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ionization chamber

Bjoern Delfs, Andreas Alexander Schoenfeld, Daniela Poppinga, Ralf-Peter Kapsch, Ping Jiang, Dietrich Harder, Bjoern Poppe, Hui Khee Looe
The optical density (OD) of EBT3 radiochromic exposed to absorbed doses to water up to D = 20 Gy in magnetic fields of B = 0.35 and 1.42 T was measured in three colour channels. A 7 cm wide water phantom with fixed film holder was placed in magnetic fields and was irradiated by a 6 MV photon beam whose axis was directed at right angles with the field lines. The doses at the film position at water depth 5 cm were measured with a calibrated ionization chamber when the magnet was switched off and were converted to the doses in presence of the magnetic field via the monitor units and by a Monte Carlo-calculated correction accounting for the slight change of the depth dose curves in magnetic fields...
November 20, 2017: Physics in Medicine and Biology
Abdullah Abuhaimed, Colin J Martin
Regular imaging is used throughout image guided radiation therapy (IGRT) to improve treatment delivery. In order for treatment procedures to be optimized, the doses delivered by imaging exposures should be taken into account. CT dosimetry methods based on the CT dose index (CTDI), measured with a 100 mm long pencil ionization chamber (CTDI<sub>100</sub>) in standard phantoms, are not designed for the cone beam CT (CBCT) imaging systems used in radiotherapy, therefore a modified version has been proposed for CBCT by the International Electrotechnical Commission (CTDI<sub>IEC</sub>)...
November 20, 2017: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
Nicholas Forwood, Kathy P Willowson, Michael Tapner, Dale L Bailey
No abstract text is available yet for this article.
November 17, 2017: Australasian Physical & Engineering Sciences in Medicine
A L Ferreira Filho, R da Silva, P A L da Cruz, C J da Silva, R Poledna, M T F Araújo, C F Arcanjo, J U Delgado, R T Lopes
The sum-peak method, an absolute measurement technique that uses coincidence counting and γ-ray spectrometry, was applied to activity standardization of (152)Eu sources. The decay branch used was that of (152)Sm, as it is almost entirely electron capture and exhibits X-rays with a high probability of coincidence with the 121.8keVgamma rays, as evidenced by the matrix technique used for complex decay schemes, a method for deriving counting rate equations describing coincidence summing of gamma and X-rays. The result was compared with the calibration performed by ionization chamber traceable to BIPM...
October 7, 2017: Applied Radiation and Isotopes
B W Raaymakers, I M Jürgenliemk-Schulz, G H Bol, M Glitzner, A N T J Kotte, B van Asselen, J C J de Boer, J J Bluemink, S L Hackett, M A Moerland, S J Woodings, J W H Wolthaus, H M van Zijp, M E P Philippens, R Tijssen, J G M Kok, E N de Groot-van Breugel, I Kiekebosch, L T C Meijers, C N Nomden, G G Sikkes, P A H Doornaert, W S C Eppinga, N Kasperts, L G W Kerkmeijer, J H A Tersteeg, K J Brown, B Pais, P Woodhead, J J W Lagendijk
The integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta...
November 14, 2017: Physics in Medicine and Biology
Shimpei Hashimoto, Yukio Fujita, Tetsurou Katayose, Hideyuki Mizuno, Hidetoshi Saitoh, Katsuyuki Karasawa
PURPOSE: We evaluated the energy responses of a radiophotoluminescent glass dosimeter (RPLD) to variations in small-field and intensity-modulated radiation therapy (IMRT) conditions using experimental measurements and Monte Carlo simulation. METHODS: Several sizes of the jaw and multileaf collimator fields and various plan-class IMRT-beam measurements were performed using the RPLD and an ionization chamber. The field-size correction factor for the RPLD was determined for 6- and 10-MV X-rays...
November 13, 2017: Medical Physics
Małgorzata Liszka, Liliana Stolarczyk, Magdalena Kłodowska, Anna Kozera, Dawid Krzempek, Natalia Mojżeszek, Anna Pędracka, Michael Patrick Russell Waligórski, Paweł Olko
PURPOSE: To evaluate the effect on charge collection in the ionization chamber (IC) in proton pencil beam scanning (PBS), where the local dose-rate may exceed the dose rates encountered in conventional MV therapy by up to 3 orders of magnitude. METHODS: We measured values of the ion recombination (ks ) and polarity (kpol ) correction factors in water, for a plane-parallel Markus TM23343 IC, using the cyclotron-based Proteus-235 therapy system with an active proton PBS of energies 30-230 MeV...
November 13, 2017: Medical Physics
Masahide Saito, Naoki Sano, Koji Ueda, Yuki Shibata, Kengo Kuriyama, Takafumi Komiyama, Kan Marino, Shinichi Aoki, Hiroshi Onishi
PURPOSE: To evaluate the basic performance of a respiratory gating system using an Elekta linac and an Abches respiratory monitoring device. METHODS: The gating system was comprised of an Elekta Synergy linac equipped with a Response(TM) gating interface module and an Abches respiratory monitoring device. The latencies from a reference respiratory signal to the resulting Abches gating output signal and the resulting monitor-ion-chamber output signal were measured...
November 13, 2017: Medical Physics
James Renaud, Arman Sarfehnia, Julien Bancheri, Jan Seuntjens
In this work, the design, operation, initial experimental evaluation, and characterization of a small-scale graphite calorimeter probe - herein referred to as the Aerrow - developed for routine use in the clinical environment, is described. Similar in size and shape to a Farmer type cylindrical ionization chamber, the Aerrow represents the first translation of calorimetry intended for direct use by clinical physicists in the radiotherapy clinic METHODS: Based on a numerically-optimized design obtained in previous work, a functioning Aerrow prototype capable of two independent modes of operation (quasi-adiabatic and isothermal) was constructed in-house...
November 13, 2017: Medical Physics
Frédéric Tessier, Claudiu Dorin Cojocaru, Carl Kenneth Ross
PURPOSE: The average energy expended by an energetic electron to create an ion pair in dry air, Wair, is a key quantity in radiation dosimetry. Although Wair is well established for electron energies up to about 3 MeV there is limited data for higher energies. The measurements by Domen and Lamperti [Med. Phys. 3, 294{301 (1976)] using electron beams in the energy range from 15 to 50 MeV can, in principle, be used to deduce values for Wair, if the electron stopping power of graphite and air are known...
November 13, 2017: Medical Physics
S Pierre, B Sabot, P Cassette, J Liang, S Courte, L Ferreux, G Ratel
Two main non-destructive techniques can be used to measure standard (222)Rn gas ampoules: well-type ionization chambers and gamma-ray spectrometry, the former being used in the Système International de Référence (SIR) for international comparison purposes. The reliability of these techniques requires that the variability of the flame-sealed gas glass ampoules used have a negligible influence on the detector response. This variability is studied in this work by considering three parameters: the volume of the ampoule, the position of the sealing point and the thickness of the glass...
October 31, 2017: Applied Radiation and Isotopes
Kosuke Matsubara, Hiroji Nagata, Rena Okubo, Tadanori Takata, Masanao Kobayashi
PURPOSE: We have proposed a method for determining the half-value layers (HVL) in dual-source dual-energy computed tomography (DS-DECT) scans without the need for the X-ray tubes to be fixed. METHODS: A custom-made lead-covered case and an ionizing chamber connected with a multi-function digitizer module (a real-time dosimeter) were used. The chamber was placed in the center of the case, and aluminum or copper filters were placed in front of the aperture. The HVL was measured using aperture widths of 1...
October 27, 2017: Physica Medica: PM
M Sahagia, A Luca, M-R Ioan, A Antohe, C Ivan
This paper describes the standardization of (67)Cu by the 4πβ(PC)-γ coincidence method, and the calibration of ionization chamber. The difficulties were. (i) One of the excited levels of (67)Zn has a half life of 9.10μs. (ii) A recent publication reconsiders the decay scheme parameters. (iii) The solution had a significant content of impurities. The conclusions were that the result of absolute standardization is less influenced by the decay scheme parameters and impurities than the measurements by ionization chamber...
October 19, 2017: Applied Radiation and Isotopes
Loϊc Grevillot, Markus Stock, Hugo Palmans, Jhonnatan Osorio Moreno, Virgile Letellier, Ralf Dreindl, Alessio Elia, Hermann Fuchs, Antonio Carlino, Stanislav Vatnitsky
PURPOSE: To describe the implementation of dosimetry equipment and phantoms into clinical practice of light ion beam therapy facilities. This work covers standard dosimetry equipment such as computerized water scanners, films, 2D-array, thimble and plane parallel ionization chambers, but also dosimetry equipment specifically devoted to the pencil beam scanning delivery technique such as water columns, scintillating screens or multi-layer ionization chambers. METHOD: Advanced acceptance testing procedures developed at MedAustron and complementary to the standard acceptance procedures proposed by the manufacturer are presented...
November 4, 2017: Medical Physics
Jácint Jónás, János Somlai, Anita Csordás, Edit Tóth-Bodrogi, Tibor Kovács
In petroleum engineering, the produced drilling mud sometimes contains elevated amounts of natural radioactivity. In this study, a remediated Hungarian drilling mud depository was investigated from a radiological perspective. The depository was monitored before and after a clay layer was applied as covering. In this study, the ambient dose equivalent rate H*(10) of the depository has been measured by a Scintillator Probe (6150AD-b Dose Rate Meter). Outdoor radon concentration, radon concentration in soil gas, and in situ field radon exhalation measurements were carried out using a pulse-type ionization chamber (AlphaGUARD radon monitor)...
November 2, 2017: Journal of Environmental Radioactivity
Ming-Chen Yuan, Yi-Chun Lin, Wei-Han Chu, Chin-Hsien Yeh
(109)Cd is quite a useful nuclide for the calibration of X-ray spectroscopy, gamma-ray spectroscopy or as an excitation source in X-ray fluorescence. In this work, 4π(PC)e-X coincidence counting and 4π(LS)ce counting were used to determine the activity of the (109)Cd solution. The two methods showed good agreement in their counting results. On the other hand, the mean value came from the results of the two methods was used to calibrate the well type ionization chambers to maintain the radioactivity measurement standard of (109)Cd at INER...
October 2, 2017: Applied Radiation and Isotopes
Denis E Bergeron, Jeffrey T Cessna, Brian E Zimmerman
In nuclear medicine, (68)Ge is used to generate (68)Ga for imaging by positron emission tomography (PET) and sealed sources containing (68)Ge/(68)Ga in equilibrium have been adopted as long-lived calibration surrogates for the more common PET nuclide, (18)F. We prepared several (68)Ge sources for measurement on a NaI(Tl) well counter and a pressurized ionization chamber, following their decay for 110 weeks (≈ 2.8 half-lives). We determined values for the (68)Ge half-life of T1/2 = 271.14(15) d and T1/2 = 271...
October 20, 2017: Applied Radiation and Isotopes
Peter Lackner, Joong Il Jake Choi, Ulrike Diebold, Michael Schmid
A sputter deposition source for the use in ultrahigh vacuum (UHV) is described, and some properties of the source are analyzed. The operating principle is based on the design developed by Mayr et al. [Rev. Sci. Instrum. 84, 094103 (2013)], where electrons emitted from a filament ionize argon gas and the Ar(+) ions are accelerated to the target. In contrast to the original design, two grids are used to direct a large fraction of the Ar(+) ions to the target, and the source has a housing cooled by liquid nitrogen to reduce contaminations...
October 2017: Review of Scientific Instruments
Quan Yu, Qian Zhang, Xinqiong Lu, Xiang Qian, Kai Ni, Xiaohao Wang
The performance of a miniature mass spectrometer in atmospheric analysis is closely related to the design of its sampling system. In this study, a simplified vacuum electrospray ionization (VESI) source was developed based on a combination of several techniques, including the discontinuous atmospheric pressure interface, direct capillary sampling, and pneumatic-assisted electrospray. Pulsed air was used as a vital factor to facilitate the operation of electrospray ionization in the vacuum chamber. This VESI device can be used as an efficient atmospheric sampling interface when coupled with a miniature rectilinear ion trap (RIT) mass spectrometer...
November 14, 2017: Analytical Chemistry
Colm T Morrison, Kirsty L Symons, Simon J Woodings, Michael J House
A volumetric modulated arc therapy (VMAT) approach to total body irradiation (TBI) has recently been introduced at our institution. The planning target volume (PTV) is divided into separate sub-volumes, each being treated with 2 arcs with their own isocentre. Pre-treatment quality assurance of beams is performed on a Sun Nuclear ArcCHECK diode array. Measurement of junction regions between VMAT arcs with separate isocentres has previously been performed with point dose ionization chamber measurements, or with films...
October 29, 2017: Journal of Applied Clinical Medical Physics
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