keyword
MENU ▼
Read by QxMD icon Read
search

ionization chamber

keyword
https://www.readbyqxmd.com/read/28636564/radiation-dosimetry-in-magnetic-fields-with-farmer-type-ionization-chambers-determination-of-magnetic-field-correction-factors-for-different-magnetic-field-strengths-and-field-orientations
#1
Claudia Katharina Spindeldreier, Oliver Schrenk, Anna Bakenecker, Iwan Kawrakow, Lucas Norberto Burigo, Christian P Karger, Steffen Greilich, Asja Pfaffenberger
The aim of this work was to determine magnetic field correction factors that are needed for dosimetry in hybrid devices for MR-guided radiotherapy for Farmer-type ionization chambers for different magnetic field strengths and field orientations. The response of six custom-built Farmer-type chambers irradiated at a 6 MV linac was measured in a water tank positioned in a magnet with magnetic field strengths between 0.0 T and 1.1 T. Chamber axis, beam and magnetic field were perpendicular to each other and both magnetic field directions were investigated...
June 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28610703/air-density-dependence-of-the-response-of-the-ptw-sourcecheck-4pi-ionization-chamber-for-125-i-brachytherapy-seeds
#2
J Torres Del Río, A M Tornero-López, D Guirado, J Pérez-Calatayud, A M Lallena
PURPOSE: To analyze the air density dependence of the response of the new SourceCheck 4pi ionization chamber, manufactured by PTW. METHODS: The air density dependence of three different SourceCheck 4pi chambers was studied by measuring (125)I sources. Measurements were taken by varying the pressure from 746.6 to 986.6hPa in a pressure chamber. Three different HDR 1000 Plus ionization chambers were also analyzed under similar conditions. A linear and a potential-like function of the air density were fitted to experimental data and their achievement in describing them was analyzed...
June 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28610700/computation-of-the-electron-beam-quality-formula-see-text-factors-for-the-ne2571-ne2571a-and-ne2581a-thimble-ionization-chambers-using-penelope
#3
F Erazo, L Brualla, A M Lallena
The quality correction factor [Formula: see text] for electron beams was calculated for three thimble ionization chambers, namely, NE2571, NE2571A and NE2581A. The Monte Carlo code PENELOPE was used to estimate the overall correction factor fc,Q of these chambers for electron beams with nominal energies ranging between 6 and 22MeV, corresponding to a Varian Clinac 2100 C/D. A (60)Co beam was used as reference quality Q0. Also eight monoenergetic electron beams reproducing the quality index R50 of the Clinac beams were considered...
June 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28608392/volatile-organic-compounds-analysis-by-pulsed-glow-discharge-time-of-flight-mass-spectrometry-as-a-structural-elucidation-tool
#4
M Bouza, J Fandino, N Bordel, R Pereiro, A Sanz-Medel
Pulsed glow discharge (PGD) coupled to time of flight mass spectrometry (TOFMS) has been investigated for volatile organic compounds (VOCs) identification and determination. Optimization of PGD operational conditions (chamber design, applied power, pressure and duty cycle) was performed using acetone and benzene as model compounds. During the different optimizations, molecular, fragment and elemental information were obtained when characteristic GD pulse regions were measured. An exploratory study for several VOCs (lineal hydrocarbons, oxygen-containing compounds and aromatic compounds) revealed the capability of the PGD to provide crucial information to elucidate structures (fragments), molecular ions or even proton affinity nature of the molecules; this last information is a consequence of the enriched proton environment generated along the afterglow region for the ionization chamber used...
June 12, 2017: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/28605568/technical-note-ion-chamber-angular-dependence-in-a-magnetic-field
#5
Michael Reynolds, Satyapal Rathee, B Gino Fallone
PURPOSE: There have been several studies investigating dose deposition effects within radiation detectors in the presence of a magnetic field. However, to date there has only been a passing investigation which explicitly investigates detector dose response as a function of detector orientation. Herein we will investigate the dose response as a function angular orientation of a PR06C ionization chamber. We will also benchmark the Monte Carlo code PENELOPE with the newly developed magnetic field Fano test...
June 12, 2017: Medical Physics
https://www.readbyqxmd.com/read/28604370/development-of-a-synthetic-single-crystal-diamond-dosimeter-for-dose-measurement-of-clinical-proton-beams
#6
Cyril Moignier, Dominique Tromson, Ludovic de Marzi, Fanny Marsolat, Juan Carlos García Hernández, Mathieu Agelou, Michal Pomorski, Romuald Woo, Jean-Michel Bourbotte, Fabien Moignau, Delphine Lazaro, Alejandro Mazal
The scope of this work was to develop a synthetic single crystal diamond dosimeter (SCDD-Pro) for accurate relative dose measurements of clinical proton beams in water. Monte Carlo simulations were carried out based on the MCNPX code in order to investigate and reduce the dose curve perturbation caused by the SCDD-Pro. In particular, various diamond thicknesses were simulated to evaluate the influence of the active volume thickness (e AV) as well as the influence of the addition of a front silver resin (250 µm in thickness in front of the diamond crystal) on depth-dose curves...
July 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28591854/correction-factors-for-attenuation-and-scattering-of-the-wall-of-a-cylindrical-ionization-chamber-in-the-6-7-mev-high-energy-photon-reference-field
#7
M Kowatari, H Zutz, O Hupe
In high-energy photon reference fields the value of the air kerma rate is determined by using ionization chambers (ICs). From the charge collected inside the IC the dose can be calculated using a set of calibration and correction factors according to ISO 4037-2. A crucial parameter is the correction for the attenuation and scattering of the primary radiation due to the chamber wall. This parameter can be determined using Monte Carlo calculations. The evaluation of the factor was performed for a commercially available IC of the type Victoreen 550-3 under different build-up conditions...
June 7, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28582266/a-beam-monitoring-and-validation-system-for-continuous-line-scanning-in-proton-therapy
#8
Grischa Klimpki, Serena Psoroulas, Christian Bula, Urs Rechsteiner, Michael Eichin, Damien Weber, Antony Lomax, David Meer
Line scanning represents a faster and potentially more flexible form of pencil beam scanning than conventional <i>step-and-shoot</i> irradiations. It seeks to minimize dead times in beam delivery whilst preserving the possibility to modulate the dose at any point in the target volume. Our second generation proton gantry features irradiations in line scanning mode, but it still lacks a dedicated monitoring and validation system that guarantees patient safety throughout beam delivery. We report on its design and implementation in this paper...
June 5, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28574219/optimization-of-the-dosimetric-leaf-gap-for-use-in-planning-vmat-treatments-of-spine-sabr-cases
#9
Nigel D Middlebrook, Bess Sutherland, Tanya Kairn
The dosimetric leaf gap (DLG) is a beam configuration parameter used in the Varian Eclipse treatment planning system, to model the effects of rounded MLC leaf ends. Measuring the DLG using the conventional sliding-slit technique has been shown to be produce questionable results for some volumetric modulated arc therapy (VMAT) treatments. This study therefore investigated the use of radiochromic film measurements to optimize the DLG specifically for the purpose of producing accurate VMAT plans using a flattening-filter-free (FFF) beam, for use in treating vertebral targets using a stereotactic (SABR, also known as SBRT) fractionation schedule...
June 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28574211/comparison-of-the-recommendations-of-the-aapm-tg-51-and-tg-51-addendum-reference-dosimetry-protocols
#10
Travis J McCaw, Min-Sig Hwang, Si Young Jang, M Saiful Huq
This work quantified differences between recommendations of the TG-51 and TG-51 addendum reference dosimetry protocols. Reference dosimetry was performed for flattened photon beams with nominal energies of 6, 10, 15, and 23 MV, as well as flattening-filter free (FFF) beam energies of 6 and 10 MV, following the recommendations of both the TG-51 and TG-51 addendum protocols using both a Farmer(®) ionization chamber and a scanning ionization chamber with calibration coefficients traceable to absorbed dose-to-water (Dw ) standards...
June 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28571708/quality-assurance-of-the-jaws-only-intensity-modulated-radiation-therapy-plans-for-head-and-neck-cancer
#11
Duong Thanh Tai, Nguyen Dong Son, Truong Thi Hong Loan, H P W Anson
Intensity-modulated radiation therapy (IMRT) is a treatment technique which has become routine in developed countries. In most centers this technique is delivered with multi-leaf collimators (MLCs). However, the use of MLCs is not mandatory. Several oncology centres in developing countries are still using linear accelerators (LINAC) without MLCs, and can potentially deliver IMRT plans with the use of collimator jaws. In this report, we present the results of quality assurance of this Jaws-Only-IMRT (JO-IMRT) technique in treating nasopharyngeal carcinoma (NPC) patients...
June 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28535915/virtual-patient-3d-dose-reconstruction-using-in-air-epid-measurements-and-a-back-projection-algorithm-for-imrt-and-vmat-treatments
#12
Igor Olaciregui-Ruiz, Roel Rozendaal, René F M van Oers, Ben Mijnheer, Anton Mans
PURPOSE: At our institute, a transit back-projection algorithm is used clinically to reconstruct in vivo patient and in phantom 3D dose distributions using EPID measurements behind a patient or a polystyrene slab phantom, respectively. In this study, an extension to this algorithm is presented whereby in air EPID measurements are used in combination with CT data to reconstruct 'virtual' 3D dose distributions. By combining virtual and in vivo patient verification data for the same treatment, patient-related errors can be separated from machine, planning and model errors...
May 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28535914/does-gantry-rotation-time-influence-accuracy-of-volume-computed-tomography-dose-index-ctdivol-in-modern-ct
#13
Atsushi Fukuda, Nao Ichikawa, Yoshiharu Fujita, Pei-Jan Paul Lin, Kosuke Matsubara, Tosiaki Miyati
PURPOSE: The purpose of this study was to develop a gantry overrun corrected CTDIvol (cCTDIvol) dosimetry and evaluate the differences between the displayed CTDIvol (dCTDIvol), measured CTDIvol (mCTDIvol), and the cCTDIvol. METHODS AND MATERIALS: The each 8 rotation times between 275 and 1000ms of two CT scanners were investigated. Rotation time (Trot) and the beam-on time (Tbeam) in axial scanning were measured accurately to determine the gantry overrun time (Tover) as Tbeam-Trot...
May 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28532617/first-french-experiences-of-total-body-irradiations-using-helical-tomotherapy-%C3%A2
#14
R Sun, X Cuenca, R Itti, S Nguyen Quoc, J-P Vernant, J-J Mazeron, C Jenny, M Chea
PURPOSE: Dynamic conformal radiotherapy with helical TomoTherapy(®) (HT) offers a more quantitative paradigm for total body irradiation. Treatment planning, delivery, dose verification of the first French experiences of total body irradiation using helical TomoTherapy(®) are presented. MATERIALS AND METHODS: Patients planned for total body irradiation at our institution from February 2012 to May 2013 were reported. Total body irradiation consisted in a single fraction of 2Gy...
May 19, 2017: Cancer Radiothérapie: Journal de la Société Française de Radiothérapie Oncologique
https://www.readbyqxmd.com/read/28528467/changes-in-deviation-of-absorbed-dose-to-water-among-users-by-chamber-calibration-shift
#15
Tetsurou Katayose, Hidetoshi Saitoh, Mitsunobu Igari, Weishan Chang, Shimpei Hashimoto, Mie Morioka
PURPOSE: The JSMP01 dosimetry protocol had adopted the provisional (60)Co calibration coefficient [Formula: see text], namely, the product of exposure calibration coefficient N C and conversion coefficient k D,X. After that, the absorbed dose to water D w standard was established, and the JSMP12 protocol adopted the [Formula: see text] calibration. In this study, the influence of the calibration shift on the measurement of D w among users was analyzed. MATERIALS AND METHODS: The intercomparison of the D w using an ionization chamber was annually performed by visiting related hospitals...
May 20, 2017: Japanese Journal of Radiology
https://www.readbyqxmd.com/read/28506453/challenges-of-dosimetry-of-ultra-short-pulsed-very-high-energy-electron-beams
#16
Anna Subiel, Vadim Moskvin, Gregor H Welsh, Silvia Cipiccia, David Reboredo, Colleen DesRosiers, Dino A Jaroszynski
Very high energy electrons (VHEE) in the range from 100 to 250MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetric properties compared with 6-20MV photons generated by clinical linear accelerators (LINACs). VHEE beams have characteristics unlike any other beams currently used for radiotherapy: femtosecond to picosecond duration electron bunches, which leads to very high dose per pulse, and energies that exceed that currently used in clinical applications...
May 11, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28504642/ion-recombination-correction-factor-in-scanned-light-ion-beams-for-absolute-dose-measurement-using-plane-parallel-ionisation-chambers
#17
S Rossomme, J Horn, S Brons, O Jäkel, A Mairani, M Ciocca, V Floquet, F Romano, D Rodriguez Garcia, S Vynckier, H Palmans
Based on international reference dosimetry protocols for light-ion beams, a correction factor (k s) has to be applied to the response of a plane-parallel ionisation chamber, to account for recombination of negative and positive charges in its air cavity before these charges can be collected on the electrodes. In this work, k s for IBA PPC40 Roos-type chambers is investigated in four scanned light-ion beams (proton, helium, carbon and oxygen). To take into account the high dose-rates used with scanned beams and LET-values, experimental results are compared to a model combining two theories...
July 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28488238/trans-oral-miniature-x-ray-radiation-delivery-system-with-endoscopic-optical-feedback
#18
Axel Boese, Fredrick Johnson, Till Ebert, Ali Mahmoud-Pashazadeh, Christoph Arens, Michael Friebe
PURPOSE: Surgery, chemo- and/or external radiation therapy are the standard therapy options for the treatment of laryngeal cancer. Trans-oral access for the surgery reduces traumata and hospitalization time. A new trend in treatment is organ-preserving surgery. To avoid regrowth of cancer, this type of surgery can be combined with radiation therapy. Since external radiation includes healthy tissue surrounding the cancerous zone, a local and direct intraoral radiation delivery would be beneficial...
May 9, 2017: International Journal of Computer Assisted Radiology and Surgery
https://www.readbyqxmd.com/read/28486216/ionization-chamber-radial-response-deconvolution-in-megavoltage-photon-beam
#19
Antti Juhani Kulmala, Mikko Tenhunen
The aim of this paper is to study a radial response model as a method, to correct output factor results gathered with ionization chambers of different size and shape in cone collimated RT fields. An enhanced version of a non-parametric super-resolution deconvolution method able to model a radial response function of a small cylinder symmetric ionization chamber is described and demonstrated. The radial response of four ionization chambers with different geometry and radius are estimated using 6 MV photon beam in water at the isocentre plane...
May 9, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28479873/comparison-of-surface-dose-delivered-by-7%C3%A2-mv-unflattened-and-6%C3%A2-mv-flattened-photon-beams
#20
Ashokkumar Sigamani, Arunai Nambiraj
AIM: The purpose of this study is to determine the central-axis dose in the buildup region and the surface dose delivered by a 6 MV flattened photon beam (6 MV-FB) and a higher energy unflattened (7 MV-FFF) therapeutic photon beam for different-sized square fields with open fields and modifying filters. MATERIALS AND METHODS: The beams are produced by a Siemens Artiste linear accelerator with a NACP-02 ionization chamber and the dose is measured by using GafChromic film and two different, commonly used, dosimeters: a p-type photon semiconductor dosimeter (PFD) and a cylindrical ionization chamber (CC13)...
May 2017: Reports of Practical Oncology and Radiotherapy
keyword
keyword
57699
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"