Dose Variation Research Articles

Evaluation of deep learning-based scatter correction on a long-axial field-of-view PET scanner.

Long-axial field-of-view (LAFOV) positron emission tomography (PET) systems allow higher sensitivity, with an increased number of detected lines of response induced by a larger angle of acceptance. However this extended angle increases the number of multiple scatters and the scatter contribution within oblique planes. As scattering affects both quality and quantification of the reconstructed image, it is crucial to correct this effect with more accurate methods than the state-of-the-art single scatter simulation (SSS) that can reach its limits with such an extended field-of-view (FOV). In this work, which is an extension of our previous assessment of deep learning-based scatter estimation (DLSE) carried out on a conventional PET system, we aim to evaluate the DLSE method performance on LAFOV total-body PET. The proposed DLSE method based on an convolutional neural network (CNN) U-Net architecture uses emission and attenuation sinograms to estimate scatter sinogram. The network was trained from Monte-Carlo (MC) simulations of XCAT phantoms [ F]-FDG PET acquisitions using a Siemens Biograph Vision Quadra scanner model, with multiple morphologies and dose distributions. We firstly evaluated the method performance on simulated data in both sinogram and image domain by comparing it to the MC ground truth and SSS scatter sinograms. We then tested the method on seven [ F]-FDG and [ F]-PSMA clinical datasets, and compare it to SSS estimations. DLSE showed superior accuracy on phantom data, greater robustness to patient size and dose variations compared to SSS, and better lesion contrast recovery. It also yielded promising clinical results, improving lesion contrasts in [ F]-FDG datasets and performing consistently with [ F]-PSMA datasets despite no training with [ F]-PSMA. LAFOV PET scatter can be accurately estimated from raw data using the proposed DLSE method.

Development of an mPBPK machine learning framework for early target pharmacology assessment of biotherapeutics.

Development of antibodies often begins with the assessment and optimization of their physicochemical properties, and their efficient engagement with the target of interest. Decisions at the early optimization stage are critical for the success of the drug candidate but are constrained due to the limited knowledge of the antibody and target pharmacology. In the present work, we propose a machine learning-based target pharmacology assessment framework that utilizes minimal physiologically based pharmacokinetic (mPBPK) modeling and machine learning (ML) to infer optimal physicochemical properties of antibodies and their targets. We use a mPBPK model previously developed by our group that incorporates a multivariate quantitative relationship between antibodies' physicochemical properties such as molecular weight (MW), size, charge, and in silico + in vitro derived descriptors with their PK properties. In this study, we perform a high-throughput exploration of virtual antibody drug candidates with varying physicochemical properties (binding affinity, charge, etc.), and virtual target candidates with varying characteristics (baseline expression, half-life, etc.) to unravel rules for antibody drug candidate selection that achieve favorable drug-target interaction, which is defined by target occupancy (TO) percentage. We identified that variations in the antibody dose and dosing scheme, target form (soluble or membrane-bound), antibody charge, and site of action had a significant effect on the TO and selection criteria for antibody drug candidates. By unraveling new design rules for antibody drug properties that are dependent on ML-based TO assessment, we deliver a first-in-class ML-based target pharmacology assessment framework toward better understanding of the biology-specific PK and ADME processes of antibody drug candidate proteins and reduce the overall time for drug development.

Baricity of spinal bupivacaine and the incidence of hypotension in non-obstetric surgery: A systematic review.

Bupivacaine is commonly used for spinal anaesthesia. The baricity of bupivacaine (isobaric vs. hyperbaric) may influence the spread, level of the block and the subsequent haemodynamic effects of the spinal anaesthesia. This review considers the available literature on the effect of baricity on the haemodynamic sequelae of spinal anaesthesia with bupivacaine. A literature search was conducted of the MEDLINE and EMBASE databases up to February 2024, following PRISMA guidelines. Randomised controlled trials (RCTs) comparing isobaric and hyperbaric bupivacaine in non-obstetric surgeries were included. Ten studies comprising 586 patients were included. While the literature suggests a trend towards greater incidence of hypotension with hyperbaric bupivacaine, no statistically significant difference was found. Variations in bupivacaine doses and volumes, spinal techniques and definitions of hypotension hindered definitive conclusions. Lower doses relevant to current practice also remain underexplored.

A comparative study of dosage strategies in HIPEC: BSA-based vs fixed dose methods.

832 Background: Peritoneal metastases commonly occur in ovarian, gastric, and colorectal cancers, significantly contributing to patient morbidity and mortality. Hyperthermic Intraperitoneal Chemotherapy (HIPEC) is a promising approach for managing peritoneal surface cancers. This procedure involves cytoreductive surgery to remove visible tumors, followed by the perfusion of heated chemotherapy (41-42°C) directly into the peritoneal cavity. HIPEC addresses the limitation of systemic chemotherapy, which often fails to penetrate the peritoneal cavity effectively. HIPEC dosing may either be a flat-fixed dose or be calculated based on Body Surface Area (BSA). BSA can be determined using three methods: actual BSA (based on weight and height), ideal BSA (based on sex and height), and adjusted BSA (considering lean and fat mass). Methods: A retrospective chart review was conducted on 151 metastatic cancer patients at UVMMC. Patient BMI, weight, and height at diagnosis were collected to calculate BSA values (actual, adjusted, and ideal) for estimating a hypothetical chemotherapy dosage. Statistical analysis using SPSS involved linear mixed models and paired t-tests to compare Mitomycin-C dosages between a fixed dose (40 mg) and a BSA-derived dose (30 mg/m²). Results: The average dosage of Mitomycin-C differed significantly depending on whether the dose was calculated using actual, adjusted, or ideal BSA. The largest discrepancy in dosage was observed between the actual BSA method and the flat-fixed dose, with an average difference of 16 mg. The smallest difference in dose was between the adjusted and ideal BSA methods. When stratifying by BMI, the greatest variation in Mitomycin-C dosage was found among overweight and obese patients (BMI ≥ 25). For these patients, the average dosage difference between the flat fixed dose and the actual BSA dose was 20 mg. In comparison, in patients with a BMI under 18.5 (underweight) the actual BSA dose was comparable to the fixed dose. Conclusions: Different institutions utilize a variety of dosing strategies for the HIPEC procedure. Differences in BSA calculation methods and perfusate volumes (literature values of 2, 3 and 4 L is most common) contribute to the complexity of establishing standardized dosing. The significant dosing variations observed, especially in overweight and obese patients, are of concern, as 70% of the U.S. population has a BMI ≥ 25. Our study demonstrates significant variability in HIPEC chemotherapy dosing, especially among patients with higher BMI. The discrepancy between BSA-based methods and flat-fixed doses may impact treatment efficacy and toxicity. Standardizing dosing approaches is important to ensure consistent therapeutic outcomes and patient safety.

P-1702. Evaluation of Prescribing Practices and Treatment Failure in Obese Patients Diagnosed with Purulent Skin and Soft Tissue Infections in Outpatient Settings Across Michigan

Abstract Background Obesity has been associated with increased risk of antibiotic treatment failure in skin and soft tissue infections (SSTI), however optimal treatment of SSTIs in obesity is unclear with limited data available. The goal of this analysis was to assess prescribing practices and risk factors for treatment failure in obese patients treated for purulent SSTI with oral antibiotics in the outpatient setting. Methods This retrospective, multicenter cohort study evaluated patients treated for purulent SSTI from February 1, 2020 - August 31, 2023, at Michigan outpatient locations within a health system. Patients ≥ 18 years with a body mass index (BMI) ≥ 30 kg/m2 and creatinine clearance ≥ 30 mL/min who received a ≥ 5-day course of oral antibiotics for purulent SSTI were included. Key exclusion criteria were chronic infections, antibiotic treatment within the past 30 days, and those requiring hospital admission. The primary endpoint was to describe prescribing practices. Secondary endpoints included comparing risk factors for treatment failure, revisit, or admission within 30 days between patients with treatment success (Tx-S) and treatment failure (Tx-F). Treatment failure was defined as a recurrence of infection or need for re-treatment within 30 days. Results 200 patients were included (Tx-S, n = 100; Tx-F, n = 100). Baseline characteristics were similar between groups. Patients received 11 different antibiotic regimens with 26 dosing variations. Cephalexin monotherapy was most commonly prescribed (30%); 67% of patients received MRSA-active therapy, however, no patient received linezolid. Treatment failure was similar between those appropriately dosed (46.4%) vs. under-dosed (54.4%) (p=0.256), those who received 5-7 days of therapy (47.1%) vs. 10-14 days (54.4%) (p=0.311), and those who received MRSA-active therapy (52.2%) vs. no MRSA therapy (45.5%) (p=0.367). Patients treated with clindamycin were more likely to experience treatment failure (73.7% vs 47.5%, p=0.030) and had a higher rate of 30-day revisit (68.4% vs 47%, p=0.075). Conclusion Antimicrobial prescribing for outpatient treatment of purulent SSTIs in obese patients was heterogenous across a Michigan health system. Opportunities exist to optimize agent selection, dosing, and duration of therapy in this population. Disclosures All Authors: No reported disclosures

Dose Evaluation and Optimization of Amoxicillin in Children Treated for Lyme Disease.

Amoxicillin is commonly used to treat erythema migrans in the first stage of Lyme disease in children, with a recommended dose of 50 mg/kg/day, administered three times a day (q8h). This model-based simulation study aimed to determine whether splitting the same daily dose into two administrations (q12h) would provide comparable drug exposure. A pharmacokinetic model suitable for a pediatric population (age: 1 month to 18 years, weight: 4-80 kg) was selected through a literature review. Simulations were performed with 15,000 virtual patients receiving 16.67 mg/kg/dose q8h, 25 mg/kg/dose q12h, or other q12h dosing variations. The target therapeutic level was defined by the percentage of time that the unbound drug concentration remained above the minimum inhibitory concentration (% fT > MIC) specific to Borrelia burgdorferi, with MICs of 0.06, 0.25, 1, 2, and 4 mg/L, requiring at least 40% and 50% of time for effective treatment. Probability of target attainment (PTA) was considered acceptable if it exceeded 50%, allowing for comparison of dosing schedules. Results indicated that the 50 mg/kg/day divided q12h regimen provided similar drug exposure to the q8h regimen for MICs below 2 mg/L (PTAs >50%). For a MIC of 2 mg/L, PTA was achieved with a higher dose of 30 mg/kg/dose q12h. However, for a MIC of 4 mg/L, the PTA criterion was not met. These findings suggest that a twice-daily dosing of 25 mg/kg/dose provides comparable bactericidal activity to the thrice-daily regimen for MICs between 0.06 and 1 mg/L. This simplified regimen may improve adherence and treatment implementation in children.

Exploring low-dose glucagon for exercise-induced hypoglycaemia in type 1 diabetes: A randomised controlled trial.

This study was designed to compare the effectiveness of a single subcutaneous (s.c.) glucagon dose versus the same total dose split into a dose before and after and placebo (PBO) in preventing exercise-induced hypoglycaemia in adults with type 1 diabetes (T1D). Twenty-two adults with T1D participated in a randomised, single-blinded, three-arm crossover study. Participants underwent a 60-min bout of moderate-intensity cycle ergometry (~50% HRmax) in fasted state, followed by 2 h of rest. Plasma glucose (PG) concentrations were monitored at 5- and 15-minute intervals. Participants were randomly assigned to receive two separate injections before (t = 0 min) and just after (t = 60 min) exercise: (i) 150 μg s.c. glucagon (G150) before and PBO after; (ii) 75 μg s.c. glucagon (G75*2) before and after; or (iii) PBO before and after. Insulin pump users reduced their basal insulin rate by 50% during cycling. The occurrence of hypoglycaemia did not significantly differ between arms (G150: 7, G75*2: 5 and PBO: 6 events, p = 0.078). Mean PG levels throughout the trial were lower in the PBO arm compared to both glucagon arms (G150: 8.6 ± 2.9, G75*2: 8.9 ± 3.4 and PBO: 7.3 ± 2.6 mmol/L, p = 0.015). Time spent with PG in target range (3.9-10.0 mmol/L) was higher in the PBO arm versus both glucagon arms (G150: 63.9 ± 38.9%, G75*2: 60.0 ± 34.1% and PBO: 82.7 ± 29.6%, p = 0.005), driven by less time above range (G150: 32.9 ± 41.3%, G75*2: 35.9 ± 36.4% and PBO: 13.2 ± 30.2%, p = 0.007). Low-dose native glucagon did not offer any advantages in preventing exercise-induced hypoglycaemia in individuals with T1D, regardless of glucagon dosing variations.

THE EFFECT OF CORN SILK ETHANOL EXTRACT (Zea mays L.) ON THE BLOOD GLUCOSE LEVELS AND HISTOPATHOLOGY OF PANCREAS IN ALLOXAN-INDUCED MICE

Diabetes Mellitus is a metabolic disorder that occurs because pancreatic cells produce insulin in small amounts. The purpose of this study was to determine the effect of giving corn silk (Stigma maydis) to alloxan-induced mice to determine the effective dose of corn silk extract that can reduce blood glucose levels in hyperglycemic mice and histopathological features. This research is an experimental type that uses 24 male white mice as experimental animals, divided into 6 groups and each group consists of 4 mice consisting of negative control, positive control, dose variation 100mg/kgBW, 200mg/kgBW, 400mg/kgBW and the comparison group (Glibenclamide 0.65mg/kgBW). The inducer used was alloxan 150 mg/kg bw. Alloxan induction was carried out for 3 days and then the test preparation was given until the 17th day. Mice's blood was taken through the lateral tail vein to see blood sugar levels. Based on the results of measuring the blood glucose levels of mice on day 17, the average value of blood glucose levels was negative control (86.25 mg/dl), positive control (223 mg/dl), dose 100 mg/kgbb (109.75 mg /dl), dose 200 mg/kgbb (103.5 mg/dl), dose 400 mg/kgbb (92.5 mg/dl), glibenclamide 0.65mg/kgbb (95 mg/dl). Based on the results of statistical data analysis, two-way ANOVA showed significantly different results (p<0.05). The results of reducing blood glucose levels that were closest to the negative control were shown by corn silk extract at a dose of 400 mg/kgbb, while histopathological observations of the pancreas after administration of ethanol extract of corn silk at a dose of 200 mg/kgbb showed the best healing in the islets of Langerhans.

Variations in Octreotide Dosing in Published Reports of Sulfonylurea Toxicity: A Systematic Review, 1988-Present.

Octreotide is commonly used to treat hypoglycemia due to sulfonylurea toxicity, but optimal dosing for this indication is not well defined. We performed a systematic review to identify cases in the medical literature of octreotide use for sulfonylurea poisoning. Literature published on octreotide and sulfonylureas between octreotide's FDA approval on 10/21/1988 and 8/15/2024 was reviewed. Eighty unique patient cases (66 adults/adolescents and 14 pediatric patients) from 61 sources were included in the final analysis. These included 41 octreotide dosing strategies that differed in dose, frequency, and/or route of administration. Subcutaneous dosing, primarily within the range of 50-100 mcg per dose at a frequency of every 6-8h, was the most common regimen in adults while intravenous dosing of 1 mcg/kg was most prevalent in pediatrics. There were no significant differences in duration of therapy or total dose of octreotide in adults with intermittent subcutaneous vs intravenous dosing. Treatment of hypoglycemia and maintenance of euglycemia was similar among all routes of administration. Infusions had similar durations but higher total doses of octreotide. Higher intermittent bolus doses were associated with shorter durations of therapy. Intentional exposures were associated with higher doses and longer duration oftreatment with octreotide. Three adverse reactions to octreotide were reported. Except for 2 cases, all patients survived without any long-term complications. Despite widespread variation in octreotide dosing and administration, our report showed similar efficacy and safety with various octreotide dosing practices.

Pemanfaatan Senyawa Hepatoprotektif dalam Ekstrak Lumut Hati (Marchantia polymorpha) Sebagai Obat Hepatitis Berdasarkan Penurunan SGOT SGPT

Bryophyta plants contain secondary metabolite compounds that can have potential as drugs, such as liverwort (Marchantia polymoprha) which contains secondary metabolite compounds that have hepatoprotective properties against liver damage that have the potential as hepatitis drugs. The purpose of this study was to describe the effect of liverwort extract administration in treating hepatitis. This study used an experimental approach, with a postest only control group design, 16 male white rats (Rattus norvegicus) were grouped into 4 treatments with dose variations of 200 mg / kgBB, 300 mg / kgBB, 400 mg / kgBB, 500 mg / kgBB. Experimental animals were induced with 30% alcohol for 10 days to be exposed to hepatitis, and given treatment for 14 days. Data were analyzed by One Way Anova test, with a significance of 0.05, normally distributed data with a significance of SGOT 0.20 and SGPT 0.81. The results of data analysis showed that the concentration of 500 mg/kgBB extract dose had the strongest effect in reducing SGOT and SGPT enzymes.

Establishment of Local Diagnostic Reference Levels for Head CT Imaging in the Madina Region, Saudi Arabia.

Background: Computed Tomography (CT) is crucial in medical diagnosis, particularly for head examinations. Diagnostic Reference Levels (DRLs) are pivotal in balancing diagnostic efficacy with radiation safety. International organizations such as the International Atomic Energy Agency (IAEA) and the International Commission on Radiological Protection (ICRP) provide guidelines for establishing DRLs, emphasizing their importance in optimizing radiation doses. Aim: This study aimed to establish and standardize DRLs for head CT imaging in institutional and regional settings, emphasizing the need for tailored reference levels specific to each region's practices and standards. Method: Data collection included patient demographics, imaging parameters, and radiation dose indices, namely volume-weighted CT dose index (CTDIvol) and dose-length product (DLP). Statistical analyses were conducted to determine the median and 3rd quartile values for establishing DRLs. The results were compared with national and international benchmarks to assess variations in radiation doses across regions. Results: Demographic profiles detailed gender distributions and ages across hospitals. Imaging parameters exhibited variability in tube voltage, milliampere-seconds (mAs), pitch, scan length, and field of view (FOV). For CTDIvol, the 3rd quartile value was 65.8 mGy (range: 24.8-85.9 mGy), and for DLP, it was 1230.95 mGy·cm (range: 382.3-1189.0 mGy·cm). These values were slightly higher than the national DRLs for Saudi Arabia in 2021 and other international benchmarks, underscoring the need for further optimization and alignment of protocols. Conclusion: Optimizing and standardizing DRLs for head CT imaging is crucial for effectively managing radiation doses while ensuring diagnostic accuracy. Comparison with national and international benchmarks highlighted the importance of tailoring reference levels to regional practices and standards, ensuring patient safety without compromising diagnostic efficacy.

Estimation of effective dose and risk of exposure-induced cancer death, and diagnostic reference level for CT scans in Tabriz, Iran.

This study aimed to estimate the effective dose and the risk of exposure-induced cancer death (REID), as well as to establish diagnostic reference levels (DRLs) for common CT examinations conducted in Tabriz, Iran. The investigation included adult patients undergoing abdomen-pelvis, brain, neck, sinus, and chest CT scans. Patient data, exposure parameters, and radiation dose metrics, such as volume CT dose index (CTDIvol) and dose length product (DLP), were collected and analyzed. The results showed significant variations in radiation dose across different centers for the CT scans. The average effective doses for the different CT scans were 5.65, 1.08, 1.40, 0.46, and 3.68mSv for abdomen-pelvis, brain, neck, sinus, and chest scans, respectively. The REID values ranged from 14 per million (for sinus scans) to 196 per million (for abdomen-pelvis scans). Additionally, the DRL values for CTDIvol were 11.03 (for abdomen-pelvis), 59.52 (for brain), 8.33 (for neck), 17.05 (for sinus), and 7.83mGy (for chest). Our results showed that most of the investigated CT scans had lower effective doses compared to the literature and the REIDs were estimated to be low. Minimizing radiation risk can be achieved by reducing CT exams and keeping doses as low as reasonably achievable. The local DRLs from this study were comparable to previous reports and can serve as benchmarks for setting national and international DRLs, helping healthcare facilities optimize radiation practices and improve patient safety in diagnostic imaging.

Does deformation of immobilization devices impact treatment accuracy in thoracic cancer radiotherapy?

Immobilization devices are essential for maintaining accurate and repeatable patient positioning in radiotherapy. This study aimed to evaluate the setup errors and dosimetric deviation induced by the deformation of immobilization devices in thoracic cancer radiotherapy using CT-linac. A retrospective analysis was conducted on 40 thoracic cancer patients who underwent radiotherapy, using vacuum cushion (VC) and thermoplastic mask (TM) for immobilization. A total of 206 weekly Fan-beam CT (FBCT) images (4-7 per patient) were analyzed to manually delineate immobilization devices and assess their geometric deformations against setup errors. Dosimetric deviations between the clinical plan (CT-plan) and the delivered plan (FBCT-plan) were compared for planning target volume (PTV) and organs at risk (OARs). Correlations between dose variations and setup errors were analyzed in lateral (LAT), longitudinal (LNG), and vertical (VRT) axes. The conformity of the VC (Nup) and TM (Ndown) with the patient in simulation CT exhibited moderate to strong correlations with VRT setup errors (Ndown: r=-0.484, p<0.01;Nup: r=-0.697, p<0.01). However, intra-fraction deformation of immobilization devices (in FBCT) showed no significant correlation with setup errors. In the dosimetric analysis of OARs, lung dose parameters (Dmean, V5, V20) and heart Dmean exhibited a consistent absolute difference with increasing setup errors. Dose variation decreased significantly when errors exceeded 5 mm, particularly in the VRT direction for most PTV indices, with the exception of CI and HI. Spinal cord Dmax variation correlated significantly with setup accuracy along the LNG axis, but not along other axes. The conformity of immobilization devices in simulation CT exhibits a stronger correlation with setup accuracy than the deformation of these devices in intra-fraction FBCT. FBCT is recommended for improving treatment precision through dosimetric assessment and planning adjustments.

Insights of phosphor charging upon exposure to intense illumination

Storage phosphors, known for their delayed emission after charging, have shown great potential for applications in radiation detection, bio-imaging, and medical diagnosis. Despite their promise, the underlying mechanisms governing their charging behavior have not been sufficiently investigated. In this Letter, we elucidate the response of storage phosphors, focusing on the Y3Sc2Ga3O12:Pr3+ composition, when subjected to intense illumination. Our findings reveal that upon exposure to 266 nm ultraviolet or 450 nm blue lasers, the phosphor efficiently captures excitation energy through direct photoionization or upconversion charging (UCC), leading to subsequent trap filling. Thermoluminescence measurements, incorporating variations in irradiation power and dose, confirm that UCC enables an impressive fast charging time of 0.01 s. The unique two-step ionization and nonlinear charging characteristics of UCC are visually demonstrated using a portable laser engraver. Furthermore, we illustrate the versatility of UCC across different phosphor systems, highlighting its potential for advanced information storage applications. This research significantly advances the understanding of phosphor charging dynamics, paving the way for future innovations in luminescent materials.

Dose-dependent interaction of parasites with tiers of host defense predicts "wormholes" that prolong infection at intermediate inoculum sizes.

Immune responses are induced by parasite exposure and can in turn reduce parasite burden. Despite such apparently simple rules of engagement, key drivers of within-host dynamics, including dose-dependence of defense and infection duration, have proven difficult to predict. Here, we model how varied inoculating doses interact with multi-tiered host defenses at a site of inoculation, by confronting barrier, innate, and adaptive tiers with replicating and non-replicating parasites across multiple orders of magnitude of dose. We find that, in general, intermediate parasite doses generate infections of longest duration because they are sufficient in number to breach barrier defenses, but insufficient to strongly induce subsequent tiers of defense. These doses reveal "wormholes" in defense from which parasites might profit: Deviation from the hypothesis of independent action, which postulates that each parasite has an independent probability of establishing infection, may therefore be widespread. Interestingly, our model predicts local maxima of duration at two doses-one for each tier transition. While some empirical evidence is consistent with nonlinear dose-dependencies, testing the predicted dynamics will require finer-scale dose variation than experiments usually incorporate. Our results help explain varied infection establishment and duration among differentially-exposed hosts and elucidate evolutionary pressures that shape both virulence and defense.

International survey on diagnostic reference levels based on clinical indications in plain radiography.

To collect and analyze radiation dose-related data as part of international cooperation; to define diagnostic reference levels (DRL) for 24 X-ray projections in plain radiography (DX) considering anatomical region, clinical task, and procedural technique; and to harmonize the exposure practice across country borders. A multicenter study was performed in Austria, Germany, Italy, and Switzerland in 2022-23 to provide dose-related data. Healthcare facilities were asked to provide processed data from their dose management systems. A 5%-level was used for assessing the statistical significance of dose differences between various groups. Dose-related data from 85 radiographic systems in academic and non-academic, public, and private healthcare facilities were analyzed. Dose-related parameters differed significantly for many projections with different clinical tasks and techniques. Dose-related data of the procedures varied by a maximum factor of 16 for the same system, and median dose values also differed between hospitals by a maximum factor of 31. A fifth of the surveyed systems exhibit doses above more than half of the new DRLs defined in this study. Apart from the three reference procedures, no significant dose differences were observed between X-ray systems of different ages, from different manufacturers, or from different countries. This is the first survey in which exposure practices were investigated in institutions in different central European countries by establishing clinical DRLs for radiography. The observed dose variations could be explained by different reasons, such as non-optimized dose protocols. The new DRLs help to harmonize the exposure practice across country borders. Question What is the exposure practice for plain radiography procedures for which no clinical diagnostic reference levels (DRLs) have been defined? Are there differences between countries? Findings The dose for the same clinical task and technique can vary considerably among institutions but, on average, do not significantly differ between neighboring countries in Europe. Clinical relevance In this international multicenter study, clinical DRLs were defined for 24 plain radiography projections to promote the optimization of the exposure practice, to reduce dose variations among institutions even across national borders, and to strengthen international cooperation among users.

Optimization of Radiation Dose and Effective Dose for CT Pelvis Examinations in Main Hospitals in ALTaif Region

Introduction: CT scan is one of the medical imaging methods that irradiate patients with significant amounts of radiation. These amount of radiation doses must be well estimated if the imaging area is in part containing radiation-sensitive organs such as the pelvic area. Objectives: the objectives of the current study were to assess radiation dose during pelvis and Abdomen CT imaging and estimate the effective dose as well as to propose diagnostic reference level (DRL).Methodology: 200 adult patients irradiated in two major governmental hospital in Taif city, Saudi Arabia, patients’ demographic data from was collected such as weight, height, and age. Scanner specifications and scan parameters for each pelvis examination were recorded in special data collection sheet. Volume CT dose index (CTDIvol and dose length product (DLP) were utilized to estimate the radiation dose and effective dose. Microsoft Excel was used to analyse the data.Main Results: there was variation in scanning parameters among two hospitals under study and this result in variation in effective dose between two hospitals. The average DLP, CTDIvol and effective dose were 368.5, 390.7 mGy-cm,10.2,10.8 mGy and 7, 7.4 mSv for hospital one and two respectively. Conclusion: Based on the third quartile of DLP and CTDIw, the recommended DRL for both hospitals was 405 mGy-cm and 21.75 mGy, respectively. The findings revealed a reduced effective dose value when compared with previous studies.

Verification of daily dose recalculation accuracy for an adaptive radiation therapy monitoring tool in helical tomotherapy for nasopharyngeal carcinoma.

PreciseART, an adaptive radiation therapy (ART) software for helical tomotherapy (HT), was integrated into the Precision treatment planning system (Accuray, Inc., Sunnyvale, CA). It supports automatic monitoring of dose variations to both the target and organs at risk (OARs) throughout the treatment course. This study aims to verify the accuracy of PreciseART's automatic dose recalculation and assess the effectiveness of its notification function. The Radixact X9's kVCT image-guided system (ClearRT) was used to acquire daily images for dose recalculations. We assessed the accuracy of PreciseART's automatic dose recalculation by comparing it with the treatment planning system (TPS) recalculation for the PTV70, spinal cord, and bilateral parotid glands. We also evaluated the efficacy of its notification function by comparing each dose metric for each notification color to TPS recalculation, assessing its role as a trigger tool. In the phantom study, dosimetric analysis indicated no statistically significant differences between TPS and PreciseART recalculations (p>0.05), with dose variations under 1.5%. Similarly, in the patient study (n=10), no significant dosimetric discrepancies were found (p>0.05), with a maximum variation of 2.3%. The notification system performed effectively, providing accurate notifications in accordance with predefined dose criteria. PreciseART's daily dose recalculation demonstrated good agreement with TPS recalculation, and its notification function is effective for identifying dose threshold compliance, supporting its use in clinical ART.

Safety and Effectiveness of Glargine 300 U/ml After Switching from Basal Insulins in Patients with Type1 Diabetes: COMET-T Study.

Appropriate glycemic control is paramount for people with type 1 diabetes (PwT1D) by the effective delivery of exogenous insulin. However, glycemic variability and the risk of severe hypoglycemia must be reliably controlled. COMET-T is a prospective, multicenter, observational study conducted in Germany, Austria, and Switzerland during 2021-2022 to assess the effectiveness and safety of insulin glargine 300 U/ml (Gla-300) after switching from other basal insulins. Out of 135 PwT1D, data of 94 patients were analyzed. The primary endpoint was the change in time in range (TIR) approximately 12 and 24 weeks after switching to Gla-300. Secondary endpoints were: change in HbA1c, fasting plasma glucose (FPG), coefficient of variation (CV%) of plasma glucose, body weight (BW) and insulin dose. Patients had mean age of 48.6 ± 16.5 years, included 39.4% males and had 18.2 ± 15.5 years T1D duration. From baseline (54.3%), TIR changed at week 12 (mean change 0.3% [± 14.3]; p = 0.8383) and at week 24 (+ 4.5% [± 14.9], p = 0.078). At week 24, TIR significantly increased in patients with body mass index > 30kg/m2 (8.4% [± 12.8] p = 0.0057) and patients who previously received insulin detemir (10.5%; [± 12.93]; p = 0.0005). At week 24, there was a significant reduction in the HbA1c value (8.1 ± 0.6% vs. 7.7 ± 0.9%; p < 0.001), a reduction in the CV% of plasma glucose (36.1 ± 12.4% vs. 32.8 ± 9.6%, p = 0.056), and increase in bolus insulin dose (26.5 ± 16.3 vs. 27.9 ± 16.6 U/day; p = 0.042). FPG, BW, and basal insulin doses were not significantly changed. Although switching to Gla-300 in poorly controlled PwT1D did not significantly reduce TIR, it significantly decreased HbA1c values and glycemic variability without changes in BW and basal insulin dose.

Assessing radiation exposure of fingers of PET/CT technologists during 18F-FDG procedures using active extremity dosimeters: a single-center study

Extremity radiation exposure in nuclear medicine is a growing concern because it may surpass the maximum permissible dose of 500 mSv. This study aimed to assess the occupational finger dose received by technologists during the preparation and administration of18F-FDG radiopharmaceuticals in positron emission tomography-computed tomography (PET-CT) whole-body scan procedures. Fifty scans were selected, with one procedure excluded due to a high administered activity. The mean administered activity per scan was 207.2 ± 41.8 MBq, with preparation and administration times averaging 1.44 ± 1.30 min and 0.46 ± 0.31 min, respectively. The technologist's mean total finger dose received during preparation and administration was 253.5 ± 153.3 µSv per procedure. A significant positive correlation was found between the administered activity and occupational dose, with patient's body mass index, preparation time, and administration time also contributing to dose variation. Based on 703 PET-CT procedures conducted in 2022, the estimated occupational finger dose for a technologist was 178.2 mSv annually. This value is well below the International Commission on Radiological Protection's maximum permissible dose of 500 mSv. The findings of this study have a significant impact on extremity dosimetry in nuclear medicine in Sri Lanka, as this is the first study of its kind.