Dose Measurements Research Articles

A Million Person Study Innovation: Evaluating Cognitive Impairment and other Morbidity Outcomes from Chronic Radiation Exposure Through Linkages with the Centers for Medicaid and Medicare Services Assessment and Claims Data.

The study of One Million U.S. Radiation Workers and Veterans, the Million Person Study (MPS), examines the health consequences, both cancer and non-cancer, of exposure to ionizing radiation received gradually over time. Recently the MPS has focused on mortality patterns from neurological and behavioral conditions, e.g., Parkinson's disease, Alzheimer's disease, dementia, and motor neuron disease such as amyotrophic lateral sclerosis. A fuller picture of radiation-related late effects comes from studying both mortality and the occurrence (incidence) of conditions not leading to death. Accordingly, the MPS is identifying neurocognitive diagnoses from fee-for-service insurance claims from the Centers for Medicare and Medicaid Services (CMS), among Medicare beneficiaries beginning in 1999 (the earliest date claims data are available). Linkages to date have identified ∼540,000 workers with available health information. Such linkages provide individual information on important co-factor and confounding variables such as smoking, alcohol consumption, blood pressure, obesity, diabetes and many other health and demographic characteristics. The total person-level set of time-dependent variables, outcomes, organ-specific dose measures, co-factors, and demographics will be massive and much too large to be evaluated with standard software. Thus, development of specialized open-source software designed for large datasets (Colossus) is nearly complete. The wealth of information available from CMS claims data, coupled with individual dose reconstructions, will thus greatly enhance the quality and precision of health evaluations for this new field of low-dose radiation and neurocognitive effects.

Optimisation of cone beam CT radiotherapy imaging protocols using a novel 3D printed head and neck anthropomorphic phantom

Objective.This study aimed to optimise Cone Beam Computed Tomography (CBCT) protocols for head and neck (H&N) radiotherapy treatments using a 3D printed anthropomorphic phantom. It focused on precise patient positioning in conventional treatment and adaptive radiotherapy (ART).Approach.Ten CBCT protocols were evaluated with the 3D-printed H&N anthropomorphic phantom, including one baseline protocol currently used at our centre and nine new protocols. Adjustments were made to milliamperage and exposure time to explore their impact on radiation dose and image quality. Additionally, the effect on image quality of varying the scatter correction parameter for each of the protocols was assessed. Each protocol was compared against a reference CT scan. Usability was assessed by three Clinical Scientists using a Likert scale, and statistical validation was performed on the findings.Main results. The work revealed variability in the effectiveness of protocols. Protocols optimised for lower radiation exposure maintained sufficient image quality for patient setup in a conventional radiotherapy pathway, suggesting the potential for reducing patient radiation dose by over 50% without compromising efficacy. Optimising ART protocols involves balancing accuracy across brain, bone, and soft tissue, as no single protocol or scatter correction parameter achieves optimal results for all simultaneously.Significance.This study underscores the importance of optimising CBCT protocols in H&N radiotherapy. Our findings highlight the potential to maintain the usability of CBCT for bony registration in patient setup while significantly reducing the radiation dose, emphasizing the significance of optimising imaging protocols for the task in hand (registering to soft tissue or bone) and aligning with the as low as reasonably achievable principle. More studies are needed to assess these protocols for ART, including CBCT dose measurements and CT comparisons. Furthermore, the novel 3D printed anthropomorphic phantom demonstrated to be a useful tool when optimising CBCT protocols.

Design of Moderator Assemblies for Fast, Epithermal, or Thermal Neutron–Dominated n-γ Mixed Fields Using a D-D Neutron Source

The treatment field of boron neutron capture therapy (BNCT) is a n-γ mixed field. In the Osaka University BNCT project, a material-filtered radio-photoluminescence glass dosimeter (RPLGD) was proposed for the simultaneous measurement of neutron and gamma-ray doses. In this study, to validate the material-filtered RPLGD, various types of n-γ mixed fields are designed by irradiating different moderator assemblies with a D-D neutron source at the OKTAVIAN facility, Osaka University, Japan. The n-γ mixed fields are classified into fast neutron–, epithermal neutron–, or thermal neutron–dominated fields and a gamma-ray-only field with the specific characteristics as follows: (1) the dose ratios of gamma ray to neutron are 1.0% to 977.0% for the fast neutron–dominated field, 5.0% to 921.1% for the epithermal neutron–dominated field, 5.0% to 921.1% for the thermal neutron–dominated field, and 11880.6% for the gamma-ray-only field; (2) the proportions of fast, epithermal, and thermal neutron doses to total neutron dose are 98.4% to 100.0% for the fast neutron–dominated field, 74.0% to 85.4% for the epithermal neutron–dominated field, and 90.1% to 90.8% for the thermal neutron–dominated field, respectively; and (3) the maximum gamma-ray energy is up to 12 MeV.

Characterization of brass mesh bolus for electron beam therapy

Purpose. Bolus is often required for targets close to or on skin surface, however, standard bolus on complex surfaces can result in air gaps that compromise dosimetry. Brass mesh boluses (RPD, Inc., Albertville, MN) are designed to conform to the patient's surface and reduce air gaps. While they have been well characterized for their use with photons, minimal characterization exists in literature for their use with electrons.Methods and materials.Dosimetric characteristics of brass mesh bolus was investigated for use with 6, 9 and 12 MeV electrons using a 10×10 cm2applicator on standard multi-energy LINAC. Measurements for bolus equivalence and percentage depth doses (PDDs) under brass mesh, as well as surface dose measurements were performed on solid water and a 3D printed resin breast phantom (Anycubic Photon MonoX, Shenzhen, China) using Markus®parallel-plate ionization chamber (Model 34045, PTW Freiburg, Germany), thermoluminescent detectors (TLD) and EBRT film. After obtaining surface dose measurements, these were compared to dose calculated on the Pinnacle3 treatment planning system (TPS, 16.2, Koninklijke Philips N.V.).Results. Measurements of surface dose under brass mesh showed consistently higher dose than without bolus, confirming that brass mesh can increase the PDD at surface up to ∼ 94% of dose at dmax, depending on incident electron energy. This increase is equivalent to using ∼ 7.2 mm water equivalent bolus for 6 MeV, ∼ 3.6 mm for 9 MeV and ∼ 2.2 mm bolus for 12 MeV electrons. TPS results showed close agreement within-vivomeasurements, confirming the potential for brass mesh as bolus for electron irradiation, provided blousing effect is correctly modelled.Conclusions. To increase electron surface dose, a brass mesh can be used with equivalent effect of water-density bolus varying with electron energy. Proper implementation could allow for ease of treatment, as well as increase bolus conformality in electron-only plans.

The NEW Soul Study: Implementation and Evaluation Impact From the Secular Trend of the COVID-19 Pandemic.

In process evaluation research, secular trends refer to external factors unrelated to an intervention that impact implementation. The COVID-19 pandemic was a secular trend that affected the implementation of the Nutritious Eating with Soul (NEW Soul) study. This paper describes steps taken in modifying intervention delivery due to the secular trend of the pandemic. This paper also addresses process evaluation measures of dose delivered, dose received, and satisfaction. This study is a longitudinal study. The study took place in Columbia, SC, from 2018 to 2021. African American adults between 18 and 65years old. The NEW Soul study, a dietary lifestyle intervention, lasted 24months. Process evaluation variables of dose delivered, dose received, and satisfaction. The study team shifted intervention delivery and maintained the timeline of classes for participants and intervention activities. Dose delivered was higher in-person (7.0 out of 8) compared to online (6.4 out of 8; t =-3.92, P =.002). Attendance was higher in-person compared to online (t =2.80, P =.006). Overall, satisfaction of the intervention was favorable in-person and online. Helpfulness of nutrition information in the class was rated lower online compared to in-person (t =2.05, P =.04). Even though the study team successfully shifted intervention delivery online, dose delivered was higher in-person. Evaluations of classes remained high across cohorts and for in-person and online classes. Future lifestyle interventions working with African American adults requires consistent flexibility in intervention delivery.

Influence of X-ray spectrum and bowtie filter characterisation on the accuracy of Monte Carlo simulated organ doses: Validation in a whole-body CT scanning mode

PurposeFor patient-specific CT dosimetry, Monte Carlo dose simulations require an accurate description of the CT scanner. However, quantitative spectral information and information on the bowtie filter material and shape from the manufacturer is often not available. In this study, the influence of different X-ray spectra and bowtie filter characterisation methods on simulated CT organ doses is studied. MethodsUsing ImpactMC, organ doses of whole-body CTs were simulated in twenty adult whole-body voxel models, generated from PET/CT examinations previously conducted in these patients. Simulated CT organ doses based on the manufacturer X-ray spectra and bowtie filter data were compared with those obtained using alternative characterisation models, including spectrum generators and experimentally measured dose data. A total of four different X-ray spectra and one bowtie filter model were defined based on these data. ResultsFor all X-ray spectra and bowtie filter combinations, estimated CT organ doses are within 6% from those resulting from simulations with the CT characterisation models provided by the manufacturer. While varying the bowtie filter model results in CT organ dose differences smaller than 1%, dose differences up to 6% are observed when X-ray spectra are not based on the quantitative data from the manufacturer. ConclusionsEstimated organ doses slightly depend on the applied CT characterisation model. When manufacturer’s data are not available, half-value layer and dose measurements provide sufficient input to obtain equivalent X-ray spectra and bowtie filter profiles, respectively.

Gamma Dose Rate Measurements in Northern Spain: Influence of Local Meteorological Scenarios on Radiological “False Alarms” in a Real-Time Radiological Monitoring Network

The present study characterizes gamma dose rate (GDR) concentrations in Bilbao, located in the northern Iberian Peninsula, utilizing a comprehensive 10-min interval database spanning from 2009 to 2018. This station belongs to the radiological environmental monitoring of the Basque Country network. The daily average GDR was found to be 0.07624 ± 0.00004 µSv/h, with the daily 95th percentile averaging 0.08026 ± 0.00007 µSv/h throughout the entire period. Our analysis specifically addresses the impact of precipitation on GDR, revealing a higher correlation coefficient for daily 95th percentile values compared to daily averages. Additionally, the influence of the Galerna (GL) event, a natural meteorological phenomenon in this region, on GDR was investigated, noting that it can develop both with and without precipitation. Understanding the interaction between GDR and this meteorological scenario is vital for the development of more reliable radiological monitoring strategies and for safeguarding public health. For this purpose, 40 GL events were analyzed. The present results indicate that GDR values frequently exceed alarm levels when a GL is formed. These GDR peaks should be considered natural radiological events, necessitating the classification of such GDR peaks as false alarms within the radiological monitoring network. To explain them in detail, 10-min time series of precipitation and radon outdoor concentrations were analyzed. The results demonstrate that the GL event with precipitation is a meteorological scenario that can be associated with false alarms. The present analysis provides a distinct contrast in radon behavior under the same meteorological event in case of being developed with precipitation or without precipitation. The findings from this analysis are crucial for avoiding and understanding false radiological alarms triggered in the monitoring network, thereby enhancing the accuracy of radiological data interpretation and improving public safety measures.

IPEM topical report: the first UK survey of cone beam CT dose indices in radiotherapy verification imaging for adult patients.

Cone beam CT is integral to most modern radiotherapy treatments. The application of daily and repeat CBCT imaging can lead to high imaging doses over a large volume of tissue that extends beyond the treatment site. Hence, it is important to ensure exposures are optimised to keep doses as low as reasonably achievable, whilst ensuring images are suitable for the clinical task. 
This IPEM topical report presents the results of the first UK survey of dose indices in radiotherapy CBCT. Dose measurements, as defined by the Cone Beam Dose Index (CBDIw), were collected along with protocol information for seven treatment sites. Where a range of optimised protocols were available in a centre, a sample of patient data demonstrating the variation in protocol use were requested. Protocol CBDIw values were determined from the average dosimetry data for each type of linear accelerator, and median CBDIw and scan length were calculated for each treatment site at each centre. Median CBDIw values were compared and summary statistics derived that enable the setting of national dose reference levels (DRLs). 
A total of 63 UK radiotherapy centres contributed data. The proposed CBDIw DRLs are; prostate 20.6 mGy, gynaecological 20.8 mGy, breast 5.0 mGy, 3D-lung 6.0 mGy, 4D-lung 11.8 mGy, brain 3.5 mGy and head/neck 4.2 mGy. However, large differences between models of imaging system were noted. Where centres had pro-active optimisation strategies in place, such as sized based protocols with selection criteria, dose reductions on the 'average' patient were possible compared with vendor defaults. Optimisation of scan length was noted in some clinical sites, with Elekta users tending to fit different collimators for prostate imaging (relatively short) compared with gynaecological treatments (longest). This contrasts with most Varian users who apply the default scan length in most cases.

Performance evaluation of an inorganic optical fibre dosimeter for use in external beam radiotherapy with pulsed beams

Objective. Optical fibre dosimeters (OFDs) offer great promise for real-timein vivodose measurement in radiation-based treatment modalities such as radiotherapy and brachytherapy. This is attributed to their many useful qualities such as high spatial resolution and sensitivity. However, there are several requirements that an optical fibre dosimeter must meet to be acceptable for dose measurement in a specified treatment modality. In this work, the dosimetric performance of a novel optical fibre dosimeter for use in external beam radiotherapy is presented.Approach. The dosimeter was characterised for photon beam energies between 6-15 MV using a Varian TrueBeam Linac at dose rates between 100-2400 MU/min and assessed based on its repeatability, dose dependence, dose rate dependence, energy dependence and dose-per-pulse dependence.Main Results. The results demonstrated excellent short-term repeatability of 0.3%, good linearity in response (R2>0.9997), and minor dose rate dependence between 0.53%-2.49% for all beam qualities investigated. As the scintillator of the OFD is non-water equivalent, Monte-Carlo-TOPAS simulations were used to calculate the absorbed dose energy dependence. A dose-per-pulse dependence was also investigated and compared with dosimetry measurements made with an ionisation chamber and simulated from the treatment planning system. An over-response of 20%was found at the lowest investigated dose-per-pulse, and an under-response of 34%was found at the highest investigated dose-per-pulse. This is believed to be due to an intrinsic energy dependence making this type of OFD unsuitable for external beam radiotherapy dosimetry.Significance. The OFD evaluated in this work was primarily designed for high-dose-rate brachytherapy whereas this study includes the first measurements made in external beam radiotherapy and highlights the challenges of transferability of the dosimeter to a different radiation source.

Long-Term Reproducibility of BMD-Measurements with Clinical QCT Using Simultaneous and Asynchronous Calibration Methods and Different Measurement and Reconstruction Protocols.

Osteoporosis is underdiagnosed and undertreated. To improve timely fracture risk assessment optimized densitometry methods are required such as opportunistic spinal quantitative computed tomography (QCT). However, it is unclear how to best calibrate these scans and correct for potential scanner drift of QCT when used for monitoring bone mineral density (BMD) changes. We compared gold standard simultaneous calibration with asynchronous calibration methods, assessing mid-term (12weeks) and long-term (1.5years) reproducibility of BMD measurements. Cortical and trabecular compartments of the European Spine Phantom were studied with ten different protocols including low dose and high resolution (HR)-modes. Based on weekly phantom data, we compared simultaneous calibration to asynchronous single (termed global) or monthly calibration. The accuracy was better for trabecular measurements than for cortical measurements for all calibration methods. Reproducibility was excellent for all methods and slightly better for asynchronous than for simultaneous calibration both for trabecular and cortical bone. For HR protocols, reproducibility was better than for low dose measurements. In trabecular compartments averaged HR-BMD remained stable for global (- 0.1%/year, ns) but not for simultaneous calibration (- 1.5%/year, p < 0.001). No significant drifts could be detected for averaged low dose BMD (- 0.9 to + 0.8%/year) for either calibration method. Our data suggest that with regard to precision and accuracy measurements with asynchronous calibration are suitable for vertebral BMD assessment (no contrast agents) in clinical practice. Regular (e.g., monthly) stability tests using a calibration phantom could assure long term stability of at least 1year.

A Fast 3D Range-Modulator Delivery Approach: Validation of the FLUKA Model on a Varian ProBeam System Including a Robustness Analysis

A 3D range-modulator (RM), optimized for a single energy and a specific target shape, is a promising and viable solution for the ultra-fast dose delivery in particle therapy. The aim of this work was to investigate the impact of potential beam and modulator misalignments on the dose distribution. Moreover, the FLUKA Monte Carlo model, capable of simulating 3D RMs, was adjusted and validated for the 250 MeV single-energy proton irradiation from a Varian ProBeam system. A 3D RM was designed for a cube target shape rotated 45° around two axes using a Varian-internal research version of the Eclipse treatment planning software, and the resulting dose distribution was simulated in a water phantom. Deviations from the ideal alignment were introduced, and the dose distributions from the modified simulations were compared to the original unmodified one. Finally, the FLUKA model and the workflow were validated with base-line data measurements and dose measurements of the manufactured modulator prototype at the HollandPTC facility in Delft. The adjusted FLUKA model, optimized particularly in the scope of a single-energy FLASH irradiation with a PMMA pre-absorber, demonstrated very good agreement with the measured dose distribution resulting from the 3D RM. Dose deviations resulting from modulator-beam axis misalignments depend on the specific 3D RM and its shape, pin aspect ratio, rotation angle, rotation point, etc. A minor modulator shift was found to be more relevant for the distal dose distribution than for the spread-out Bragg Peak (SOBP) homogeneity. On the other hand, a modulator tilt (rotation away from the beam axis) substantially affected not only the depth dose profile, transforming a flat SOBP into a broad, Gaussian-like distribution with increasing rotation angle, but also shifted the lateral dose distribution considerably. This work strives to increase awareness and highlight potential pitfalls as the 3D RM method progresses from a purely research concept to pre-clinical studies and human trials. Ensuring that gantry rotation and the combined weight of RM, PMMA, and aperture do not introduce alignment issues is critical. Given all the other range and positioning uncertainties, etc., not related to the modulator, the RM must be aligned with an accuracy below 1° in order to preserve a clinically acceptable total uncertainty budget. Careful consideration of critical parameters like the pin aspect ratio and possibly a novel robust modulator geometry optimization are potential additional strategies to mitigate the impact of positioning on the resulting dose. Finally, even the rotated cube 3D modulator with high aspect ratio pin structures (~80 mm height to 3 mm pin base width) was found to be relatively robust against a slight misalignment of 0.5° rotation or a 1.5 mm shift in one dimension perpendicular to the beam axis. Given a reliable positioning and QA concept, the additional uncertainties introduced by the 3D RM can be successfully managed adopting the concept into the clinical routine.

Dosimetry in MRgPT: Impact of magnetic fields on TLD dose response during proton irradiation.

Proton beam therapy, when integrated with MRI guidance, presents complex dosimetric challenges due to interactions with magnetic fields. Prior research has emphasized the nuanced impact of magnetic fields on dosimetry. For thermoluminescent dosimeters (TLDs) the electron-return effect, alongside small air cavities surrounding the pellets, can lead to nonuniform dose distributions. Future MR-guided proton therapy will require reliable methods for end-to-end tests and dosimetric audits, which so far are often performed using TLDs equipped with phantoms. This implicates the necessity of accounting for theseinteractions. This study investigates the influence of magnetic fields on TLDs at two proton energies, using magnetic field strengths of 0, 0.25, and , aiming to clarify their impact on dose measurementaccuracy. The study was conducted at a synchrotron-based ion beam therapy beam line, enhanced by a resistive dipole magnet for creating magnetic fields up to to simulate MR-guided proton therapy. Individual correction factors were applied for TLD measurements. The impact of air gaps on the TLD signal was evaluated using three dedicated TLD holders with air gaps of 0.1, 0.25, and 0.5 mm surrounding the TLD pellets using the highest available proton energy of . Additionally, the influence of the magnetic field strength on the TLD response was evaluated for two proton energies of and . The study found no statistically significant variation in TLD dose response attributable to changes in the air gap or the presence of magnetic fields. A power analysis indicated an upper limit on a potential change in dose-response as small as 1.5%. The findings suggested that the impact of air gap variations and magnetic field strengths on the TLD response was below the detection threshold of TLD sensitivity. This emphasizes the suitability of TLDs for dose measurement in MR-guided proton therapy, indicating that additional correction factors may not be necessary despite the influence of magneticfields.

AVATAR 2.0: next level communication systems for radiotherapy through face-to-face video, biofeedback, translation, and audiovisual immersion.

This paper discusses an advanced version of our audiovisual-assisted therapeutic ambience in radiotherapy (AVATAR) radiolucent display systems designed for pediatric radiotherapy, enabling anesthesia-free treatments, video communication, and biofeedback. The scope of the AVATAR system is expanded here in two major ways: (i) through alternative mounting systems to accommodate a broader range of radiotherapy machines (specifically to fit robotic-arm and toroidal geometry photon radiotherapy and proton radiotherapy systems) and (ii) through additional hardware to provide video-calling, optimized audio for clear communication, and combined video inputs for biofeedback, translation, and other advanced functionalities. Because robustness requires strong parts and radio-transparency requires thin, light parts, three-dimensional printing was used to rapidly prototype hollow structures and to iteratively improve robustness. Two system designs were made: one that mounts superior and another that mounts inferior to the patient's head. Radiation dose measurements and calculations were conducted to assess dose perturbations at surface and depth due to the screen. For 6-MV volumetric modulated arc therapy (VMAT) plans, with and without the screen, the mean and maximum dose differences inside the planning target volume were 0.2% and 2.6% of the 200 cGy prescription, respectively. For a single static beam through the screen, the maximum measured excess surface dose was 13.4 ± 0.5%, and the largest measured dose attenuation at 5-cm water-equivalent depth was 2.1 ± 0.2%. These percentages are relative to the dose without the screen at those locations. The radiolucent screen systems provided here are shown to give minimal dosimetric effects on megavoltage VMAT photon treatments. For static beams, however, surface dose effects should be considered when these beams pass through the thickest components of the screen. Design files are also provided.

Evaluation of patient-specific quality assurance for fractionated stereotactic treatment plans with 6 and 10MV photon beams in beam-matched linacs.

Beam-matched linear accelerators (LA's) require accurate and precise dosimetry for fractionated stereotactic treatment. In this study, the beam data were validated by comparing the three-beam-matched LA's measured data and the vendor reference data. Upon its validation, the accuracy of the volumetric dose delivery for eighty patient-specific fractionated stereotactic treatment plans was evaluated. Measurements of the percentage depth dose (PDD), beam profiles, output factors (OFs), absolute output, and dynamic multi-leaf collimator (MLC) transmission factors for 6MV and 10MV flattening filter (FF) and flattening filter-free (FFF) photon beams were obtained from three-beam-matched LA's. The patient-specific quality assurance evaluation for all eighty plans was performed using PTW Octavius 1000 SRS™ array detectors for two-dimensional (2D) fluence measurement. The following 2D gamma passing criteria were used: 1%/1mm, 2%/1mm, 1%/2mm, 2%/2mm and 3%/2mm. In all three LA's, gamma analysis for PDD and profile were above 97% with gamma criteria of 1%/1mm. The differences OFs, absolute output, and dynamic MLC transmission factors were less than ± 1% of base value. For all eighty cases, the median passing rates on the three LA's were above 76%, 88%, 92%, 96%, and 98% for the above-mentioned gamma criteria of the three LA's. The beam-matched LA's showed good agreement between the measured and treatment planning system (TPS) calculated values for fractionated stereotactic VMAT plans with 6MV and 10MV (FF and FFF) photon beams. Patients can be shifted and treated on any beam-matched linac without the need of re-planning.

Gamma radiation dose rate measurements in granite quarries and schools in two mountainous towns in Benin

Gamma radiation dose rate measurements in granite quarries and schools in two mountainous towns in Benin

Environmental Radioactivity Monitoring and Radiological Impact Assessment of Agbara Industrial Area, Ogun State, Nigeria

This study assessed the naturally occurring radioactivity of 40K, 238U, and 232Th, which pose a significant threat to human health, particularly when their concentrations exceed the threshold. Background radiation levels were measured at two specific locations, Access Bank and Market areas, across a total of forty (40) sample points. The measurements were taken using a calibrated RS125 Gamma Spectrometer (a portable NaI [Tl] detector) designed in Canada, in conjunction with a global positioning system (GPS) to accurately record the research coordinates within the Agbara industrial area, Ogun State, Nigeria. The mean activity concentrations of the primordial radionuclides were 177.87 Bqkg-1, 20.01 Bqkg-1, and 52.90 Bqkg-1 for 40K, 238U, and 232Th, respectively. More so, the in-situ measured dose rate (DR) ranges between 12.18 nGyh-1 (Access Bank area) and 97.95 nGyh-1 (Market area), with an average value of 47.22 nGyh-1. The average measured and estimated absorbed dose rates were within the safe limit of 57 nGyh-1 provided by UNSCEAR. However, the measured dose rates exceeded the recommended limit in ten locations, while measured activity for thorium exceeded the world average value for over half of the study locations. Although all estimated radiological parameters were within recommended threshold values, suggesting the low risk of exposure to higher levels of ionising radiation in most locations in the Agbara industrial area, there is a potential cancer risk for individuals who have resided in the area for 70 years or more due to long-term exposure to ionising radiation.

Evaluating the Transmission Type Reference Chamber for Small Field Dosimetry

AbstractTo assess the efficacy of a transmission‐type parallel plane reference chamber (T‐REF) for small‐field percentage depth dose (PDD) measurements using two high‐resolution detectors. The study utilizes microSilicon and microDiamond detectors for small‐field measurements, both with and without a T‐REF reference chamber. TrueBeam linear accelerator provides various photon energies (6X, 6XFFF, 10X, 10XFFF) for depth dose measurements. A sun‐nuclear 3D water tank is used to measure the PDD up to a depth of 15 cm. Analysis of the data includes a 1D gamma passing rate calculated using an in‐house MATLAB program. The study compares the PDD measurements obtained with and without the T‐REF. The T‐REF exhibits negligible beam perturbations across different field sizes and energies. The overall maximum mean PDD differences are 0.31 ± 0.16% for microSilicon and 0.33 ± 0.17% for microdiamond. The overall mean 1D gamma passing rate is 99.6 ± 0.2%. This study demonstrates that the T‐REF is a reliable and effective reference detector for small‐field radiation dosimetry.

Radiation dose to health care workers measured by thermoluminescent dosimetry

To evaluate radiation dose among physicians, nurses, nuclear medicine (NM) technicians, and radiographers at a single institution and to compare the difference in the measured dose during COVID-19 with other periods. A retrospective analysis of the occupational radiation doses received by all workers in diagnostic radiography and NM departments at a single institution during a 5-year period (2018-2022) was performed. Dose measurements were recorded for 94 radiology personnel: radiographers, NM technicians, physicians, and nurses. In addition to descriptive statistics, the Mann-Whitney U-test was used to compare the average annual effective dose between male and female workers and between the periods before and during COVID-19. Kruskal-Wallis test was used to compare effective radiation doses from different quadrants. The annual average effective doses were found to be between 0.58 and 0.72 mSv for males and 0.68 and 0.85 mSv for females. All radiographers, 86% of nurses, and 69% of physicians have received annual average effective doses below 0.99 mSv. The average annual effective doses for all radiation workers were similar in the period before COVID-19 when compared to the period during COVID-19 except for nurses who had significantly lower (P<0.05) doses before COVID-19. The average annual effective doses of radiation workers during 2018-2022 were well below the annual dose limit. A relatively higher average effective dose was received among NM technicians compared with other radiation occupational workers. While the caseload during the COVID-19 pandemic was lower due to government policies, the radiation dose to healthcare workers during the pandemic was similar to that before the pandemic.

Impact of an institutional process change adopting end-systolic coronary CTA acquisition and automated dose selection on patient throughput and image quality

IntroductionGuidelines recommend prospective ECG-triggered mid-diastolic coronary computed tomographic angiography (CCTA) acquisition after achieving optimal heart rate (HR) control in order to optimize scan image quality. With dual-source CCTA, prospective end-systolic acquisition has been shown to be less prone to motion artifacts at higher heart rates and may improve scan and CT laboratory efficiency by allowing CCTA without routine pre-scan beta-blocker (BB) administration. MethodsWe implemented an institutional process change in CCTA performance effective January 2023, comprising a transition from prospective ECG-triggered mid-diastolic acquisitions individually supervised by a physician at the scanner to an algorithmic approach predominately utilizing prospective end-systolic acquisition (200–400 ​ms after R peak), employing an automated dose selection algorithm, without BB administration. All scans were performed on a third-generation 192-slice dual-source scanner. We reviewed 300 consecutive CCTAs done pre- and post-process change in Jan 2022 (phase 0), Jan 2023 (phase 1), and in May 2023 (phase 2) after implementation of a process improvement involving more selective utilization of automated tube potential/current algorithms (CARE kV) to optimize image quality. Coronary segmental image quality was assessed by two experienced CCTA readers by consensus using an 18-segment SCCT model on a 5-point Likert scale (1 ​= ​non-interpretable; 2 ​= ​poor; 3 ​= ​acceptable; 4 ​= ​good; 5 ​= ​excellent). Measures of radiation dose, medication administration, and time required for patient scanning were compared. Logistic regression was used to determine factors associated with patient-level reduction in image quality (IQ) and with repeat scans. ResultsPost-process change, there was a significant reduction in the median overall patient appointment [phase 0: 95 (75–125) min vs. phase 1: 68 (52–88) min and phase 2: 72 (59–90) min; P ​< ​0.001] and scan times [phase 0: 13 (10–16) min vs. phase 1: 8 (6–13) min and phase 2: 9 (7–13) min; P ​< ​0.001]. Median IQ score in both post-process change phases was 4 (4–5) compared to a median score of 5 (4–5) pre-process change (P for comparison <0.001). The majority of segments post-process change had “good” IQ (Phase 1 segmental IQ scores: 5 ​= ​36.7 ​%, 4 ​= ​46.8 ​%, 3 ​= ​13 ​%, 2 ​= ​2.6 ​%, 1 ​= ​0.9 ​%; Phase 2 segmental IQ scores: 5 ​= ​26 ​%, 4 ​= ​49.7 ​%, 3 ​= ​16.3 ​%, 2 ​= ​6.1 ​%, 1 ​= ​1.9 ​%), whereas pre-process change, the majority of segments had “excellent” IQ (Phase 0 segmental IQ scores: 5 ​= ​56 ​%, 4 ​= ​34.3 ​%, 3 ​= ​7.5 ​%, 2 ​= ​1.8 ​%, 1 ​= ​0.4 ​%) There was no significant increase in non-interpretable scans at the patient level. The 22 ​% re-scan rate in phase 1 (vs. 6 ​% in phase 0, P ​= ​.002) improved to 15 ​% in phase 2. While patient related factors of body mass index [adjusted OR obese 2.64, 95 ​% CI 1.12–6.51, P ​= ​0.03; aOR morbidly obese 6.94, 95 ​% CI 2.21–23.52, P ​= ​0.001] and average HR [aOR (per 10 bpm increase) 1.51, 95 ​% CI 1.21–1.9, P ​< ​0.001] were associated with the scoring of any segment as ​≤ ​3 ​at the patient level in a fully adjusted model, the improved phase 2 of the process change was not [aOR 1.61, 95 ​% CI 0.78–3.32]. ConclusionImplementation of an institutional process change utilizing prospective ECG-triggered dual-source end-systolic acquisition avoided the use of beta-blockers, significantly reduced patient appointment and scan times with acceptable diagnostic performance.

Bidirectional uptake and redistribution, bio-stimuli responsive xyloglucan-based nanodelivery system for enhanced translocation of non-systemic pesticide in soybean plants

Non-systemic pesticides, like fludioxonil, have the advantages of broad-spectrum and fast-acting, but the limited space of action restricts their effectiveness. This study proposed a nano-delivery strategy (Flu@EXG) by loading fludioxonil on aminated xyloglucan-based nanoparticles (EXG) to enhance the systematicity of fludioxonil in vivo and consequently achieve systemic defense against soybean diseases. The resulting Flu@EXG had an average diameter of 75.6 nm and exhibited responsive release properties to dual-stimuli of hemicellulases and pH value. The combined measurements of target dose and efficacy demonstrated that the Flu@EXG achieved bi-directional uptake and redistribution of fludioxonil, consequently inhibiting both Phytophthora sojae in roots and Botrytis cinerea on leaves meanwhile with a single application method (root irrigation or foliar spraying) in soybean. In contrast, fludioxonil commercial suspensions (Flu SC) hardly reached the roots to control root diseases when applied to foliage. Additionally, the direct inhibition of Flu@EXG against oomycetes was 2.0 times higher than Flu SC at high test concentrations as EXG could directly provide additional membrane damage. Finally, Flu@EXG provided comparable foliar performance to Flu SC and do not affect the growth of soybeans during the test cycle. Thus, the bio-stimuli responsive Flu@EXG nanodelivery system has promising for achieving the systemic prevention by overcoming the spatial and temporal limitations of non-systemic pesticide application, providing new perspectives and technologies for prompting sustainable development of agriculture.