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https://www.readbyqxmd.com/read/28921931/technical-note-a-simple-algorithm-to-convert-epid-grey-values-into-absorbed-dose-to-water-without-prior-knowledge
#1
Christine Boutry, Aurélie Sors, Jimmy Fontaine, Nolwenn Delaby, Gregory Delpon
PURPOSE: Full integration of EPID-based dosimetry in a global quality control workflow is still complicated. All the actual solutions are based on a relation between image grey-level signal and total linac delivered dose. In this study, we propose a simple algorithm relying pixel grey-level of EPID image with average linac delivered dose per acquisition frame. METHODS: Calibration models are constructed for Varian and Elekta linacs including scattering conditions and EPID-arm backscatter specific corrections...
September 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28887827/a-universal-parameterized-gradient-based-method-for-photon-beam-field-size-determination
#2
Sharon Lebron, Guanghua Yan, Jonathan Li, Bo Lu, Chihray Liu
PURPOSE: To propose a universal, parameterized gradient-based method (PGM) for radiation field size determination. METHODS: The PGM locates the beam profile's edge by parameterizing its penumbra region with a modified sigmoid function where the inflection point can be determined in a closed form. The parametrization was validated with filter-flattened (FF), flattening-filter-free (FFF) and wedged profiles measured on two Elekta linac models (Synergy and Versa HD)...
September 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/28886048/a-single-source-photon-source-model-of-a-linear-accelerator-for-monte-carlo-dose-calculation
#3
Obioma Nwankwo, Gerhard Glatting, Frederik Wenz, Jens Fleckenstein
PURPOSE: To introduce a new method of deriving a virtual source model (VSM) of a linear accelerator photon beam from a phase space file (PSF) for Monte Carlo (MC) dose calculation. MATERIALS AND METHODS: A PSF of a 6 MV photon beam was generated by simulating the interactions of primary electrons with the relevant geometries of a Synergy linear accelerator (Elekta AB, Stockholm, Sweden) and recording the particles that reach a plane 16 cm downstream the electron source...
2017: PloS One
https://www.readbyqxmd.com/read/28871971/financial-relationships-with-industry-of-editorial-board-members-of-the-three-journals-of%C3%A2-the-american-society-for-radiation-oncology
#4
Vivek Verma
PURPOSE: To quantitate financial conflicts of interest (FCOIs) among radiation oncology peer-reviewers, specifically editorial board members of the 3 American Society for Radiation Oncology journals. METHODS AND MATERIALS: The public Centers for Medicare and Medicaid Services Open Payments database delineates payments in 3 categories (general payments, research funding, and company ownership). After excluding non-US and non-MDs, names of board members were searched...
October 1, 2017: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/28869651/technical-note-investigating-the-impact-of-field-size-on-patient-selection-for-the-1-5t-mr-linac
#5
Robert W Chuter, Philip Whitehurst, Ananya Choudhury, Marcel van Herk, Alan McWilliam
PURPOSE: The 1.5T Elekta MR-Linac, due to the construction of the system will have a maximum radiation field size in the superior-inferior patient direction of 22cm at isocentre. The field size may impact on the patient groups which can be treated on the system. This technical note aims to address the question of which treatment sites will be affected by field size limitations on the MR-Linac. METHODS: Using historical data for 11,595 cases over 2 years treated at the authors' institution, the proportion of plans that would fit the MR-Linac's field size was determined for eleven patient groups...
September 4, 2017: Medical Physics
https://www.readbyqxmd.com/read/28857432/volumetric-modulated-arc-therapy-and-intensity-modulated-radiation-therapy-treatment-planning-for-prostate-cancer-with-flattened-beam-and-flattening-filter-free-linear-accelerators
#6
Marius Treutwein, Matthias Hipp, Oliver Koelbl, Barbara Dobler
This study on patients with localized prostate cancer was set up to investigate valuable differences using flattened beam (FB) and flattening filter free (FFF) mode in the application of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). For ten patients, four different plans were calculated with Oncentra planning system of Elekta, using Synergy machines: IMRT and VMAT, with and without flattening filter. Homogeneity and conformity indexes, dose to the organs at risk, and measurements of peripheral dose and dosimetric plan verification including record of the delivery times were analyzed and statistically evaluated...
August 30, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28834109/implementation-of-respiratory-gated-vmat-on-a-versa-hd-linear-accelerator
#7
Jeffrey E Snyder, Ryan T Flynn, Daniel E Hyer
The accurate delivery of respiratory-gated volumetric modulated arc therapy (VMAT) treatment plans presents a challenge since the gantry rotation and collimator leaves must be repeatedly stopped and set into motion during each breathing cycle. In this study, we present the commissioning process for an Anzai gating system (AZ-733VI) on an Elekta Versa HD linear accelerator and make recommendations for successful clinical implementation. The commissioning tests include central axis dose consistency, profile consistency, gating beam-on/off delay, and comparison of gated versus nongated gamma pass rates for patient-specific quality assurance using four clinically commissioned photon energies: 6 MV, 6 FFF, 10 MV, and 10 FFF...
August 18, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28810243/evaluating-critical-brain-radiation-doses-in-the-treatment-of-multiple-brain-lesions-with-gamma-knife-radiosurgery
#8
Mustafa Aziz Hatiboglu, Kerime Akdur
BACKGROUND: Treatment of patients with multiple brain metastases has shifted to stereotactic radiosurgery, withholding whole-brain (WB) radiation therapy. However, radiation toxicity to the brain is a concern when treating multiple brain lesions with single-fraction stereotactic radiosurgery. OBJECTIVE: The purpose of this study was to determine the changes in brain radiation doses when treating various numbers of targets and lesion volumes. METHODS: We simulated different treatment plans with different combinations of varying tumor volumes including 0...
2017: Stereotactic and Functional Neurosurgery
https://www.readbyqxmd.com/read/28801965/improved-electron-collimation-system-design-for-elekta-linear-accelerators
#9
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
Prototype 10 × 10 and 20 × 20-cm(2) electron collimators were designed for the Elekta Infinity accelerator (MLCi2 treatment head), with the goal of reducing the trimmer weight of excessively heavy current applicators while maintaining acceptable beam flatness (±3% major axes, ±4% diagonals) and IEC leakage dose. Prototype applicators were designed initially using tungsten trimmers of constant thickness (1% electron transmission) and cross-sections with inner and outer edges positioned at 95% and 2% off-axis ratios (OARs), respectively, cast by the upstream collimating component...
August 12, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28791962/is-the-ptw-60019-microdiamond-a-suitable-candidate-for-small-field-reference-dosimetry
#10
Vanessa De Coste, Paolo Francescon, Marco Marinelli, Laura Masi, Lucia Paganini, Maria Pimpinella, Giuseppe Prestopino, Serenella Russo, Antonella Stravato, Claudio Verona, Gianluca Verona-Rinati
A systematic study of the PTW microDiamond (MD) output factors (OF) is reported, aimed at clarifying its response in small fields and investigating its suitability for small field reference dosimetry. Ten MDs were calibrated under (60)Co irradiation. OF measurements were performed in 6 MV photon beams by a CyberKnife M6, a Varian DHX and an Elekta Synergy linacs. Two PTW silicon diodes E (Si-D) were used for comparison. The results obtained by the MDs were evaluated in terms of absorbed dose to water determination in reference conditions and OF measurements, and compared to the results reported in the recent literature...
August 9, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28766904/technical-note-trog-15-01-spark-trial-multi-institutional-imaging-dose-measurement
#11
Kimberley Legge, Peter B Greer, Paul J Keall, Jeremy T Booth, Sankar Arumugam, Trevor Moodie, Doan T Nguyen, Jarad Martin, Daryl John O'Connor, Joerg Lehmann
PURPOSE: The Trans-Tasman Radiation Oncology Group (TROG) 15.01 Stereotactic Prostate Adaptive Radiotherapy utilizing Kilovoltage intrafraction monitoring (SPARK) trial is a multicenter trial using Kilovoltage Intrafraction Monitoring (KIM) to monitor prostate position during the delivery of prostate radiation therapy. KIM increases the accuracy of prostate radiation therapy treatments and allows for hypofractionation. However, an additional imaging dose is delivered to the patient. A standardized procedure to determine the imaging dose per frame delivered using KIM was developed and applied at four radiation therapy centers on three different types of linear accelerator...
August 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28765594/evaluation-of-realistic-layouts-for-next-generation-on-scalp-meg-spatial-information-density-maps
#12
Bushra Riaz, Christoph Pfeiffer, Justin F Schneiderman
While commercial magnetoencephalography (MEG) systems are the functional neuroimaging state-of-the-art in terms of spatio-temporal resolution, MEG sensors have not changed significantly since the 1990s. Interest in newer sensors that operate at less extreme temperatures, e.g., high critical temperature (high-T c) SQUIDs, optically-pumped magnetometers, etc., is growing because they enable significant reductions in head-to-sensor standoff (on-scalp MEG). Various metrics quantify the advantages of on-scalp MEG, but a single straightforward one is lacking...
August 1, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28761391/the-accuracy-of-treatment-planning-system-dose-modelling-in-the-presence-of-brass-mesh-bolus
#13
Neil Richmond
AIM: This work assesses the dosimetric accuracy of three commercial treatment planning system (TPS) photon dose calculation algorithms in the presence of brass mesh used as a bolus. BACKGROUND: Bolus material is used in radiotherapy to provide dose build-up where superficial tissues require irradiation. They are generally water equivalent but high density materials can also be used. MATERIALS AND METHODS: Dose calculations were performed on Monaco and Masterplan TPS (Elekta AB, Sweden) using phantoms defined by the three DICOM CT image sets of water equivalent blocks (no bolus, 1 layer and 2 layers of brass mesh) exported from the CT scanner...
September 2017: Reports of Practical Oncology and Radiotherapy
https://www.readbyqxmd.com/read/28750134/performance-evaluation-of-a-collapsed-cone-dose-calculation-algorithm-for-hdr-ir-192-of-apbi-treatments
#14
Dario Terribilini, Veronika Vitzthum, Werner Volken, Daniel Frei, Kristina Loessl, Bob van Veelen, Peter Manser, Michael K Fix
PURPOSE: Most dose calculations for HDR brachytherapy treatments are based on the AAPM-TG43 formalism. Because patient's anatomy, heterogeneities and applicator shielding are not considered, the dose calculation based on this formalism is inaccurate in some cases. Alternatively, Collapsed Cone (CC) methods as well as Monte Carlo (MC) algorithms belong to the model based dose calculation algorithms, which are expected to improve the accuracy of calculated dose distributions. In this work, the performance of a CC algorithm, ACE in Oncentra Brachy 4...
July 27, 2017: Medical Physics
https://www.readbyqxmd.com/read/28749375/towards-fast-online-intrafraction-replanning-for-free-breathing-stereotactic-body-radiation-therapy-with-the-mr-linac
#15
C Kontaxis, G H Bol, B Stemkens, M Glitzner, F M Prins, L G W Kerkmeijer, J J W Lagendijk, B W Raaymakers
The hybrid MRI-radiotherapy machines, like the MR-linac (Elekta AB, Stockholm, Sweden) installed at the UMC Utrecht (Utrecht, The Netherlands), will be able to provide real-time patient imaging during treatment. In order to take advantage of the system's capabilities and enable online adaptive treatments, a new generation of software should be developed, ranging from motion estimation to treatment plan adaptation. In this work we present a proof of principle adaptive pipeline designed for high precision stereotactic body radiation therapy (SBRT) suitable for sites affected by respiratory motion, like renal cell carcinoma (RCC)...
August 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28740907/functional-imaging-equivalence-and-proof-of-concept-for-image-guided-adaptive-radiotherapy-with-fixed-gantry-and-rotating-couch
#16
Ilana Feain, Chun-Chien Shieh, Paul White, Ricky O'Brien, Sandra Fisher, William Counter, Peter Lazarakis, David Stewart, Simon Downes, Michael Jackson, Siddhartha Baxi, Brendan Whelan, Kuldeep Makhija, Chen-Yu Huang, Michael Barton, Paul Keall
PURPOSE: The purpose of this article is to present the first imaging experiments to demonstrate the functional equivalence between a conventional rotational gantry and a fixed-beam imaging geometry, and the feasibility of an iterative image-reconstruction technique under gravitational deformation. METHODS AND MATERIALS: Experiments were performed using an Elekta Axesse with Agility MLC and XVI, a custom-built rotating phantom stage, a Catphan QA phantom, and a porcine heart...
October 2016: Advances in Radiation Oncology
https://www.readbyqxmd.com/read/28714454/a-back-projection-algorithm-in-the-presence-of-an-extra-attenuating-medium-towards-epid-dosimetry-for-the-mr-linac
#17
I Torres-Xirau, I Olaciregui-Ruiz, R A Rozendaal, P González, B J Mijnheer, J-J Sonke, U A van der Heide, A Mans
In external beam radiotherapy, electronic portal imaging devices (EPIDs) are frequently used for pre-treatment and for in vivo dose verification. Currently, various MR-guided radiotherapy systems are being developed and clinically implemented. Independent dosimetric verification is highly desirable. For this purpose we adapted our EPID-based dose verification system for use with the MR-Linac combination developed by Elekta in cooperation with UMC Utrecht and Philips. In this study we extended our back-projection method to cope with the presence of an extra attenuating medium between the patient and the EPID...
July 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28711480/commissioning-of-small-field-size-radiosurgery-cones-in-a-6-mv-flattening-filter-free-beam
#18
Juan Diego Azcona, Benigno Barbés, Verónica Morán, Javier Burguete
This study aimed to describe the commissioning of small field size radiosurgery cones in a 6-MV flattening filter free (FFF) beam and report our measured values. Four radiosurgery cones of diameters 5, 10, 12.5, and 15 mm supplied by Elekta Medical were commissioned in a 6-MV FFF beam from an Elekta Versa linear accelerator. The extraction of a reference signal for measuring small fields in scanning mode is challenging. A transmission chamber was attached to the lower part of the collimators and used for percentage depth dose (PDD) and profile measurements in scanning mode with a stereotactic diode...
July 12, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/28688120/electron-beam-water-calorimetry-measurements-to-obtain-beam-quality-conversion-factors
#19
Bryan R Muir, Claudiu D Cojocaru, Malcolm R McEwen, Carl K Ross
PURPOSE: To provide results of water calorimetry and ion chamber measurements in high-energy electron beams carried out at the National Research Council Canada (NRC). There are three main aspects to this work: (a) investigation of the behavior of ionization chambers in electron beams of different energies with focus on long-term stability, (b) water calorimetry measurements to determine absorbed dose to water in high-energy beams for direct calibration of ion chambers, and (c) using measurements of chamber response relative to reference ion chambers, determination of beam quality conversion factors, kQ , for several ion chamber types...
July 8, 2017: Medical Physics
https://www.readbyqxmd.com/read/28679448/simultaneous-integrated-boost-therapy-of-carcinoma-of-the-hypopharynx-larynx-with-and-without-flattening-filter-a-treatment-planning-and-dosimetry-study
#20
Barbara Dobler, Tina Obermeier, Matthias G Hautmann, Amine Khemissi, Oliver Koelbl
BACKGROUND: The aim of this study was to investigate if the flattening filter free (FFF) irradiation mode of a linear accelerator (linac) is advantageous as compared to the flat beam (FF) irradiation mode in intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for carcinoma of the hypopharynx / larynx. METHODS: Four treatment plans were created for each of 10 patients for an Elekta Synergy linac with Agility collimating device, a dual arc VMAT and a nine field step and shoot IMRT each with and without flattening filter...
July 5, 2017: Radiation Oncology
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