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https://www.readbyqxmd.com/read/29891095/design-and-clinical-use-of-a-rotational-phantom-for-dosimetric-verification-of-imrt-vmat-treatments
#1
Michael P Grams, Luis E Fong de Los Santos
PURPOSE: To describe the design and clinical use of a rotational phantom for dosimetric verification of IMRT/VMAT treatment plans using radiochromic film. METHODS: A solid water cylindrical phantom was designed with separable upper and lower halves and rests on plastic bearings allowing for 360° rotation about its central axis. The phantom accommodates a half sheet of radiochromic film, and by rotating the cylinder, the film can be placed in any plane between coronal and sagittal...
June 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29891094/estimation-of-extremely-small-field-radiation-dose-for-brain-stereotactic-radiotherapy-using-the-vero4drt-system
#2
Shinichi Nakayama, Hajime Monzen, Yuichi Onishi, Soichiro Kaneshige, Ikuo Kanno
The purpose of this study was a dosimetric validation of the Vero4DRT for brain stereotactic radiotherapy (SRT) with extremely small fields calculated by the treatment planning system (TPS) iPlan (Ver.4.5.1; algorithm XVMC). Measured and calculated data (e.g. percentage depth dose [PDD], dose profile, and point dose) were compared for small square fields of 30 × 30, 20 × 20, 10 × 10 and 5 × 5 mm2 using ionization chambers of 0.01 or 0.04 cm3 and a diamond detector. Dose verifications were performed using an ionization chamber and radiochromic film (EBT3; the equivalent field sizes used were 8...
June 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29866337/comparison-of-dose-response-functions-for-ebt3-model-gafchromic%C3%A2-film-dosimetry-system
#3
Saad Aldelaijan, Slobodan Devic
OBJECTIVE: Different dose response functions of EBT3 model GafChromic™ film dosimetry system have been compared in terms of sensitivity as well as uncertainty vs. error analysis. We also made an assessment of the necessity of scanning film pieces before and after irradiation. METHODS: Pieces of EBT3 film model were irradiated to different dose values in Solid Water (SW) phantom. Based on images scanned in both reflection and transmission mode before and after irradiation, twelve different response functions were calculated...
May 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29779953/a-quality-assurance-device-for-measuring-afterloader-performance-and-transit-dose-for-nasobiliary-high-dose-rate-brachytherapy
#4
Christopher L Deufel, John P Mullins, Mark J Zakhary
PURPOSE: Nasobiliary high-dose-rate (HDR) brachytherapy has emerged as an effective tool to boost the radiation dose for patients with unresectable perihilar cholangiocarcinoma. This work describes a quality assurance (QA) tool for measuring the HDR afterloader's performance, including the transit dose, when the source wire travels through a tortuous nasobiliary catheter path. METHODS AND MATERIALS: The nasobiliary QA device was designed to mimic the anatomical path of a nasobiliary catheter, including the nasal, stomach, duodenum, and bile duct loops...
May 17, 2018: Brachytherapy
https://www.readbyqxmd.com/read/29763970/technical-note-experimental-verification-of-magnetic-field-induced-beam-deflection-and-bragg-peak-displacement-for-mr-integrated-proton-therapy
#5
Sonja M Schellhammer, Sebastian Gantz, Armin Lühr, Bradley M Oborn, Michael Bussmann, Aswin L Hoffmann
PURPOSE: Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for on-line anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg peak...
May 15, 2018: Medical Physics
https://www.readbyqxmd.com/read/29746014/dosimetric-and-geometric-characteristics-of-a-small-animal-image-guided-irradiator-using-3d-dosimetry-optical-ct-scanner
#6
Yong Hum Na, Yi-Fang Wang, Paul J Black, Christian Velten, Xin Qian, Shih-Chi Lin, John Adamovics, Cheng-Shie Wuu
PURPOSE: The precise dosimetric and geometric characteristics of small animal irradiators are essential to achieving reproducible dose delivery, especially in cases where image-guidance is utilized. Currently, radiochromic film is the established measurement tool used to evaluate beam characteristics for these systems. However, only 2D information can be acquired with film. This study characterized both the dosimetric and geometric properties of the small animal research radiation platform (SARRP, Xstrahl) for commissioning purposes using a 3D radiochromic dosimetry system with a sub-millimeter resolution optical computed tomography (OCT) scanner...
May 10, 2018: Medical Physics
https://www.readbyqxmd.com/read/29728224/establishment-of-postal-audit-system-in-intensity-modulated-radiotherapy-by-radiophotoluminescent-glass-dosimeters-and-a-radiochromic-film
#7
Hiroyuki Okamoto, Toshiyuki Minemura, Mitsuhiro Nakamura, Hideyuki Mizuno, Naoki Tohyama, Teiji Nishio, Akihisa Wakita, Satoshi Nakamura, Shie Nishioka, Kotaro Iijima, Daisuke Fujiyama, Jun Itami, Yasumasa Nishimura
We developed an efficient postal audit system to independently assess the delivered dose using radiophotoluminescent glass dosimeters (RPLDs) and the positional differences of fields using EBT3 film at the axial plane for intensity-modulated radiotherapy (IMRT). The audit phantom had a C-shaped target structure as a planning target volume (PTV) with four measurement points for the RPLDs and a cylindrical structure as the organ at risk (OAR) for one measurement point. The phantoms were sent to 24 institutions...
April 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29722290/feasibility-of-polymer-gel-based-measurements-of-radiation-isocenter-accuracy-in-magnetic-fields
#8
Stefan Dorsch, Philipp Mann, Clemens Lang, Peter Häring, Armin Runz, Christian P Karger
For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, radiation and imaging isocenter test, however, it has to be shown first that PG reveals comparable results as the conventionally applied films...
May 3, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29716332/spectral-calibration-of-ebt3-and-hd-v2-radiochromic-film-response-at-high-dose-using-20-mev-proton-beams
#9
Yiwei Feng, Henry F Tiedje, Katherine Gagnon, Robert Fedosejevs
Radiochromic film is used extensively in many medical, industrial, and scientific applications. In particular, the film is used in analysis of proton generation and in high intensity laser-plasma experiments where very high dose levels can be obtained. The present study reports calibration of the dose response of Gafchromic EBT3 and HD-V2 radiochromic films up to high exposure densities. A 2D scanning confocal densitometer system is employed to carry out accurate optical density measurements up to optical density 5 on the exposed films at the peak spectral absorption wavelengths...
April 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29714197/synchrotron-radiation-external-beam-rotational-radiotherapy-of-breast-cancer-proof-of-principle
#10
Francesca Di Lillo, Giovanni Mettivier, Roberta Castriconi, Antonio Sarno, Andrew W Stevenson, Chris J Hall, Daniel Häusermann, Paolo Russo
The principle of rotational summation of the absorbed dose for breast cancer treatment with orthovoltage X-ray beams was proposed by J. Boone in 2012. Here, use of X-ray synchrotron radiation for image guided external beam rotational radiotherapy treatment of breast cancer is proposed. Tumor irradiation occurs with the patient in the prone position hosted on a rotating bed, with her breast hanging from a hole in the bed, which rotates around a vertical axis passing through the tumor site. Horizontal collimation of the X-ray beam provides for whole breast or partial breast irradiation, while vertical translation of the bed and successive rotations allow for irradiation of the full tumor volume, with dose rates which permit also hypofractionated treatments...
May 1, 2018: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/29707904/investigation-of-ebt3-radiochromic-film-s-response-to-humidity
#11
Elsa Y León-Marroquín, José M Lárraga-Gutiérrez, J Alfredo Herrera-González, Miguel A Camacho-López, José E Villarreal Barajas, Olivia A García-Garduño
PURPOSE: The aim of this work is to investigate the effects of immersing EBT3 radiochromic film in water and to evaluate its contribution to the total uncertainty in dose determination. MATERIALS AND METHODS: We used 3 cm × 3 cm EBT3 radiochromic films irradiated in the range of 0-70 Gy to study the impact of water immersion on the change in net optical density. These films were placed in a water container for a period of 24 h. The net optical density was measured before (0 h) and after of the immersion in water (1, 3, 6, 12, 18, and 24 h)...
April 29, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29626289/dosimetric-changes-with-computed-tomography-automatic-tube-current-modulation-techniques
#12
Sofia Spampinato, Anna Maria Gueli, Pietro Milone, Luigi Angelo Raffaele
The study is aimed at a verification of dose changes for a computed tomography automatic tube-current modulation (ATCM) technique. For this purpose, anthropomorphic phantom and Gafchromic® XR-QA2 films were used. Radiochromic films were cut according to the shape of two thorax regions. The ATCM algorithm is based on noise index (NI) and three exam protocols with different NI were chosen, of which one was a reference. Results were compared with dose values displayed by the console and with Poisson statistics...
June 2018: Radiological Physics and Technology
https://www.readbyqxmd.com/read/29609823/evaluation-of-a-led-based-flatbed-document-scanner-for-radiochromic-film-dosimetry-in-transmission-mode
#13
José Manuel Lárraga-Gutiérrez, Olivia Amanda García-Garduño, Carlos Treviño-Palacios, José Alfredo Herrera-González
Flatbed scanners are the most frequently used reading instrument for radiochromic film dosimetry because its low cost, high spatial resolution, among other advantages. These scanners use a fluorescent lamp and a CCD array as light source and detector, respectively. Recently, manufacturers of flatbed scanners replaced the fluorescent lamp by light emission diodes (LED) as a light source. The goal of this work is to evaluate the performance of a commercial flatbed scanner with LED based source light for radiochromic film dosimetry...
March 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29609815/monte-carlo-uncertainty-analysis-of-dose-estimates-in-radiochromic-film-dosimetry-with-single-channel-and-multichannel-algorithms
#14
Juan Antonio Vera-Sánchez, Carmen Ruiz-Morales, Antonio González-López
PURPOSE: To provide a multi-stage model to calculate uncertainty in radiochromic film dosimetry with Monte-Carlo techniques. This new approach is applied to single-channel and multichannel algorithms. MATERIAL AND METHODS: Two lots of Gafchromic EBT3 are exposed in two different Varian linacs. They are read with an EPSON V800 flatbed scanner. The Monte-Carlo techniques in uncertainty analysis provide a numerical representation of the probability density functions of the output magnitudes...
March 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29603564/film-based-dose-validation-of-monte-carlo-algorithm-for-cyberknife-system-with-a-cirs-thorax-phantom
#15
Yuxi Pan, Ruijie Yang, Jun Li, Xile Zhang, Lu Liu, Junjie Wang
Monte Carlo (MC) simulation, as the most accurate dose calculation algorithm, is available in the MultiPlan treatment planning system for Cyberknife. The main purpose of this work was to perform experiments to thoroughly investigate the accuracy of the MC dose calculation algorithm. Besides the basic MC beam commissioning, two test scenarios were designed. First, single beam tests were performed with a solid water phantom to verify the MC source model in simple geometry. Then, a lung treatment plan on a CIRS thorax phantom was created to mimic the clinical patient treatment...
May 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29571934/multi-institutional-evaluation-of-end-to-end-protocol-for-imrt-vmat-treatment-chains-utilizing-conventional-linacs
#16
Brian Loughery, Cory Knill, Evan Silverstein, Viatcheslav Zakjevskii, Kathryn Masi, Elizabeth Covington, Karen Snyder, Kwang Song, Michael Snyder
We conducted a multi-institutional assessment of a recently developed end-to-end monthly quality assurance (QA) protocol for external beam radiation therapy treatment chains. This protocol validates the entire treatment chain against a baseline to detect the presence of complex errors not easily found in standard component-based QA methods. Participating physicists from 3 institutions ran the end-to-end protocol on treatment chains that include Imaging and Radiation Oncology Core (IROC)-credentialed linacs...
March 20, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/29547397/fixed-object-specific-intensity-compensation-for-cone-beam-optical-ct-radiation-dosimetry
#17
Kurtis H Dekker, Rubin Hazarika, Matheus A Silveira, Kevin J Jordan
Optical cone beam computed tomography (CT) scanning of radiochromic gel dosimeters, using a CCD camera and a low stray light convergent source, provides fast, truly 3D radiation dosimetry with high accuracy. However, a key limiting factor in radiochromic gel dosimetry at large (⩾10 cm diameter) volumes is the initial attenuation of the dosimeters. It is not unusual to observe a 5-10×  difference in signal intensity through the dosimeter center versus through the surrounding medium in pre-irradiation images...
March 16, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29532785/radiation-characterisation-and-dosimetric-measurements-of-a-femtosecond-pulsed-laser-ablation-system
#18
J Prieto-Pena, F Gómez, D M González-Castaño, M T Flores-Arias, J Arines, C Bao-Varela, F Cambronero-López, A Martínez Maqueira
This work describes the radiation characterisation and dosimetric measurements performed on the low-energy micromachining station of the femtosecond STELA (Santiago TErawatt LAser) at the University of Santiago de Compostela (Spain). For this aim, ionisation chambers, solid state detectors, and radiochromic films were used. The results show the emission of pulsed x-ray produced by laser-accelerated electrons from the ablated material exhibiting both bremsstrahlung and characteristic radiation. Although this radiation was produced unintentionally, a high superficial dose rate can be achieved...
March 13, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
https://www.readbyqxmd.com/read/29498970/influence-of-backscatter-radiation-on-cranial-bone-fixation-devices
#19
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
https://www.readbyqxmd.com/read/29474189/characteristic-of-ebt-xd-and-ebt3-radiochromic-film-dosimetry-for-photon-and-proton-beams
#20
Suphalak Khachonkham, Ralf Dreindl, Gerd Heilemann, Wolfgang Lechner, Hermann Fuchs, Hugo Palmans, Dietmar Georg, Peter Kuess
Recently, a new type of radiochromic film, the EBT-XD film, has been introduced for high dose radiotherapy. The EBT-XD film contains the same structure as the EBT3 film but has a slightly different composition and a thinner active layer. This study benchmarks the EBT-XD against EBT3 film for 6 MV and 10 MV photon beams, as well as for 97.4 MeV and 148.2 MeV proton beams and 15-100 kV x-rays. Dosimetric and film reading characteristics, such as post irradiation darkening, film orientation effect, lateral response artifact (LRA), film sensitivity, energy and beam quality dependency were investigated...
March 15, 2018: Physics in Medicine and Biology
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