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ionization chamber

Alfredo Mirandola, Giuseppe Magro, Marco Lavagno, Andrea Mairani, Silvia Molinelli, Stefania Russo, Edoardo Mastella, Alessandro Vai, Davide Maestri, Vanessa La Rosa, Mario Ciocca
PURPOSE: To dosimetrically characterize a multi-layer ionization chamber (MLIC) prototype for quality assurance (QA) of pristine integral ionization curves (ICs) and spread-out-Bragg-peaks (SOBPs) for scanning light ion beams. METHODS: QUBE (De.Tec.Tor., Torino, Italy) is a modular detector designed for QA in particle therapy (PT). Its main module is a MLIC detector, able to evaluate particle beam relative depth ionization distributions at different beam energies and modulations...
March 14, 2018: Medical Physics
Mohammadbagher Tavakoli, Reihane Faraji, Zahra Alirezaei, Zohre Nateghian
Computed tomography coronary angiography (CTCA) has generated a great interest over the past two decades, due to its high diagnostic accuracy and efficacy in the assessment of patients having coronary artery disease. This method is associated with high radiation dose and this has raised serious concerns in the literature. Effective dose (E) is a single parameter meant to reflect the relative risk from exposure to ionizing radiation. Therefore, it is necessary to calculate this parameter to indicate ionizing radiation relative risk...
January 2018: Journal of Medical Signals and Sensors
Yuji Nakaguchi, Takeshi Oono, Masato Maruyama, Yoshinobu Shimohigashi, Yudai Kai, Yuya Nakamura
In this study, we evaluated the basic performance of the three-dimensional dose verification system COMPASS (IBA Dosimetry). This system is capable of reconstructing 3D dose distributions on the patient anatomy based on the fluence measured using a new transmission detector (Dolphin, IBA Dosimetry) during treatment. The stability of the absolute dose and geometric calibrations of the COMPASS system with the Dolphin detector were investigated for fundamental validation. Furthermore, multileaf collimator (MLC) test patterns and a complicated volumetric modulated arc therapy (VMAT) plan were used to evaluate the accuracy of the reconstructed dose distributions determined by the COMPASS...
March 12, 2018: Radiological Physics and Technology
Deepak Bhandari, Brett A Bowman, Anish B Patel, David M Chambers, Víctor R De Jesús, Benjamin C Blount
This work describes a quantitative high-throughput analytical method for the simultaneous measurement of small aliphatic nitrogenous biomarkers, i.e., 1,6-hexamethylenediamine (HDA), isophoronediamine (IPDA), β-methylamino-l-alanine (BMAA), and trimethylamine N-oxide (TMAO), in human urine. Urinary aliphatic diamines, HDA and IPDA, are potential biomarkers of environmental exposure to their corresponding diisocyanates. Urinary BMAA forms as a result of human exposure to blue-green algae contaminated food. And, TMAO is excreted in urine due to the consumption of carnitine- and choline-rich diets...
March 2, 2018: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
Julia Torres Del Río, Cristina Forastero, Ana M Tornero-López, Jesús J López, Damián Guirado, José Perez-Calatayud, Antonio M Lallena
PURPOSE: We studied the dependence on air density of the response of the PTW 34013 ionization chamber, recently upgraded for dosimetry control of low energy X-ray beams. METHODS: Measurements were performed by changing the pressure conditions inside a pressure chamber. The behavior of the measurements against the air density inside this chamber was analyzed. X-ray beams generated with 50, 70, 100, 150 and 200 kVp and the two electrometer polarities were considered...
February 2018: Physica Medica: PM
Putha Suman Kumar, S Banerjee, E S Arun Kumar, Challapalli Srinivas, B M Vadhiraja, P U Saxena, Ramamoorthy Ravichandran, Dinesh Pai Kasturi
Objective: This study presents a method to estimate midplane dose (Diso, transit ) in vivo from transit signal (St ) measured with thimble ionization chamber in cancer of the middle-third esophagus patients treated with three-dimensional radiotherapy (RT). This detector is positioned at the level of electronic portal imaging device in the gantry of a medical linear accelerator. Materials and Methods: Efficacy of inhomogeneity corrections of three dose calculation algorithms available in XiO treatment planning system (TPS) for planned dose (for open fields) (Diso, TPS ) was studied with three heterogeneous phantoms...
January 2018: Journal of Cancer Research and Therapeutics
Hui Khee Looe, Bjoern Delfs, Daniela Poppinga, Dietrich Harder, Bjoern Poppe
This study aims at developing an optimization strategy for photon-beam dosimetry in magnetic fields using ionization chambers. Similar to the familiar case in absence of a magnetic field, detectors should be selected under the criterion that their measured two-dimensional signal profiles M(x,y) approximate the absorbed dose to water profiles D(x,y) as closely as possible. Since the conversion of D(x,y) into M(x,y) is known as the convolution with the "lateral dose response function" K(x-, y-) of the detector, the ideal detector would be characterized by a vanishing magnetic field dependence of this convolution kernel (Looe et al 2017b)...
March 8, 2018: Physics in Medicine and Biology
David O De Haan, Enrico Tapavicza, Matthieu Riva, Tianqu Cui, Jason Douglas Surratt, Adam C Smith, Mary-Caitlin Jordan, Shiva Nilakantan, Marisol Almodovar, Tiffany N Stewart, Alexia de Loera, Audrey C De Haan, Mathieu Cazaunau, Aline Gratien, Edouard Pangui, Jean-Francois Doussin
Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon aerosol particles collected from cloud cycling / photolysis chamber experiments, where gaseous methylglyoxal and methylamine interacted with glycine, ammonium or methylammonium sulfate seed particles. Eighteen N-containing oligomers were identified in the particulate phase by liquid chromatography / diode array detection / electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry...
March 6, 2018: Environmental Science & Technology
Masahide Saito, Naoki Sano, Yuki Shibata, Kengo Kuriyama, Takafumi Komiyama, Kan Marino, Shinichi Aoki, Kazunari Ashizawa, Kazuya Yoshizawa, Hiroshi Onishi
The purpose of this study was to compare the MLC error sensitivity of various measurement devices for VMAT pre-treatment quality assurance (QA). This study used four QA devices (Scandidos Delta4, PTW 2D-array, iRT systems IQM, and PTW Farmer chamber). Nine retrospective VMAT plans were used and nine MLC error plans were generated for all nine original VMAT plans. The IQM and Farmer chamber were evaluated using the cumulative signal difference between the baseline and error-induced measurements. In addition, to investigate the sensitivity of the Delta4 device and the 2D-array, global gamma analysis (1%/1, 2%/2, and 3%/3 mm), dose difference (1%, 2%, and 3%) were used between the baseline and error-induced measurements...
March 3, 2018: Journal of Applied Clinical Medical Physics
Baozhou Sun, Dao Lam, Deshan Yang, Kevin Grantham, Tiezhi Zhang, Sasa Mutic, Tianyu Zhao
PURPOSE: Clinical treatment planning systems for proton therapy currently do not calculate monitor units (MUs) in passive scatter proton therapy due to the complexity of the beam delivery systems. Physical phantom measurements are commonly employed to determine the field-specific output factors (OFs) but are often subject to limited machine time, measurement uncertainties and intensive labor. In this study, a machine learning based approach was developed to predict output (cGy/MU) and derive MUs, incorporating the dependencies on gantry angle and field size for a single-room proton therapy system...
March 3, 2018: Medical Physics
Yoshiaki Sakamoto, Naoyoshi Koike, Hideyuki Takei, Mari Ohno, Naoyuki Shigematsu, Kazuo Kishi
Postoperative radiation can cause ulcer formation, leading to the denudation of skin over alloplastic materials. The influence of backscatter radiation from fixation devices has not been investigated. The aim of this study is to evaluate backscatter dose variations for different cranial bone fixation devices in an experimental model designed to simulate postoperative radiotherapy. The authors assessed the radiation backscatter doses associated with resorbable (PLLA-PGA) and titanium plates. The samples were irradiated with 6 and 10 MV photon beams from a linear accelerator...
March 1, 2018: Journal of Craniofacial Surgery
Shelby Grzetic, Ahmet S Ayan, Jeffrey Woollard, Nilendu Gupta
AAPM Report 142 recommends and the State of Ohio requires that the imaging dose be quantified in radiotherapy applications. Using the TG51 dose calibration protocol for MV Imaging dose measurement requires knowledge of the kQ parameter for the beam quality and the ionization chamber type under investigation. The %dd(10)x of the Varian TrueBeam 2.5 MV imaging beam falls outside the range of the available data for the calculation of the kQ value. Due to the similarities of the 2.5 MV imaging beam and the60 Co beam, we and others made the assumption that kQ = 1...
March 1, 2018: Journal of Applied Clinical Medical Physics
Kewin Desjardins, Michel Bordessoule, Michal Pomorski
The performance of a diamond X-ray beam position monitor is reported. This detector consists of an ionization solid-state chamber based on a thin single-crystal chemical-vapour-deposition diamond with position-sensitive resistive electrodes in a duo-lateral configuration. The detector's linearity, homogeneity and responsivity were studied on beamlines at Synchrotron SOLEIL with various beam sizes, intensities and energies. These measurements demonstrate the large and homogeneous (absorption variation of less than 0...
March 1, 2018: Journal of Synchrotron Radiation
A Astuto, S S Fernandes, K C S Patrão, E S Fonseca, W W Pereira, R T Lopes
The standard thermal neutron flux unit, TNF2, in the Brazilian National Ionizing Radiation Metrology Laboratory was rebuilt. Fluence is still achieved by moderating of four 241Am-Be sources with 0.6 TBq each. The facility was again simulated and redesigned with graphite core and paraffin added graphite blocks surrounding it. Simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The resulting neutron fluence quality in terms of intensity, spectrum and cadmium ratio was evaluated...
February 21, 2018: Radiation Protection Dosimetry
Heinrich Eder, Helmut Schlattl
PURPOSE: Lead free protective clothing can create a higher part of secondary radiation (SR) than products that are based on lead. Hence, the attenuation properties may be downgraded. The international measuring standard IEC 61331-1:2014 declares the "inverse broad beam geometry" (IBG) as standard method, which has recently been modified to IBG∗ by the Physikalisch Technische Bundesanstalt (PTB). Because of the unspecific partial irradiation of the ionization chamber problems in the evaluation of lead equivalence values (LEVs) can occur...
January 2018: Physica Medica: PM
Maria Pimpinella, Claudio Caporali, Antonio Stefano Guerra, Luca Silvi, Vanessa De Coste, Assunta Petrucci, Frank Delaunay, Stéphane Dufreneix, Jean Gouriou, Aimé Ostrowsky, Benjamin Rapp, Jean-Marc Bordy, Josiane Daures, Maïwenn Le Roy, Line Sommier, Didier Vermesse
PURPOSE: To investigate the feasibility of using the ratio of dose-area product at 20 cm and 10 cm water depths (DAPR20,10 ) as a beam quality specifier for radiotherapy photon beams with field diameter below 2 cm. METHODS: Dose-area product was determined as the integral of absorbed dose to water (Dw ) over a surface larger than the beam size. 6 MV and 10 MV photon beams with field diameters from 0.75 cm to 2 cm were considered. Monte Carlo (MC) simulations were performed to calculate energy-dependent dosimetric parameters and to study the DAPR20,10 properties...
January 2018: Physica Medica: PM
Lalageh Mirzakhanian, Hamza Benmakhlouf, Frederic Tessier, Jan Seuntjens
PURPOSE: Using Monte Carlo simulation, to calculate the kQmsr,Q0fmsr,fref factors for nine common ionization chamber types following the small fields dosimetry formalism for the calibration of the Leksell Gamma Knife R(LGK) PerfexionTM. This study also provides the first independent comparison of EGSnrc and PENELOPE for the calculation of kQmsr,Q0fmsr,fref correction factors and proposes a practical method to predict these factors based on chamber type, chamber orientation and phantom electron density METHODS: The ionization chambers are modeled using the EGSnrc and PENELOPE Monte Carlo codes based on the blueprints provided by the manufacturers...
February 22, 2018: Medical Physics
Eva Marxen, Liang Jin, Jette Jacobsen, Christian Janfelt, Birgitte Hyrup, Joseph A Nicolazzo
PURPOSE: The purpose of this study was to assess the effect of several chemical permeation enhancers on the buccal permeability of nicotine and to image the spatial distribution of nicotine in buccal mucosa with and without buccal permeation enhancers. METHODS: The impact of sodium taurodeoxycholate (STDC), sodium dodecyl sulphate (SDS), dimethyl sulfoxide (DMSO) and Azone® on the permeability of [3 H]-nicotine and [14 C]-mannitol (a paracellular marker) across porcine buccal mucosa was studied ex vivo in modified Ussing chambers...
February 21, 2018: Pharmaceutical Research
A Sonig, S V Setlur Nagesh, V S Fennell, S Gandhi, L Rangel-Castilla, C N Ionita, K V Snyder, L N Hopkins, D R Bednarek, S Rudin, A H Siddiqui, E I Levy
BACKGROUND AND PURPOSE: The ROI-dose-reduced intervention technique represents an extension of ROI fluoroscopy combining x-ray entrance skin dose reduction with spatially different recursive temporal filtering to reduce excessive image noise in the dose-reduced periphery in real-time. The aim of our study was to compare the image quality of simulated neurointerventions with regular and reduced radiation doses using a standard flat panel detector system. MATERIALS AND METHODS: Ten 3D-printed intracranial aneurysm models were generated on the basis of a single patient vasculature derived from intracranial DSA and CTA...
February 15, 2018: AJNR. American Journal of Neuroradiology
L Brualla-González, A Vázquez-Luque, M Zapata, D M González-Castaño, V Luna-Vega, J Guiu-Souto, J Prieto-Pena, T García, D Granero, A Vicedo, J Rosellò, M Pombar, F Gómez, J Pardo-Montero
PURPOSE: To present a novel 2041 liquid-filled ionization chamber array for high-resolution verification of radiotherapy treatments. MATERIALS AND METHODS: The prototype has 2041 ionization chambers of 2.5×2.5 mm2 area filled with isooctane. The detection elements are arranged in a central square grid of 43×43, totally covering an area of 107.5×107.5 mm2 . The central inline and crossline are extended to 227 mm and the diagonals to 321 mm in order to be able to perform profile measurements of large fields...
February 15, 2018: Medical Physics
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