Dose Rate Research Articles

Space radiation measurements during the Artemis I lunar mission

Space radiation is a notable hazard for long-duration human spaceflight1. Associated risks include cancer, cataracts, degenerative diseases2 and tissue reactions from large, acute exposures3. Space radiation originates from diverse sources, including galactic cosmic rays4, trapped-particle (Van Allen) belts5 and solar-particle events6. Previous radiation data are from the International Space Station and the Space Shuttle in low-Earth orbit protected by heavy shielding and Earth’s magnetic field7,8 and lightly shielded interplanetary robotic probes such as Mars Science Laboratory and Lunar Reconnaissance Orbiter9,10. Limited data from the Apollo missions11–13 and ground measurements with substantial caveats are also available14. Here we report radiation measurements from the heavily shielded Orion spacecraft on the uncrewed Artemis I lunar mission. At differing shielding locations inside the vehicle, a fourfold difference in dose rates was observed during proton-belt passes that are similar to large, reference solar-particle events. Interplanetary cosmic-ray dose equivalent rates in Orion were as much as 60% lower than previous observations9. Furthermore, a change in orientation of the spacecraft during the proton-belt transit resulted in a reduction of radiation dose rates of around 50%. These measurements validate the Orion for future crewed exploration and inform future human spaceflight mission design.

Effects of Sterilization on Cellobiose Dehydrogenase and Glucose Oxidase Based Glucose Biosensors

AbstractResearch on implantable glucose biosensors is driven by the need for innovative medical devices for continuous glucose monitoring in patients with diabetes mellitus. However, biosensor sterilization is a step that is widely omitted during the process of innovation. To compare the effects of gamma irradiation and chemical treatment with ethylene oxide (carbon microarray electrodes are fabricated, functionalized with glucose oxidizing enzymes (cellobiose dehydrogenase CDH or glucose oxidase GOx), and coated with a specifically designed zwitterionic polymer prior to the sterilization step. Cyclic voltammetry in the presence of 100 mm glucose of the biosensors before and after sterilization shows that gamma irradiation with a low radiation rate (25 kGy, 260 Gy h−1) does not induce a sensor performance loss, unlike the EtO treatment. In addition, no cytotoxic by‐products are released after gamma sterilization. Based on these results obtained with both glucose oxidizing enzymes (CDH and GOx), gamma irradiation of the glucose biosensors with a low dose rate is preferable to exposure to EtO for biosensor terminal sterilization.

Current views on mechanisms of the FLASH effect in cancer radiotherapy.

FLASH radiotherapy (FLASH-RT) is a new modality of radiotherapy that delivers doses with ultra-high dose rates. The FLASH effect was defined as the ability of FLASH-RT to suppress tumor growth while sparing normal tissues. Although the FLASH effect has been proven to be valid in various models by different modalities of irradiation and clinical trials of FLASH-RT have achieved promising initial success, the exact underlying mechanism is still unclear. This article summarizes mainstream hypotheses of the FLASH effect at physicochemical and biological levels, including oxygen depletion and free radical reactions, nuclear and mitochondria damage, as well as immune response. These hypotheses contribute reasonable explanations to the FLASH effect and are interconnected according to the chronological order of the organism's response to ionizing radiation. By collating the existing consensus, evidence and hypotheses, this article provides a comprehensive overview of potential mechanisms of the FLASH effect and practical guidance for future investigation in the field of FLASH-RT.

Investigation of radioactivity and heavy metal levels in soil samples from neutral and vegetation land of Punjab, India.

In this work, radioactivity investigations of soil samples from neutral and agricultural sites in Punjab (India) have been carried out to study the impact of land use patterns. Analyzing soil samples radiological, mineralogical, and physicochemical attributes has employed state-of-the-art techniques. The mean activity concentration of 238U/226Ra, 232Th, 40K, 235U, and 137Cs, measured using a carbon fiber endcap p-type HPGe detector, in neutral land was observed as 58.03, 83.95, 445.18, 2.83, and 1.16Bqkg-1, respectively. However, in vegetation land, it was found to be 40.07, 64.68, 596.74, 2.26, and 1.90Bqkg-1, respectively. In the detailed activity analysis, radium equivalent (Raeq) radioactivity is in the safe prescribed limit of 370Bqkg-1 for all investigated soil samples. However, the dosimetric investigations revealed that the outdoor absorbed gamma dose rate (96.08 nGy h-1) and consequent annual effective dose rate (0.12mSv y-1) for neutral land and the gamma dose rate (82.46 nGy h-1) and subsequent annual effective dose rate (0.10mSv y-1) for vegetation land marginally exceeded the global average. The soil's physicochemical parameters (pH, EC, and porosity) from both sites were measured, and their correlations with radionuclides were analyzed. Various heavy metals of health concern, namely, chromium (Cr), arsenic (As), copper (Cu), cobalt (Co), cadmium (Cd), lead (Pb), mercury (Hg), selenium (Se), and zinc (Zn), were also evaluated in soil samples using Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS). Pollution Load Index (PLI) and Ecological Risk Index (RI) revealed that vegetation land was more anthropogenically contaminated than neutral land, with maximum contamination from Hg and As.

DEGRADATION KINETICS OF TEXTILE AZO DYE REACTIVE ORANGE-16 BY GAMMA IRRADIATION

Gamma radiation have become attention since their high potential for degrading compounds, especially organic pollutants. In this research, gamma radiation was studied for degrading the Reactive Orange-16 (RO-16) dye, a toxic and carcinogenic pollutant. The radiolytic degradation process was studied in a batch reactor with a gamma-ray dose rate of 2.930 kGy/h. The effect of experimental variable such as initial peroxide concentration, initial pH, initial dye concentration, and addition of inorganic anion were studied. The highest degradation rates were achieved at a peroxide concentration ranging from 2 to 4 mM. In contrast, the higher peroxide concentration indicated the slower degradation process caused by the scavenging effect of the peroxide. Degradation of 88% RO-16 dye with 0.1 mM initial concentration, was achieved at 2.0 kGy irradiation dose and 97.4% degradation in the presence of 4 mM peroxide. The dose constant (d) for those degradation processes was 1.0657 kGy-1 and 1.8420 kGy-1 respectively. The degradation was more efficient in acid pH. The degradation process increased with lower initial dye concentrations. The degradation of RO-16 dye by gamma-ray was inhibited by the presence of inorganic anions in the following sequence: NO3-→ CO32− → HCO3− → CH3COO-→ Cl-.

The Aspects of Radiation Safety When Working With Ore from the Tomtor Integrated Rare Metal Deposit in Yakutia, Used as a Modifying Additive in Welding Materials

The results of measurements of the content of radioactive elements in ore samples from the Tomtor integral rare metal deposit are considered with the aim of safe use of ore with rare earth elements as a modifier of the weld pool during the processes of manual arc welding and fusing. It was revealed using a semiconductor gamma spectrometer that a significantly larger proportion of ionizing radiation activity is represented by the thorium-232 family. It is noted that natural concentrate is added to the composition of welding materials in very small quantities, and during welding operations in the room next to the welder, the values of the exposure dose rate will correspond to the initial radiation background in the room, therefore, both the welder and those people who will be in contact with the welded materials will not receive additional radiation dose to the natural background. It was concluded that the process of manufacturing the welding materials, welding, fusing and the use of welded structures are completely safe in terms of radiation.

Secondary solid malignancies in long-term survivors after total body irradiation

BackgroundTotal body irradiation (TBI)-based allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for selected patients with acute myeloid leukemia (AML). Yet, secondary malignancies contribute to long-term morbidity and mortality with TBI potentially influencing these risks.MethodsThis retrospective study analyzed the cumulative incidences of secondary solid malignancies and precancerous lesions of 89 consecutive AML patients after TBI-based conditioning before 1st allo-HSCT between 2000 and 2016. TBI was performed with an average dose rate of 4 cGy/min and a twice-daily fractionation. Cause-specific hazard models analyzed risk factors for secondary malignancies/precancerous lesions and the competing risks of dying before developing secondary malignancies/precancerous lesions.ResultsThe median patient age at TBI was 42.5 years (interquartile range, 32.5–51.2), while the median follow-up was 15.2 years (interquartile range, 13.0-18.2). Most patients received a myeloablative conditioning (MAC) containing 8 Gy (n = 47) and 12 Gy TBI (n = 11). Reduced-intensity regimens (RIC, 4 Gy TBI) were applied in 31 patients. Of note, patients receiving RIC were older than patients receiving MAC. The most common cancer types were non-squamous cell carcinomas (n = 14) after exclusion of a patient diagnosed with sarcoma within less than a year after TBI. The cumulative incidences of secondary malignancies and precancerous lesions were 8% (95%CI, 4–16), 14% (95%CI, 7–23), and 17% (95%CI, 9–27) at 10, 15 and 20 years, while the cumulative incidences of premature deaths were 59% (95%CI, 48–69), 59% (95%CI, 48–69), and 64% (95%CI, 49–76). In multivariate analyses, higher patient age at TBI was associated with lower rates of secondary malignancies/precancerous lesions, while higher patient age translated into a trend towards premature deaths (before patients could develop malignancies). Higher TBI doses, mainly applied in younger patients, translated into lower rates of secondary malignancies/precancerous lesions while lacking associations with mortality. Chronic GVHD requiring systemic immunosuppression was associated with premature deaths.ConclusionsAlthough this study indicates an inverse relationship between TBI doses applied and treatment-related malignancies, confounding by competing risks is present. The age dependency may be explained by the fact that older patients had a lower life expectancy independent of malignancies, illustrating the pitfalls of competing risks.Trial registrationThe study was retrospectively registered.

A microscopic oxygen transport model for ultra-high dose rate radiotherapy in vivo: The impact of physiological conditions on FLASH effect.

Ultra-high dose rate irradiation (≥40Gy/s, FLASH) has been shown to reduce normal tissue toxicity, while maintaining tumor control compared to conventional dose-rate radiotherapy. The radiolytic oxygen (O2) depletion (ROD) resulting from FLASH has been proposed to explain the normal tissue protection effect; however, in vivo experiments have not confirmed that FLASH induced global tissue hypoxia. Nonetheless, the experiments reported are based on volume-averaged measurement, which have inherent limitations in detecting microscopic phenomena, including the potential preservation of stem cells niches due to local FLASH-induced O2 depletion. Computational modeling offers a complementary approach to understand the ROD caused by FLASH at the microscopic level. We developed a comprehensive model to describe the spatial and temporal dynamics of O2 consumption and transport in response to irradiation in vivo. The change of oxygen enhancement ratio (OER) was used to quantify and investigate the FLASH effect as a function of physiological and radiation parameters at microscopic scale. We considered time-dependent O2 supply and consumption in a 3D cylindrical geometry, incorporating blood flow linking the O2 concentration ([O2]) in the capillary to that within the tissue through the Hill equation, radial and axial diffusion of O2, metabolic and zero-order radiolytic O2 consumption, and a pulsed radiation structure. Time-evolved distributions of [O2] were obtained by numerically solving perfusion-diffusion equations. The model enables the computation of dynamic O2 distribution and the relative change of OER (δROD) under various physiological and radiation conditions in vivo. Initial [O2] level and the subsequent changes during irradiation determined δROD distribution, which strongly depends on physiological parameters, i.e., intercapillary spacing, ultimately determining the tissue area with enhanced radioresistance. We observed that the δROD/FLASH effect is affected by and sensitive to the interplay effect among physiological and radiation parameters. It renders that the FLASH effect can be tissue environment dependent. The saturation of FLASH normal tissue protection upon dose and dose rate was shown. Beyond ∼60Gy/s, no significant decrease in radiosensitivity within tissue region was observed. In turn, for a given dose rate, the change of radiosensitivity became saturated after a certain dose level. Pulse structures with the same dose and instantaneous dose rate but with different delivery times were shown to have distinguishable δROD thus tissue sparing, suggesting the average dose rate could be a metric assessing the FLASH effect and demonstrating the capability of our model to support experimental findings. On a macroscopic scale, the modeling results align with the experimental findings in terms of dose and dose rate thresholds, and it also indicates that pulse structure can vary the FLASH effect. At the microscopic level, this model enables us to examine the spatially resolved FLASH effect based on physiological and irradiation parameters. Our model thus provides a complementary approach to experimental methods for understanding the underlying mechanism of FLASH radiotherapy. Our results show that physiological conditions can potentially determine the FLASH efficacy in tissue protection. The FLASH effect may be observed under optimal combination of physiological parameters, not limited to radiation conditions alone.

The effect of low-intensity radiation on the speed of CMOS microcircuits

Aim. The degradation of CMOS microcircuits exposed to ionizing radiation was analysed. Three MOS defect formation processes at the Si-SiO2 boundary were examined. Methods. Using the example of test logic elements, the dependence of the time of conditional speed failure on the gamma dose rate was analysed. Findings. A critical defect at the Si-SiO2 boundary was identified. Conclusions. The approach proposed in the paper allows identifying the causes of CMOS microcircuit failures. Calculated failure times for three dose rates are presented.

Effect of gamma irradiation on proliferation and growth of friable embryogenic callus and in vitro nodal cuttings of ugandan cassava genotypes.

Cassava (Manihot esculenta Crantz) production and productivity in Africa is affected by two viral diseases; cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). Induced mutagenesis of totipotent/embryogenic tissues or in vitro plant material can lead to the generation of CMD and/or CBSD tolerant mutants. To massively produce non-chimeric plants timely and with less labor, totipotent cells or tissues are a pre-requisite. This study aimed to determine the effect of gamma radiation on the proliferation and growth of friable embryogenic callus (FEC) and in vitro nodal cuttings respectively. To obtain FEC, 2-6 mm sized leaf lobes of nine cassava genotypes were plated on Murashige and Skoog (MS) basal media supplemented with varying levels (37, 50, 70, 100) μM of picloram for production of organized embryogenic structures (OES). The OES of five cassava genotypes (Alado, CV-60444, NASE 3, NASE 13 and TME 204) were crushed and plated in Gresshoff and Doy (GD) basal media in combination with the amino acid tyrosine in varying concentrations for FEC production. FEC from five cassava genotypes and in vitro nodal cuttings of nine genotypes were irradiated using five different gamma doses (0, 5, 10, 15, 20 and 25 Gy) at a dose rate of 81Gy/hr. The lethal dose (LD)50 was determined using the number of roots produced and flow cytometry was done to determine the ploidy status of plants. The highest production of OES was noted in Alado across varying picloram concentrations, while TME 204 obtained the highest amount of FEC. The irradiated FEC gradually died and by 28 days post irradiation, FEC from all five cassava genotypes were lost. Conversely, the irradiated in vitro nodal cuttings survived and some produced roots, while others produced callus. The LD50 based on number of roots varied from genotype to genotype, but plants remained diploid post-irradiation. Accordingly, the effect of gamma irradiation on Ugandan cassava genotypes (UCGs) was genotype-dependent. This information is foundational for the use of in vitro tissues as target material for cassava mutation breeding.

Water-Stable and Sensitive X-ray Detectors by Supramolecular Interaction-Enhanced Polyoxometalates.

Polyoxometalates (POMs) have shown prominence in the field of semiconductive materials in recent years. However, electronic applications based on these emerging materials are still in their early stages. Here, a sensitive and water-stable F-PEA-ZnW12 X-ray detector has been designed and constructed for hard X-ray detection and imaging. Supramolecular interactions of H···O bonding, electrostatic, and anion-π interactions not only enable FPEA-ZnW12 excellent water stability but also shorten the distance between [ZnW12O40]6- clusters, which reduces ion migration and dark current simultaneously, resulting in the conductivity of 3.2 × 10-11 S cm-1. Furthermore, the heteropoly blue formed on the surface of the O-FPEA-ZnW12 wafer device promotes the effective separation and extraction of X-ray-induced carriers, enhancing the sensitivity for X-ray detection. The R/O-FEPA-ZnW12 wafer device yields a high sensitivity of 3.1 × 104 μC Gyair-1 cm-2 with the lowest detectable dose rate of 69 nGyair s-1 under 120 kV hard X-ray irradiation. In addition, the O-FPEA-ZnW12 wafer detector exhibits the potential for X-ray detection in water with a sensitivity of 1.0 × 104 μC Gyair-1 cm-2. Moreover, the fabricated POM X-ray detector shows excellent X-ray imaging capability and long-term operational stability without any attenuation of 1 year exposure to air without any encapsulation.

Influence of gamma radiation on the composition and physicochemical characteristics of olefins: post-radiation effects

The effect of gamma radiation on olefins was studied under static conditions at an absorbed dose of 65 kGy and at a dose rate ofP= 0.076 Gy/s. The effect of radiation on the physicochemical characteristics and structural and group composition of the resulting olefins has been established. Post-irradiation effects were studied immediately after irradiation and during 1, 2, 4, and 7 months later. When fuels are irradiated, polymerization of unsaturated hydrocarbons occurs. After cessation of irradiation, the postpolymerization process occurs The chemical instability of olefins in fuels leads to the formation of carbon deposits in the engine system, tanks, and valves. IR spectra, iodine values, density, and kinematic viscosity of irradiated samples were measured.

Dose rate dependent genotoxic and metabolic effects predict onset of impaired development and mortality in Atlantic salmon (S. salar) embryos exposed to chronic gamma radiation

Release of radionuclides to the environment from either nuclear weapon and fuel cycles or from naturally occurring radionuclides (NORM) may cause long term contamination of aquatic ecosystems and chronic exposure of living organisms to ionizing radiation, which in turn could lead to adverse effects compromising the sustainability of populations. To address the effects of chronic ionizing radiation on the development of fish, Atlantic salmon embryos were exposed from fertilization until hatching (88 days, 550 day-degree) to dose rates from 1 to 30 mGy·h−1 gamma radiation (60Co). The lowest adopted dose rate was similar to the highest doses measured in some water bodies right after the Chernobyl accident (1 mGy·h−1), however, well above current environmentally realistic scenarios (20 μGy·h−1), or the threshold assumed for significant effects on fish population (40 μGy·h−1). Dose dependent effects were observed on survival, hatching, morbidity, DNA damage, antioxidant defenses, and metabolic status. Histopathological analysis showed dose rate dependent impairment of eye and brain tissues development and establishment of epidermal mucus cell layers accompanied by increased DNA damage at doses ≥1.3 Gy (dose rates ≥1 mGy·h−1).At ≥32.8 Gy (dose rates ≥20 mGy·h−1) deformities and developmental growth defects resulted in respective 46 and 95 % pre-hatch mortality. The 10 mGy·h−1 exposure (≥ 12 Gy total dose) caused significantly increased DNA damage, impaired eye development, and both premature and delayed hatching, while no deformities or effect on survival were observed. We observed a dose rate dependent reduction from dose rate ≥ 20 mGy·h−1 (≥ 27 Gy total dose) on antioxidant SOD, catalase and glutathione reductase enzyme activities. The reduction of antioxidant enzyme activities was in line with observed developmental delay and disturbance to time of hatching. Metabolomic profiles showed a clear shift at dose rates ≥10 mGy·h−1 (≥ 12 Gy total dose) in pathways related to oxidative stress, detoxification, DNA damage and repair. Due to gamma radiation exposure, a switch of central metabolism from glycolysis, citric acid cycle and lactate production towards pentose phosphate pathway indicated a rewiring mechanism for increased production of reductive equivalents to maintain redox homeostasis at the expense of energy output and thus embryonic development.

May 11–12 Extreme Space Weather Events Brief and Dose Rate Model Response

In this brief paper, we analyze space weather events that occurred on May 11 and 12, 2024, from the perspective of an operational space weather center that provides advisories for civil aviation. One of the key metrics monitored by the center is the radiation dose rate at operational flight altitudes. A model implemented by the center provides the dose rate in real time. The model showed that dangerous levels were momentarily exceeded just above the usual 30,000 feet level during the events. This paper highlights differences in models used by various space weather centers, emphasizing the need for harmonization.

276 Use of triaxial accelerometers and a machine learning algorithm for behavioral identification to assess the effectiveness of a joint supplement in old domestic cats (Felis catus)

Abstract Degenerative joint disease (DJD) has a 90% prevalence in older cats and adversely affects quality of life1. Long-term administration of non-steroidal anti-inflammatory drugs is usually required but can have adverse effects2. Nutraceuticals have been shown to relieve joint pain in cats without such side effects; however, due to differences in dose rates and formulations there is no consensus as to their efficacy. Most studies have utilized subjective insensitive measures such as veterinary or owner-assessed changes in activity. Accelerometers can provide objective data on cat activity and can identify specific behaviors3.Triaxial accelerometers (ActiGraph, Pensacola, FL) were fitted to the collars of 16 cats (aged 11 to 16 yr; Massey University, Palmerston North, NZ) for 20 wk to assess their activity and behavior. The cats were fed the same diet (Chef: Kraft Heinz Wattie’s Ltd., Hastings, NZ) for 4 wk to collect baseline acceleration data, before being divided into two groups balanced for physical activity. After 4 wk, a blood sample were taken from all of the cats to establish their baseline levels of a range of inflammatory markers (e.g., IL-6, TNFα, INF- γ, SDF-1). The test group (n = 8) then received a joint supplement added to the baseline diet while the control group (n = 8) were fed the diet unsupplemented for 16 wk. The commercial joint supplement contained glucosamine, chondroitin sulphate, and green-lipped mussel (Tandem, Wellington, NZ), at daily doses shown previously to be effective in cats4,5,6. The aim of the work was to assess the efficacy of the joint supplement in maintaining or promoting activity and specific behaviors in the cats. At the end of the period of supplementation a second blood sample was taken and assessed for the same range of inflammatory markers. Overall physical activity was not different between groups at baseline but was greater over the study in the test group compared with the control (P < 0.03). Grooming, as identified by the algorithm, showed a tendency (P = 0.051) to be greater in the test group than the control. These results suggest that the supplement had a positive effect on both overall activity and more specifically on grooming behavior in old cats. However, no differences in the range of inflammatory markers were seen before or after supplementation. While the behavioral measures could indicate the supplement reduced the effects of DJD, further research is required to confirm this.1Cunningham et al (2022) Journal of Feline Medicine and Surgery 24, 962-974. 2Lemetayer and Taylor (2014) Journal of Feline Medicine and Surgery 16, 547-562; 3Smit et al., (2023) Sensors 23, 7165; 4Corbee (2022) Veterinary Medicine and Science 8, 1025–1035; 5Corbee et al. (2013) Journal of Animal Physiology and Animal Nutrition 97, 846–853; 6Lascelles et al. (2010) Journal of Veterinary Internal Medicine, 24, 487–495.

Monte Carlo simulation of shielding materials in storage drums for 241Am-Be disused sealed radioactive sources

Disused Sealed Radioactive Sources (DSRS) containing neutron sources such as 241Am-Be require careful management due to neutron radiation. However, finding readily available and effective combination layer shielding materials for practical use to safely contain 241Am-Be can be challenging. The main objective of this study is to investigate the configuration of shielding materials and determine the maximum activity of 241Am-Be sources that can be safely stored in a 200-L drum. A three-layer shielding approach using a 200-L drum as a storage container, with sequential layers of lead (Pb), polyethylene (PE), and ordinary Portland concrete (OPC), achieves the lowest dose rates compared to other combination sequences, as shown by Monte Carlo simulations. With a fixed lead thickness and varying polyethylene and ordinary Portland concrete thicknesses, Monte Carlo simulations using the Particle and Heavy Ion Transport code System (PHITS) demonstrate that this drum design can safely accommodate activities ranging from 22.01 Ci to 72.92 Ci of 241Am-Be. The fitted model equation determines the required polyethylene thickness for any activity within this range. Additionally, case-based simulation results indicate that Indonesia's total inventory of 241Am-Be DSRS can be stored in three 200-L drums with a polyethylene thickness of 15 cm. This configuration meets international standards, ensuring the dose rate does not exceed 2 mSv/h at the surface and 0.1 mSv/h at 1 m from the drum's surface.

Расчетное определение радиационных характеристик активируемых средне- и высокоактивных радиоактивных отходов, образующихся при эксплуатации АЭС с ВВЭР

The article describes the methodology of computational determination of specific activity of radionuclides in the radioactive waste in the form of spent neutron measurement channels (NMCs) TVS-2M of VVER-1000 reactor. The results of research on the dependence of the specific activity of radionuclides on the NMC lifetime, number of fuel elements, gadolinium amount, enrichment and initial burn-up of fuel assemblies are given. The calculations have been carried out by the Monte Carlo method using the MCU-6 computer program. To verify the results of calculations, a method based on measurements of the gamma radiation dose rate from activated radioactive waste is proposed.

Systematic review and recommendations for re-irradiation for intraprostatic radiorecurrent prostate cancer after definitive radiation therapy.

Intraprostatic recurrence (IRR) of prostate cancer after radiation therapy is increasingly identified. Our objective was to review the literature to determine the optimal workup for identifying IRR, the management options, and practical considerations for the delivery of re-irradiation as salvage local therapy. We performed a systematic review of available publications and ongoing studies on the topics of IRR, with a focus on salvage re-irradiation. Work up of biochemically recurrent prostate cancer includes PSMA PET/CT and multiparametric MRI, followed by biopsy to confirm IRR. Management options include continued surveillance, palliative hormonal therapy, and salvage local therapy. Salvage local therapy can be delivered using re-irradiation with low dose rate brachytherapy, high dose rate (HDR) brachytherapy, and stereotactic body radiotherapy (SBRT), as well as non-radiation modalities, such as cryotherapy, high-intensity focused ultrasound, irreversible electroporation and radical prostatectomy. Data demonstrate that HDR brachytherapy and SBRT have similar efficacy compared to the other salvage local therapy modalities, while having more favorable side effect profiles. Recommendations for radiation therapy planning and delivery using HDR and SBRT based on the available literature are discussed. Salvage re-irradiation is safe and effective and should be considered in patients with IRR.

Dose titration of intravenously administered gamma-hydroxybutyric acid for sedation in Holstein-Friesian calves

Gamma-hydroxybutyric acid (GHB) is a short-chain fatty acid that can potentially provide safe, prolonged sedation with minimal cardiorespiratory effects. This preliminary trial, performed in 10 three-week-old male Holstein-Friesian calves, investigated the effects of GHB administered intravenously over 5 min at a dose of 100 (G100, n=2), 150 (G150, n=4) or 200 mg/kg (G200, n=4). Once lateral recumbency was achieved, scores for sedation depth (range: 0 = no sedation to 3 = marked) and response to noxious stimulation (range: 0 = strong to 3 = absent), heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP) and arterial blood gases were monitored every 15 min until sternal recumbency. Times from end of administration to lateral recumbency and return to sternal/standing positions were recorded. Dose G100 resulted in mild sedation and ataxia without decubitus. Doses G150 and G200 respectively resulted in time to lateral recumbency 8 ± 2 and 9 ± 3 min, lasting 189 ± 41 and 283 ± 29 min, while overall median (range) scores for sedation were 3 (1−3) and 3 (2−3) respectively and response to noxious stimulation 0 (0−3) and 0 (0−3) respectively. The mean ± SD for HR was 110 ± 10 and 106 ± 11 bpm respectively; for MAP 87±9 and 94±5 mmHg respectively; and for RR 28 ± 5 and 26 ± 5 bpm respectively. The mean ± SD for arterial partial pressure of oxygen (PaO2) at these two dose rates was 74 ± 6 and 74 ± 2 mmHg respectively, while the arterial partial pressure of carbon dioxide oxygen (PaCO2) was 53 ± 3 and 47 ± 0.8 mmHg respectively. Based on these preliminary results we conclude that GHB has the potential to be used as a long-acting sedative in calves. Further studies are needed to confirm this.

Investigation of the linear accelerator low dose rate mode for pulsed low-dose-rate radiotherapy delivery

Purpose. Pulsed volumetric modulated arc therapy (VMAT) was proposed as an advanced treatment that combines the biological benefits of pulsed low dose rate (PLDR) and the dosimetric benefits of the intensity-modulated beams. In our conventional pulsed VMAT technique, a daily fractional dose of 200 cGy is delivered in 10 arcs with 3 min intervals between the arcs. In this study, we are testing the feasibility of pulsed VMAT that omits the need to split into ten arcs and excludes any beam-off gaps. Methods. The study was conducted using computed tomographic images of 24 patients previously treated at our institution with the conventional PLDR technique. Our newly installed Elekta machine has a low dose rate option on the order of 25 MU min−1. PLDR requires an effective dose rate of 6.7 cGy min−1 with attention being paid to the maximum dose received within any point within the target not to exceed 13 cGy min−1. The quality of treatment plans was judged based on dose-volume histograms, isodose distribution, dose conformality to the target, and target dose homogeneity. The dose delivery accuracy was assessed by measurements using the MatriXX Evolution 2D array system. Results. All cases were normalized to cover 95% of the target volume with 100% of the prescription dose. The average conformity index was 1.03 ± 0.08 while the average homogeneity index was 1.05 ± 0.02. The maximum reported dose rate at any point within the target was 10.44 cGy min−1. The mean dose rate for all pulsed VMAT plans was 6.88 ± 0.1 cGy min−1. All cases passed our gamma analysis with an average passing rate of 99.00% ± 0.48%. Conclusion. The study showed the applicability of planning pulsed VMAT using Eclipse and its successful delivery on our Elekta linac. Pulsed VMAT using the machine’s low dose rate mode is more efficient than our previous pulsed VMAT delivery.