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ionization chamber

Henry Finlay Godson, Ravikumar Manickam, Sathiyan Saminathan, Kadirampatti Mani Ganesh, Retna Ponmalar
Intensity-modulated radiation therapy (IMRT) requires a patient-specific quality assurance (QA) program to validate the treatment plan and a high level of dosimetric accuracy in the treatment delivery. Dosimetric verification generally consists of both absolute- and relative-dose measurements in a phantom using ionization chambers. Measurements were carried out with three different ionization chambers (Scanditronix FC 65G, Exradin A18, and PTW PinPoint 31014) to assess the effects of influence quantities such as the stability, pre- and post-irradiation leakage, stem effect, polarity, and ion recombination on the IMRT point-dose verification with two different orientations...
December 1, 2016: Radiological Physics and Technology
Pedro L Esquinas, Jesse Tanguay, Marjorie Gonzalez, Milan Vuckovic, Cristina Rodríguez-Rodríguez, Urs O Häfeli, Anna Celler
PURPOSE: In the nuclear medicine department, the activity of radiopharmaceuticals is measured using dose calibrators (DCs) prior to patient injection. The DC consists of an ionization chamber that measures current generated by ionizing radiation (emitted from the radiotracer). In order to obtain an activity reading, the current is converted into units of activity by applying an appropriate calibration factor (also referred to as DC dial setting). Accurate determination of DC dial settings is crucial to ensure that patients receive the appropriate dose in diagnostic scans or radionuclide therapies...
December 2016: Medical Physics
Paolo Farace, Roberto Righetto, Sylvain Deffet, Arturs Meijers, Francois Vander Stappen
PURPOSE: To introduce a fast ray-tracing algorithm in pencil proton radiography (PR) with a multilayer ionization chamber (MLIC) for in vivo range error mapping. METHODS: Pencil beam PR was obtained by delivering spots uniformly positioned in a square (45 × 45 mm(2) field-of-view) of 9 × 9 spots capable of crossing the phantoms (210 MeV). The exit beam was collected by a MLIC to sample the integral depth dose (IDDMLIC). PRs of an electron-density and of a head phantom were acquired by moving the couch to obtain multiple 45 × 45 mm(2) frames...
December 2016: Medical Physics
R Botha, R T Newman, R Lindsay, P P Maleka
This is the first known study of exposure of Rn (radon) and secondarily Rn (thoron) in-air activity concentrations assessed within nine selected wine cellars in four wine districts of the Western Cape (South Africa) and the associated annual occupational effective doses. E-PERM electret ion chambers (EIC) and RAD-7 α-detectors were used to perform these measurements. The radon in-air levels ranged from 12 ± 4 Bq m to 770 ± 40 Bq m within the nine selected wine cellars. Eight of the nine wine cellars (excluding results from cellar w-6) had a median radon in-air activity concentration of 48 ± 8 Bq m...
January 2017: Health Physics
Mario Ciocca, Alfredo Mirandola, Silvia Molinelli, Stefania Russo, Edoardo Mastella, Alessandro Vai, Andrea Mairani, Giuseppe Magro, Andrea Pella, Marco Donetti, Francesca Valvo, Piero Fossati, Guido Baroni
PURPOSE: The aim of this work was the commissioning of delivery procedures for the treatment of moving targets in scanning pencil beam hadrontherapy. METHODS: EBT3 films fixed to the Anzai Respiratory Phantom were exposed to carbon ion scanned homogeneous fields (E=332MeV/u). To evaluate the interplay effect, field size and flatness for 3 different scenarios were compared to static condition: gated irradiation or repainting alone and combination of both. Respiratory signal was provided by Anzai pressure sensor or optical tracking system (OTS)...
November 24, 2016: Physica Medica: PM
Catherine Chambers-Bédard, Brian M Ross
The quantification of trace compounds in alcoholic beverages is a useful means to both investigate the chemical basis of beverage flavor and to facilitate quality control during the production process. One compound of interest is methanol which, due to it being toxic, must not exceed regulatory limits. The analysis of headspace gases is a desirable means to do this since it does not require direct sampling of the liquid material. One established means to conduct headspace analysis is selected ion flow tube mass spectrometry (SIFT-MS)...
2016: European Journal of Mass Spectrometry
A R Barbeiro, A Ureba, J A Baeza, R Linares, M Perucha, E Jiménez-Ortega, S Velázquez, J C Mateos, A Leal
A model based on a specific phantom, called QuAArC, has been designed for the evaluation of planning and verification systems of complex radiotherapy treatments, such as volumetric modulated arc therapy (VMAT). This model uses the high accuracy provided by the Monte Carlo (MC) simulation of log files and allows the experimental feedback from the high spatial resolution of films hosted in QuAArC. This cylindrical phantom was specifically designed to host films rolled at different radial distances able to take into account the entrance fluence and the 3D dose distribution...
2016: PloS One
C Bobin, C Thiam, B Chauvenet
Due to their stability and reproducibility, re-entrant pressurized ionization chambers (also called radionuclide calibrators) are widely used for activity measurements in nuclear medicine services as well as in national metrology institutes to maintain reference standards. Generally, these secondary instruments yield accurate activity measurements for γ-emitting radionuclides. Ionization chambers are easy to use and thus well-adapted to guarantee the metrological traceability between national metrology institutes and end-users...
January 2017: Applied Radiation and Isotopes
Massimo Pasquino, Claudia Cutaia, Lorenzo Radici, Serena Valzano, Eva Gino, Carlo Cavedon, Michele Stasi
OBJECTIVES: The aim of this work is to investigate the main dosimetric characteristics and the performance of an A26 Exradin ionization microchamber (A26 IC) and a W1 Exradin plastic scintillation detector (W1 PSD) in small photon beam dosimetry for Treatment Planning System (TPS) commissioning and Quality Assurance (QA) program. METHODS: Detectors' characterization measurements (short term stability, dose linearity, angular dependence and energy dependence) were performed in water for field sizes up to 10 x 10 cm2...
November 9, 2016: British Journal of Radiology
R Visser, J Godart, D J L Wauben, J A Langendijk, A A Van't Veld, E W Korevaar
In pre-treatment dose verification, low resolution detector systems are unable to identify shifts of individual leafs of high resolution multi leaf collimator (MLC) systems from detected changes in the dose deposition. The goal of this study was to introduce an alternative approach (the shutter technique) combined with a previous described iterative reconstruction method to accurately reconstruct high resolution MLC leaf positions based on low resolution measurements. For the shutter technique, two additional radiotherapy treatment plans (RT-plans) were generated in addition to the original RT-plan; one with even MLC leafs closed for reconstructing uneven leaf positions and one with uneven MLC leafs closed for reconstructing even leaf positions...
December 7, 2016: Physics in Medicine and Biology
Beatrice Steiniger, René Berger, Sabine Eilzer, Christine Kornhuber, Kathleen Lorenz, Torsten Peil, Carsten Reiffenstuhl, Johannes Schilz, Dirk Schröder, Michael Schwedas, Stephanie Pensold, Mathias Walke, Kirsten Weibert, Ulrich Wolf, Tilo Wiezorek
PURPOSE: This project compares the different patient-related quality assurance systems for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques currently used in the central Germany area with an independent measuring system. MATERIALS AND METHODS: The participating institutions generated 21 treatment plans with different combinations of treatment planning systems (TPS) and linear accelerators (LINAC) for the QUASIMODO (Quality ASsurance of Intensity MODulated radiation Oncology) patient model...
November 3, 2016: Strahlentherapie und Onkologie: Organ der Deutschen Röntgengesellschaft ... [et Al]
P Trnková, A Bolsi, F Albertini, D C Weber, A J Lomax
PURPOSE: A detailed analysis of 2728 intensity modulated proton therapy (IMPT) fields that were clinically delivered to patients between 2007 and 2013 at Paul Scherrer Institute (PSI) was performed. The aim of this study was to analyze the results of patient specific dosimetric verifications and to assess possible correlation between the quality assurance (QA) results and specific field metrics. METHODS: Dosimetric verifications were performed for every IMPT field prior to patient treatment...
November 2016: Medical Physics
Arash Darafsheh, Reza Taleei, Alireza Kassaee, Jarod C Finlay
PURPOSE: Proton beam dosimetry using bare plastic optical fibers has emerged as a simple approach to proton beam dosimetry. The source of the signal in this method has been attributed to Čerenkov radiation. The aim of this work was a phenomenological study of the nature of the visible light responsible for the signal in bare fiber optic dosimetry of proton therapy beams. METHODS: Plastic fiber optic probes embedded in solid water phantoms were irradiated with proton beams of energies 100, 180, and 225 MeV produced by a proton therapy cyclotron...
November 2016: Medical Physics
Hugo Palmans, Stanislav M Vatnitsky
PURPOSE: To propose a formalism for the reference dosimetry of scanned light-ion beams consistent with IAEA TRS-398 and Alfonso et al. [Med. Phys. 35, 5179-5186 (2008)]. To identify machine-specific reference (msr) fields and plan-class specific reference (pcsr) fields consistent with the definitions given by Alfonso et al. To review the literature of beam monitor calibration in scanned beams using three different methods in terms of this common formalism. METHODS: Four types of msr fields are identified as those that are meant to calibrate the beam monitor for scanned beams with particular energies...
November 2016: Medical Physics
Leonhard Karsch
PURPOSE: Gas-filled ionization chambers are the most important radiation detectors in radiotherapy. The collected charge at the electrodes does not represent the total released charge due to the unavoidable recombination processes. This needs to be considered for precise dose measurements. A quantitative description and correction of the recombination effects is established for two cases: continuous radiation exposure and pulsed radiation fields of single pulses with vanishing pulse duration...
November 2016: Medical Physics
Thanh Tat Nguyen, Tsuyoshi Kajimoto, Kenichi Tanaka, Chien Cong Nguyen, Satoru Endo
PURPOSE: Fast neutron, gamma-ray, and boron doses have different relative biological effectiveness (RBE). In boron neutron capture therapy (BNCT), the clinical dose is the total of these dose components multiplied by their RBE. Clinical dose monitoring is necessary for quality assurance of the irradiation profile; therefore, the fast neutron, gamma-ray, and boron doses should be separately monitored. To estimate these doses separately, and to monitor the boron dose without monitoring the thermal neutron fluence, the authors propose a triple ionization chamber method using graphite-walled carbon dioxide gas (C-CO2), tissue-equivalent plastic-walled tissue-equivalent gas (TE-TE), and boron-loaded tissue-equivalent plastic-walled tissue-equivalent gas [TE(B)-TE] chambers...
November 2016: Medical Physics
Petter Ström, Per Petersson, Marek Rubel, Göran Possnert
A dedicated detector system for heavy ion elastic recoil detection analysis at the Tandem Laboratory of Uppsala University is presented. Benefits of combining a time-of-flight measurement with a segmented anode gas ionization chamber are demonstrated. The capability of ion species identification is improved with the present system, compared to that obtained when using a single solid state silicon detector for the full ion energy signal. The system enables separation of light elements, up to Neon, based on atomic number while signals from heavy elements such as molybdenum and tungsten are separated based on mass, to a sample depth on the order of 1 μm...
October 2016: Review of Scientific Instruments
Robert Anigstein, Richard H Olsher, Donald A Loomis, Armin Ansari
The detonation of a radiological dispersion device or other radiological incidents could result in widespread releases of radioactive materials and intakes of radionuclides by affected individuals. Transportable radiation monitoring instruments could be used to measure radiation from gamma-emitting radionuclides in the body for triaging individuals and assigning priorities to their bioassay samples for in vitro assessments. The present study derived sets of calibration factors for four instruments: the Ludlum Model 44-2 gamma scintillator, a survey meter containing a 2...
December 2016: Health Physics
Scott R Evans, Andrea M Hujer, Hongyu Jiang, Carol B Hill, Kristine M Hujer, Jose R Mediavilla, Claudia Manca, Thuy Tien T Tran, T Nicholas Domitrovic, Paul G Higgins, Harald Seifert, Barry N Kreiswirth, Robin Patel, Michael R Jacobs, Liang Chen, Rangarajan Sampath, Thomas Hall, Christine Marzan, Vance G Fowler, Henry F Chambers, Robert A Bonomo
The widespread dissemination of carbapenem-resistant Acinetobacter spp. has created significant therapeutic challenges. At present, rapid molecular diagnostics (RMDs) that can identify this phenotype are not commercially available. Two RMD platforms, polymerase chain reaction combined with electrospray ionization mass spectrometry (PCR/ESI-MS) and molecular beacons (MB), for detecting genes conferring resistance/susceptibility to carbapenems in Acinetobacter spp. were evaluated. An archived collection of 200 clinical Acinetobacter spp...
October 26, 2016: Journal of Clinical Microbiology
Rosa Carotenuto, Margherita Tussellino, Giovanni Mettivier, Paolo Russo
To determine the radiosensitivity of Xenopus laevis embryos, aquatic organism model, for toxicity studies utilizing X-rays at acute high dose levels, by analysing its survival fraction and phenotype alterations under one-exposure integral dose. We used the standard Frog Embryo Teratogenesis Assay Xenopus test during the early stages of X. laevis development. The embryos were harvested until st. 46 when they were irradiated. The radiation effects were checked daily for a week and the survival, malformations and growth inhibition were assessed...
October 25, 2016: Biochemical and Biophysical Research Communications
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