Radiation Dose Rate Research Articles

The seasonal variation of ambient gamma radiation dose rate and health risk assessment in North Coast, Mediterranean Sea

The seasonal variation of ambient gamma radiation dose rate and health risk assessment in North Coast, Mediterranean Sea

Reference Materials of Absorbed Dose: Expanding Dynamic Range and Improving Measurement Accuracy

Establishment and control of metrological characteristics of measurements of absorbed ionizing radiation doses in the range of 0.01 and 200 kGy by reference materials is an urgent task due to their wide application in various industries. The most convenient means of metrological support for transferring a unit of absorbed dose rate of intense photon, electron, and beta radiation to measuring instruments in radiation technologies are reference materials with established metrological traceability to the International System of Units (SI). In the present study, a method for expanding the dynamic range of measuring the absorbed dose of high-intensity ionizing radiation by radiochromic film dosimetry systems was considered and tested. The accuracy (uncertainty) of dose measurements was estimated depending on the initial optical density of the radiation-sensitive layer of the radiochromic composition. The possibility of expanding the dose characteristics and improving the metrological characteristics of the existing reference materials of absorbed dose (in water) for use as secondary standards (Measures) of the absorbed dose of ionizing radiation reproducing and (or) storing one or more points of the selected measurement scale of the absorbed dose with increased accuracy (uncertainty) of the measured values of the absorbed dose (in water) in an extended dynamic range was shown.

Radioactive remote signatures derived from Sentinel-2 images and field verification in West Sulawesi, Indonesia.

Mamuju, West Sulawesi, is an area in Indonesia with high radiation levels. A high radiation dose rate was detected in Adang volcanic rock. Activities related to radioactive minerals contained in rocks and soil may release hazardous radiation into the environment. The study area generally exhibits a highly irregular morphology that provides limited access because of the high slope gradient of the volcanic terrain. Therefore, it is challenging to identify and map minerals carrying radioactive elements via Sentinel-2 remote sensing. Since optical satellite images are superior in land cover detection, we proposed a mapping technique for radioactive carrier minerals based on vegetation indices verified by chlorophyll field measurements. We applied band rationing to identify the distribution of hydrothermal alteration minerals and vegetation stress, while field chlorophyll measurements of Dryopteris marginalis and Nephrolepis exaltata were conducted. The Sentinel-2 color composite of images with 4/2, 8A/11, and 11/12 RGB band ratios revealed the distribution of iron oxide, ferromagnesian silicates, and clay minerals. High levels of uranium (U) were scattered in leucite basalt rocks, with a broad distribution of iron oxide minerals and small amounts of ferromagnesian minerals. In contrast, the presence of thorium was not affected by the presence of these minerals. In addition, band rationing of chlorophyll spectra captured by the red edge vegetation index (REVI) was used as the basis for vegetation stress mapping related to radiation exposure based on the chlorophyll content in ferns in the study area. The REVI image showed an anomalous vegetation stress concordant with the high radioactivity. To obtain more accurate results, ground measurements were also performed to identify the vegetation stress due to the presence of minerals carrying radioactive elements. The areas with radioactive mineralization and vegetation stress were located upstream of the Mamuju River and the Botteng and Ahu areas in Tapalang.

Implications of "flash" radiotherapy for biodosimetry.

Extremely high dose rate radiation delivery (FLASH) for cancer treatment has been shown to produce less damage to normal tissues while having the same radiotoxic effect on tumor tissue (referred to as the FLASH effect). Research on the FLASH effect has two very pertinent implications for the field of biodosimetry: (1) FLASH is a good model to simulate delivery of prompt radiation from the initial moments after detonating a nuclear weapon and (2) the FLASH effect elucidates how dose rate impacts the biological mechanisms that underlie most types of biological biodosimetry. The impact of dose rate will likely differ for different types of biodosimetry, depending on the specific underlying mechanisms. The greatest impact of FLASH effects is likely to occur for assays based on biological responses to radiation damage, but the consequences of differential effects of dose rates on the accuracy of dose estimates has not been taken into account.

FLASH-RT does not affect chromosome translocations and junction structures beyond that of CONV-RT dose-rates

Background and purposeThe impact of radiotherapy (RT) at ultra high vs conventional dose rate (FLASH vs CONV) on the generation and repair of DNA double strand breaks (DSBs) is an important question that remains to be investigated. Here, we tested the hypothesis as to whether FLASH-RT generates decreased chromosomal translocations compared to CONV-RT. Materials and methodsWe used two FLASH validated electron beams and high-throughput rejoin and genome-wide translocation sequencing (HTGTS-JoinT-seq), employing S. aureus and S. pyogenes Cas9 “bait” DNA double strand breaks (DSBs) in HEK239T cells, to measure differences in bait-proximal repair and their genome-wide translocations to “prey” DSBs generated after various irradiation doses, dose rates and oxygen tensions (normoxic, 21% O2; physiological, 4% O2; hypoxic, 2% and 0.5% O2). Electron irradiation was delivered using a FLASH capable Varian Trilogy and the eRT6/Oriatron at CONV (0.08–0.13 Gy/s) and FLASH (1x102-5x106 Gy/s) dose rates. Related experiments using clonogenic survival and γH2AX foci in the 293T and the U87 glioblastoma lines were also performed to discern FLASH-RT vs CONV-RT DSB effects. ResultsNormoxic and physioxic irradiation of HEK293T cells increased translocations at the cost of decreasing bait-proximal repair but were indistinguishable between CONV-RT and FLASH-RT. Although no apparent increase in chromosome translocations was observed with hypoxia-induced apoptosis, the combined decrease in oxygen tension with IR dose-rate modulation did not reveal significant differences in the level of translocations nor in their junction structures. Furthermore, RT dose rate modality on U87 cells did not change γH2AX foci numbers at 1- and 24-hours post-irradiation nor did this affect 293T clonogenic survival. ConclusionIrrespective of oxygen tension, FLASH-RT produces translocations and junction structures at levels and proportions that are indistinguishable from CONV-RT.

The dose-related plateau effect of surviving fraction in normal tissue during the ultra-high-dose-rate radiotherapy

Objective. Ultra-high-dose-rate radiotherapy, referred to as FLASH therapy, has been demonstrated to reduce the damage of normal tissue as well as inhibiting tumor growth compared with conventional dose-rate radiotherapy. The transient hypoxia may be a vital explanation for sparing the normal tissue. The heterogeneity of oxygen distribution for different doses and dose rates in the different radiotherapy schemes are analyzed. With these results, the influence of doses and dose rates on cell survival are evaluated in this work. Approach. The two-dimensional reaction–diffusion equations are used to describe the heterogeneity of the oxygen distribution in capillaries and tissue. A modified linear quadratic model is employed to characterize the surviving fraction at different doses and dose rates. Main results. The reduction of the damage to the normal tissue can be observed if the doses exceeds a minimum dose threshold under the ultra-high-dose-rate radiation. Also, the surviving fraction exhibits the ‘plateau effect’ under the ultra-high dose rates radiation, which signifies that within a specific range of doses, the surviving fraction either exhibits minimal variation or increases with the dose. For a given dose, the surviving fraction increases with the dose rate until tending to a stable value, which means that the protection in normal tissue reaches saturation. Significance. The emergence of the ‘plateau effect’ allows delivering the higher doses while minimizing damage to normal tissue. It is necessary to develop appropriate program of doses and dose rates for different irradiated tissue to achieve more efficient protection.

A comparison of bolus track and test bolus computed tomography pulmonary angiography and the implications on pulmonary and aortic vessel enhancement, effective dose and suboptimal scan rate.

Bolus track and test bolus are the most commonly used contrast timing protocols to undertake computed tomography pulmonary angiography (CTPA). The aim of this study was to compare test bolus and bolus track contrast enhancement protocols in terms of enhancement of the pulmonary vessels and aorta, radiation dose and suboptimal scan rate to determine the optimal technique for CTPA. A total of 200 CTPA examinations (100 using each protocol) performed between January and February 2021 were assessed retrospectively. All scans were performed on a 2x128 Dual Source Siemens Drive Scanner. CT attenuation was measured in Hounsfield Units (HU), with measurements taken from the main pulmonary trunk, right pulmonary artery and left pulmonary artery, ascending and descending aorta. The mean effective dose was calculated from the dose-length product (DLP). The suboptimal scan rate was calculated as the percentage of examinations below 210HU. The average HU of the pulmonary arteries was 358 HU ± SD 129.2 in the test bolus group and increased to 394 HU ± SD 133.9 in the bolus track group with a P value of ≤0.05. The average HU of the aorta was 235 HU ± SD 82.8 in the test bolus group and increased to 319 HU ± SD 91.8 in the bolus track group with a P value of <0.001. Although not statistically significant, the mean effective dose was reduced by 4.2% for the bolus track protocol (2.4 mSv vs. 2.5 mSv, P > 0.05). Fewer suboptimal scans were performed with the bolus track protocol (5 scans <210HU Bolus Track vs. 9 scans <210HU Test Bolus). The bolus track protocol results in increased enhancement of the pulmonary arteries and aorta, with the added benefits of a lower suboptimal scan rate and lower effective dose.

Assessment of radiation level and potential risk to public living around major hospitals in central and western Bangladesh

Human beings are continuously bathed in radiation coming from natural and artificial sources. Although the use of radiation in medical applications is beneficial to patients, it also contributes significantly to the health hazard for radiation workers and the public if radiation-generating equipment and radioactive sources are not handled properly. 96% dose contributed from medical uses of ionizing radiation in the US population among man-made sources as per NCRP Report No. 160. There is no extensive study conducted on the large hospitals in Bangladesh following the In-Situ method. We used a real-time digital portable radiation monitor with Garmin eTrex Global Positioning System at 320 monitoring points for radiation monitoring and positioning around the ten largest hospitals in central & western Bangladesh from September to November 2021. The mean radiation dose rates around Bangabandhu Sheikh Mujib Medical University, Dhaka Medical College Hospital, Evercare Hospital, Khulna Medical College Hospital, Mitford Hospital, National Institute of Cancer Research Hospital, Popular Hospital, Rajshahi Medical College Hospital, Shaheed Suhrawardy Medical College Hospital, and Square Hospitals were measured as 0.145 ± 0.012 μSv/h, 0.135 ± 0.009 μSv/h, 0.148 ± 0.008 μSv/h, 0.139 ± 0.01 μSv/h, 0.133 ± 0.007 μSv/h, 0.153 ± 0.011 μSv/h, 0.144 ± 0.012 μSv/h, 0.137 ± 0.008 μSv/h, 0.145 ± 0.01 μSv/h, and 0.153 ± 0.009 μSv/h, respectively. The mean excess lifetime cancer risk (ELCR) of the public who lives nearby the hospital's boundary was estimated at 1.05 × 10−3, 0.983 × 10−3, 1.071 × 10−3, 1.004 × 10−3, 0.964 × 10−3, 1.084 × 10−3, 1.043 × 10−3,0.996 × 10−3, 1.051 × 10−3 & 1.112 × 10−3 respectively. ELCR in most of the locations around the ten largest hospitals in central & western Bangladesh is higher than the global average value. Radiation monitoring is significant for minimizing the public's radiation risk and keeping hospital environments as radiation-free as possible.

Assessment of Background Radiation Around Telecommunication Masts of the Major Network Service Providers in Kaduna South, Kaduna State, Nigeria

This work assessed the electromagnetic radiation from telecommunication masts of major service providers (AIRTEL, ETISALAT, GLO, and MTN) around residential areas in Kaduna South, Nigeria. The Radio Frequency Electromagnetic Force (RF EMF) strength meter of serial number (480836) and a measuring tape were used to obtain readings away from the masts. The electric field strengths E, magnetic field strengths H, and power densities were measured at 0 m, 100 m, 200 m, 300 m, 400 m, and 500 m away from the mast base in V/m, A/m, and W/m2, respectively. The power densities measured were: 0.000091 W/m2 for Airtel, 0.000195 W/m2 for Etisalat, 0.000488 W/m2 for GLO, and 0.421352 W/m2 for MTN. These readings were compared with the standard valve (4.5 W/m2) recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the 6.05 W/m2 recommended by the Institute of Electrical and Electronic Engineers (IEEE) for exposure limits of radio frequency waves and the Federal Communications Commission (FCC) and were discovered to be below the recommended values. The radiological health effects, absorbed radiation dose rates, the annual effective dose equivalent (AEDE), and the excess lifetime cancer risks (ELCR) were evaluated. The values of absorbed dose rates were 0.000091 Gys-1 for Airtel, 0.000195333 Gys-1 for Etisalat, 0.000488333 Gys-1 for GLO, and 0.421352 Gys-1 for MTN, which were observed to be far lower than the world permissible value of 0.02472 Gys-1, except that of MTN, which is higher than the permissible value. However, the estimated annual effective dose equivalents (AEDE) were found to be higher than the ICNIRP permissible limits of 1.00 mSvy-1 for the public, which implies that the base stations do pose radiological risks in the long term. Also, the excess lifetime cancer risk for the stations’ users was all above the 0.29 × 10-3 per Sievert world recommended value by the United Nations Scientific Committee on the Effects of Atomic Radiations, UNSCEAR (2018), and Audu et al., (2019). This, therefore, suggests there is a high probability of the base station workers and residents within 500 m of the base mast to develop radiation-related illnesses over a long time. Regular radiological monitoring of all the base stations is recommended.

Personalized Carbon Monoxide‐Loaded Biomimetic Single‐Atom Nanozyme for Ferroptosis‐Enhanced FLASH Radioimmunotherapy

AbstractUltra‐high dose rate radiotherapy (FLASH‐RT) has emerged as a novel tool for cancer radiotherapy owing to its extremely rapid radiation delivery to target species. Although FLASH‐RT can protect normal tissues and organs, tumor self‐protection mechanisms limit its therapeutic effect, thus necessitating technological improvement. Here, a multipathway ferroptosis‐enhanced radioimmunotherapeutic strategy that combines single‐atom nanozyme (SAzyme)‐based GSH depletion and CO gas therapy is reported. Personalized FLASH radioimmunotherapy is achieved through encapsulation of the carbon monoxide donor (MnCO)‐loaded porous Pd‐C SAzyme (SM) within 4T1 cancer cell membranes (CSM). Camouflaging with the cancer cell membrane enables the navigation of the MnCO‐loaded Pd‐C SAzyme to the tumor region via homologous targeting. There, it releases MnCO, which generates CO from overexpressed H2O2 to induce mitochondrial apoptosis. Furthermore, the generated CO and Pd‐C SAzyme oxidized glutathione and downregulates glutathione peroxidase 4 (GPX4) expression to induce ferroptosis. The palladium in the SAzyme of the CSM further enhances the photoelectric effects of FLASH‐RT. The CSM‐mediated FLASH‐RT also invokes potent antitumor immunity, suppressing distant tumors, and immune memory, inhibiting tumor recurrence. This work presents a unique personalized nanozyme and CO gas synergistic approach wherein FLASH radioimmunotherapy avoids damage of normal tissues while simultaneously inducing ferroptosis for orthotopic tumor treatment.

Characterization of a 0.8 mm3 Medscint plastic scintillator detector system for small field dosimetry

Objective. Plastic scintillator detectors (PSDs) have demonstrated ability to meet requirements of small field dosimetry. Medscint developed a 1 mm long, 1 mm diameter cylindrical PSD with effective volume of 0.8 mm3. Clinically relevant, small field dosimetric properties of this detector, combined with a novel scintillation dosimetry system—HYPERSCINT RP-200, and HYPERDOSE analysis software were evaluated in this study. Approach. This novel scintillator-based dosimetry system was characterized with 6 MV-WFF and 10 MV-FFF x-ray beams delivered by Varian TrueBeamTM linear accelerator. The detector was characterized for leakage, short-term repeatability, dose response linearity, angular response, dose rate response, and field size dependence for radiation field sizes of 0.25 × 0.25 to 10 × 10 cm2. Measured detector specific output ratios were compared with microDiamond output factors to determine small field output correction factors, Main results. The dosimetry system showed excellent short-term repeatability with standard deviation of only 0.04 ± 0.01%. It demonstrated good dose linearity with variations less than 1.0% for 14.4 cGy and above. The dosimetry system was found to be independent of dose rate and angle of irradiation, with deviations for both below 0.5%. Leakage was found to be comparable to background readings. For 6 MV-WFF energy beams, detector specific output ratios for field sizes down to 1 × 1 cm2 agreed with output factors measured with PTW TN60019 microDiamond, thus, equates to unity for these field sizes. For 10 MV-FFF energy beams, detector specific output ratios for field sizes down to 2 × 2 cm2 agreed with PTW TN60019 microDiamond output factors, thus, equates to unity for these field sizes. for field sizes down to 0.5 × 0.5 cm2 were determined to be within 6% of unity for both 6 MV-WFF and 10 MV-FFF energy beams. Significance. The HYPERSCINT RP-200 dosimetry system coupled with a 0.8 mm3 PSD showed excellent dosimetric properties and was found to be clinically relevant for relative dosimetry down to field sizes of 0.5 × 0.5 cm2 and potentially smaller.

The presence of NORMs and toxic heavy metals in talcum baby powder

Baby talcum powder is one of the popular baby care products used for keeping the baby's skin dry and preventing diaper rash. In the past few years, there has been a growing concern on the presence of toxic heavy metals within the baby talcum powder due to its potential threat to human health and environmental effects. However, its natural radioactivity content is much less considered where it may pose similar health risks to the consumers. The present study examines the radioactivity and heavy metals concentration towards the commonly used baby powders in Malaysia, including Pureen, Johnson's, Carrie Junior and Zwitsal, utilizing the High Purity Germanium (HPGe) gamma-ray spectrometry and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Individual health risk assessment has been conducted through the estimation of absorbed dose rate due to the exposure of ionizing radiation from the three long-lived primordial radionuclides of 226Ra, 228Ra and 40K through the usage of baby powders. The assessment revealed that an individual might be exposed to an average radiation dose rate of 0.518 pGy h−1, albeit lower than the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reference exposure dose limit of 59 nGy h−1 for terrestrial radionuclides. In regards to heavy metals toxicity, all baby powders are within the permissible limits of heavy metals concentration recommended by the National Pharmaceuticals Regulatory Agency (NPRA), ASEAN Cosmetic Scientific Body (ACSB) and the United States Food and Drug Administration (FDA) except for Ni where its concentrations were slightly above the permissible value of 0.6 ppm outlined by FDA. Prolonged use of baby powders contaminated with such heavy metal may pose a significant risk to human health and the environment due to its toxic metal loading. These results emphasize the need for periodic monitoring and quality control of baby powders to ensure they meet safety standards and minimize potential risks to human health and the environment.

In-situ critical current measurements of REBCO coated conductors during gamma irradiation

Rare-earth-barium-copper-oxide (REBCO) coated conductor tapes within next-generation tokamak pilot and power plant magnets will be exposed to broad-spectrum gamma-ray and neutron irradiation concurrently. It has been known since the 1980s that cumulative neutron fluence affects the superconducting properties of REBCO, but the effects of gamma rays are less certain, as are the effects of radiation (of any kind) during current flow. However, the use of superconductors as photon detectors suggests that energetic photons interact directly with the superconducting state, locally destroying superconductivity. Hence, as well as the effect of the overall radiation dose (fluence), the effect of radiation dose rate (flux) on the superconductor’s properties must be quantified to understand how REBCO magnets will perform during fusion magnet operation. In-situ measurements of the self-field critical current at 77 K, of several REBCO coated conductor tapes were performed during Co-60 gamma ray exposure at a dose rate of 86 Gy min−1. Samples were fully submerged in liquid nitrogen throughout the measurements. No change in the critical current of any sample during or after irradiation was observed within standard error. These are the first reported in-situ measurements of critical current during fusion-relevant gamma irradiation. Two samples were irradiated to a further dose of 208 kGy at room temperature and a second round of in-situ measurements was performed. No change in the critical current of these samples was observed within standard error. This corroborates recent studies, but is in conflict with older literature.

Safety analysis and evaluation of transport and storage container for very Low-Level liquid radioactive waste

Safe temporary storage and transportation of the very low-level liquid radioactive waste generated during the Decommissioning and Decontamination (D&D) of nuclear power plants (NPPs) must be ensured. This study proposes a composite shielding transport container for very low-level liquid radioactive waste, which adheres to the industrial package (IP)-2 technical standards for packaging and transportation of radioactive materials. A shielding container based on barium sulfate (BaSO4) (a shielding material harmless to the human body) and a structurally reinforced frame were developed. Then, to confirm the structural safety of the container according to the regulations on the packaging and transportation of radioactive materials under drop weight and stacking tests, the Abaqus/Explicit program was used and on-site evaluations were performed. The maximum strains of about 8.8% and 2.2% were obtained in the drop-weight and stacking performance tests, respectively. Compared to the strain values of 40% at which high-density polyethylene (HDPE) could break, it was derived to be about 22% and 5.5%, respectively. The test satisfaction standard, that is, no loss or dispersion of radioactive contents and no shielding loss that could increase the radiation dose rate by more than 20% on the outer surface, were satisfied, confirming the safety of the container.

Comparison of Tumor Control and Skin Damage in a Mouse Model after Ultra-High Dose Rate Irradiation and Conventional Irradiation.

Recent studies suggest ultra-high dose rate radiation treatment (UHDR-RT) reduces normal tissue damage compared to conventional radiation treatment (CONV-RT) at the same dose. In this study, we compared first, the kinetics and degree of skin damage in wild-type C57BL/6 mice, and second, tumor treatment efficacy in GL261 and B16F10 dermal tumor models, at the same UHDR-RT and CONV-RT doses. Flank skin of wild-type mice received UHDR-RT or CONV-RT at 25 Gy and 30 Gy. Normal skin damage was tracked by clinical observation to determine the time to moist desquamation, an endpoint which was verified by histopathology. Tumors were inoculated on the right flank of the mice, then received UHDR-RT or CONV-RT at 1 × 11 Gy, 1 × 15, 1 × 25, 3 × 6 and 3 × 8 Gy, and time to tumor tripling volume was determined. Tumors also received 1 × 11, 1 × 15, 3 × 6 and 3 × 8 Gy doses for assessment of CD8+/CD4+ tumor infiltrate and genetic expression 96 h postirradiation. All irradiations of the mouse tumor or flank skin were performed with megavoltage electron beams (10 MeV, 270 Gy/s for UHDR-RT and 9 MeV, 0.12 Gy/s for CONV-RT) delivered via a clinical linear accelerator. Tumor control was statistically equal for similar doses of UHDR-RT and CONV-RT in B16F10 and GL261 murine tumors. There were variable qualitative differences in genetic expression of immune and cell damage-associated pathways between UHDR and CONV irradiated B16F10 tumors. Compared to CONV-RT, UHDR-RT resulted in an increased latent period to skin desquamation after a single 25 Gy dose (7 days longer). Time to moist skin desquamation did not significantly differ between UHDR-RT and CONV-RT after a 30 Gy dose. The histomorphological characteristics of skin damage were similar for UHDR-RT and CONV-RT. These studies demonstrated similar tumor control responses for equivalent single and fractionated radiation doses, with variable difference in expression of tumor progression and immune related gene pathways. There was a modest UHDR-RT skin sparing effect after a 1 × 25 Gy dose but not after a 1 × 30 Gy dose.

Mean dose rate in ultra-high dose rate electron irradiation is a significant predictor for O2 consumption and H2O2 yield

Objective. The objective of this study was to investigate the impact of mean and instantaneous dose rates on the production of reactive oxygen species (ROS) during ultra-high dose rate (UHDR) radiotherapy. The study aimed to determine whether either dose rate type plays a role in driving the FLASH effect, a phenomenon where UHDR radiotherapy reduces damage to normal tissues while maintaining tumor control. Approach. Assays of hydrogen peroxide (H2O2) production and oxygen consumption (ΔpO2) were conducted using UHDR electron irradiation. Aqueous solutions of 4% albumin were utilized as the experimental medium. The study compared the effects of varying mean dose rates and instantaneous dose rates on ROS yields. Instantaneous dose rate was varied by changing the source-to-surface distance (SSD), resulting in instantaneous dose rates ranging from 102 to 106 Gy s−1. Mean dose rate was manipulated by altering the pulse frequency of the linear accelerator (linac) and by changing the SSD, ranging from 0.14 to 1500 Gy s−1. Main results. The study found that both ΔH2O2 and ΔpO2 decreased as the mean dose rate increased. Multivariate analysis indicated that instantaneous dose rates also contributed to this effect. The variation in ΔpO2 was dependent on the initial oxygen concentration in the solution. Based on the analysis of dose rate variation, the study estimated that 7.51 moles of H2O2 were produced for every mole of O2 consumed. Significance. The results highlight the significance of mean dose rate as a predictor of ROS production during UHDR radiotherapy. As the mean dose rate increased, there was a decrease in oxygen consumption and in H2O2 production. These findings have implications for understanding the FLASH effect and its potential optimization. The study sheds light on the role of dose rate parameters and their impact on radiochemical outcomes, contributing to the advancement of UHDR radiotherapy techniques.

Proton and Electron Ultrahigh-Dose-Rate Isodose Irradiations Produce Differences in Reactive Oxygen Species Yields

Investigations into ultra-high dose rate (UHDR) radiotherapy have dramatically risen because of the observed normal tissue sparing FLASH effect without sacrificing tumor control. The purpose of this study was to provide a direct beamline comparison of protons and electrons to determine where UHDR to conventional dose rates (CDR) changes affect the resultant radiochemistry. We used well characterized assays of reactive oxygen species (ROS) and oxygen consumption to assess the radiolysis in protein solutions. Three optical reporters related to ROS (CellROX Deep Red, reflects highly reactive radicals; Amplex Red reflects H2O2; and Oxyphor reflects partial pressure loss (ΔpO2)). A Varian ProBeam proton cyclotron and a converted Varian Trilogy electron linac were used for irradiation at both their CDR and UHDR capable level, to assess the assay change per unit dose. For both protons and electrons an expected reduction in ROS was noted going from CDR to UHDR, and results interpreted as a reduction in the ratio of UHDR/CDR yield. The CellROX assay showed no difference between beamlines, each showing ∼80% reduction in ROS from CDR to UHDR. The Amplex assay showed the largest inter-beamline difference, with ∼5% loss using protons vs ∼69% loss with electrons, in protein solution. The Oxyphor assay of ΔpO2 showed a small difference in CDR to UHDR with a 23% loss with protons and 43% loss with electrons. Interpretation of ROS assays and oxygen consumption is notoriously challenging. These assays might be interpreted by their most activating species' lifetime. The assay for highly reactive OH●, appeared independent of beamline, whereas the assays for the longer lived H2O2 species and DpO2 assay showed differences between beamlines via the UHDR/CDR ratio. This work can be used for FLASH hypothesis testing by comparing these assays to isodose biological FLASH effects in vivo.

Gamma radiation dose rate in high-altitude areas in the Bageshwar, Champawat and Pithoragarh districts of Uttarakhand, India.

Radiation has a deteriorating effect on humans as well as on the environment depending on its level, although we have all been exposed to natural gamma radiation from birth. The presence of radionuclides in rocks, soil, plants, and water is a major factor behind the natural gamma radiation. The present study deals with the study of natural gamma radiation at Bageshwar, Champawat and Pithoragarh districts of Uttarakhand. It also consists of seasonal variations in gamma radiation and its relationship with altitude and geology. The purpose of this study was to investigate the influence of altitude and geology on natural gamma radiation dose rate data in high-altitude areas of India. The highest gamma radiation value was 444nSv/h in the summer and 342nSv/h in the winter. The investigation recorded the gamma radiation up to 2542.20maltitude, indicating that the geology of the areas is more relevant than the altitude. Few sites in such a high-altitude zone were found to exceed the value of 200nSv/h, as reported by UNSCEAR. This research is necessary in order to consider the human health and climate changes, both of which are part of the action plan for the United Nation's Sustainable Development Goals (SDG 3, SDG 13).

AIEgen-based nanotherapeutic strategy for enhanced FLASH irradiation to prevent tumour recurrence and avoid severe side effects

Compared with conventional radiotherapy, ultrahigh dose-rate (FLASH) radiotherapy spares normal tissues through oxygen exhaustion. However, residual cancer stem cells (CSCs) may generate tumour cells, causing tumour recurrence, which represents a critical problem after radiotherapy. Here we developed platelet cell membrane-camouflaged hollow TaOx nanospheres encapsulated with aggregation-induced emission luminogens (AIEgen) (named TPT). With characteristics derived from platelets, TPT nanoparticles (NPs) specifically target tumour regions and enhance FLASH radiotherapy via promoting the photoelectric effect by high Z-element tantalum and elevating reactive oxygen species levels through AIEgen-mediated photodynamic therapy (PDT). Under FLASH radiotherapy, TPT NPs exhibited a remarkable CSC killing effect, significantly inhibiting tumour recurrence. More important, compared with conventional radiotherapy, TPT NPs-promoted FLASH radiotherapy to efficiently eliminate tumours while reducing reoccurrence and severity of complications affecting normal tissues. This strategy provides a novel design to suppress tumour recurrence as well as to avoid adverse side effects.

Effects on hematopoietic and immune system of ultra-high dose rate radiotherapy (FLASH-RT).

166 Background: Ultra-high dose rate radiotherapy, so-called FLASH radiotherapy (FLASH-RT) has shown to reduce radiation-induced damage including lung fibrosis, brain damage, skin fibrosis, etc. We investigated the effect of FLASH-RT compared of conventional dose rate radiotherapy (CONV-RT) at 5Gy of TBI on survival of hematopoietic system, peripheral blood cells, and immune-related responses. Methods: Mice were divided into 3 groups: control (0 Gy), FLASH-RT (109Gy/s), and CONV-RT (0.067Gy/s). FLASH-RT was performed with DIRAMS LINAC producing 6 MeV electron beams. Irradiated mice were sacrificed at 1, 2, 4, 7, 14, 21 and 28 post-TBI of 5 Gy and cellularity of peripheral blood and bone marrow, histological evaluation of immune organ such as spleen and thymus, and T and B lymphocytes in mouse spleen by flow cytometry were investigated. Results: In peripheral blood cell counts, RBC, neutrophil, lymphocyte counts were not significantly different between FLASH-RT and CONV-RT groups from day 1 to day 28 post-TBI. However, FLASH-RT initially induced more apoptosis of bone marrow cells, platelets, and eosinophils of peripheral blood compared to CONV-RT. FLASH-RT and CONV-RT groups showed similar histological changes in the thymus and spleen after 5Gy of TBI, but T lymphocytes of CONV-RT group in day 28 were less recovered compared to those of FLASH-RT group. Our results indicated that FLASH-RT affected more radiation-induced damage of hematopoietic system in early stages compared to CONV-RT, but FLASH-RT showed higher recovery of T lymphocytes after irradiation. Conclusions: These results show that FLASH-RT can induce similar damage and recovery pattern on hematopoietic system with CONV-RT in first week, but FLASH-RT might affect less T-lymphopenia in long-term than CONV-RT.