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https://www.readbyqxmd.com/read/28730606/technical-note-empirical-altitude-correction-factors-for-well-chamber-measurements-of-permanent-prostate-and-breast-seed-implant-sources
#1
Elizabeth Watt, David P Spencer, Tyler Meyer
PURPOSE: Previous studies in the literature have measured an altitude effect for low-energy brachytherapy seeds; a correction factor applied in addition to PTP to account for the breakdown of Bragg-Gray cavity theory at low energies in well-type ionization chambers. In clinical practice, many centres use altitude correction factors that are not seed-model-specific. The purpose of this work is to present altitude correction factors for several seed models without documented factors in the literature...
July 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28719153/in-source-collision-induced-dissociation-is-cid-applications-issues-and-structure-elucidation-with-single-stage-mass-analyzers
#2
Jon F Parcher, Mei Wang, Amar G Chittiboyina, Ikhlas A Khan
A discussion of the definition, advantages and issues with the formation of ions in the transition region between an ESI source and the ion optics of a mass analyzer is presented. The various types of ions formed in the so-called in-source collision induced dissociation (IS-CID) process are illustrated. Applications of IS-CID with single-stage mass analyzers, such as structure elucidation and quantitation, are demonstrated. The discussion is illustrated by examples of the in-source fragmentation of ginkgolides, which are marker compounds found only in Ginkgo biloba...
July 18, 2017: Drug Testing and Analysis
https://www.readbyqxmd.com/read/28719019/initial-testing-of-a-pixelated-silicon-detector-prototype-in-proton-therapy
#3
Andrew J Wroe, Grant McAuley, Anthony V Teran, Jeannie Wong, Marco Petasecca, Michael Lerch, James M Slater, Anatoly B Rozenfeld
As technology continues to develop, external beam radiation therapy is being employed, with increased conformity, to treat smaller targets. As this occurs, the dosimetry methods and tools employed to quantify these fields for treatment also have to evolve to provide increased spatial resolution. The team at the University of Wollongong has developed a pixelated silicon detector prototype known as the dose magnifying glass (DMG) for real-time small-field metrology. This device has been tested in photon fields and IMRT...
July 18, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28715250/the-development-of-technology-for-effective-respiratory-gated-irradiation-using-an-image-guided-small-animal-irradiator
#4
M A Hill, J Thompson, A Kavanagh, I D C Tullis, R G Newman, J Prentice, J Beech, S Gilchrist, S Smart, E Fokas, B Vojnovic
The development of image-guided small animal irradiators represents a significant improvement over standard irradiators by enabling preclinical studies to mimic radiotherapy in humans. The ability to deliver tightly collimated targeted beams, in conjunction with gantry or animal couch rotation, has the potential to maximize tumor dose while sparing normal tissues. However, the current commercial platforms do not incorporate respiratory gating, which is required for accurate and precise targeting in organs subject to respiration related motions that may be up to the order of 5 mm in mice...
July 17, 2017: Radiation Research
https://www.readbyqxmd.com/read/28710866/response-of-synthetic-diamond-detectors-in-proton-carbon-and-oxygen-ion-beams
#5
Séverine Rossomme, Marco Marinelli, Gianluca Verona-Rinati, Francesco Romano, G A Pablo Cirrone, Andrzej Kacperek, Stefaan Vynckier, Hugo Palmans
PURPOSE: In this work, the LET-dependence of the response of synthetic diamond detectors is investigated in different particle beams. METHOD: Measurements were performed in three non-modulated particle beams (proton, carbon and oxygen). The response of five synthetic diamond detectors was compared to the response of a Markus or an Advanced Markus ionization chamber. The synthetic diamond detectors were used with their axis parallel to the beam axis and without any bias voltage...
July 15, 2017: Medical Physics
https://www.readbyqxmd.com/read/28708603/monte-carlo-skin-dose-simulation-in-intraoperative-radiotherapy-of-breast-cancer-using-spherical-applicators
#6
Farhad Moradi, Ngie Min Ung, M U Khandaker, Ghafour Amouzad Mahdiraji, Marniza Saad, Rozita Abdul Malik, Anita Zarina Bustam, Zainor Zaili, David A Bradley
The relatively new treatment modality electronic intraoperative radiotherapy (IORT) is gaining popularity, irradiation being obtained within a surgically produced cavity being delivered via a low-energy X-ray source and spherical applicators, primarily for early stage breast cancer. Due to the spatially dramatic dose-rate fall off with radial distance from the source and effects related to changes in the beam quality of the low keV photon spectra, dosimetric account of the Intrabeam system is rather complex...
July 14, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28707381/radiation-associated-lens-changes-in-the-cardiac-catheterization-laboratory-results-from-the-ic-cataract-cataracts-attributed-to-radiation-in-the-cath-lab-study
#7
Aris Karatasakis, Harilaos S Brilakis, Barbara A Danek, Judit Karacsonyi, Jose Roberto Martinez-Parachini, Phuong-Khanh J Nguyen-Trong, Aya J Alame, Michele K Roesle, Bavana V Rangan, Kenneth Rosenfield, Roxana Mehran, Ehtisham Mahmud, Charles E Chambers, Subhash Banerjee, Emmanouil S Brilakis
OBJECTIVE: To examine the relationship between occupational exposure to ionizing radiation and the prevalence of lens changes in interventional cardiologists (ICs) and catheterization laboratory ("cath-lab") staff. BACKGROUND: Exposure to ionizing radiation is associated with the development of lens opacities. ICs and cath-lab staff can receive high doses of ionizing radiation without protection, and may thus be at risk for lens opacity formation. METHODS: We conducted a cross-sectional study at an interventional cardiology conference...
July 14, 2017: Catheterization and Cardiovascular Interventions
https://www.readbyqxmd.com/read/28706355/the-influence-of-acquisition-mode-on-the-dosimetric-performance-of-an-amorphous-silicon-electronic-portal-imaging-device
#8
Omemh Bawazeer, Sisira Herath, Siva Sarasanandarajah, Tomas Kron, Pradip Deb
AIMS: This study investigates the impact of cine acquisition mode on the dosimetric characteristics of a Varian aS500 amorphous silicon electronic portal imaging device (a-Si EPID). MATERIALS AND METHODS: The performance of an a-Si EPID operated in cine mode was assessed and compared to its performance when operated in an integrated mode and dose measurements using an ionization chamber. This study was conducted at different photon energies and the EPID performance was assessed as function of the delivered dose, dose rate, multileaf collimator speed, field size, phantom thickness, and intensity-modulated radiation therapy fields...
April 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28706351/beam-characterization-of-10-mv-photon-beam-from-medical-linear-accelerator-without-flattening-filter
#9
Tomohiro Shimozato, Yuichi Aoyama, Takuma Matsunaga, Katsuyoshi Tabushi
AIM: This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations. MATERIALS AND METHODS: The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber...
April 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28691256/clinical-usefulness-of-mlcs-in-robotic-radiosurgery-systems-for-prostate-sbrt
#10
Masashi Tomida, Takeshi Kamomae, Junji Suzuki, Yoichi Ohashi, Yoshiyuki Itoh, Hiroshi Oguchi, Takahito Okuda
Stereotactic body radiation therapy (SBRT) using recently introduced multileaf collimators (MLC) is preferred over circular collimators in the treatment of localized prostate cancer. The objective of this study was to assess the clinical usefulness of MLCs in prostate SBRT by comparing the effectiveness of treatment plans using fixed collimators, variable collimators, and MLCs and by ensuring delivery quality assurance (DQA) for each. For each patient who underwent conventional radiation therapy for localized prostate cancer, mock SBRT plans were created using a fixed collimator, a variable collimator, and an MLC...
July 10, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28688120/electron-beam-water-calorimetry-measurements-to-obtain-beam-quality-conversion-factors
#11
Bryan R Muir, Claudiu D Cojocaru, Malcolm R McEwen, Carl K Ross
PURPOSE: To provide results of water calorimetry and ion chamber measurements in high-energy electron beams carried out at the National Research Council Canada (NRC). There are three main aspects to this work: 1) investigation of the behavior of ionization chambers in electron beams of different energies with focus on long-term stability, 2) water calorimetry measurements to determine absorbed dose to water in high-energy beams for direct calibration of ion chambers, and 3) using measurements of chamber response relative to reference ion chambers, determination of beam quality conversion factors, kQ, for several ion chamber types...
July 8, 2017: Medical Physics
https://www.readbyqxmd.com/read/28679448/simultaneous-integrated-boost-therapy-of-carcinoma-of-the-hypopharynx-larynx-with-and-without-flattening-filter-a-treatment-planning-and-dosimetry-study
#12
Barbara Dobler, Tina Obermeier, Matthias G Hautmann, Amine Khemissi, Oliver Koelbl
BACKGROUND: The aim of this study was to investigate if the flattening filter free (FFF) irradiation mode of a linear accelerator (linac) is advantageous as compared to the flat beam (FF) irradiation mode in intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for carcinoma of the hypopharynx / larynx. METHODS: Four treatment plans were created for each of 10 patients for an Elekta Synergy linac with Agility collimating device, a dual arc VMAT and a nine field step and shoot IMRT each with and without flattening filter...
July 5, 2017: Radiation Oncology
https://www.readbyqxmd.com/read/28678241/enhanced-sensitivity-and-metabolite-coverage-with-remote-laser-ablation-electrospray-ionization-mass-spectrometry-aided-by-coaxial-plume-and-gas-dynamics
#13
Jarod A Fincher, Andrew R Korte, Brent Reschke, Nicholas J Morris, Matthew J Powell, Akos Vertes
Laser ablation electrospray ionization-mass spectrometry (LAESI-MS) allows for direct analysis of biological tissues at atmospheric pressure with minimal to no sample preparation. In LAESI, a mid-IR laser beam (λ = 2.94 μm) is focused onto the sample to produce an ablation plume that is intercepted and ionized by an electrospray at the inlet of the mass spectrometer. In the remote LAESI platform, the ablation process is removed from the mass spectrometer inlet and takes place in an ablation chamber, allowing for incorporation of additional optics for microscopic imaging and targeting of specific features of the sample for laser ablation sampling...
July 5, 2017: Analyst
https://www.readbyqxmd.com/read/28678023/error-detection-capability-of-a-novel-transmission-detector-a-validation-study-for-online-vmat-monitoring
#14
Marlies Pasler, Kilian Michel, Livia Marrazzo, Michael Obenland, Stefania Pallotta, Mari Bjoernsgard, Johannes Lutterbach
The purpose of this study was to characterize a new single large-area ionization chamber, the Integral Quality Monitor (IQM) system (iRT, Germany), for online and real-time beam monitoring. Signal stability, monitor unit (MU) linearity and dose rate dependence were investigated for static and arc deliveries and compared to independent ionization chamber measurements. The dose verification capability of the transmission detector system was evaluated by comparing calculated and measured detector signals for 15 volumetric modulated arc therapy (VMAT) plans...
July 5, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28666767/towards-breast-cancer-rotational-radiotherapy-with-synchrotron-radiation
#15
Francesca Di Lillo, Giovanni Mettivier, Antonio Sarno, Roberta Castriconi, Paolo Russo
PURPOSE: We performed the first investigations, via measurements and Monte Carlo simulations on phantoms, of the feasibility of a new technique for synchrotron radiation rotational radiotherapy for breast cancer (SR(3)T). METHODS: A Monte Carlo (MC) code based on Geant4 toolkit was developed in order to simulate the irradiation with the SR(3)T technique and to evaluate the skin sparing effect in terms of centre-to-periphery dose ratio at different energies in the range 60-175keV...
June 27, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28665529/a-novel-and-fast-method-for-proton-range-verification-using-a-step-wedge-and-2d-scintillator
#16
Jiajian Shen, Bryce C Allred, Daniel G Robertson, Wei Liu, Terence T Sio, Nicholas B Remmes, Sameer R Keole, Martin Bues
PURPOSE: To implement and evaluate a novel and fast method for proton range verification by using a planar scintillator and step wedge. METHODS: A homogenous proton pencil beam plan with 35 energies was designed and delivered to a 2D flat scintillator with a step wedge. The measurement was repeated 15 times (three different days, 5 times per day). The scintillator image was smoothed, the Bragg peak and distal fall off regions were fitted by an analytical equation, and the proton range was calculated using simple trigonometry...
June 30, 2017: Medical Physics
https://www.readbyqxmd.com/read/28662851/dosimetric-properties-of-a-solid-water-high-equivalency-sw557-phantom-for-megavoltage-photon-beams
#17
Fujio Araki
The dosimetric properties of the recently developed SW557 phantom have been investigated by comparison with those of the existing SW457 phantom in megavoltage photon beams. The electron fluence ratio φpl(w), and chamber ionization ratio kpl, of water to SW457 and water to SW557 for 4-15MV photons were calculated as a function of depth using Monte Carlo simulations, and compared with measured values. Values of φpl(w) for SW457 were in the range of 1.004-1.014 for 4MV, and 1.014-1.018 for 15MV photons. The φpl(w) for SW557 ranged from 1...
July 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28656604/consistency-in-quality-correction-factors-for-ionization-chamber-dosimetry-in-scanned-proton-beam-therapy
#18
Jefferson Sorriaux, Mauro Testa, Harald Paganetti, Damien Bertrand, John Aldo Lee, Hugo Palmans, Stefaan Vynckier, Edmond Sterpin
PURPOSE: The IAEA TRS-398 code of practice details the reference conditions for reference dosimetry of proton beams using ionization chambers and the required beam quality correction factors (kQ ). Pencil beam scanning (PBS) systems cannot approximate reference conditions using a single spot. However, dose distributions requested in TRS-398 can be reproduced with PBS using a combination of spots. This study aims to demonstrate, using Monte Carlo (MC) simulations, that kQ factors computed/measured for broad beams can be used with scanned beams for similar reference dose distributions with no additional significant uncertainty...
June 28, 2017: Medical Physics
https://www.readbyqxmd.com/read/28645509/a-fast-and-reliable-method-for-daily-quality-assurance-in-spot-scanning-proton-therapy-with-a-compact-and-inexpensive-phantom
#19
Nicola Bizzocchi, Francesco Fracchiolla, Marco Schwarz, Carlo Algranati
In a radiotherapy center, daily quality assurance (QA) measurements are performed to ensure that the equipment can be safely used for patient treatment on that day. In a pencil beam scanning (PBS) proton therapy center, spot positioning, spot size, range, and dose output are usually verified every day before treatments. We designed, built, and tested a new, reliable, sensitive, and inexpensive phantom, coupled with an array of ionization chambers, for daily QA that reduces the execution times while preserving the reliability of the test...
June 20, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/28643752/dosimetric-characterization-of-optically-stimulated-luminescence-dosimeter-with-therapeutic-photon-beams-for-use-in-clinical-radiotherapy-measurements
#20
Retna Ponmalar, Ravikumar Manickam, K M Ganesh, Sathiyan Saminathan, Arun Raman, Henry Finlay Godson
AIM: The modern radiotherapy techniques impose new challenges for dosimetry systems with high precision and accuracy in in vivo and in phantom dosimetric measurements. The knowledge of the basic characterization of a dosimetric system before patient dose verification is crucial. This incites the investigation of the potential use of nanoDot optically stimulated luminescence dosimeter (OSLD) for application in radiotherapy with therapeutic photon beams. MATERIALS AND METHODS: Measurements were carried out with nanoDot OSLDs to evaluate the dosimetric characteristics such as dose linearity, dependency on field size, dose rate, energy and source-to-surface distance (SSD), reproducibility, fading effect, reader stability, and signal depletion per read out with cobalt-60 (60 Co) beam, 6 and 18 MV therapeutic photon beams...
April 2017: Journal of Cancer Research and Therapeutics
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