Linear Dose Research Articles

Assessment of using an Octavius 4D Measuring System for Patient-specific VMAT Quality Assurance in Togo

Purpose and objective: Quality assurance (QA) programs are designed to improve the quality and the safety of radiation treatments, including machine- and patient-specific QA (PSQA). The objective of this study was to evaluate the current state of PSQA practice and identify the area for potential improvement for VMAT delivery. Materials and methods: The Octavius 4D (O4D) system accuracy was evaluated using an O4D homogeneous phantom for different field sizes. The system response to dose linearity, field sizes, and PDD difference tests were performed against the calculated dose of the treatment planning system (TPS) for a 6 MV photon beam. The deviation of the delivered dose was evaluated at the isocenter and different depths. Moreover, pretreatment verification of 40 VMAT plans was performed including prostate cancer (PC), head and neck cancer (HNC), uterine and cervical cancer (UCC), and breast cancer (BC). The PTW VeriSoft software was used to perform the local and global 3D gamma analysis by comparing the reconstructed 3D dose against the calculated dose using criteria 2%/2 mm and 3%/3 mm, 20% of low-dose threshold, and 95% of gamma passing rate (%GP) tolerance level. In the clinical scenario, the sensitivity of the O4D system in detecting VMAT delivery and setup errors has been investigated by measuring the variation of %GP values before and after the simulated errors using one of the VMAT plans related to each treatment site. Results: The O4D system reported good agreement for linearity, field size, and PDD differences with TPS dose being within ± 2% tolerance for a 6 MV photon beam. Output factors were consistent between the ionization chamber and the O4D detector 1500 array down to 4 x 4 cm2 field size with a maximum deviation of less than 1%. The introduction of deliberate errors caused the decrease of %GP values. In most scenarios, the %GP value of simulated errors was detected with 2%/2 mm and ranged between the detection threshold and gamma passing threshold. Conclusion: The results indicate that the O4D system is sensitive to detect delivery and setup errors with restrictive criteria of 2%/2 mm for routine pretreatment verification. Moreover, this system should be used in combination with kV-CBCT to improve dosimetry accuracy and treatment reproducibility.

The Effect of Obstructive Sleep Apnea on Subclinical Target Organ Damage in Patients With Resistant Hypertension

IntroductionAmong all patients with hypertension, those with resistant hypertension (RH) have the highest rates of subclinical organ damage (SOD). The prevalence of obstructive sleep apnea (OSA) is high in RH patients, and it could contribute to SOD. We aimed to investigate how OSA and its treatment are related to SOD in a large cohort of RH patients. MethodsThis is an ancillary analysis to the SARAH study, a multicentre observational cohort aiming to evaluate the impact of OSA on RH. Individuals with RH who were undergoing a sleep study and have information on at least one of the SOD variables (vascular, cardiac or renal damage) were selected. Patients were followed-up for three years. ResultsIn total, 503 subjects were included. The participants were predominantly male, obese, and the median (IQR) apnea–hypopnea index (AHI) was 15.5 (7.90–31.5)events/h. No differences in the presence of vascular or cardiac damage were observed between OSA and non-OSA patients. A lower estimated glomerular filtration rate (eGFR) was observed in participants with OSA than in those without OSA, with an adjusted effect of −8.69mL/min/1.73m2 (−13.59, −3.79; p value<0.001). Kidney damage was also greater in subjects with OSA, with an adjusted OR (95% CI) of 1.77 (1.09, 2.87; p value=0.02). The eGFR showed a linear dose–response relationship with OSA severity. Among patients treated with CPAP, lower eGFR values were observed in noncompliant subjects. ConclusionsOSA could contribute to worsening renal function in patients with RH. No compliance with CPAP was associated with lower values of eGFR.

The Emission of Internal Conversion Electrons Rather Than Auger Electrons Increased the Nucleus-Absorbed Dose for 161Tb Compared with 177Lu with a Higher Dose Response for [161Tb]Tb-DOTA-LM3 Than for [161Tb]Tb-DOTATATE.

Preclinical data have shown that 161Tb-labeled peptides targeting the somatostatin receptor are therapeutically more effective for peptide receptor radionuclide therapy than are their 177Lu-labeled counterparts. To further substantiate this enhanced therapeutic effect, we performed cellular dosimetry to quantify the absorbed dose to the cell nucleus and compared dose-response curves to evaluate differences in relative biological effectiveness invitro. Methods: CA20948 cell survival was assessed after treatment with [161Tb]Tb- and [177Lu]Lu-DOTATATE (agonist) and with [161Tb]Tb- and [177Lu]Lu-DOTA-LM3 (antagonist) via a clonogenic assay. Cell binding, internalization, and dissociation assays were performed up to 7 d to acquire time-integrated activity coefficients. Separate S values for each type of particle emission (Auger/internal conversion [IC] electrons and β- particles) were computed via Monte Carlo simulations, while considering spheric cells. Once the absorbed dose to the cell nucleus was calculated, survival curves were fitted to the appropriate linear or linear-quadratic model and corresponding relative biological effectiveness was evaluated. Results: Although the radiopeptide uptake was independent of the radionuclide, [161Tb]Tb-DOTATATE and [161Tb]Tb-DOTA-LM3 delivered a 3.6 and 3.8 times higher dose to the nucleus, respectively, than their 177Lu-labeled counterparts on saturated receptor binding. This increased nucleus-absorbed dose was mainly due to the additional emission of IC and not Auger electrons by 161Tb. When activity concentrations were considered, both [161Tb]Tb-DOTATATE and [161Tb]Tb-DOTA-LM3 showed a lower survival fraction than did labeling with 177Lu. When the absorbed dose to the nucleus was considered, no significant difference could be observed between the dose-response curves for [161Tb]Tb- and [177Lu]Lu-DOTATATE. [161Tb]Tb-DOTA-LM3 showed a linear-quadratic dose response, whereas [161Tb]Tb-DOTATATE showed only a linear dose response within the observed dose range, suggesting additional cell membrane damage by Auger electrons. Conclusion: The IC, rather than Auger, electrons emitted by 161Tb resulted in a higher absorbed dose to the cell nucleus and lower clonogenic survival for [161Tb]Tb-DOTATATE and [161Tb]Tb-DOTA-LM3 than for the 177Lu-labeled analogs. In contrast, [161Tb]Tb-DOTATATE showed no higher dose response than [177Lu]Lu-DOTATATE, whereas for [161Tb]Tb-DOTA-LM3 an additional quadratic response was observed. Because of this quadratic response, potentially caused by cell membrane damage, [161Tb]Tb-DOTA-LM3 is a more effective radiopeptide than [161Tb]Tb-DOTATATE for labeling with 161Tb.

An investigation on thermoluminescence properties and kinetic parameters of Çankırı rock salt

This study investigates the thermoluminescence (TL) dosimetric properties and kinetic parameters of natural salt samples sourced from the Çankırı rock salt cave in Turkey using β irradiation. Obvious effective TL maximum observed at around 85 and 230°C. A preheat condition was determined to apply a thermal cleaning for the lower temperature side of TL spectrum. Dose sensitivity, linearity and reusability characteristics were investigated for effective TL maximum on the high temperature side of the spectrum. TL kinetic parameters were determined via various heating rates (VHR) experiment, and whole TL glow curve was studied via Tm−Tstop experiment and glow curve deconvolution. General order kinetics approach was utilized for glow curve deconvolution analysis. Kinetic parameters were determined for at least eight electron trap levels which has activation energies in the range of 0.8–1.53 eV.

Influence of Age on Leukemia Mortality Associated with Exposure to γ rays and 2-MeV Fast Neutrons in Male C3H Mice.

The relative biological effectiveness (RBE) of densely ionizing radiation can depend on the biological context. From a radiological perspective, age is an important factor affecting health risks of radiation exposure, but little is known about the modifying impact of age on the effects of densely ionizing radiation. Herein, we addressed the influence of age on leukemogenesis induced by accelerator-generated fast neutrons (mean energy, ∼2 MeV). Male C3H/HeNrs mice were exposed to 137Cs γ rays (0.2-3.0 Gy) or neutrons (0.0485-0.97 Gy, γ ray contamination 0.0105-0.21 Gy) at 1, 3, 8, or 35 weeks of age and observed over their lifetimes under specific pathogen-free conditions. Leukemia and lymphoma were diagnosed pathologically. Hazard ratio (HR) and RBE for myeloid leukemia mortality as well as the age dependence of these two parameters were modeled and analyzed using Cox regression. Neutron exposure increased HR concordant with a linear dose response. The increase of HR per dose depended on age at exposure, with no significant dose dependence at age 1 or 3 weeks but a significant increase in HR of 5.5 per Gy (γ rays) and 16 per Gy (neutrons) at 8 weeks and 5.8 per Gy (γ rays) and 9 per Gy (neutrons) at 35 weeks. The RBE of neutrons was 2.1 (95% confidence interval, 1.1-3.7), with no dependence on age. The development of lymphoid neoplasms was not related to radiation exposure. The observed increasing trend of radiation-associated mortality of myeloid leukemia with age at exposure supports previous epidemiological and experimental findings. The results also suggest that exposure at the susceptible age of 8 or 35 weeks does not significantly influence the RBE value for neutrons for induction of leukemia, unlike what has been documented for breast and brain tumors.

Comparative analysis of predose effects on TL and OSL signals in BeO dosimeters

This study investigates in detail the effects of predose on TL and OSL signals for BeO dosimeters. The TL and OSL signals were deconvoluted to each peak and component. As a result of deconvolution, the variations in the kinetic parameters (E, Tmax, b) for the TL signals and the lifetime values of the OSL signals were investigated. In addition, sensitivity changes according to predose were monitored for each peak and component. Finally, dose response curves were studied using the dose linearity index (f(D)) for each peak and component. Accordingly, the peak structures and kinetic parameters did not change according to the predose for the TL signal, whereas variations in the lifetime values for the OSL signal were observed, especially at the initial dose values (0.1 and 0.2 Gy). There was no change in sensitivity according to the predose for the total area condition although each peak and component exhibited independent behavior. Therefore, TL and OSL signals should be evaluated based on the total area in predose applications. The TL and OSL dose response curves exhibited different behaviors according to predose. TL dose response curves were not affected by the predose except for 1000 Gy, while the OSL dose response curves were affected by the predose considering the total area condition. The possible reason for the differences between the TL and OSL dose response curves is the significant transfer effect in the OSL signal at low doses, which results in greater changes at low doses compared to the TL signal. Also, thermal quenching effects may have resulted in lower intensity in the case of the TL signal. In future studies, preheating tests and thermal quenching corrections on TL peaks at high predoses may increase our understanding of deep trap interactions in BeO dosimeters.

Association between Life's Essential 8 and cognitive function among older adults in the United States

The American Heart Association (AHA) recently redefined cardiovascular health (CVH) with the introduction of Life's Essential 8 (LE8), which encompasses eight areas (diet, physical activity, nicotine exposure, sleep duration body mass index, non-HDL cholesterol, blood glucose, and blood pressure). This study aimed to explore the relationships between both the aggregate and individual CVH metrics, as defined by Life's Essential 8, and cognitive function in older adults in the United States. This cross-sectional, population-based study analyzed data from the National Health and Nutrition Examination Survey conducted between 2011 and 2014, focusing on individuals aged 60 years and older. CVH was categorized as low (0–49), moderate (50–79), or high (80–100). Cognitive function was assessed through the CERAD tests, Animal Fluency test, and Digit Symbol Substitution test. Multivariable logistic models and restricted cubic spline models were employed to investigate these associations. This study included a total of 2279 older adults in the United States. Only 11% of adults achieved a high total CVH score, while 12% had a low score. After further adjustment for potential confounding factors, higher LE8 scores were significantly associated with higher scores on CERAD: delayed recall score (0.02[0.01, 0.03]; P < 0.001), CERAD: total score (3 recall trials) (0.04[0.02, 0.06]; P < 0.001), animal fluency: total score (0.09[0.05, 0.12]; P < 0.001), and digit symbol: score (0.29[0.18, 0.41]; P < 0.001), demonstrating a linear dose–response relationship. Similar patterns were also observed in the associations between health behavior and health factor scores with cognitive function tests. LE8 scores exhibited positive linear associations with cognitive function. Maintaining better levels of CVH may be associated with higher levels of cognitive function in older Americans, but further research is needed to confirm the causal and temporal relationships between LE8 and cognitive function.

Exploring the viability of desiccant silica gel beads as A novel material for radiation dosimetry: A preliminary investigation

Silica gel bead material, with its porous structure, high surface area, uniform particle size, stability, and excellent adsorption capacity, is a key material for advancing dosimeter technologies. These qualities make it ideal for accurately measuring and monitoring ionizing radiation in various environments. The research aims to characterize the response of different ionizing radiation sources on desiccant silica gel beads, laying the groundwork for potential applications in medical dosimetry. In this study, silica gel bead samples were subjected to various radiation sources, including gamma rays with an average energy of 1.25 MeV, photons (6 MV), and electrons (6 MeV). The radiation was administered at doses within the range of 2 Gy–20 Gy, which is commonly used in radiotherapy to evaluate the dosimetric behaviour of the desiccant silica gel bead samples using the conventional thermoluminescence (TL) technique. The silica gel bead samples have been found to provide a highly linear dose response within the dose range of interest, with the coefficient of determination (R2) ranging between 0.91 and 0.96. Additionally, the samples show high sensitivity at lower doses and maintain excellent reproducibility, with a standard deviation of less than 4%. In regard to fading evaluation, desiccant silica gel beads exhibit minimal signal loss within 35 days post-irradiation, averaging between 20% and 38%. The findings of this study are promising for developing a new dosimeter, which will enhance radiation monitoring and measurement practices in various environments. These improvements cover dosimetric applications in medical and industrial fields including food safety and agricultural development.

MR-OCTAVIUS 4D with 1500 MR and 1600 MR arrays is suitable for plan QA in a 1.5 T MRI-linac

To ensure the accuracy of radiation delivery to patients in a 1.5 T MRI-linac, the implementation of quality assurance (QA) devices compatible with MR technology is essential. The OCTAVIUS 4D MR, made by PTW (Freiburg, Germany) is designed to ensure consistent and ideal alignment of its detectors with the direction of each beam segment. This study focuses on investigating the fundamental characteristics of the detector response for the OCTAVIUS Detector (OD) 1500 MR and OCTAVIUS 1600 MR when used in the MR-compatible OCTAVIUS 4D. Characteristics examined included short-term reproducibility, dose linearity, field size dependency, monitor unit (MU) rate dependency, dose-per-pulse dependency, and angular dependency. The evaluation of OD 1500 MR also involved measuring 25 clinical treatment plans across diverse target sizes and anatomical sites, including the liver/pancreas, rectum, prostate, lungs, and lymph nodes. One plan was measured with the standard setup and with a 5 cm left offset. The OD 1600 MR was not available for these measurements. The capability of the OD 1500 MR to identify potential errors was assessed by introducing a MU and positional shift within the software. The results demonstrated no significant differences in short-term reproducibility ( <0.2% ), dose linearity ( <1% ), field size dependency ( <0.7% for field sizes larger than 5 cm × 5 cm), MU rate dependency ( <0.8% ), dose-per-pulse dependency ( <0.4% ) and angular dependency (standard deviation <0.5% ). All tests of clinical plans were successfully completed. The OD 1500 MR demonstrated compatibility with the standard 95% pass rate when employing a global 3%/3 mm gamma criterion, and a 90% pass rate using a global 2%/2 mm gamma criterion. The detector demonstrated the capacity to measure treatment plans with a 5 cm left offset. With the standard parameters, the gamma test was sensitive to position errors but required an addition tests of mean/median dose or point dose in order to detect small dose difference.

Optically stimulated luminescence detectors for LET determination and dosimetry in ion beam therapy

Optically stimulated luminescence detectors (OSLDs) have been utilized for various dosimetry applications for many years. The use of Al2O3:C OSLDs for proton dosimetry began over a decade ago, taking advantage of the correlation between the ionization density of the radiation field and the ratio of intensities of the material’s two emission bands. The correlation allows for determining both linear energy transfer (LET) and dose in proton beams, with corrections for ionization quenching derived from the LET. However, the previous methodology for proton dosimetry and simultaneous LET determination with Al2O3:C OSLDs was cumbersome and occasionally associated with large uncertainties, while carbon beam dosimetry posed further challenges due to an elevated LET.This paper reviews the recent advancements in ion beam dosimetry and LET determination using OSLDs. Employing Al2O3:C,Mg OSLDs alongside improved, automatized read-out techniques, and the use of other radiation quality metrics than averaged LET, has removed most of the previous obstacles for ion beam dosimetry with OSLDs.The feasibility of simultaneous LET determination and dosimetry in ion beams is demonstrated through two case studies involving realistic proton and carbon ion therapy scenarios.

Associations of remnant cholesterol in early pregnancy with gestational diabetes mellitus risk: a prospective birth cohort study

BackgroundRemnant cholesterol (RC) reportedly contributes to the development of diabetes mellitus. However, evidence on the relationship between maternal RC and the risk of developing gestational diabetes mellitus (GDM) during pregnancy is limited. This study aimed to assess the relationship between maternal RC and GDM risk during early pregnancy, and explore the potential pathways involved in the relationship between RC levels and GDM risk.MethodsFrom 2018 to 2021, a prospective birth cohort study was designed and carried out in China. The associations of maternal RC and other lipid parameters with GDM risk were estimated using logistic regression models and restricted cubic splines. Subgroup analyses were performed stratified by prepregnancy body mass index (pre-BMI), maternal age and gravidity. Mediation analyses were conducted to explore the mediating effect of some related factors on the relationship between RC levels and the risk of GDM.ResultsA total of 33,018 pregnant women were included. The median RC level was 0.47 ± 0.20 mmol/L. The prevalence of GDM was 15.19%. As RC quartiles increased, the incidence of GDM increased substantially, reaching 19.24% for the highest quartile of RC (P < 0.001). Maternal RC in the first trimester was positively correlated with GDM risk (OR: 2.254, 95% CI: 1.943–2.615). Compared to the lowest RC quartile, higher RC quartiles were correlated with an increased risk of GDM, and the ORs (95% CIs) for Q3 and Q4 were 1.208 (1.101–1.325) and 1.489 (1.364–1.626), respectively. Moreover, a linear dose–response relationship was found for this association (P for all < 0.001, P for nonlinearity > 0.05) and was consistent across subgroups with different pre-BMIs, maternal ages and gravidities (all P values for interactions > 0.05). Furthermore, the correlation between RC level and GDM risk was partially mediated by pre-BMI (9.20%) and blood glucose level (-11.1%).ConclusionsHigher maternal RC levels in the early stage of pregnancy was positively associated with an increased risk of developing GDM. This association was partially mediated by pre- BMI and blood glucose levels.

Measurement of ionising radiation dose absorbed by bones by using a bone-imitating polymer gel dosimeter

Three-dimensional radiotherapy dosimetry allows for high-resolution dose distribution measurements using dosimeters imitating various tissues. This work concerns bone-imitating dosimeters. The following are investigated: (i) manufacturing of bone-imitating dosimeters with two types of calcium hydroxyapatite, (ii) dose response characteristics after irradiation with a 6 MV photon beam, and (iii) tissue equivalence. The main findings include the dosimetric compositions with two types of calcium hydroxyapatite. For 18 % of one type of hydroxyapatite, the dosimeter imitates trabecular bone. For much higher concentrations (>40 %, another hydroxyapatite), the dosimeter approaches the properties of dense bone. The dynamic dose response is not greater than 30 Gy, the linear dose range is <20 Gy (computed tomography and nuclear magnetic resonance measurements), and the dose sensitivity is 0.11–0.18 Gy−1 s −1 (nuclear magnetic resonance measurements) for different weight fractions of hydroxyapatites. In summary, a bone-imitating polymer gel dosimeter can be used to measure the radiation dose in radiotherapy.

Luminescence and dosimetry investigations of Eu(III) doped Ca2CeVO6 novel double perovskite

A novel composition of vanadate double perovskite Ca2CeVO6 doped with Eu3+ was successfully synthesized using combustion synthesis, wherein the doping levels of Eu3+ ranged from 1 to 6 mol%. The Rietveld refinement of the powder X-ray diffraction (XRD) data confirmed the orthorhombic structure of the phosphors. Scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX) were employed to investigate the surface morphology and elemental distribution in the phosphor, respectively. Under the excitation at 280 nm and 467 nm, the phosphor exhibited strong down-conversion red photoluminescence (PL) emission, attributed to Eu3+ transitions (5D0-7FJ, where J = 0–3) originating from its 4f states. The intensity of PL emission shows increasing trend with increasing doping concentration. However, exceeding the threshold doping concentrations led reduction in PL intensity due to multipolar interaction effects. Additionally, the Eu3+ doped Ca2CeVO6 phosphors were subjected to irradiation with a radioactive 90Sr/90Y beta source to explore their thermoluminescence (TL) properties. Post-irradiation, the phosphors displayed prominent TL glow curves, with the most intense peak at around 94 °C, followed by peaks at 160 °C and 288 °C. The TL intensity of these peaks exhibited a linear dose response within the dose range of 1 Gy–50 Gy. Besides, the TL fading and reproducibility tests showed satisfactory results. Furthermore, Tmax-Tstop experiments revealed the presence of three trap centres within the trap depth range of 0.7–2.1 eV in the Ca2CeVO6:Eu3+ phosphor. Additionally, the glow curve deconvolution (GCD) was employed to determine trapping parameters, providing valuable insights into the TL behaviour of the phosphor. Overall, the results suggest that the novel phosphor under study holds promise for its applications in lighting devices and TL dosimetry (TLD).

Comparative pharmacology and abuse potential of oral dexamphetamine and lisdexamfetamine-A literature review.

To compare the pharmacology and abuse potential of oral dexamphetamine and lisdexamfetamine (LDX). A search of Medline and Embase was conducted to identify relevant articles for this literature review. Dexamphetamine and LDX, a prodrug of dexamphetamine, are indicated for the treatment of attention-deficit/hyperactivity disorder. It has been suggested that LDX may have a reduced potential for oral abuse compared to immediate-release dexamphetamine. As a prodrug, LDX has the same pharmacodynamic properties as dexamphetamine. A study in healthy adults showed that the pharmacokinetic profile of dexamphetamine following oral administration of LDX is essentially identical to that of an equimolar dose of dexamphetamine administered 1h later. In addition, dexamphetamine produced subjective drug liking effects comparable to those produced by LDX. LDX showed linear dose proportional pharmacokinetics up to a dose of 250mg, indicating a lack of overdose protection at supratherapeutic doses. Furthermore, the exposure to dexamphetamine released from LDX may be prolonged by the consumption of alkalizing agents. The available evidence from pharmacodynamic, pharmacokinetic and abuse liability studies suggests a comparable potential for oral abuse of dexamphetamine and LDX.

Impact of sample preparation temperature on Li and Ce co-doped MgB4O7 dosimetry performance: A plausible scenario for controlling defect clustering

MgB4O7 co-doped with Ce and Li has been recognized as a promising dosimetric material for spatially-resolved optically stimulated luminescence (OSL) measurements. Nevertheless, conflicting information exists in the literature regarding its dosimetric characteristics. These include discrepancies in fading, the proportion of shallow traps, the range of linear dose response, and a notable absence of direct sensitivity comparisons. These discrepancies are likely attributed to variations in the synthesis methods utilized to produce this material. As part of our research initiative aiming at elucidating the influence of synthesis on the luminescence properties, we are examining in this contribution a single parameter – specifically, the sample preparation temperature – and assessing its impact on the luminescence properties. For the first time, we identified a correlation between the width of the thermoluminescence (TL) glow curves, the TL, optically stimulated luminescence (OSL), and radioluminescence (RL) intensities, as well as the fading characteristics over time and annealing temperature. We show that annealing at higher temperature leads to narrowing of the main TL peak (c.a. 240 °C at 5 °C/s heating rate) compared with samples prepared at lower temperatures, which in turn leads to a decrease in the integrated TL intensity of that peak. Despite exhibiting lower intensity, samples prepared at temperatures above 800 °C show less than 10 % TL/OSL fading over 60 days. Our measurements suggest an involvement of clustered defects for the samples prepared at 600 °C, with a shift towards a scenario of delocalized transitions in samples prepared at higher temperatures.

Secondary cancer risk in six anatomical sites when using PAT, IMPT, and VMAT/IMRT radiotherapy

Background and purposeCompared to intensity modulated proton therapy (IMPT), proton arc therapy (PAT) is expected to improve dose conformality, delivery efficiency, and provide a more favorable LET distribution. Alternatively, the low-dose bath is potentially spread over larger volumes, which could impact the likelihood of developing a radiation-induced, secondary cancer (SC). The goal of this study was to evaluate this risk in several anatomical sites using newly developed commercial tools. Materials and methodsTreatment plans encompassing six anatomical sites, five patients per site, and three techniques per patient were created using RayStation. Techniques included PAT and IMPT for protons, and either volumetrically modulated radiotherapy (VMAT) or intensity modulated radiotherapy (IMRT) for photons. Risk estimates were based on the organ-equivalent dose (OED) concept using both Schneider’s mechanistic dose–response model for carcinoma induction and a linear dose–response model. ResultsWith few exceptions, mean and integral dose were lowest with PAT. For protons, the factor OEDIMPT/OEDPAT ranged from 0.7 to 1.8 with both the mechanistic and linear model, while for photons OEDphoton/OEDPAT ranged from 1.5 to 10 using the mechanistic model and 1.3 to using the linear model. A strong correlation was found between mean dose and OED for organs with significant repopulation/repair (high R value) and less cell death from single hit interactions (low α value). ConclusionBased on results from both mechanistic and linear risk models, the transition from IMPT to PAT should not substantially affect SC risk in patients treated with proton therapy. Additionally, when using Schneider’s model, the shapes of the dose–response curves can be used as a good predictor of how SC risk will respond to shifts from intermediate dose to low dose as anticipated when moving from IMPT to PAT.

Thermoluminescence characteristics of gamma-irradiated Gd:Mg doped silica glass

This study explores the characteristics of thermoluminescence (TL) yield of silica glass doped with Gd2O3 and MgO for dosimetry via sol-gel route, with varying concentrations of rare earth metal oxides, ranging from 0.1 to 0.8 mol%. Gamma irradiation was delivered using 1.25 MeV 60Co, with entrance doses of 2–10 Gy. The characterization of Gd:Mg-doped SiO2 included assessing TL dose response, sensitivity, linearity index, glow curve, and fading. It has been found that 0.2 mol% Gd:Mg-doped SiO2 shows promising TL dosimetric properties due to its high linearity, high sensitivity, and low thermal fading. In addition, it demonstrated exceptional dosimetric response across the entire dose range studied, with a coefficient of determination R2 exceeding 91%. A computerized glow curve deconvolution method was conducted to determine the kinetic parameters by using Glowfit software. The glow curves include five peaks associated with activation energies and frequency factors with values 0.88–2.42 eV and 5.58 × 106–7.22 × 1026 s−1, respectively. The 0.2 mol% Gd:Mg-doped SiO2 demonstrates minimal fading effects, retaining a significant portion of the TL signal with ∼33% of the initial signal lost over 28 days post-irradiation. The results indicate that the Gd:Mg-doped SiO2 offers a promising performance as a low-cost passive radiation dosimeters.

Characterization of the First Prototype of an Angular Independent Silicon Diode Array for Quality Assurance in Stereotactic Radiosurgery

Quality assurance (QA) ensures the accurate and safe delivery of radiation treatment. However, there are several challenges for advanced radiotherapy techniques, such as stereotactic radiosurgery (SRS), where substantial doses of radiation with multi-directional beams and variable dose rates are delivered to specific areas. Current dosimeters lack high precision, exhibiting issues with dependency on the angle of measurement and the dose rate. This study investigates the characterization of a two-dimensional edgeless silicon diode array for QA in SRS. This detector underwent evaluation of its dose linearity, percentage depth dose (PDD), output factors (OFs), dose rate variability, and angular dependence with megavoltage linear accelerator beams. The edgeless array demonstrated a linear response in the direct detection of MV therapeutic X-rays with sensitivity of 6.95 × 10−3 ± 2.3 × 10−5 Gy/nC, and the percentage differences for PDD and OF measurements were found to be within 2% compared to the reference detector. A dose per pulse dependence of ±2% was demonstrated across the range of 0.12 to 0.39 mGy/pulse. The angular dependence was within 2% variation for irradiation angles greater than 80° and smaller than 120°; however, a maximum of 4% variation was observed with some diodes for angles between 80° and 120°. The improved performance of the edgeless array is likely to overcome limitations of the current dosimeters for SRS QA by operating without the need of any corrections.

Investigating luminescence signals of pharmaceuticals and dietary supplements for emergency dosimetry

This study investigates the potential use of dietary supplements and pharmaceuticals containing magnesium, calcium or potassium for emergency dosimetry applications using the phenomenon of optically stimulated luminescence (OSL). Signal measurements were carried out using different stimulation wavelengths, and blue light stimulation was found to be the most efficient. More than half of the samples exhibited a measurable OSL signal and relatively high radiation sensitivity compared to other previously measured emergency detectors. Moreover, samples generally demonstrated a linear dose response. Possible causes of their high zero-dose signal were investigated: mechanical processing and UV light excitation. As variability in sensitivity was observed, the test-dose protocol was used during measurements. Furthermore, the study showed a significant loss of OSL signal intensity within 24 h after irradiation, which suggests the necessity for a fading correction. Finally, a dose recovery test was performed to evaluate the materials and the test-dose protocol under realistic conditions. The findings indicate the potential for using pharmaceuticals and dietary supplements in the event of a radiation emergency due to their dosimetric properties and ease of obtaining.

Serum albumin, genetic susceptibility, and risk of venous thromboembolism

BackgroundPrevious research on the association between serum albumin (ALB) and venous thromboembolism (VTE) has produced inconclusive results. The polygenic risk score is constructed from a set of independent risk variants associated with a disorder, enabling the identification of a larger fraction of the population at comparable or greater disease risk. It is still unknown whether ALB and genetic factors jointly contribute to the incidence of VTE. ObjectivesThe present study aimed to explore ALB, genetic susceptibility, and the risk of VTE. MethodsThe present investigation was an analysis of prospectively collected data from UK Biobank, a population-based, longitudinal cohort. Cox proportional models were used to calculate hazard ratios and 95% CIs for VTE. The Kaplan–Meier curve was utilized to visualize the cumulative risk of VTE according to different serum ALB levels, and the restricted cubic spline model was leveraged to explore the exposure–response relationship among ALB levels and VTE risk. ResultsDuring median follow-up of 13.5 years, 11,502 cases with VTE were diagnosed among 417,113 participants in the UK Biobank. The lower ALB levels were associated with a higher risk for VTE. Individuals with both a high genetic risk and lowest ALB level had the highest risk of VTE (hazard ratio, 3.89; 95% CI, 3.41-4.43), compared with those with low genetic risk and highest ALB level. The positive joint effects of low ALB and polygenic risk score increased the risk of VTE in individuals with high genetic risk. This study excluded non-European patients and primarily focused on the European population, which may limit the generalizability of the findings. ConclusionLow serum ALB levels were linked to an increased risk of VTE, which was in accordance with a linear dose–response relationship. There was a positive additive effect of ALB and genetic susceptibility on the risk of VTE. ALB could serve as a biomarker for predicting the risk of VTE.