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ionization chamber

Michael S Kent, Davide Berlato, Isabelle Vanhaezebrouck, Ira K Gordon, Katherine S Hansen, Alain P Theon, Randall W Holt, Earl A Trestrail
Radiation therapy of the head and neck can result in mucositis and other acute affects in the oral cavity. This prospective pilot study evaluated a novel, intraoral, beam-blocking device for use during imaging and therapeutic procedures. The beam-blocking device was made from a metal alloy inserted into a coated frozen dessert mold (Popsicle® Mold, Cost Plus World Market, Oakland, CA). The device was designed so that it could be inserted into an outer shell, which in turn allowed it to be placed or removed depending on the need due to beam configuration...
October 17, 2016: Veterinary Radiology & Ultrasound
Kenion H Blakeman, Craig A Cavanaugh, William M Gilliland, J Michael Ramsey
RATIONALE: There are many chemical measurement scenarios that would benefit from hand portable mass spectrometry tools including forensics, environmental monitoring, and safety and security. High pressure mass spectrometry (HPMS) facilitates miniaturization by significantly reducing vacuum system requirements. Previous work demonstrated HPMS using helium buffer gas, but HPMS conducted using ambient air would further reduce the size and weight of a portable instrument while also reducing logistical demands by eliminating the need for a helium supply...
October 17, 2016: Rapid Communications in Mass Spectrometry: RCM
A Lourenço, N Wellock, R Thomas, M Homer, H Bouchard, T Kanai, N MacDougall, G Royle, H Palmans
Water-equivalent plastics are frequently used in dosimetry for experimental simplicity. This work evaluates the water-equivalence of novel water-equivalent plastics specifically designed for light-ion beams, as well as commercially available plastics in a clinical high-energy carbon-ion beam. A plastic- to-water conversion factor [Formula: see text] was established to derive absorbed dose to water in a water phantom from ionization chamber readings performed in a plastic phantom. Three trial plastic materials with varying atomic compositions were produced and experimentally characterized in a high-energy carbon-ion beam...
October 14, 2016: Physics in Medicine and Biology
Daniel A Thomas, Matthew M Coggon, Hanna Lignell, Katherine Ann Schilling, Xuan Zhang, Rebecca H Schwantes, Richard C Flagan, John H Seinfeld, Jesse Lee Beauchamp
The complexation of iron (III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron (II) and the carbon dioxide anion radical. Importantly, iron (III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown...
October 12, 2016: Environmental Science & Technology
Johanne Penafiel, Amelia V Hesketh, Ori Granot, J Scott McIndoe
Electron ionization (EI) is a reliable mass spectrometric method for the analysis of the vast majority of thermally stable and volatile compounds. In direct EI-MS, the sample is placed into the probe and introduced to the source. For air- and moisture-sensitive organometallic complexes, the sample introduction step is critical. A small quantity must be briefly exposed to the atmosphere, during which time decomposition can occur. Here we present a simple tool that allows convenient analysis of air- and moisture-sensitive organometallic species by direct probe methods: a small purge-able glove chamber affixed to the front end of the mass spectrometer...
October 4, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
M F Ahmed, N Shrestha, E Schnell, S Ahmad, M S Akselrod, E G Yukihara
This work evaluates the dosimetric properties of newly developed optically stimulated luminescence (OSL) films, fabricated with either Al2O3:C or Al2O3:C,Mg, using a prototype laser scanning reader, a developed image reconstruction algorithm, and a 6 MV therapeutic photon beam. Packages containing OSL films (Al2O3:C and Al2O3:C,Mg) and a radiochromic film (Gafchromic EBT3) were irradiated using a 6 MV photon beam using different doses, field sizes, with and without wedge filter. Dependence on film orientation of the OSL system was also tested...
October 7, 2016: Physics in Medicine and Biology
Kouji Katsura, Satoru Utsunomiya, Eisuke Abe, Hironori Sakai, Naotaka Kushima, Satoshi Tanabe, Takumi Yamada, Takahide Hayakawa, Yoshihiko Yamanoi, Syuhei Kimura, Shinichi Wada, Hidefumi Aoyama, Takafumi Hayashi
The changes in dose distribution caused by backscatter radiation from a common commercial dental alloy (Au-Ag-Pd dental alloy; DA) were investigated to identify the optimal material and thicknesses of a dental device (DD) for effective prevention of mucositis. To this end, 1 cm(3) of DA was irradiated with a 6-MV X-ray beam (100 MU) in a field size of 10 × 10 cm(2) using a Novalis TX linear accelerator. Ethylene vinyl acetate copolymer, polyolefin elastomer, and polyethylene terephthalate (PET) were selected as DD materials...
October 4, 2016: Journal of Radiation Research
Wladimir Wertelecki, Christina D Chambers, Lyubov Yevtushok, Natalya Zymak-Zakutnya, Zoriana Sosyniuk, Serhiy Lapchenko, Bogdana Ievtushok, Diana Akhmedzhanova
In the 30 years since the Chornobyl nuclear power plant disaster, there is evidence of persistent levels of incorporated ionizing radiation in adults, children and pregnant women in the surrounding area. Measured levels of Cesium-137 vary by region, and may be influenced by dietary and water sources as well as proximity to nuclear power plants. Since 2000, comprehensive, population-based birth defects monitoring has been performed in selected regions of Ukraine to evaluate trends and to generate hypotheses regarding potential causes of unexplained variations in defect rates...
September 30, 2016: European Journal of Medical Genetics
Kelsey B Mathieu, Michael F McNitt-Gray, Dianna D Cody
Rise, fall, and stabilization of the x-ray tube output occur immediately before and after data acquisition on some computed tomography (CT) scanners and are believed to contribute additional dose to anatomy facing the x-ray tube when it powers on or off. In this study, we characterized the dose penalty caused by additional radiation exposure during the rise, stabilization, and/or fall time (referred to as overscanning). A 32 cm CT dose-index (CTDI) phantom was scanned on three CT scanners: GE Healthcare LightSpeed VCT, GE Healthcare Discovery CT750 HD, and Siemens Somatom Definition Flash...
October 21, 2016: Physics in Medicine and Biology
Áine Maxwell, Niluja Thiruthaneeswaran, Gerry Lowe, Rachel Wills, Samadara Sripali, Peter J Hoskin
PURPOSE: Vaginal vault brachytherapy is an adjuvant treatment to reduce risk of local recurrence in endometrial cancer. Axial imaging has demonstrated the presence of air gaps between the surface of a cylindrical applicator and mucosal wall. The impact of these on dosimetry and applicability of the TG-43 formalism in the presence of air has been assessed. METHODS AND MATERIALS: The planning CT scans for a retrospective sample of 82 patients were examined for the presence of air gaps...
September 29, 2016: Brachytherapy
Deepak Bhandari, John Russell Erskine Ruhl, Anthony John Murphy, Ernest McGahee, David Michael Chambers, Benjamin C Blount
Urinary diamines are biomarkers of diisocyanate exposure. Diisocyanates are considered as skin and respiratory sensitizers and are the most frequently reported cause of occupational asthma. Herein, we report on the development and validation of an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the measurement of five aromatic diamines, 4,4'-methylenedianiline (MDA), 2,4-toluenediamine (4TDA), 2,6-toluenediamine (6TDA), 1,5-naphthalenediamine (NDA), and p-phenylenediamine (PPDA) in human urine...
October 1, 2016: Analytical Chemistry
Noor Mail, Muhammad Yusuf, Nazeeh Alothmany, A Abdulrahman Kinsara, Fahad Abdulkhaliq, Suliman M Ghamdi, Abdelhamid Saoudi
Cone-beam computed tomography CBCT systems are used in radiation therapy for patient alignment and positioning. The CBCT imaging procedure for patient setup adds substantial radiation dose to patient's normal tissue. This study pre-sents a complete procedure for the CBCT dosimetry using the InLight optically-stimulated-luminescence (OSL) nanoDots. We report five dose parameters: the mean slice dose (DMSD); the cone beam dose index (CBDIW); the mean volume dose (DMVD); point-dose profile, D(FOV); and the off-field Dose...
2016: Journal of Applied Clinical Medical Physics
James L Grafe, Jennifer Owen, J Eduardo Villarreal-Barajas, Rao F H Khan
A new megavoltage (MV) energy was recently introduced on Varian TrueBeam linear accelerators for imaging applications. This work describes the experimental characterization of a 2.5 MV inline portal imaging beam for commissioning, routine clinical use, and quality assurance purposes. The beam quality of the 2.5 MV beam was determined by measuring a percent depth dose, PDD, in water phantom for 10 × 10 cm2 field at source-to-surface distance 100 cm with a CC13 ion chamber, plane parallel Markus chamber, and GafChromic EBT3 film...
2016: Journal of Applied Clinical Medical Physics
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
This study provided baseline data required for a greater project, whose objective was to design a new Elekta electron collimation system having significantly lighter electron applicators with equally low out-of field leakage dose. Specifically, off-axis dose profiles for the electron collimation system of our uniquely configured Elekta Infinity accelerator with the MLCi2 treatment head were measured and calculated for two primary purposes: 1) to evaluate and document the out-of-field leakage dose in the patient plane and 2) to validate the dose distributions calculated using a BEAMnrc Monte Carlo (MC) model for out-of-field dose profiles...
2016: Journal of Applied Clinical Medical Physics
Frédéric Juget, Youcef Nedjadi, Thierry Buchillier, François Bochud, Claude Bailat
The half-life of (137)Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and (226)Ra source was used for the half-life calculation. The value found for the (137)Cs half-life is 10,955.2±10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation.
September 15, 2016: Applied Radiation and Isotopes
L Young, G Moffitt, D Argento, O Gopan, G A Sandison, R D Stewart
No abstract text is available yet for this article.
October 1, 2016: International Journal of Radiation Oncology, Biology, Physics
C W Kong, H Geng, W W Lam, S G Lo, C W Cheung, T L Chiu, S K Yu, K Y Cheung
No abstract text is available yet for this article.
October 1, 2016: International Journal of Radiation Oncology, Biology, Physics
Aime M Gloi
Traditionally, lead has been used for field shaping in megavoltage electron beams in radiation therapy. In this study, we analyze the dosimetric parameters of a nontoxic, high atomic number (Z = 83), bismuth-loaded material called Gamma Putty that is malleable and can be easily molded to any desired shape. First, we placed an ionization chamber at different depths in a solid water phantom under a Gamma Putty shield of thickness (t = 0, 3, 5, 10, 15, 20, and 25 mm, respectively) and measured the ionizing radiation on the central axis (CAX) for electron beam ranging in energies from 6 to 20 MeV...
July 2016: Journal of Medical Physics
Yen-Hsien Li, Chung-Yu Chen, Cheng-Hsiung Kuo, Maw-Rong Lee
During the electrospray ionization (ESI) process, ions move through a heated capillary aperture to be detected on arrival at a mass analyzer. However, the ESI process creates an ion plume, which expands into an ion cloud with an area larger than that of the heated capillary aperture, significantly contributing to an ion loss of 50% due to coulombic repulsion. The use of DC and RF fields to focus ions from the ion source into the vacuum chamber has been proposed in the literature, but the improvement of ion transmission efficiency is limited...
September 28, 2016: Analytica Chimica Acta
G Duporté, P-M Flaud, E Geneste, S Augagneur, E Pangui, H Lamkaddam, A Gratien, J-F Doussin, H Budzinski, E Villenave, E Perraudin
In the present study, quasi-static reactor and atmospheric simulation chamber experiments were performed to investigate the formation of α-pinene-derived organosulfates. Organosulfates (R-OSO3H) were examined for the reactions between acidified ammonium sulfate particles exposed to an individual gaseous volatile organic compound, such as α-pinene and oxidized products (α-pinene oxide, isopinocampheol, pinanediol and myrtenal). Molecular structures were elucidated by liquid chromatography interfaced to high-resolution quadrupole time-of-flight mass spectrometry equipped with electrospray ionization (LC/ESI-HR-QTOFMS)...
October 13, 2016: Journal of Physical Chemistry. A
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