Correcting radiation survey data to account for increased leakage during intensity modulated radiotherapy treatments

Purpose Intensity modulated radiotherapy (IMRT) treatments require more beam-on time and produce more linac head leakage to deliver similar doses to conventional, unmodulated, radiotherapy treatments. It is necessary to take this increased leakage into account when evaluating the results of radiation surveys around bunkers that are, or will be, used for IMRT. The recommended procedure of 15 applying a monitor-unit based workload correction factor to secondary barrier survey measurements, to account for this increased leakage when evaluating radiation survey measurements around IMRT bunkers, can lead to potentially-costly over estimation of the required barrier thickness. This study aims to provide initial guidance on the validity of reducing the value of the correction factor when applied to different radiation barriers (primary barriers, doors, maze walls and other walls) by 20 evaluating three different bunker designs. Methods Radiation survey measurements of primary, scattered and leakage radiation were obtained at each of five survey points around each of three different radiotherapy bunkers and the contribution of leakage to the total measured radiation dose at each point was evaluated. Measurements at each survey point were made with the linac gantry set to 12 equidistant positions from 0 to 330o, to 25 assess the effects of radiation beam direction on the results. Results For all three bunker designs, less than 0.5% of dose measured at and alongside the primary barriers, less than 25% of the dose measured outside the bunker doors and up to 100% of the dose measured outside other secondary barriers was found to be caused by linac head leakage. Conclusions Results of this study suggest that IMRT workload corrections are unnecessary, for 30 survey measurements made at and alongside primary barriers. Use of reduced IMRT workload correction factors is recommended when evaluating survey measurements around a bunker door, provided that a subset of the measurements used in this study are repeated for the bunker in question. Reduction of the correction factor for other secondary barrier survey measurements is not recommended unless the contribution from leakage is separetely evaluated.

Quantitative ultrasound computed tomography imaging of PAGAT radiation dosimetry gel

This research developed and scientifically validated a new ultrasound transmission computed tomography system with the aim of quantitative assessment of a polymer gel dosimeter including dose response verification of ultrasonic parameters of attenuation, velocity and broadband ultrasound attenuation (BUA). This work was the first to investigate and report ultrasound frequency dependent attenuation in a gel dosimeter, demonstrating a dose dependence.

What encourages sun protection among outdoor workers from four industries?

Objectives: We aimed to identify current practice of sun protection and factors associated with effective use in four outdoor worker industries in Queensland, Australia. Methods: Workplaces in four industries with a high proportion of outdoor workers (building/construction, rural/farming, local government, and public sector industries) were identified using an online telephone directory, screened for eligibility, and invited to participant via mail (n=15, recruitment rate 37%). A convenience sample of workers were recruited within each workplace (n=162). Workplaces’ sun protective policies and procedures were identified using interviews and policy analysis with workplace representatives, and discussion groups and computer-assisted telephone interviews with workers. Personal characteristics and sun protection knowledge, attitudes and behaviors were collated and analysed. Results: Just over half the workplaces had an existing policy which referred to sun protection (58%), and most provided at least some personal protective equipment (PPE), but few scheduled work outside peak sun hours (43%) or provided skin checks (21%). Several worker and workplace characteristics were associated with greater sun protection behaviour among workers, including having received education on the use of PPE (p<0.001), being concerned about being in the sun (p=0.002); and working in a smaller workplace (p=0.035). Conclusions: Uptake of sun protection by outdoor workers is affected by a complex interplay of both workplace and personal factors, and there is a need for effective strategies targeting both the workplace environment and workers’ knowledge, attitudes and behaviors to decrease harmful sun exposure further.

Characterisation of a human skin equivalent model to study the effects of ultraviolet B radiation on keratinocytes

The incidences of skin cancers resulting from chronic ultraviolet radiation (UVR) exposure are on the incline both in Australia and globally. Hence, the cellular and molecular pathways associated with UVR-induced photocarcinogenesis urgently need to be elucidated, in order to develop more robust preventative and treatment strategies against skin cancers. In vitro investigations into the effects of UVR (in particular the highly-mutagenic UVB wavelength) have, to date, mainly involved the use of cell culture and animal models. However, these models possess biological disparities to native skin, which to some extent have limited their relevance to the in vivo situation. To address this, we characterised a 3-dimensional, tissue-engineered human skin equivalent (HSE) model (consisting of primary human keratinocytes cultured on a dermal-derived scaffold) as a representation of a more physiologically-relevant platform to study keratinocyte responses to UVB. Significantly, we demonstrate that this model retains several important epidermal properties of native skin. Moreover, UVB-irradiation of the HSE constructs was shown to induce key markers of photodamage in the HSE keratinocytes, including the formation of cyclobutane pyrimidine dimers, the activation of apoptotic pathways, the accumulation of p53 and the secretion of inflammatory cytokines. Importantly, we also demonstrate that the UVB-exposed HSE constructs retain the capacity for epidermal repair and regeneration following photodamage. Together, our results demonstrate the potential of this skin equivalent model as a tool to study various aspects of the acute responses of human keratinocytes to UVB radiation damage.

Interventions to decrease skin cancer risk in outdoor workers : update to a 2007 systematic review

BACKGROUND: Outdoor workers are at high risk of harmful ultraviolet radiation exposure and are identified as an at risk group for the development of skin cancer. This systematic evidence based review provides an update to a previous review published in 2007 about interventions for the prevention of skin cancer in outdoor workers. RESULTS: This review includes interventions published between 2007-2012 and presents findings about sun protection behaviours and/or objective measures of skin cancer risk. Six papers met inclusion criteria and were included in the review. Large studies with extended follow-up times demonstrated the efficacy of educational and multi-component interventions to increase sun protection, with some higher use of personal protective equipment such as sunscreen. However, there is less evidence for the effectiveness of policy or specific intervention components. CONCLUSIONS: Further research aimed at improving overall attitudes towards sun protection in outdoor workers is needed to provide an overarching framework.

Prevention and treatment of acute radiation-induced skin reactions : a systematic review and meta-analysis of randomized controlled trials

Background Radiation-induced skin reaction (RISR) is a common side effect that affects the majority of cancer patients receiving radiation treatment. RISR is often characterised by swelling,redness, pigmentation, fibrosis, and ulceration, pain, warmth, burning, and itching of the skin. The aim of this systematic review was to assess the effects of interventions which aim to prevent or manage RISR in people with cancer. Methods We searched the following databases up to November 2012: Cochrane Skin Group Specialised Register, CENTRAL (2012, Issue 11), MEDLINE (from 1946), EMBASE (from 1974), PsycINFO (from 1806), CINAHL (from 1981) and LILACS (from 1982). Randomized controlled trials evaluating interventions for preventing or managing RISR in cancer patients were included. The primary outcomes were development of RISR, and levels of RISR and symptom severity. Secondary outcomes were time taken to develop erythema or dry desquamation; quality of life; time taken to heal, a number of skin reaction and symptom severity measures; cost, participant satisfaction; ease of use and adverse effects. Where appropriate, we pooled results of randomized controlled trials using mean differences (MD) or odd ratios (OR) with 95% confidence intervals (CI). Results Forty-seven studies were included in this review. These evaluated six types of interventions (oral systemic medications; skin care practices; steroidal topical therapies; non-steroidal topical therapies; dressings and other). Findings from two meta-analyses demonstrated significant benefits of oral Wobe-Mugos E for preventing RISR (OR 0.13 (95% CI 0.05 to 0.38)) and limiting the maximal level of RISR (MD −0.92 (95% CI −1.36 to −0.48)). Another meta-analysis reported that wearing deodorant does not influence the development of RISR (OR 0.80 (95% CI 0.47 to 1.37)). Conclusions Despite the high number of trials in this area, there is limited good, comparative research that provides definitive results suggesting the effectiveness of any single intervention for reducing RISR. More research is required to demonstrate the usefulness of a wide range of products that are being used for reducing RISR. Future efforts for reducing RISR severity should focus on promising interventions, such as Wobe-Mugos E and oral zinc.

Exposure to solar ultraviolet radiation is associated with a decreased folate status in women of childbearing age

In vitro studies indicate that folate in collected human blood is vulnerable to degradation after exposure to ultraviolet (UV) radiation. This has raised concerns about folate depletion in individuals with high sun exposure. Here, we investigate the association between personal solar UV radiation exposure and serum folate concentration, using a three-week prospective study that was undertaken in females aged 18–47 years in Brisbane, Australia (153 E, 27 S). Following two weeks of supplementation with 500 μg of folic acid daily, the change in serum folate status was assessed over a 7-day period of measured personal sun exposure. Compared to participants with personal UV exposures of <200 Joules per day, participants with personal UV exposures of 200–599 and >600 Joules per day had significantly higher depletion of serum folate (p = 0.015). Multivariable analysis revealed personal UV exposure as the strongest predictor accounting for 20% of the overall change in serum folate (Standardised B = −0.49; t = −3.75; p = <0.01). These data show that increasing solar UV radiation exposures reduces the effectiveness of folic acid supplementation. The consequences of this association may be most pronounced for vulnerable individuals, such as women who are pregnant or of childbearing age with high sun exposures.

A 3D virtual medical imaging suite : bridging the academic-clinical training boundary

Aims The Medical Imaging Training Immersive Environment (MITIE) system is a recently developed virtual reality (VR) platform that allows students to practice a range of medical imaging techniques. The aim of this pilot study was to harvest user feedback about the educational value of the application and inform future pedagogical development. This presentation explores the use of this technology for skills training and blurring the boundaries between academic learning and clinical skills training. Background MITIE is a 3D VR environment that allows students to manipulate a patient and radiographic equipment in order to produce a VR-generated image for comparison with a gold standard. As with VR initiatives in other health disciplines (1-6) the software mimics clinical practice as much as possible and uses 3D technology to enhance immersion and realism. The software was developed by the Medical Imaging Course Team at a provider University with funding from a Health Workforce Australia “Simulated Learning Environments” grant. Methods Over 80 students undertaking the Bachelor of Medical Imaging Course were randomised to receive practical experience with either MITIE or radiographic equipment in the medical radiation laboratory. Student feedback about the educational value of the software was collected and performance with an assessed setup was measured for both groups for comparison. Ethical approval for the project was provided by the university ethics panel. Results This presentation provides qualitative analysis of student perceptions relating to satisfaction, usability and educational value as well as comparative quantitative performance data. Students reported high levels of satisfaction and both feedback and assessment results confirmed the application’s significance as a pre-clinical training tool. There was a clear emerging theme that MITIE could be a useful learning tool that students could access to consolidate their clinical learning, either during their academic timetables or their clinical placement. Conclusion Student feedback and performance data indicate that MITIE has a valuable role to play in the clinical skills training for medical imaging students both in the academic and the clinical environment. Future work will establish a framework for an appropriate supporting pedagogy that can cross the boundary between the two environments. This project was possible due to funding made available by Health Workforce Australia.

The radiation therapy patient as a student assessor

Background Radiation Therapy students at Queensland University of Technology undertake clinical placement across a wide range of sites Interpersonal skills with clinical staff and patients are an essential component: – Lectures – Role playing – Expert patient input

Ad hoc radiometric calibration of a thermal-infrared camera

Many applications can benefit from the accurate surface temperature estimates that can be made using a passive thermal-infrared camera. However, the process of radiometric calibration which enables this can be both expensive and time consuming. An ad hoc approach for performing radiometric calibration is proposed which does not require specialized equipment and can be completed in a fraction of the time of the conventional method. The proposed approach utilizes the mechanical properties of the camera to estimate scene temperatures automatically, and uses these target temperatures to model the effect of sensor temperature on the digital output. A comparison with a conventional approach using a blackbody radiation source shows that the accuracy of the method is sufficient for many tasks requiring temperature estimation. Furthermore, a novel visualization method is proposed for displaying the radiometrically calibrated images to human operators. The representation employs an intuitive coloring scheme and allows the viewer to perceive a large variety of temperatures accurately.

Measuring exposure to solar ultraviolet radiation using a dosimetric technique : understanding participant compliance issues

Personal ultraviolet dosimeters have been used in epidemiological studies to understand the risks and benefits of individuals' exposure to solar ultraviolet radiation (UVR). We investigated the types and determinants of non-compliance associated with a protocol for use of polysulphone UVR dosimeters. In the AusD Study, 1,002 Australian adults (aged 18-75 years) were asked to wear a new dosimeter on their wrist each day for 10 consecutive days to quantify their daily exposure to solar UVR. Of the 10,020 dosimeters distributed, 296 (3%) were not returned or used (Type I non-compliance) and other usage errors were reported for 763 (8%) returned dosimeters (Type II non-compliance). Type I errors were more common in participants with predominantly outdoor occupations. Type II errors were reported more frequently on the first day of measurement; weekend days or rainy days; and among females; younger people; more educated participants or those with outdoor occupations. Half (50%) the participants reported a non-compliance error on at least one day during the 10-day period. However, 92% of participants had at least 7 days of usable data without any apparent non-compliance issues. The factors identified should be considered when designing future UVR dosimetry studies.

The contributions of solar ultraviolet radiation exposure and other determinants to Serum 25-Hydroxyvitamin D concentrations in Australian adults : the AusD study

The Quantitative Assessment of Solar UV [ultraviolet] Exposure for Vitamin D Synthesis in Australian Adults (AusD) Study aimed to better define the relationship between sun exposure and serum 25-hydroxyvitamin D (25(OH)D) concentration. Cross-sectional data were collected between May 2009 and December 2010 from 1,002 participants aged 18-75 years in 4 Australian sites spanning 24° of latitude. Participants completed the following: 1) questionnaires on sun exposure, dietary vitamin D intake, and vitamin D supplementation; 2) 10 days of personal ultraviolet radiation dosimetry; 3) a sun exposure and physical activity diary; and 4) clinical measurements and blood collection for 25(OH)D determination. Our multiple regression model described 40% of the variance in 25(OH)D concentration; modifiable behavioral factors contributed 52% of the explained variance, and environmental and demographic or constitutional variables contributed 38% and 10%, respectively. The amount of skin exposed was the single strongest contributor to the explained variance (27%), followed by location (20%), season (17%), personal ultraviolet radiation exposure (8%), vitamin D supplementation (7%), body mass index (weight (kg)/height (m)2) (4%), and physical activity (4%). Modifiable behavioral factors strongly influence serum 25(OH)D concentrations in Australian adults. In addition, latitude was a strong determinant of the relative contribution of different behavioral factors.

A Matlab toolbox for parametric identification of radiation-force models of ships and offshore structures

This article describes a Matlab toolbox for parametric identification of fluid-memory models associated with the radiation forces ships and offshore structures. Radiation forces are a key component of force-to-motion models used in simulators, motion control designs, and also for initial performance evaluation of wave-energy converters. The software described provides tools for preparing non-parmatric data and for identification with automatic model-order detection. The identification problem is considered in the frequency domain.