Linear Dose Research Articles

Prediction of Asbestos-Related Diseases (ARDs) and Chrysotile Asbestos Exposure Concentrations in Asbestos-Cement (AC) Manufacturing Factories in Zimbabwe.

The use of historical asbestos measurement data in occupational exposure assessment is essential as it allows more quantitative analysis of possible exposure response relationships in asbestos-related disease (ARD) occurrence. The aim of this study was to predict possible ARDs, namely lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis, in two chrysotile asbestos cement (AC) manufacturing factories. Prediction of ARDs was done using a specific designed job-exposure matrix for airborne chrysotile asbestos fibre concentrations obtained from the Harare and Bulawayo AC factories and through application of OSHA's linear dose effect model in which ARDs were estimated through extrapolation at 1, 10, 20, and 25 years of exposure. The results show that more cancer and asbestosis cases are likely to be experienced among those exposed before 2008 as exposure levels and subsequently cumulative exposure were generally much higher than those experienced after 2008. After a possible exposure period of 25 years, overall cancer cases predicted in the Harare factory were 325 cases per 100,000 workers, while for the Bulawayo factory, 347 cancer cases per 100,000 workers exposed may be experienced. Possible high numbers of ARDs are likely to be associated with specific tasks/job titles, e.g., saw cutting, kollergang, fettling table, ground hard waste, and possibly pipe-making operations, as cumulative exposures, though lower than reported in other studies, may present higher risk of health impairment. The study gives insights into possible ARDs, namely lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis, that may be anticipated at various cumulative exposures over 1, 10, 20, and 25 years of exposure in AC manufacturing factories in Zimbabwe. Additionally, results from the study can also form a basis for more in-depth assessment of asbestos cancer morbidity studies in the AC manufacturing industries.

Sugar-sweetened beverage consumption and weight gain in children and adults: a systematic review and meta-analysis of prospective cohort studies and randomized controlled trials

BackgroundSugar-sweetened beverages (SSBs) have been implicated in fueling the obesity epidemic. ObjectivesThis study aimed to update a synthesis of the evidence on SSBs and weight gain in children and adults. MethodsMEDLINE, Embase, and Cochrane databases were searched through September 8, 2022, for prospective cohort studies and randomized controlled trials (RCTs) that evaluated intake of SSBs in relation to BMI and body weight in children and adults, respectively. Eligible interventions were compared against a noncaloric control. Study-level estimates were pooled using random-effects meta-analysis and presented as β-coefficients with 95% CIs for cohorts and weighted mean differences (MDs) with 95% CIs for RCTs. ResultsWe identified 85 articles including 48 in children (40 cohorts, n = 91,713; 8 RCTs, n = 2783) and 37 in adults (21 cohorts, n = 448,661; 16 RCTs, n = 1343). Among cohort studies, each serving/day increase in SSB intake was associated with a 0.07-kg/m2 (95% CI: 0.04 kg/m2, 0.10 kg/m2) higher BMI in children and a 0.42-kg (95% CI: 0.26 kg, 0.58 kg) higher body weight in adults. RCTs in children indicated less BMI gain with SSB reduction interventions compared with control (MD: −0.21 kg/m2; 95% CI: −0.40 kg/m2, −0.01 kg/m2). In adults, randomization to addition of SSBs to the diet led to greater body weight gain (MD: 0.83 kg; 95% CI: 0.47 kg, 1.19 kg), and subtraction of SSBs led to weight loss (MD: −0.49 kg; 95% CI: −0.66 kg, −0.32 kg) compared with the control groups. A positive linear dose–response association between SSB consumption and weight gain was found in all outcomes assessed. ConclusionsOur updated systematic review and meta-analysis expands on prior evidence to confirm that SSB consumption promotes higher BMI and body weight in both children and adults, underscoring the importance of dietary guidance and public policy strategies to limit intake. This meta-analysis was registered at the International Prospective Register of Systematic Reviews as CRD42020209915.

Changes in plasma and milk choline metabolite concentrations in response to the provision of various rumen-protected choline prototypes in lactating dairy cows.

Choline feeding in the form of rumen-protected choline (RPC) has been shown to increase milk production and improve measures of metabolic health (e.g., liver triglyceride) in dairy cows. The objective was to characterize changes in plasma and milk choline and choline metabolite concentrations, including microbial-derived trimethylamine N-oxide (TMAO), in response to increasing ruminal spot-doses, different types of RPC, and ruminal stability of RPC in lactating cows. For experiment 1, 12 mid-lactation (121 ± 16.3 d in milk) Holstein cows were balanced by total plasma choline concentrations and milk yields. Cows were assigned to 1 of 3 lipid-encapsulated RPC products (main plots): prototypes P1, P2, and P3 (containing 59, 56, and 30% choline chloride, respectively). Within each main plot, cows were assigned to a sequence of doses in a 4 × 4 Latin square design: 0, 18, 36, or 54 g of choline chloride. Treatments were preconditioned with ground corn and administered as a single ruminal bolus once per experimental period 1 h postfeeding of a total mixed ration. For experiment 2, we compared a control (0 g of choline chloride) versus P2, and P4 and P5 (60 and 62% choline chloride, respectively) in a repeated 4 × 4 Latin square design. Experiment 2 followed a similar design as experiment 1 with modifications: 12 late-lactation (228 ± 7.10 d in milk) Holstein cows were used; treatments were administered as part of a premeal; and cows received a daily allowance of a total mixed ration as equal provisions every 4 h within 24 h before and after treatment. For both experiments, plasma and milk samples were collected for choline and choline metabolite quantification. Data were analyzed using a mixed model including fixed effects of treatment, period, and time. Contrast statements were used to test for linearity of dose and differences between prototypes for experiment 1 and 2, respectively. Plasma and milk TMAO concentrations increased with RPC dose (peak by h). Milk choline and betaine yields increased with RPC dose in a quadratic manner; albeit, dependent upon RPC type. Milk phosphocholine (PCho) and glycerophosphorylcholine (GPC) yields changed by select RPC dose (experiment 1), however Met, PCho, GPC, phosphatidylcholine, and total choline concentrations in milk, and plasma Met and sphingomyelin concentrations were not responsive. We conclude that plasma or milk choline, betaine, and TMAO concentrations are responsive to RPC type, dose, and stage of lactation evaluated.

Characterization of a commercial EPID-based in-vivo dosimetry and its feasibility and implementation for treatment verification in Malaysia

Abstract Introduction: In vivo dosimetry verification is currently a necessity in radiotherapy centres in Europe countries as one of the tools for patient-specific QA, and now its demand is currently rising in developed countries, such as Malaysia. The aim of this study is to characterize commercial EPID-based dosimetry and its implementation for radiotherapy treatment verification in Malaysia. Materials and Methods: In this work, the sensitivity and performance of a commercially available in vivo dosimetry system, EPIgray® (DOSIsoft, Cachan, France), were qualitatively evaluated prior to its use at our centre. EPIgray response to dose linearity, field size, off-axis, position, and angle dependency tests were performed against TPS calculated dose for 6 MV and 10 MV photon beams. Relative deviations of the total dose were evaluated at isocentre and different depths in the water. EPIgray measured dose was validated by using IMRT and VMAT prostate plan. All calculation points were at the beam isocentre and at points suggested by TG-119 with accepted tolerance of ±10% dose threshold. Results: EPIgray reported good agreement for linearity, field size, off-axis, and position dependency with TPS dose, being within 5% tolerance for both energy ranges. The average deviation was less than ±2% and ±7% in 6 MV and 10 MV photon beams, respectively, for the angle dependency test. A clinical evaluation performed for the IMRT prostate plan gave average agreement within ±3% at the plan isocentre for both energies. While for the VMAT plan, 95% and 100% of all points created lie below ±5% for 6 MV and 10 MV photon beam energy, respectively. Conclusion: In summary, based on the results of preliminary characterization, EPID-based dosimetry is believed as an important tool and beneficial to be implemented for IMRT/VMAT plans verification in Malaysia, especially for in vivo verification, alongside existing pre-treatment verification.

Increased relative biological effectiveness and periventricular radiosensitivity in proton therapy of glioma patients

PurposeCurrently, there is an intense debate on variations in intra-cerebral radiosensitivity and relative biological effectiveness (RBE) in proton therapy of primary brain tumours. Here, both effects were retrospectively investigated using late radiation-induced brain injuries (RIBI) observed in follow-up after proton therapy of patients with diagnosed glioma. MethodsIn total, 42 WHO grade 2–3 glioma patients out of a consecutive patient cohort having received (adjuvant) proton radio(chemo)therapy between 2014 and 2017 were eligible for analysis. RIBI lesions (symptomatic or clinically asymptomatic) were diagnosed and delineated on contrast-enhanced T1-weighted magnetic resonance imaging scans obtained in the first two years of follow-up. Correlation of RIBI location and occurrence with dose (D), proton dose-averaged linear energy transfer (LET) and variable RBE dose parameters were tested in voxel- and in patient-wise logistic regression analyses. Additionally, anatomical and clinical parameters were considered. Model performance was estimated through cross-validated area-under-the-curve (AUC) values. ResultsIn total, 64 RIBI lesions were diagnosed in 21 patients. The median time between start of proton radio(chemo)therapy and RIBI appearance was 10.2 months. Median distances of the RIBI volume centres to the cerebral ventricles and to the clinical target volume border were 2.1 mm and 1.3 mm, respectively. In voxel-wise regression, the multivariable model with D, D × LET and periventricular region (PVR) revealed the highest AUC of 0.90 (95 % confidence interval: 0.89–0.91) while the corresponding model without D × LET revealed a value of 0.84 (0.83–0.86). In patient-level analysis, the equivalent uniform dose (EUD11, a = 11) in the PVR using a variable RBE was the most prominent predictor for RIBI with an AUC of 0.63 (0.32–0.90). ConclusionsIn this glioma cohort, an increased radiosensitivity within the PVR was observed as well as a spatial correlation of RIBI with an increased RBE. Both need to be considered when delivering radio(chemo)therapy using proton beams.

Fumonisin B Series Mycotoxins' Dose Dependent Effects on the Porcine Hepatic and Pulmonary Phospholipidome.

Male weaned piglets n = 6/group were fed Fumonisin B1+2+3 (FBs) mycotoxins at 0, 15, or 30 mg/kg diet for 3 weeks to assess the fatty acid (FA) composition of membrane lipid classes, lipid peroxidation, and histomorphological changes in the liver and lung. Growth performance and lipid peroxidation were unaltered, but histomorphological lesion scores increased in the liver. Linear dose-response was detected in liver phosphatidylcholines for C16:1n7, C18:1n9, and total monounsaturation and in lungs for C22:6n3, total n-3 and n-3:n-6, in pulmonary phosphatidylserines C20:0 and C24:0. Alterations associated with the highest FBs dose were detected in sphingomyelins (liver: total saturation ↓, total monounsaturation ↑), phosphatidylcholines (liver: total n-6 ↓, n-6:n-3 ↑; in lungs: total monounsaturation ↑, total polyunsaturation ↑), phosphatidylethanolamines (liver: total n-3 ↓; in lungs: total monounsaturation ↑ and n-6:n-3 ↑), phosphatidylserines (liver: n-6:n-3 ↑; in lungs: total saturation ↓, total polyunsatuartion ↑, and total n-6 and its ratio to n-3 ↑), and phosphatidylinositol (n-6:n-3 ↑; lungs: C22:1n9 ↑, C22:6n3 ↓, total saturation ↓, total monounsaturaion ↑). In conclusion, FBs exposures neither impaired growth nor induced substantial lipid peroxidation, but hepatotoxicity was proven with histopathological alterations at the applied exposure period and doses. FA results imply an enzymatic disturbance in FA metabolism, agreeing with earlier findings in rats.

Investigation on the long-term storage condition of the PVA-GTA-I gel dosimeter

Radiochromic gel materials are of special interest for application to three-dimensional dosimetry, particularly in clinical settings of radiation therapy. The authors previously developed a radiochromic gel complex composed of polyvinyl alcohol (PVA), glutaraldehyde (GTA) and iodide (I) which is abbreviated hereafter as the “PVA-GTA-I gel”. While showing promising features such as linear dose response and good reusability, the PVA-GTA-I gel has suffered from natural coloration due to auto-oxidation during the long-term storage for a week or more. To find a practical solution for this issue, we examined the color intensity changes of the PVA-GTA-I gel for up to nearly two months under seven storage conditions with the variables of temperature (5.5 °C or 20 °C), air flow (in air or vacuum), and lighting (under fluorescent light or in darkness). The results showed that the condition setting of the samples stored in a vacuum case at 20 °C in darkness could significantly prevent the color intensity change of the PVA-GTA-I gel during long-term storage. This finding could give a certain practical advantage to the PVA-GTA-I gel dosimeter for future applications.

Thermoluminescence dosimetry properties of calcium and dysprosium activated zinc gallate nanocrystals

The ZnGa2O4:Ca and ZnGa2O4:Dy nanocrystals are synthesized by sol-gel method and their thermoluminescence and dosimetric characteristics have been investigated. The main TL glow peaks of ZnGa2O4:Ca and ZnGa2O4:Dy are observed at about 180 °C and 200 °C, respectively. The molar ratio of both dopants (Ca and Dy) was varied from 1 mol% to 9 mol%. It was found that the optimum concentration of both dopants is about 2 mol%, where the sensitivity of ZnGa2O4:Dy nano particles is 1.5 times higher than ZnGa2O4:Ca samples. Moreover, the linearity dose response of dosimetric peak follows a good linearity up to 5 kGy in both activated nanocrystals. The results of presented nanophosphors suggest the good candidates towards dosimetric applications.

Association between low-fat diet and liver cancer risk in 98,455 participants: Results from a prospective study.

Low-fat diet reduces the risk of chronic metabolic diseases such as obesity and diabetes, which exhibit overlapping mechanisms with liver cancer. However, the association between low-fat diet and liver cancer risk remains unclear. To investigate whether adherence to low-fat diet is associated with a reduced risk of liver cancer in a prospective study. Data of participants in this study were collected from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. A low-fat diet score was calculated to reflect adherence to low-fat dietary pattern, with higher scores indicating greater adherence. Cox regression was used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for liver cancer incidence with adjustment for potential covariates. Restricted cubic spline model was used to characterize liver cancer risk across the full range of the low-fat diet score. Prespecified subgroup analyses were used to identify potential impact modifiers. Sensitivity analyses were performed to test the robustness of this association. A total of 98,455 participants were included in the present analysis. The mean (standard deviation) age, low-fat diet score, and follow-up time were 65.52 (5.73) years, 14.99 (6.27) points, and 8.86 (1.90) years, respectively. During 872639.5 person-years of follow-up, 91 liver cancers occurred, with an overall incidence rate of 0.01 cases per 100 person-years. In the fully adjusted Cox model, the highest versus the lowest quartile of low-fat diet score was found to be associated with a reduced risk of liver cancer (HR Q4 vs. Q1: 0.458; 95% CI: 0.218, 0.964; P = 0.035 for trend), which remained associated through a series of sensitivity analyses. The restricted cubic spline model showed a linear dose-response association between low-fat diet score and liver cancer incidence (p = 0.482 for non-linear). Subgroup analyses did not show significant interaction between low-fat diet score and potential impact modifiers in the incidence of liver cancer. In this study, low-fat diet score is associated with reduced liver cancer risk in the US population, indicating that adherence to low-fat diet may be helpful for liver cancer prevention. Future studies should validate our findings in other populations.

Construction and pre-evaluation of an in-house cylindrical ionization chamber fabricated from locally available materials

Abstract Introduction: The objectives of this study were to construct a very robust in-house cylindrical ionization chamber from locally available materials to minimize cost, and to assess its suitability for use in a clinical setting. Materials and Methods: The entire body of the constructed IC was composed of Perspex (PMMA). Other components of the IC were made from locally available materials, such as paper and discarded items. The in-house IC was made waterproof by passing the triaxial cable connecting its various electrodes through a plastic tube which once served as a drainage tube of a urine bag. This connection was made such that the chamber was vented to the environment. The completed in-house IC was evaluated for: polarity effect, ion recombination, ion collection efficiency, stability, dose linearity, stem effect, leakage current, angular, dose rate and energy dependences. Results: Although the pre-evaluation results confirmed that the in-house IC satisfied the stipulated international standards for ICs, there was a need to enhance the stem effect and leakage current characteristics of the IC. The in-house IC was found to have an absorbed dose to water calibration coefficient of 4.475 x 107 Gy/C (uncertainty of 1.6%) for cobalt 60 through a cross-calibration with a commercial 0.6 cc cylindrical IC with traceability to the Germany National Dosimetry Laboratory. Using a Jaffé diagram, the in-house IC was also found to have a recombination correction factor of 1.0078 when operated at the calibration voltage of + 400 V. In terms of beam quality correction factors for megavoltage beams, the in-house IC was found to exhibit characteristics similar to those of Scanditronix-Wellhofer IC 70 Farmer type IC. Conclusion: The constructed in-house Farmer-type IC was able to meet all the recommended characteristics for an IC, and therefore, the in-house IC is suitable for beam output calibration in external beam radiotherapy.

Photoluminescence and dosimetric properties of Tb-doped Na3AlF6 ceramics

Tb-doped Na3AlF6 ceramics with different concentrations were synthesized by the spark plasma sintering (SPS) method, and photoluminescence (PL), optically-stimulated luminescence (OSL), and thermally-stimulated luminescence (TSL) properties were investigated. In the PL property, Tb-doped Na3AlF6 ceramics showed emission peaks at 420, 440, 460, 480, 550, 580, and 620 nm and the decay time constants due to 4f–4f transitions of Tb3+. Under the stimulation at 750 nm, Tb-doped Na3AlF6 ceramics showed OSL peaks due to 4f–4f transitions of Tb3+. The TSL glow peaks were detected at 120, 200, and 280 °C in Tb-doped Na3AlF6 ceramics. The 0.1 and 1% Tb-doped Na3AlF6 ceramics had linear dose response over the dose range of 0.01–1000 mGy.

Data-driven, client-centric applied behavior analysis treatment-dose optimization improves functional outcomes

BackgroundWith increasing numbers of individuals diagnosed with autism spectrum disorder (ASD) and with affirmation of applied behavior analysis (ABA) as an evidence-based standard of care for ASD, there has been a proliferation of agencies offering ABA services over the last several decades. Disagreement exists among ABA providers and health plans that reimburse those providers on the optimal number of hours of ABA services that should be reimbursed. This study aims to understand whether children who receive more hours of ABA therapy achieve better outcomes and to evaluate the impact of the COVID-19-induced shift to telehealth clinical supervision on outcomes.MethodsA retrospective cohort analysis was performed using data from the Vineland 3 Comprehensive Interview Form to assess function throughout ABA treatment. Paired sample t tests, independent sample t tests, Cohen’s D, and Pearson correlations were used to determine relationships between Vineland scores and input variables including hours of service and modality of supervision (in-person vs. telehealth).ResultsWhile statistically and clinically significant improvements in function were observed, children appear to have improved outcomes independent of the number of hours of service received. There were also no significant associations between modality of supervision and Vineland standard scores.ConclusionsThese findings challenge prior research that demonstrated a linear dose–response relationship. By tailoring treatment dosage to the individual client’s needs, providers may be able to better maximize functional progress of the client, to preserve family time, and to utilize health plan dollars more efficiently.

Neutron reactor dosimetry monitoring by optical, nanostructural, and morphological changes of NiO thin films

The effect of mixed neutron-gamma (n/γ) irradiation on microstructural, morphological, and optical properties of nickel oxide (NiO) thin films has been studied using UV–visible spectrophotometry, photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). (NiO) thin films were irradiated in a Minerve reactor core at a doses range between 100 and 1000 Gy. The fast neutron dose, mainly due to elastic neutron scattering interactions in the range of 1–5 MeV, represents around 70% of the total irradiation dose. The results obtained show that the irradiation of the NiO thin films lead to significant changes in the optical properties, in the structure and in the morphology of the materials. The optical analysis shows visible range activation, which resulted in an increase in the absorbance of the band, centered around 645 nm. Otherwise, the integrated area of the band presents a linear dose response from 85 to 115 at dose ranging from 0 to 500 Gy. Furthermore, the band gap energy of the samples was linearly decreased from 3.52 eV to 3.44 eV by increasing the dose from 100 to 500 Gy, reaching 3.62 eV at 1000 Gy of irradiation n/γ dose. Urbach energy exhibited the same linear behavior, hence increasing from 372 to 400 meV. The variability of the integrated area, band gap energy and Urbach energy did not exceed 3% during 25 days. XRD analysis demonstrates that the crystallite size and the peak intensity for each preferred orientation planes (111) change with neutron-gamma radiation dose. The lattice parameter of preferential orientation (111) plane from rises linearly from 4.171 to 4.199 Å ± 0.0021 Å. Its variability is low, not exceeding 2%. SEM picture of irradiated NiO thin films shows the pore formation whose distribution increases with a dose level up to 500 Gy. Overall, the obtained results suggest that NiO thin films could considered as new alternative mean in neutron dosimetry application in nuclear reactor.

Synthesis and thermoluminescence studies of beta particle irradiated CaAl2O4

Calcium Aluminate nanoparticles were prepared by the successful sol-gel route adopting hydrolysis of organometallic precursors. The crystalline properties, morphology, sample composition, and nanostructure of the as-synthesized samples were investigated by X-ray diffraction (XRD), Photoluminescence (PL), and Fourier transformer infrared (FTIR). Careful XRD analysis reveals the generation of orthorhombic CaAl2O4 with 54.23 nm crystalline size. The prepared sample was irradiated with beta particles for different doses from 0.11 Gy to 330 Gy. The Thermoluminescence (TL) glow curves of the samples were deconvoluted using newly designed TL software. The deconvolution displayed 14 overlapping glow peaks composing the glow curves. The prepared samples have shown a linear beta dose response in the range of 11 Gy–330 Gy. The minimum detectable dose of the prepared samples was 262 μGy. The sensitivity and reproducibility of the TL response of the prepared samples were studied and were found to be very good.

Sex-Based Differences in the Association between Serum Copper and Kidney Function: Evidence from NHANES 2011-2016.

Epidemiological evidence on the relationship between copper (Cu) and kidney function is rare, and few studies examine the sex differences in this association. We aimed to explore the overall and sex-based relationship between exposure to Cu and biomarkers of kidney function among 4331 participants of the 2011-2016 National Health and Nutrition Examination Survey. Multiple linear regression models were fitted to examine the overall and sex-specific associations between serum Cu and the kidney function indicator-estimated glomerular filtration rate (eGFR) and urinary albumin-creatinine ratio (UACR). Restricted cubic spline models (RCS) stratified by sex were performed to explore the sex-based dose-response associations. Serum Cu in the highest quartile was associated with higher levels of UACR (β = 0.203, 95% CI: 0.100 to 0.306) among overall participants. In males, there was an association of the highest Cu quartile with decreased eGFR (β = -0.023, 95% CI: -0.042 to -0.003) and increased UACR (β = 0.349, 95% CI: 0.171 to 0.527); serum Cu levels also demonstrated a negative nonlinear dose-response association with eGFR and a positive linear dose-response association with UACR in males, whereas females showed a marginally significant nonlinear positive association of eGFR with serum Cu levels. In conclusion, there were sex-specific and dose-response relationships between serum Cu and kidney function indicators. Further prospective and mechanistic studies are warranted.

Evaluation of the feasibility of cardiac gating for SBRT of ventricular tachycardia based on real-time ECG signal acquisition.

To investigate the feasibility of cardiac synchronized gating in stereotactic body radiation therapy (SBRT) of ventricular tachycardia (VT) using a real-time electrocardiogram (ECG) signal acquisition. Stability of beam characteristics during simulated ECG gating was examined by developing a microcontroller interface to a Varian Clinac iX linear accelerator allowing gating at frequencies and duty cycles relevant to cardiac rhythm. Delivery accuracy was evaluated by measuring dose linearity with an ionization chamber, and flatness and symmetry with a two-dimensional detector array, for different gating windows within typical human cardiac cycle periods. To establish a practical method of gating based on actual ECG signals, an AD8232 Heart Monitor board was used to acquire the ECG signal and synchronize the beam delivery. Real-time cardiac gated delivery measurements were performed for a single 10×10cm2 field and for a VT-SBRT plan using intensity-modulated radiation therapy (IMRT). Dose per monitor unit (MU) values were found to be linear within most gating windows investigated with maximum differences relative to non-gated delivery of <2% for gating windows ≥200ms and for >10MUs. Beam profiles for both gated and non-gated modes were also found to agree with maximum differences of 0.5% relative to central axis dose for all sets of beam-on/beam-off combinations. Comparison of dose distributions for intensity-modulated SBRT plans between non-gating and cardiac gating modes provided a gamma passing rate of 97.2% for a 2% 2mm tolerance. Beam output is stable with respect to linearity, flatness, and symmetry for gating windows within cardiac cycle periods. Agreement between dose distributions for VT-SBRT using IMRT in non-gated and cardiac cycle gated delivery modes shows that the proposed methodology is feasible. Technically, gating for delivery of SBRT for VT is possible with regard to beam stability.

Fatty Liver Is an Independent Risk Factor for Elevated Intraocular Pressure.

Elevated intraocular pressure (EIOP) is a major risk factor for glaucoma. Both EIOP and fatty liver share metabolic risk factors, which implies a possible link between EIOP and fatty liver. We aimed to determine the association of fatty liver with EIOP and estimate the effect of fatty liver on EIOP directly and indirectly through insulin resistance. Data from 16,240 adults who underwent health examinations at a single center were analyzed. Multiple logistic regression analyses revealed that fully adjusted odds ratio (OR) and 95% confidence interval (CI) for EIOP in the fatty liver group compared to the non-fatty liver group were 1.36 and 1.08-1.71. Alcoholic liver disease was associated with EIOP in subgroup analysis (OR = 1.80, 95% CI: 1.27-2.56). There was a linear dose-response relationship between EIOP and the severity of fatty liver. Mediation analysis revealed that the total effect of fatty liver on intraocular pressure was 0.90 (0.81-0.99), with a direct effect of 0.81 (0.71-0.90) and an indirect effect of 0.09 (0.06-0.11) through insulin resistance. Fatty liver is independently associated with EIOP. It primarily has a direct effect on intraocular pressure. This suggests that evaluation of EIOP should be considered in patients with fatty liver.

A Novel Micro-Dosimetry Technique to Advance Small-Field Radiation Therapy Treatment

<h3>Purpose/Objective(s)</h3> Optical fiber-based scintillating dosimetry is the most recent promising technique in modern radiation therapy owing to the miniature size, high sensitivity, flat energy dependency, etc. Despite several advantages, the major issue of using scintillating dosimeters is the Cerenkov contamination and predominantly requires extra measurement corrections. Therefore, this work highlighted a novel micro-dosimetry technique to ensure Cerenkov-free measurement and quality treatment. <h3>Materials/Methods</h3> A micro-dosimetry technique was proposed based on a novel infrared inorganic scintillator detector (IR-ISD). The detector essentially consists of a micro-scintillating head with a sensitive volume of 1.5 × 10⁻⁶ mm³ integrated with optical fiber. The proposed system was evaluated under the 6/15 MV LINAC beam as well as 320KV- ¹⁹²Ir Brachytherapy (BT) source used in patient treatment. Overall measurements were performed using IBA^TM water tank phantoms by following TRS-398 protocol for radiotherapy and TG43U1 recommendations for BT. Cerenkov measurements were performed for different small fields from 0.5 × 0.5 cm² to 10 × 10cm² under LINAC as well as till 0.25cm distance from the BT source. In addition, several dosimetric parameters such as PDD, beam profiling, field output factor, dose linearity, dose rate linearity, repeatability, and scintillation stability were investigated to verify the device's performance. Finally, a comparative study is shown using Monte-Carlo (MC) simulation, reference dosimeters (microDiamond and film), and data from recent literature. <h3>Results</h3> This study highlighted a complete removal of the Cerenkov effect using a point-like miniatured detector, especially for small-field beam treatment. Measurements demonstrated that IR-ISD has acceptable behavior with dose rate variability (maximum standard deviation ∼ 0.15%) for the dose rate of 20 cGy/s to 1000 cGy/s. An entire linear response (R²=1) was obtained with the dose delivered in the range of 4cGy to 1000 cGy, independently of the field size selected from 4 × 4 cm² to 0.5 × 0.5 cm². Perfect repeatability (0.15 % variation from average) and day-to-day reproducibility (0.25% variation) was observed. PDD profiles present accurate dose distribution with almost identical behavior to the reference dosimeter and simulation results (<1.5% variation). The small field of 0.5 × 0.5 cm² profile (inline & crossline) has been measured to characterize convolution effect and source penumbra. Eventually, in BT, a comparison with MC simulations shows that measurement agrees within 0.65% till 0.25 cm source-to-detector distance. <h3>Conclusion</h3> Unlike recent PSD systems (e.g., exradin W1/W2), the proposed micro-dosimetry system requires no Cerenkov corrections and showed efficient performance for several dosimetric measurements. Therefore, the novel IR-ISD detector could be a quality tool for small-field dose verification (e.g., in SRS, SBRT, IMRT, etc.), intra-beam characterizations, and BT treatment plan.

Surface Dose and Skin Toxicity in Low-Magnetic Field MR-Linac

<h3>Purpose/Objective(s)</h3> Radiation induced skin toxicity is a common side effect that results in poor patient satisfaction and unplanned treatment breaks thus prolonging the overall treatment time with poor outcome. It is hypothesized that treatments on low-field MR-Linac will not produce higher surface dose which is investigated in this study. <h3>Materials/Methods</h3> Skin dose has always been an area of active clinical interest that is dependent on many parameters including beam energy, field size, material thickness and atomic number in the beam, material distance from surface, source to surface distance, beam angle (obliquity factor), concomitant chemotherapy etc. Along with these parameters, magnetic field is also a critical parameter that affect surface dose. With the development of the MRL system focus has shifted towards Lawrence force giving rise to electron return effect along with other treatment parameters affecting the skin dose. A Linac equipped with 6MV FFF photons with 90 cm source to axis distance is used. A Markus parallel plate ionization chamber is used in a solid water phantom with proper correction factor to investigate surface and buildup dose with six different gantry angles 15⁰ apart gantry (equivalent of standard Linac 0⁰, 15⁰, 30⁰, 45⁰, 60⁰, and 75⁰) for field sizes of 1.66 × 1.66 cm² (small), 9.96 × 9.9 cm² (reference) and 24.1 × 24.1 cm² (maximum). Measurements were made with increasing buildup thickness in steps of 1 mm to 20 mm of solid water in 0.35 T magnetic field. <h3>Results</h3> In traditional linear accelerators surface dose is 30-40% for a 6MV photon beam, without any modifier. This value increases significantly with beam angle. In MR-Linac, surface dose is relatively low, 12.6%, 14.9% and 16.7% for small, reference and maximum fields at zero-degree gantry angle, respectively. These values are 12% to 2% higher (at 0⁰ and 75⁰ respectively) for maximum field size compared to the reference field size. For lower field sizes minimum variation of 10% was observed at 75° for reference field size. The surface dose increases with increasing radiation field size but magnitude is still lower as the case with traditional lilacs. Table 1 shows the surface dose with field size and gantry angles. <h3>Conclusion</h3> Surface dose in low-field magnetic environment is relatively lower than traditional accelerators. It is concluded that low-field MR-Linac system may not add any additional skin toxicity compared to conventional Linac. However, the effect may be different for high-field MR-Linac system, and appropriate skin evaluation needs to be performed to differentiate between radiation induced toxicity specially for the oblique beams versus RF-thermal effect.

Moderate-to-Severe Malnutrition Identified by the Controlling Nutritional Status (CONUT) Score Is Significantly Associated with Treatment Failure of Periprosthetic Joint Infection.

The prevalence and role of malnutrition in periprosthetic joint infection (PJI) remain unclear. This study aimed to use measurable nutritional screening tools to assess the prevalence of malnutrition in PJI patients during two-stage exchange arthroplasty and to explore the association between malnutrition and treatment failure. Our study retrospectively included 183 PJI cases who underwent 1st stage exchange arthroplasty and had available nutritional parameters, of which 167 proceeded with 2nd stage reimplantation. The recently proposed Musculoskeletal Infection Society (MSIS) Outcome Reporting Tool was used to determine clinical outcomes. The Controlling Nutritional Status (CONUT), Nutritional Risk Index (NRI), and Naples Prognostic Score (NPS) were used to identify malnutrition at 1st and 2nd stage exchange, respectively. Multivariate logistic regression analyses were performed to determine the association between malnutrition and treatment failure. Restricted cubic spline models were further used to explore the dose–response association. Additionally, risk factors for moderate-to-severe malnutrition were evaluated. Malnourished patients identified by CONUT, NPS, and NRI accounted for 48.1% (88/183), 98.9% (181/183), and 55.7% (102/183) of patients at 1st stage, and 9.0% (15/167), 41.9% (70/167), and 43.1% (72/167) at 2nd stage, indicating a significant improvement in nutritional status. We found that poorer nutritional status was a predictor of treatment failure, with CONUT performing best as a predictive tool. Moderate-to-severe malnutrition at 1st stage identified by CONUT was significantly related to treatment failure directly caused by PJI (odds ratio [OR] = 5.86), while the OR was raised to 12.15 at 2nd stage (OR = 12.15). The linear dose–response associations between them were also confirmed (P for nonlinearity at both 1st and 2nd stage > 0.05). As for total treatment failure, moderate-to-severe malnutrition as determined by CONUT was associated with a 1.96-fold and 8.99-fold elevated risk at the 1st and 2nd stages, respectively. Age ≥ 68 years (OR = 5.35) and an increased number of previous surgeries (OR = 2.04) may be risk factors for moderate-to-severe malnutrition. Overall, the prevalence of malnutrition in PJI patients is very high. Given the strong association between moderate-to-severe malnutrition identified by CONUT and PJI treatment failure, COUNT could be a promising tool to evaluate the nutritional status of PJI patients to optimize treatment outcomes.