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https://www.readbyqxmd.com/read/28108100/three-dimensional-quality-assurance-of-imrt-prostate-plans-using-gel-dosimetry
#1
M A Silveira, J F Pavoni, O Baffa
Intensity modulated radiotherapy (IMRT) is one of the most modern radiation therapy treatment techniques. Although IMRT can deliver high and complex conformational doses to the tumor volume, its implementation requires rigorous quality assurance (QA) procedures that include a dosimetric pre-treatment verification of individual patient planning. This verification usually involves measuring a small volume of absolute dose with an ionization chamber and checking bi-dimensional fluency with an array of detectors...
January 17, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28102948/use-of-parallel-plate-ionization-chambers-in-reference-dosimetry-of-novac-and-liac-%C3%A2-mobile-electron-linear-accelerators-for-intraoperative-radiotherapy-a-multi-center-survey
#2
Paolo Scalchi, Alessia Ciccotelli, Giuseppe Felici, Assunta Petrucci, Raffaella Massafra, Valeria Piazzi, Paola D'Avenia, Francesca Cavagnetto, Federica Cattani, Raffaella Romagnoli, Antonella Soriani
PURPOSE: LIAC(®) and NOVAC are two mobile linear accelerators dedicated to intraoperative radiation therapy (IORT), generating electron beams in the energy range of 3-12 MeV. Due to high dose-per-pulse (up to 70 mGy per pulse), in 2003 the Italian National Institute of Health (ISS) stated that "for the measure of dose to water in reference conditions, ionization chambers cannot be employed and no published dosimetry protocol can be used". As a consequence, ferrous sulphate (or, alternatively alanine) dosimetry was recommended...
January 2017: Medical Physics
https://www.readbyqxmd.com/read/28102946/a-portal-dosimetry-dose-prediction-method-based-on-collapsed-cone-algorithm-using-the-clinical-beam-model
#3
J Martínez Ortega, N Gómez González, P Castro Tejero, M Pinto Monedero, N B Tolani, L Núñez Martín, R Sánchez Montero
PURPOSE: Amorphous silicon electronical portal imaging devices (EPIDs) are widely used for dosimetric measurements in Radiation Therapy. The purpose of this work was to determine if a portal dose prediction method can be utilized for dose map calculations based on the linear accelerator model within a commercial treatment planning system (Pinnacle(3) v8.0 m). METHODS: The method was developed for a 6 MV photon beam on the Varian Clinac 21-EX, at a nominal dose rate of 400 MU/min...
January 2017: Medical Physics
https://www.readbyqxmd.com/read/28099012/aqueous-photochemistry-of-secondary-organic-aerosol-of-%C3%AE-pinene-and-%C3%AE-humulene-oxidized-with-ozone-hydroxyl-radical-and-nitrate-radical
#4
Dian E Romonosky, Ying Li, Manabu Shiraiwa, Alexander Laskin, Julia Laskin, Sergey A Nizkorodov
Formation of secondary organic aerosols (SOA) from biogenic volatile organic compounds (BVOC) occurs via O3- and OH-initiated reactions during the day and reactions with NO3 during the night. We explored the effect of these three oxidation conditions on the molecular composition and aqueous photochemistry of model SOA prepared from two common BVOC. A common monoterpene, α-pinene, and sesquiterpene, α-humulene, were used to form SOA in a smog chamber via BVOC + O3, BVOC + NO3, and BVOC + OH + NOx oxidation...
January 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28094856/percent-depth-doses-and-x-ray-beam-characterizations-of-a-fluoroscopic-system-incorporating-copper-filtration
#5
Kevin A Wunderle, Andrew R Godley, Zhilei Liu Shen, Joseph T Rakowski, Frank F Dong
PURPOSE: In this investigation, we sought to characterize X-ray beam qualities and quantify percent depth dose (PDD) curves for fluoroscopic X-ray beams incorporating added copper (Cu) filtration, such as those commonly used in fluoroscopically guided interventions (FGI). The intended application of this research is for dosimetry in soft tissue from FGI procedures using these data. METHODS: All measurements in this study were acquired on a Siemens (Erlangen, Germany) Artis zeego fluoroscope...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094853/high-dose-per-pulse-electron-beam-dosimetry-a-model-to-correct-for-the-ion-recombination-in-the-advanced-markus-ionization-chamber
#6
Kristoffer Petersson, Maud Jaccard, Jean-François Germond, Thierry Buchillier, François Bochud, Jean Bourhis, Marie-Catherine Vozenin, Claude Bailat
PURPOSE: The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semi-empirical general equation presented by Burns and McEwen. METHODS: Two independent methods were used to investigate the ion recombination: 1) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD)...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28094849/the-collimator-monitoring-fill-factor-of-a-two-dimensional-detector-array-a-measure-of-its-ability-to-detect-collimation-errors
#7
Tenzin Sonam Stelljes, Hui Khee Looe, Dietrich Harder, Björn Poppe
PURPOSE: Two-dimensional detector arrays are routinely used for constancy checks and treatment plan verification in photon-beam radiotherapy. In addition to the spatial resolution of the dose profiles, the "coverage" of the radiation field with respect to the detection of any beam collimation deficiency appears as the second characteristic feature of a detector array. The here proposed "collimator monitoring fill factor" (CM fill factor) has been conceived to serve as a quantitative characteristic of this "coverage"...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28092630/comparative-monte-carlo-study-on-the-performance-of-integration-and-list-mode-detector-configurations-for-carbon-ion-computed-tomography
#8
Sebastian Meyer, Chiara Gianoli, Lorena Magallanes, Benedikt Kopp, Thomas Tessonnier, Guillaume Landry, George Dedes, Bernd Voss, Katia Parodi
Ion beam therapy offers the possibility of a highly conformal tumor-dose distribution; however, this technique is extremely sensitive to inaccuracies in the treatment procedures. Ambiguities in the conversion of Hounsfield units of the treatment planning x-ray CT to relative stopping power (RSP) can cause uncertainties in the estimated ion range of up to several millimeters. Ion CT (iCT) represents a favorable solution allowing to directly assess the RSP. In this simulation study we investigate the performance of the integration-mode configuration for carbon iCT, in comparison with a single-particle approach under the same set-up...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28089106/-edge-on-moskin-detector-for-stereotactic-beam-measurement-and-verification
#9
Wei Loong Jong, Ngie Min Ung, Ath Vannyat, Zulaikha Jamalludin, Anatoly Rosenfeld, Jeannie Hsiu Ding Wong
Dosimetry in small radiation field is challenging and complicated because of dose volume averaging and beam perturbations in a detector. We evaluated the suitability of the "Edge-on" MOSkin (MOSFET) detector in small radiation field measurement. We also tested the feasibility for dosimetric verification in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). "Edge-on" MOSkin detector was calibrated and the reproducibility and linearity were determined. Lateral dose profiles and output factors were measured using the "Edge-on" MOSkin detector, ionization chamber, SRS diode and EBT2 film...
January 6, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28072396/quantification-of-static-magnetic-field-effects-on-radiotherapy-ionization-chambers
#10
James Paul Agnew, Frank O'Grady, Ryan Young, Simon Duane, Geoff Budgell
Integrated magnetic resonance imaging and radiotherapy delivery machines are currently being developed, with some already in clinical use. It is anticipated that the strong magnetic field used in some MR-RT designs will have a significant impact on routine measurements of dose in the MR-linac performed using ionization chambers, which provide traceability back to a primary standard definition of dose. In particular, the presence of small air gaps around ionization chambers may introduce unacceptably high uncertainty into these measurements...
January 10, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28070048/-role-of-local-citrate-anticoagulation-in-continuous-blood-purification-to-patients-at-high-risk-of-bleeding-in-icu
#11
Shangping Zhao, Hao Ou, Yue Peng, Zuoliang Liu, Mingshi Yang, Xuefei Xiao
To evaluate the safety and efficiency of citrate anticoagulant-based continuous blood purification in patients at high risk of bleeding. 
 Methods: One hundred and fifty-two patients at high risk of bleeding were divided into local citrate group (group A, n=68) and heparin group (group B, n=84). Clotting function, change of pH, ionized sodium, bicarbonate ion, ionized calcium, activated clotting time (ACT) and complications were monitored before and during treatment. 
 Results: Compared to the group A, the incidence of clotting in filter and chamber, the degree of bleeding or fresh bleeding were significantly reduced in the group B (P<0...
December 28, 2016: Zhong Nan da Xue Xue Bao. Yi Xue Ban, Journal of Central South University. Medical Sciences
https://www.readbyqxmd.com/read/28063164/separation-of-scatter-from-small-mv-beams-and-its-effect-on-detector-response
#12
Sonja Wegener, Otto A Sauer
PURPOSE: Separating the scatter from the primary component of a MV beam to study detector response separately in each case for a better understanding of the role of different effects influencing the response in non-standard fields. METHODS: Detector response in three different experimental set-ups was investigated for a variety of different types (diamond, shielded and unshielded diodes, ionization chamber and film): 1. Detectors positioned in water under a thin steel pole blocking the central part of the beam, yielding only the response to the scatter part of the beam...
January 7, 2017: Medical Physics
https://www.readbyqxmd.com/read/28048873/su-f-t-32-evaluation-of-the-performance-of-a-multiple-array-diode-detector-for-quality-assurance-tests-in-high-dose-rate-brachytherapy-with-ir-192-source
#13
K Harpool, T De La Fuente Herman, S Ahmad, I Ali
PURPOSE: To evaluate the performance of a two-dimensional (2D) array-diode- detector for geometric and dosimetric quality assurance (QA) tests of high-dose-rate (HDR) brachytherapy with an Ir-192-source. METHODS: A phantom setup was designed that encapsulated a two-dimensional (2D) array-diode-detector (MapCheck2) and a catheter for the HDR brachytherapy Ir-192 source. This setup was used to perform both geometric and dosimetric quality assurance for the HDR-Ir192 source...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048803/su-f-t-152-experimental-validation-and-calculation-benchmark-for-a-commercial-monte-carlo-pencil-beamscanning-proton-therapy-treatment-planning-system-in-heterogeneous-media
#14
L Lin, S Huang, M Kang, C Ainsley, C Simone, J McDonough, T Solberg
PURPOSE: Eclipse AcurosPT 13.7, the first commercial Monte Carlo pencil beam scanning (PBS) proton therapy treatment planning system (TPS), was experimentally validated for an IBA dedicated PBS nozzle in the CIRS 002LFC thoracic phantom. METHODS: A two-stage procedure involving the use of TOPAS 1.3 simulations was performed. First, Geant4-based TOPAS simulations in this phantom were experimentally validated for single and multi-spot profiles at several depths for 100, 115, 150, 180, 210 and 225 MeV proton beams, using the combination of a Lynx scintillation detector and a MatriXXPT ionization chamber array...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048797/su-f-j-152-accuracy-of-charge-particle-transport-in-magnetic-fields-using-egsnrc
#15
E Mainegra-Hing, H Bouchard, F Tessier, B Walters
PURPOSE: Determine accuracy of the current implementation of electron transport under magnetic fields in EGSnrc by means of single scattering (SS) and Fano convergence tests, and establish quantitatively the electron step size restriction required to achieve a desired level of accuracy for ionization chamber dosimetry. METHODS: Condensed history (CH) dose calculations are compared to SS results for a PTW30013 ionization chamber irradiated in air by a 60Co photon beam...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048793/su-f-t-72-experimental-determination-of-the-positionuncertainties-for-roos-ionization-chambers-in-clinical-electron-beams
#16
P von Voigts-Rhetz, T Pretzsch, D Czarnecki, H Vorwerk, K Zink
PURPOSE: National and international dosimetry protocols assume a position accuracy for ionization chambers of less than 0.2mm. To follow this precept the manufacturer PTW-Freiburg introduced a positioning assistance system (TRUFIX) for their particular ion chambers. Aim of this study is an experimental investigation of the positioning uncertainties for ROOS-type ionization chambers. METHODS: For all measurements a linear accelerator Elekta Synergie was used. The experiments were performed in a water-phantom...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048669/su-f-t-177-impacts-of-gantry-angle-dependent-scanning-beam-properties-for-proton-treatment
#17
Y Lin, B Clasie, H Lu, J Flanz, K Jee
PURPOSE: In pencil beam scanning (PBS), the delivered spot MU, position and size are slightly different at different gantry angles. We investigated the level of delivery uncertainty at different gantry angles through a log file analysis. METHODS: 34 PBS fields covering full 360 degrees gantry angle spread were collected retrospectively from 28 patients treated at our institution. All fields were delivered at zero gantry angle and the prescribed gantry angle, and measured at isocenter with the MatriXX 2D array detector at the prescribed gantry angle...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048608/tu-e-tour-i-00-exhibit-hall-guided-tours-dosimters-for-qc-in-diagnostic-imaging-tuesday
#18
(no author information available yet)
: Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Christina Sammet, Lurie Children's Hospital of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048572/tu-h-207a-07-comparison-of-performance-of-tube-current-modulation-of-three-commercial-mdct-scanners
#19
T Ohno, F Araki
PURPOSE: To compare performance of tube-current modulation (TCM) of three commercial MDCT scanners (TOSHIBA Aquilion One, SIEMENS SOMATOM Definition AS+, PHILIPS Brilliance iCT) from tube current measurement, image noise measurement, and Monte Carlo (MC) simulation based on time-resolved air kerma measurement. METHODS: CT image acquisitions were performed with and without TCM by means of TCM phantoms with length of 40 cm which consists of three oval phantoms (10×20 cm, 14×28 cm, 18×36 cm) and one cylindrical phantom with diameter of 10 cm...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048566/su-f-t-492-the-impact-of-water-temperature-on-absolute-dose-calibration
#20
N Islam, M Podgorsak
PURPOSE: The Task Group 51 (TG 51) protocol prescribes that dose calibration of photon beams be done by irradiating an ionization chamber in a water tank at pre-defined depths. Methodologies are provided to account for variations in measurement conditions by applying correction factors. However, the protocol does not completely account for the impact of water temperature. It is well established that water temperature will influence the density of air in the ion chamber collecting volume...
June 2016: Medical Physics
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