Time filter

Source Type

Richmond, Australia

Biggs S.,Riverina Cancer Care Center | Sobolewski M.,Riverina Cancer Care Center | Murry R.,Radiation Oncology Queensland | Kenny J.,Epworth Radiation Oncology
Physica Medica | Year: 2015

There are many methods available to predict electron output factors; however, many centres still measure the factors for each irregular electron field. Creating an electron output factor prediction model that approaches measurement accuracy - but uses already available data and is simple to implement - would be advantageous in the clinical setting. This work presents an empirical spline model for output factor prediction that requires only the measured factors for arbitrary insert shapes. Equivalent ellipses of the insert shapes are determined and then parameterised by width and ratio of perimeter to area. This takes into account changes in lateral scatter, bremsstrahlung produced in the insert material, and scatter from the edge of the insert. Agreement between prediction and measurement for the 12 MeV validation data had an uncertainty of 0.4% (1SD). The maximum recorded deviation between measurement and prediction over the range of energies was 1.0%. The validation methodology showed that one may expect an approximate uncertainty of 0.5% (1SD) when as little as eight data points are used. The level of accuracy combined with the ease with which this model can be generated demonstrates its suitability for clinical use. Implementation of this method is freely available for download at https://github.com/SimonBiggs/electronfactors. © 2015 Associazione Italiana di Fisica Medica. Source

Crowe S.B.,Royal Brisbane and Womens Hospital | Crowe S.B.,Queensland University of Technology | Kairn T.,Queensland University of Technology | Middlebrook N.,Genesis CancerCare Queensland | And 5 more authors.
Physics in Medicine and Biology | Year: 2015

This study aimed to provide a detailed evaluation and comparison of a range of modulated beam evaluation metrics, in terms of their correlation with QA testing results and their variation between treatment sites, for a large number of treatments. Ten metrics including the modulation index (MI), fluence map complexity, modulation complexity score (MCS), mean aperture displacement (MAD) and small aperture score (SAS) were evaluated for 546 beams from 122 intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) treatment plans targeting the anus, rectum, endometrium, brain, head and neck and prostate. The calculated sets of metrics were evaluated in terms of their relationships to each other and their correlation with the results of electronic portal imaging based quality assurance (QA) evaluations of the treatment beams. Evaluation of the MI, MAD and SAS suggested that beams used in treatments of the anus, rectum, head and neck were more complex than the prostate and brain treatment beams. Seven of the ten beam complexity metrics were found to be strongly correlated with the results from QA testing of the IMRT beams (p<0.00008). For example, values of SAS (with multileaf collimator apertures narrower than 10mm defined as 'small') less than 0.2 also identified QA passing IMRT beams with 100% specificity. However, few of the metrics are correlated with the results from QA testing of the VMAT beams, whether they were evaluated as whole 360 arcs or as 60 sub-arcs. Select evaluation of beam complexity metrics (at least MI, MCS and SAS) is therefore recommended, as an intermediate step in the IMRT QA chain. Such evaluation may also be useful as a means of periodically reviewing VMAT planning or optimiser performance. © 2015 Institute of Physics and Engineering in Medicine. Source

Russell B.,Center for Palliative Care | Collins A.,Center for Palliative Care | Dally M.,Epworth Radiation Oncology | Dowling A.,St. Vincents Hospital Melbourne | And 3 more authors.
Journal of Neuro-Oncology | Year: 2014

The long-term survival of patients with adult high-grade glioma (HGG) remains poor, but for those who do live longer functional status and neurocognitive ability may be influenced by residual or recurrent tumour, or treatment-related complications. The aim of this review was to examine the current literature regarding the quality of life and experience of patients living longer with adult HGG and their caregivers, with a view to understanding the burden of treatment on patient abilities and deficits over time. Medline, PsychINFO and CINAHL databases were searched for the core concept of HGG in combination with an aspect of quality of long-term survival. Key findings of the 12 included studies were identified and synthesised thematically. There is a paucity of dedicated studies which have investigated the experiences of this cohort. The strength of existing literature is limited by the systematic exclusion of the poorest functioning patients and the under-representation of caregiver perspectives. Discrepancies in how patients view their quality of life were highlighted, despite consistent findings of significant physical and functional impairment. This review confirmed the presence of important differences between patient and caregiver views regarding patient abilities following treatment. Caregiver burden was found to be high, due to multiple dynamic and relentless stressors. The true experience of patients living longer with adult HGG and their caregivers remains unclear, particularly for patients with poorer neurocognitive and functional outcomes. Further research is required to clarify and replicate findings, explore discrepancies between patient and caregiver views, and to specifically investigate how caregiver needs and experiences may evolve over time. © 2014, Springer Science+Business Media New York. Source

Charles P.H.,Princess Alexandra Hospital | Charles P.H.,Queensland University of Technology | Cranmer-Sargison G.,Saskatchewan Cancer Agency | Cranmer-Sargison G.,University of Saskatchewan | And 9 more authors.
Medical Physics | Year: 2014

Results: 1.0 mm of air was required to make the PTWe diode correction-free. This modified diode (PTWeair) produced output factors equivalent to those in water at all field sizes (5-50 mm). The optimal air thickness required for the EDGEe diode was found to be 0.6 mm. The modified diode (EDGEeair) produced output factors equivalent to those in water, except at field sizes of 8 and 10 mmwhere it measured pproximately 2% greater than the relative dose to water. The experimentally calculated k fclin, f msr Qclin,Qmsrfor both the PTWe and the EDGEe diodes (without air) matched Monte Carlo simulated results, thus proving that it is feasible to transfer k fclin, f msr Qclin,Qmsrfrom one commercially available detector to another using experimental methods and the recommended experimental setup.Conclusions: It is possible to create a diode which does not require corrections for small field output factor measurements. This has been performed and verified experimentally. The ability of a detector to be correction-free depends strongly on its design and composition. A nonwater-equivalent detector can only be correction-free if competing perturbations of the beam cancel out at all field sizes. This should not be confused with true water equivalency of a detector.Purpose: Two diodes which do not require correction factors for small field relative output measurements are designed and validated using experimental methodology. This was achieved by adding an air layer above the active volume of the diode detectors, which canceled out the increase in response of the diodes in small fields relative to standard field sizes.Methods: Due to the increased density of silicon and other components within a diode, additional electrons are created. In very small fields, a very small air gap acts as an effective filter of electrons with a high angle of incidence. The aim was to design a diode that balanced these perturbations to give a response similar to a water-only geometry. Three thicknesses of air were placed at the proximal end of a PTW 60017 electron diode (PTWe) using an adjustable air cap. A set of output ratios (ORfclin Det) for square field sizes of side length down to 5 mm was measured using each air thickness and compared to ORfclin Detmeasured using an IBA stereotactic field diode (SFD). kfclin, f msr Qclin,Qmsrwas transferred from the SFD to the PTWe diode and plotted as a function of air gap thickness for each field size. This enabled the optimal air gap thickness to be obtained by observing which thickness of air was required such that k fclin, f msr Qclin,Qmsrwas equal to 1.00 at all field sizes. A similar procedure was used to find the optimal air thickness required to make a modified Sun Nuclear EDGE detector (EDGEe) which is correction-free in small field relative dosimetry. In addition, the feasibility of experimentally transferring k fclin, f msr Qclin,Qmsrvalues from the SFD to unknown diodes was tested by comparing the experimentally transferred k fclin, f msr Qclin,Qmsrvalues for unmodified PTWe and EDGEe diodes to Monte Carlo simulated values. © 2014 Am. Assoc. Phys. Med. Source

Lim K.,Liverpool Cancer Therapy Center | Erickson B.,Medical College of Wisconsin | Jurgenliemk-Schulz I.M.,University Utrecht | Gaffney D.,University of Utah | And 13 more authors.
Practical Radiation Oncology | Year: 2015

Purpose: The purpose of this study was to assess variability in contouring the gross tumor volume (GTV) and clinical target volume (CTV) of 3 clinical cervix cancer cases by a cohort of international experts in the field in preparation for the development of an online teaching atlas. Methods and materials: Twelve international experts participated. Three clinical scenarios: node positivity (PLN), retroverted uterus (RV), and parametrial invasion (PI) were used. Sagittal and axial magnetic resonance images of the clinical cases were downloaded to participants' treatment planning systems for contouring. The GTV/cervix/uterus/parametria/vagina and nodal CTV were contoured. Contour consensus was assessed for sensitivity/specificity using an expectation maximization algorithm called Simultaneous Truth and Performance Level Estimation and experts' overall agreement was summarized by kappa statistics. Results: Agreement for GTV in the 3 clinical cases was high (Simultaneous Truth and Performance Level Estimation sensitivity, 0.54-0.92; specificity, 0.97-0.98; and kappa measure for PLN, RV, and PI was 0.86, 0.76, and 0.42; P <.0001). Moderate to substantial agreement was seen for nodal CTV (kappa statistics for PLN, RV, and PI was 0.65, 0.58, and 0.62; P <.0001), uterus (kappa for PLN, RV, and PI was 0.45, 0.74, and 0.77; P <.0001), and parametria (kappa for PLN, RV, and PI was 0.49, 0.62, and 0.50; P <.0001). Contouring heterogeneity was greatest for the cervix (kappa measure for PLN, RV, and PI was 0.15, 0.4, and 0.24; P <.0001) and vagina (kappa for PLN, RV, and PI was 0.47, 0.36 and 0.46; P <.0001), reflecting difficulties in determining the interface between GTV and these tissues. Conclusion: Kappa statistics of the different CTV components generally demonstrated moderate to substantial agreement among international experts in the field of gynecological radiation therapy. Further planning target volume margins accounting for organ motion and setup errors are a necessary addition to the CTV. © 2015 Published by Elsevier Inc. Source

Discover hidden collaborations