. To create two non-coplanar, stereotactic ablative radiotherapy (SABR) lung patient treatment plans compliant with the radiation therapy oncology group (RTOG) 0813 dosimetric criteria using a simple, isocentric, therapy with kilovoltage arcs (SITKA) system designed to provide low cost external radiotherapy treatments for low- and middle-income countries (LMICs). Approach. A treatment machine design has been proposed featuring a 320 kVp x-ray tube mounted on a gantry. A deep learning cone-beam CT (CBCT) to synthetic CT (sCT) method was employed to remove the additional cost of planning CTs. A novel inverse treatment planning approach using GPU backprojection was used to create a highly non-coplanar treatment plan with circular beam shapes generated by an iris collimator. Treatments were planned and simulated using the TOPAS Monte Carlo (MC) code for two lung patients. Dose distributions were compared to 6 MV volumetric modulated arc therapy (VMAT) planned in Eclipse on the same cases for a Truebeam linac as well as obeying the RTOG 0813 protocols for lung SABR treatments with a prescribed dose of 50 Gy. Main results. The low-cost SITKA treatments were compliant with all RTOG 0813 dosimetric criteria. SITKA treatments showed, on average, a 6.7 and 4.9 Gy reduction of the maximum dose in soft tissue organs at risk (OARs) as compared to VMAT, for the two patients respectively. This was accompanied by a small increase in the mean dose of 0.17 and 0.30 Gy in soft tissue OARs. Significance. The proposed SITKA system offers a maximally low-cost, effective alternative to conventional radiotherapy systems for lung cancer patients, particularly in low-income countries. The system’s non-coplanar, isocentric approach, coupled with the deep learning CBCT to sCT and GPU backprojection-based inverse treatment planning, offers lower maximum doses in OARs and comparable conformity to VMAT plans at a fraction of the cost of conventional radiotherapy.

Experimental research on radiation blockage of the fuel vapor and flame in pool fires

Pool fires are the most prevalent accidents in the process industry. Revealing the physical mechanism of pool fire has both fundamental and practical applications in process safety and risk analysis. This paper intends to study the radiation blockage phenomenon caused by fuel vapor and flame in pool fires. Combustion and evaporation (non-combustion) experiments under different external radiative heat fluxes have been conducted to differentiate the radiation blockage of the fuel vapor and the flame. Four different sooting fuels including methanol, ethanol, n-heptane and toluene were used in the experiments. The radiation blockage of fuel vapor was determined through evaporation experiments. The radiation blockage of flame and the total radiation blockage of pool fires were investigated by burning experiments. Based on the assumptions of radiation gray for flame radiation and external radiation, the effective radiation blockage was determined. It is found that the effective radiation blockage coefficient of the fuel vapor increases with fuel mass flux first, and then gradually approaches a constant value because the radiation absorption capacity of the fuel vapor tends to saturate with the increase of fuel mass flux. The correlations between the fuel vapor radiation blockage coefficient and fuel mass flux are established based on theoretical analysis and experimental data. Moreover, the flame blockage coefficient decreases with external radiation for methanol, ethanol and n-heptane because the fire expands, causing enhanced radiative heat feedback from the flame. For the heavily sooting fuel, toluene, the flame radiation blockage almost remains constant with external radiation due to high soot concentrations.

Identification of Factors Contributing to Testosterone Recovery After Hormone Therapy Combined With External Radiation Therapy.

When hormone therapy (HT) is combined with radiotherapy, understanding the recovery of testosterone levels after the end of HT becomes crucial for considering subsequent therapy. The aim of this study was to determine the factors influencing the time to recovery of testosterone levels after discontinuation of HT and the likelihood of recovery. The study included a total of 108 patients with prostate cancer who were treated with GnRH agonist in combination with radiotherapy and followed up for at least 12 months after discontinuation of the GnRH agonist. The presence of recovery of testosterone levels and the time to recovery were investigated. Univariate and multivariate analyses were performed on several factors contributing to testosterone recovery, including age at initiation of HT, and the duration of HT. Testosterone levels recovered in 61 cases (56.5%). The median time to recovery was 14.8 months. There was a significant difference in the recovery of testosterone levels between patients aged ≥71 years and those aged <71 years at the start of HT (p=0.002), and between those who had been on HT for ≥34 months and those for <34 months (p=0.031). In both univariate and multivariate analyses, age at initiation of HT and duration of HT contributed to the recovery of testosterone levels. The rate of recovery of testosterone levels after long-term (median 34.3 months) HT was lower in patients who were older than 71 years at the start of HT.

A dosimetric evaluation of intensity modulated radiotherapy and three-dimensional conformal radiotherapy for prostate cancer in Ghana.

External beam radiotherapy incorporates treatment techniques such as three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), image-guided radiotherapy and volumetric modulated arc therapy to deliver high-energy radiation to cancer. The use of IMRT for cancer treatment is also associated with significant costs for patients in low-middle-income countries. The purpose of this study was to compare the dosimetric properties of 3DCRT and IMRT treatment plans for the external beam irradiation of patients with prostate cancer (Pca) to ascertain the superiority of IMRT in terms of dose homogeneity, conformity and dose limitation to organs at risk (OAR) in a resource-limited setting. One hundred and sixty treatment plans for 80 patients were created using 3DCRT and IMRT on the Eclipse treatment planning system (version 13.6). Data were collected and assessed from the dose-volume histogram of each plan. The conformity and homogeneity index (HI) for each of the plans were calculated. The doses to the OAR were also recorded and evaluated. The mean HIs for the IMRT and 3DCRT treatment techniques were 0.04 ± 0.02 (range: 0.01-0.011) and 0.09 ± 0.02 (range: 0.04-0.016), respectively. The mean conformity index (CI) for IMRT and 3DCRT techniques were 1.257 ± 0.112 (range: 0.99-1.58) and 1.302 ± 0.196 (range: 1.10-2.26). IMRT had a better significant mean HI and CI compared to 3DCRT. Generally, for this study, IMRT had better organ sparing compared to 3DCRT. The mean doses for the OARs ranged from 4.3-74.6 Gy for IMRT and 3.1-75.9 Gy for the 3DCRT technique. Overall, this study demonstrates that IMRT may offer an enhanced therapeutic profile, potentially reducing toxicity to the patient and ensuring more precise dose delivery to the target volume compared to 3DCRT in PCa external beam irradiation.

Implementation of 3D Printing and Modeling Technologies for the Fabrication of Dose Boluses for External Radiotherapy at the CLCC of Sétif, Algeria.

Objective: In external radiotherapy, dose boluses and compensators are used for treatment of irregular facial topography surfaces. In such cases, skewed isodose curves need to be addressed using a bolus that gives the deep dose distribution a shape adapted to the anatomical structures to be protected or irradiated. The combination of 3D modeling and printing technologies is a promising alternative to the conventional inaccurate and uncomfortable bolus fabrication technique. In this work, the proposed technologies will be used in the design and fabrication of high-performance and high-accuracy boluses that respond to the main constraints on metrology, adhesion to the patient's surface, comfort, and dose delivery. Methods: As a first phase in the implementation of the proposed solution, 3D printing materials, to be used in the fabrication of radiotherapy boluses, were selected and characterized to check how they respond to the required criteria on functionality, safety, and quality. Results: The obtained results show that among the studied materials, thermoplastic polyurethane (TPU) was found to be slightly more suitable than polylactic acid (PLA) for the fabrication of 3D printing boluses but for some kinds of treatments, PLA may be preferred despite its relative rigidity. Conclusion: In this work, procedures for dose bolus fabrication were proposed, and necessary data were obtained for some available 3D printing materials (TPU and PLA) that can be used for targeted applications. This achievement is a major step toward the final implementation of 3D modeling and printing technologies for the efficient fabrication of radiotherapy dose boluses.

Robot-assisted salvage lymphadenectomy in prostate cancer with radiointerventional lymph note tagging

Prostate cancer is the second most common tumor in men worldwide, with lethality directly related to its staging. In general, radical prostatectomy represents the first line in the treatment of patients with prostate cancer, but even with improvements in diagnosis and advances in surgical techniques for the treatment of localized prostate cancer, it still occurs in up to 35% of cases. there will be biochemical recurrence over the years¹. Therefore, when this neoplasm recurs after the primary approach, treatment may vary according to its location and dissemination pattern. In cases of lymph node recurrence, adjunctive treatment with external radiotherapy is routinely indicated, associated or not with hormonal blockade.² However, in recent years, due to the advent of new imaging modalities with high sensitivity in cases of biochemical recurrence, the use of salvage lymphadenectomy has been proposed.² Thus, robotic salvage lymphadenectomy has emerged as an alternative to the treatment of patients with lymph node recurrence of prostate cancer. In this way, we seek to share, through a case report, the surgical technique of rescue lymphadenectomy with a lymph node marked by radiointervention. There are no conflicts of interest in this report.

Theoretical Models of Composite Materials for the Protection Technologies

The work develops the concept of shielding external radiation using composite materials that are a single condensed structure with incorporated specially configured impurities and (or) defects. Using the example of a one-dimensional model of an inhomogeneous power chain, the possibility of the existence of blocking and transparency effects with respect to external radiation, which arise already in the presence of binary impurities, which, in turn, act as the simplest models of composite systems, is shown. It is proposed to use the above property (isomorphic to the experimentally observed Ramsauer-Townsend effect) for the synthesis of composite materials in radiation protection technologies.

Small molecule targeted therapies for endometrial cancer: progress, challenges, and opportunities.

Endometrial cancer (EC) is a common malignancy among women worldwide, and its recurrence makes it a common cause of cancer-related death. Surgery and external radiation, chemotherapy, or a combination of strategies are the cornerstone of therapy for EC patients. However, adjuvant treatment strategies face certain drawbacks, such as resistance to chemotherapeutic drugs; therefore, it is imperative to explore innovative therapeutic strategies to improve the prognosis of EC. With the development of pathology and pathophysiology, several biological targets associated with EC have been identified, including PI3K/Akt/mTOR, PARP, GSK-3β, STAT-3, and VEGF. In this review, we summarize the progress of small molecule targeted therapies in terms of both basic research and clinical trials and provide cases of small molecules combined with fluorescence properties in the clinical applications of integrated diagnosis and treatment. We hope that this review will facilitate the further understanding of the regulatory mechanism governing the dysregulation of oncogenic signaling in EC and provide insights into the possible future directions of targeted therapeutic regimens for EC treatment by developing new agents with fluorescence properties for the clinical applications of integrated diagnosis and treatment.

Application of Intraoperative Radiotherapy in Early-Stage Breast Cancer Patients in a Clinical Setting.

Background: Intraoperative radiation therapy (IORT) has gained popularity in recent years as an alternative to external beam whole breast radiation therapy (WBRT) for early-stage breast cancer. Here, we report 43-month recurrence and survival outcomes in a multiethnic cohort treated with IORT in a clinical context. Method: Two hundred and eleven patients with low-risk features were treated with IORT for early-stage breast cancer from 2014 to 2021. Selection criteria were based on Group Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) guidelines: preferably unifocal intraductal carcinoma (IDC), aged > 50, tumor size ≤ 2.0 cm, and without lymph node involvement. All patients received 20 Gy of radiation dose during the lumpectomy. Information on patient and tumor characteristics was collected. Results: The mean age of this cohort was 67.5 years; 95.2% of patients are Jewish, and the rest are Bedouins (4.7%). Most tumors were intraductal carcinoma (97.2%) and stage 1 (94.8%). The mean follow-up time was 43.4 months. Bedouins had larger tumor sizes (mean 1.21 vs. 1.13 cm) and were younger at diagnosis than Jewish patients (mean 65.4 vs. 67.6 years), although the differences are not significant. The overall recurrence rate was 1.4%. One case of local recurrence (0.5%) and two cases of metastasis (0.9%) were observed during the study period. One patient died from metastasis. Conclusion: Our findings suggest that IORT in selected low-risk patients can achieve an excellent prognosis with low rates of recurrence and metastasis.

Cardiac doses with deep inspiration breath hold in breast cancer radiotherapy: direct comparison between WBI, PBI, and interstitial APBI.

The optimal radiotherapy technique for cardiac sparing in left-sided early breast cancer (EBC) is not clear. In this context, the aim of our dosimetric study was to compare cardiac and lung doses according to the type of radiotherapy - whole breast irradiation (WBI), external partial breast irradiation (PBI), and multicatheter interstitial brachytherapy-accelerated partial breast irradiation (MIB-APBI). The dosimetric results with the WBI and PBI were calculated with and without DIBH. Dosimetric study of 23 patients treated with WBI, PBI, with and without DIBH, or MIB-APBI. The prescribed dose was 40 Gy in 15 fractions for WBI and PBI and 34 Gy in 10 fractions (bid) for MIB-APBI. Doses to the organs-at-risk (OAR) - heart, left anterior descending coronary artery (LAD), left ventricle (LV), and left lung - were recalculated to the equivalent dose in 2-Gy fractions (EQD2). The addition of DIBH significantly reduced EQD2 doses to all OARs (except for the left lung maximal dose) in WBI and PBI. MHD values were 0.72 Gy for DIBH-WBI, 1.01 Gy for MIB-APBI and 0.24 Gy for DIBH-PBI. There were no significant differences in cardiac doses between WBI with DIBH and PBI without DIBH. DIBH-PBI resulted in significantly lower mean doses to all OARs (except for maximum lung dose) compared to MIB-APBI. Conclusions: These results show that the use of DIBH significantly reduces cardiac doses in patients with left EBC. Partial irradiation techniques (PBI, MIB-APBI) significantly reduced cardiac doses due to the smaller clinical target volume. The best results were obtained with DIBH-PBI.

Theoretical study on resonance frequencies of vibration modes of Janus-Helmholtz transducer

Janus-Helmholtz transducer has the characteristics of high-power and broadband transmission due to the coupling between the longitudinal resonance of the driver and the liquid cavity resonance of Helmholtz resonator. Traditional view holds that the low frequency resonance peak in the transmitting voltage response curve in water is fluid cavity mode of Helmholtz resonator while the high frequency resonance is the longitudinal mode of Janus transducer. However, in the past few decades, a large number of experimental studies have found that this conclusion is questionable. This work is to distinguish the two resonances in the response curve and the two vibration modes of Janus-Helmholtz transducer. Based on the Janus-Helmholtz transducer prototype reported in the literature, the resonance frequencies of the vibration modes of Janus-Helmholtz transducer are studied theoretically. The structure dimensions and material parameters of the prototype are listed in detail. The test results and simulation results of conductivity are also presented. The longitudinal resonance of the driver is determined by using the equivalent circuit method and finite element analysis. Radiation masses of both Janus transducer and typical longitudinal vibration transducer are also calculated to analyze the phenomenon of the sharp decrease of longitudinal resonance frequency in water. Acoustic modal analysis by using ANSYS software is performed to investigate the resonance frequency of complex Helmholtz resonator in Janus-Helmholtz transducer. Correction length on the vent introduced by external fluid sound radiation is used to obtain the accurate Helmholtz resonance frequency. The sound pressure distribution of Helmholtz resonator obtained through finite element method is investigated, and the correct equivalent formula for solving the Helmholtz resonance frequency is obtained. The results reveal that the first resonance in the response curve is driver resonance while the second one is Helmholtz resonance, which is contrary to the traditional view. The considerable reduction of driver resonance frequency in water is mainly due to the large radiation mass on the four large radiation surfaces of the Janus transducer, which also causes the sharp response of driver resonance. In Janus-Helmholtz transducer, there are two Helmholtz resonators with the same size, instead of only one resonator in the traditional view. The two resonance frequencies solved by the method proposed in this work are in good agreement with the test and simulation results. These conclusions play an important role in correctly understanding the structure and characteristics of Janus-Helmholtz transducer at source, as well as provide technical support for structural optimization and innovation, thus improving the acoustic emission properties of the transducer.

Calculation of orbit external heat flow and radiation characteristics of space target

Calculation of orbit external heat flow and radiation characteristics of space target

Complex firing activities and bifurcations in memristor-coupled Hindmarsh–Rose neuron

Due to the unique synaptic plasticity and memory effect, a memristor can not only mimic biological synapses but also characterize the influence of external electromagnetic radiation. In this paper, a ReLU-type non-ideal memristor with a simple structure is first coupled to a classical three-dimensional Hindmarsh–Rose neuron to describe the electromagnetic induction effect, which can show period-doubling, period-adding, and saddle-node bifurcations by varying the coupling strength of the memristor. Furthermore, complex discharge behaviors of the system, including bursting discharge and spiking discharge, are exhibited, and some coexisting discharge modes associated with initial values are also presented. Finally, an analog circuit scheme consuming fewer circuit components is designed, and it was found that the experimental results are consistent with the numerical results.

ИСПОЛЬЗОВАНИЕ РАДИАЦИОННЫХ ТЕХНОЛОГИЙ В ЖИВОТНОВОДСТВЕ

Experiments were carried out on the boulders of fine-wooled sheep of the Prekos breed in the conditions of the sheep farm. Lambs of the first three experimental groups aged, respectively, 1, 2 and 3 months were subjected to a single external gamma radiation at a dose of 0,4 Gy at the Gamma installation «Puma». Animals of the fourth group served as control and were not subjected to radiation. The data obtained indicate that a single radiation of lambs at a dose of 0,4 Gy led to a significant increase in intensity of their growth, meat, wool productivity, survival, natural length of wool fibers, increased resistance to cod of the facial layer of the skin and the strength of the skin tissue of manufactured and ennobled sheepskin semi-finished products compared to control analogues.

Pembrolizumab with external radiation therapy effectively controlled TMB-high unresectable recurrent parathyroid cancer: a case report with review of literature.

Parathyroid cancer (PC) is extremely resistant to chemotherapy and radiotherapy (RT), but hormonally functional by producing excessive parathyroid hormone (PTH), causing remarkable hypercalcemia even in biochemical disease recurrence. Accordingly, management of hypercalcemia by calcimimetics and bisphosphonates has been main treatment for unresectable PC. Here, we report a case of unresectable tumor mutational burden (TMB)-high recurrent PC that has been effectively controlled by pembrolizumab (PEM) with RT. A 48-year-old male patient, with previous history of left single parathyroidectomy for primary hyperparathyroidism, underwent surgeries for recurrent hyperparathyroidism at 47 and 48 years of age, and was pathologically diagnosed with PC. He was referred to our hospital due to persistent hypercalcemia and elevated PTH. The recurrent tumors were identified in the superior mediastinum and radically resected, then the hyperparathyroidism was improved. A FoundationOne® CDx of the specimen called TMB-high. He demonstrated recurrent hyperparathyroidism at 49 years of age, and underwent a gross curative resection. However, hyperparathyroidism achieved only insufficient improvement, indicating biochemical residual cancer cells. PEM treatment was initiated in combination with RT to the left central-lateral neck and superior mediastinum. He successfully achieved evocalcet and zoledronate withdrawal, and the PTH level improvement was continuously observed for 8 months at present, with only grade 2 subclinical hypothyroidism. Interestingly, leukocyte fraction ratios were reversed corresponding to disease improvement. A combination of PEM and RT is a promising treatment of unresectable TMB-high PC. Recent evidence on the immunomodulatory effect of RT provides the rationale for the combination of RT and PEM.

Evaluation of Air-Kerma and Absorbed Dose to Water for External Radiotherapy Beam Using Ionization Chamber

Evaluation of Air-Kerma and Absorbed Dose to Water for External Radiotherapy Beam Using Ionization Chamber

Temporal evolution of postsurgical bone repair in a rabbit model: A [99mTc]Tc-MDP scintigraphic study.

Bone regeneration is crucial for repairing bone tissue following various injuries. Research techniques that enable the study of metabolic changes in bone tissue under different conditions are important for understanding bone repair and remodeling. This study used bone scintigraphy to evaluate osteogenesis secondary to osteotomy in a preclinical model of New Zealand rabbits. For this purpose, we conducted a longitudinal, prospective, case-control study in which scintigraphic variables were measured in both the right forearm (case-operated) and the left forearm (control - non-operated). The study sample consisted of 10 rabbits subjected to osteotomy, followed by a 12-week postoperative evaluation period, divided into six imaging stages at 1, 2, 3, 4, 8, and 12 weeks. We observed that the operated forearm showed significantly higher external radiation than the control side, using the pinhole collimator, denoting an increase in the biodistribution and tropism of the radiopharmaceutical to the operated forearm. Among the three evaluated time points, osteoblastic activity was highest in the second week and presented a significant decline in the 8th and 12th weeks, denoting regeneration and resolution of the surgical injury; the control forearm was also influenced by the inactivity imposed by the operated forearm. This fact was notably evidenced by the reduction in the metabolic activity of osteoblasts in the left forearm. Our study suggested that bone scintigraphy was sensitive enough to semi-quantitatively differentiate the metabolic activity of osteoblasts in the operated forearm in the three temporal landmarks evaluated in the study.