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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
#1
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
#2
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
#3
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
#4
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
#5
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
#6
Severine Rossomme, Julian Horn, Stephan Brons, Oliver Jaekel, Andrea Mairani, Mario Ciocca, Vincent Floquet, Francesco Romano, Diana Rodriguez Garcia, Stefaan Vynckier, Hugo Palmans
Based on international reference dosimetry protocols for light-ion beams, a correction factor (<i>k<sub>s</sub></i>) 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, <i>k<sub>s</sub></i> for IBA PPC40 Roos-type chambers is investigated in four scanned light-ion beams (proton, helium, carbon and oxygen)...
May 15, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28488238/trans-oral-miniature-x-ray-radiation-delivery-system-with-endoscopic-optical-feedback
#7
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
#8
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
#9
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
https://www.readbyqxmd.com/read/28477371/quantitative-ionization-chamber-alignment-to-a-water-surface-performance-of-multiple-chambers
#10
James D Ververs, Malcolm R McEwen, Jeffrey V Siebers
PURPOSE: To experimentally examine the reliability of the gradient chamber alignment point (gCAP) determination method for accurately identifying water surface location with a range of ionization chambers (ICs). METHOD & MATERIALS: Twelve cylindrical ICs were scanned from depth through a water surface into air using a customized high-accuracy scanning system which allows for accurate alignment of the IC with respect to the true water surface. Thirteen other cylindrical ICs and five parallel-plate ICs were scanned using a standard commercially available scanning system...
May 5, 2017: Medical Physics
https://www.readbyqxmd.com/read/28477370/quantitative-ionization-chamber-alignment-to-a-water-surface-theory-and-simulation
#11
Jeffrey V Siebers, James D Ververs, Frédéric Tessier
PURPOSE: To examine the response properties of cylindrical cavity ionization chambers (ICs) in the depth-ionization buildup region so as to obtain a robust chamber-signal-based method for definitive water surface identification, hence absolute ionization chamber depth localization. METHOD & MATERIALS: An analytical model with simplistic physics and geometry is developed to explore the theoretical aspects of ionization chamber response near a phantom water surface...
May 5, 2017: Medical Physics
https://www.readbyqxmd.com/read/28477127/live-cell-imaging-to-study-real-time-atm-mediated-recruitment-of-dna-repair-complexes-to-sites-of-ionizing-radiation-induced-dna-damage
#12
Burkhard Jakob, Gisela Taucher-Scholz
Measurements of protein recruitment and the formation of repair complexes at DNA double-strand breaks in real time provide valuable insight into the regulation of the early DNA damage response. Here, we describe the use of live cell microscopy in combination with ionizing radiation as a tool to evaluate the influence of ATM and its site-specific phosphorylation of target proteins on these processes. Recommendations are made for the preparation of the cells and the design of specialized cell chambers for the localized (and/or targeted) irradiation with charged particles at accelerator beamlines as well as the microscopic equipment and protocol to obtain high-resolution, sensitive fluorescence measurements...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28473460/corneal-dose-reduction-using-a-bismuth-coated-latex-shield-over-the-eyes-during-brain-spect-ct
#13
Norikazu Matsutomo, Masaaki Fukunaga, Onishi Hideo, Tomoaki Yamamoto
Objective: This study aimed to determine whether a bismuth-coated latex shield (B-shield) could protect the eyes during brain SPECT/CT. Methods: A B-shield containing the heavy metal bismuth (0.15 mm lead equivalent) was placed over a cylindrical phantom and the eyes of a three-dimensional brain phantom filled with Tc-99m solution. Subsequently, phantoms with and without the B-shield were compared using SPECT/CT. The CT parameters were 30-200 mA and 130 kV. The dose reduction achieved by the B shield was measured using a pencil-shaped ionization chamber...
May 4, 2017: Journal of Nuclear Medicine Technology
https://www.readbyqxmd.com/read/28464743/monte-carlo-simulations-of-a-low-energy-proton-beamline-for-radiobiological-experiments
#14
Tordis J Dahle, Anne Marit Rykkelid, Camilla H Stokkevåg, Andrea Mairani, Andreas Görgen, Nina J Edin, Eivind Rørvik, Lars Fredrik Fjæra, Eirik Malinen, Kristian S Ytre-Hauge
BACKGROUND: In order to determine the relative biological effectiveness (RBE) of protons with high accuracy, radiobiological experiments with detailed knowledge of the linear energy transfer (LET) are needed. Cell survival data from high LET protons are sparse and experiments with low energy protons to achieve high LET values are therefore required. The aim of this study was to quantify LET distributions from a low energy proton beam by using Monte Carlo (MC) simulations, and to further compare to a proton beam representing a typical minimum energy available at clinical facilities...
June 2017: Acta Oncologica
https://www.readbyqxmd.com/read/28452566/hypothermia-after-cranial-irradiation-protects-neural-progenitor-cells-in-the-subventricular-zone-but-not-in-the-hippocampus
#15
Magnus Sabel, Marie Kalm, Thomas Björk-Eriksson, Birgitta Lannering, Klas Blomgren
PURPOSE: To explore if hypothermia can reduce the harmful effects of ionizing radiation on the neurogenic regions of the brain in young rats. MATERIAL AND METHODS: Postnatal day 9 rats were randomized into two treatment groups, hypo- and normothermia, or a control group. Treatment groups were placed in chambers submerged in temperature-controlled water baths (30˚C and 36˚C) for 8 h, after receiving a single fraction of 8 Gy to the left hemisphere. Seven days post-irradiation, we measured the sizes of the subventricular zone (SVZ) and the granule cell layer (GCL) of the hippocampus, and counted the number of proliferating (phospho-histone H3+) cells and microglia (Iba1+ cells)...
April 28, 2017: International Journal of Radiation Biology
https://www.readbyqxmd.com/read/28452341/reference-dosimetry-of-proton-pencil-beams-based-on-dose-area-product-a-proof-of-concept
#16
Carles Gomà, Sairos Safai, Sándor Vörös
This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a (60)Co beam, the Monte Carlo calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam...
April 28, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28444359/realistic-dosimetry-for-studies-on-biological-responses-to-x-rays-and-%C3%AE-rays
#17
Mehrdad Shahmohammadi Beni, Dragana Krstic, Dragoslav Nikezic, Kwan Ngok Yu
A calibration coefficient R (= DA/DE) for photons was employed to characterize the photon dose in radiobiological experiments, where DA was the actual dose delivered to cells and DE was the dose recorded by an ionization chamber. R was determined using the Monte Carlo N-Particle version 5 (MCNP-5) code. Photons with (i) discrete energies, and (ii) continuous-energy distributions under different beam conditioning were considered. The four studied monoenergetic photons had energies E = 0.01, 0.1, 1 and 2 MeV...
April 24, 2017: Journal of Radiation Research
https://www.readbyqxmd.com/read/28432792/monte-carlo-study-of-the-chamber-phantom-air-gap-effect-in-a-magnetic-field
#18
Daniel J O'Brien, Gabriel O Sawakuchi
PURPOSE: The aim of this study was to examine the effect of sub-millimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed in a magnetic field. METHODS: Geant4 Monte Carlo simulations were performed using a model of a PTW 30013 Farmer chamber in a water phantom. Symmetrical and asymmetrical air gaps of various thicknesses were modeled surrounding the chamber, and the dose to the air cavity of the chamber was scored in each case...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28428474/evaluation-of-absorbed-dose-for-cbct-in-image-guided-radiation-therapy-comparison-of-each-devices-and-facilities
#19
Yumiko Kitazato, Noriyuki Kuga, Katsutoshi Shirieda, Masahiro Enzaki, Yuji Nakaguchi, Yoshinobu Shimohigashi, Toshihisa Kawasaki, Masahiko Toyoda, Daisuke Kawahara, Fujio Araki, Shinji Kawamura
Recently, intensity-modulated radiation therapy (IMRT) is used worldwide, highly accurate verification of the location using image-guided radiation therapy (IGRT) has become critical. However, the use of cone-beam computed tomography (CBCT) to ascertain the location each time raises concerns about its influence on radiotherapy dosage and increased radiation exposure. The purpose of this study was to measure the absorbed dose using nine kilovoltage (kV) devices and two megavoltage (MV) devices (total 11 devices) at eight facilities, compare the absorbed dose among the devices, and assess the characteristics of the respective devices to ensure optimal clinical operation...
2017: Nihon Hoshasen Gijutsu Gakkai Zasshi
https://www.readbyqxmd.com/read/28407496/study-of-the-wall-effect-of-the-sample-position-well-of-the-frisch-grid-ionization-chamber
#20
Huaiyong Bai, Zhimin Wang, Luyu Zhang, Haoyu Jiang, Yi Lu, Jinxiang Chen, Guohui Zhang
When measuring the charged particles using a Frisch-grid ionization chamber, the sample is usually placed at the bottom of a sample position well on the common cathode. Thus, there will be the wall effect of the sample position well and this will change the measured energy spectrum of the charged particles. The wall effect of the sample position well is proved to be noticeable by the present work using experiments and simulations.
April 7, 2017: Applied Radiation and Isotopes
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