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JOURNAL ARTICLE
Stephan Frick, Moritz Schneider, Ralf-Peter Kapsch, Daniela Thorwarth
BACKGROUND AND PURPOSE: For dosimetry in magnetic resonance (MR) guided radiotherapy, assessing the magnetic field correction factors of air-vented ionization chambers is crucial. Novel MR-optimized chambers reduce MR-imaging artefacts, enhancing their quality assurance utility. This study aimed to characterize two new MR-optimized ionization chambers with sensitive volumes of 0.07 and 0.016 cm3 regarding magnetic field correction factors and intra-type variation and compare them to their conventional counterparts...
January 2024: Physics and Imaging in Radiation Oncology
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JOURNAL ARTICLE
Tadahiro Mizoguchi, Yuji Tameshige, Tatsuya Kaneda, Yoshiji Ogawa, Yoshiyuki Muranaka, Hiroyasu Tamamura
PURPOSE: When performing single-point dose verification in VMAT, it is necessary to avoid the regions with steep dose gradient. We propose a method to obtain the estimated value ( Uplan ) of uncertainty of the absolute dose measurement due to the phantom setup error by using dose gradient calculated from treatment planning system (TPS), for evaluating the appropriate measurement points. METHODS: The dose gradient was calculated from the planned dose values in the vicinity of the isocenter point using TPS...
March 5, 2024: Nihon Hoshasen Gijutsu Gakkai Zasshi
#23
JOURNAL ARTICLE
Matthew James Large, Aishah Bashiri, Yashiv Dookie, Joanne McNamara, Luca Antognini, Saba Aziz, Lucio Calcagnile, Anna Paola Caricato, Roberto Catalano, Deborah Chila, Giuseppe Antonio Pablo Cirrone, Tomasso Croci, Giacomo Cuttone, Sylvain Dunand, Michele Fabi, Luca Frontini, Catia Grimani, Maria Ionica, Keida Kanxheri, Valentino Liberali, Martino Maurizio, Giuseppe Maruccio, Giovanni Mazza, Mauro Menichelli, Anna Grazia Monteduro, Arianna Morozzi, Francesco Moscatelli, Stefania Pallotta, Daniele Passeri, Maddalena Pedio, Giada Petringa, Francesca Peverini, Lorenzo Piccolo, Pisana Placidi, Gianluca Quarta, Silvia Rizzato, Federico Sabbatini, Leonello Servoli, Alberto Stabile, Cinzia Talamonti, Jonathan Emanuel Thomet, Luca Tosti, Mattia Villani, Richard James Wheadon, Nicolas Wyrsch, Nicola Zema, Marco Petasecca
BACKGROUND: The increasing use of complex and high dose-rate treatments in radiation therapy necessitates advanced detectors to provide accurate dosimetry. Rather than relying on pre-treatment quality assurance (QA) measurements alone, many countries are now mandating the use of in vivo dosimetry, whereby a dosimeter is placed on the surface of the patient during treatment. Ideally, in vivo detectors should be flexible to conform to a patient's irregular surfaces. PURPOSE: This study aims to characterize a novel hydrogenated amorphous silicon (a-Si:H) radiation detector for the dosimetry of therapeutic x-ray beams...
March 3, 2024: Medical Physics
#24
JOURNAL ARTICLE
Xinhua Li, Theodore A Marschall, Kai Yang, Bob Liu
BACKGROUND: Mobile C-arms may be used in fixed locations, and it is recommended that qualified experts evaluate structural shielding. PURPOSE: To assess clinical workload distributions for mobile C-arms used in gastrointestinal endoscopy and determine the Archer equation parameters for the C-arm beam spectra. METHODS: Consecutive (30 months) gastrointestinal endoscopic procedures on two Cios Alpha systems (Siemens) were retrospectively analyzed...
February 29, 2024: Medical Physics
#25
JOURNAL ARTICLE
Chris Heintz, Lisa Schnödewind, Oliver Braubach, Hendrik Kersten, Thorsten Benter, Walter Wißdorf
Electrospray ionization (ESI) is one of the most prominent atmospheric pressure ionization techniques in modern mass spectrometry. It generates charged droplets from an analyte-containing solution as an initial step in the ionization process. Textbooks and the majority of the articles assume the entire droplet evaporation and release of bare analyte ions within the ionization chamber. However, non-mass-spectrometry-related literature and recent reports demonstrate droplet observation in regions of the vacuum systems of a variety of mass spectrometers...
February 26, 2024: Journal of the American Society for Mass Spectrometry
#26
JOURNAL ARTICLE
Hideyuki Mizuno, Taku Nakaji, Shigekazu Fukuda, Shingo Kato
BACKGROUND: End-to-end dosimetry audit for brachytherapy is challenging due to the steep dose gradient. However, it is an efficient method to detect unintended errors in actual clinical practice. PURPOSE: We aimed to develop an on-site end-to-end test phantom for three-dimensional image-guided brachytherapy (IGBT) for cervical cancer. METHODS: The test phantom we developed consisted of a water tank with an applicator/detector holder. The holder was designed to accommodate the applicator and insert an ionization chamber (PinPoint; PTW, Freiburg, Germany) to measure the dose at point A...
February 22, 2024: Physica Medica: PM
#27
JOURNAL ARTICLE
Tej Varma Yenupuri, Safi Rafie-Zinedine, Lena Worbs, Michael Heymann, Joachim Schulz, Johan Bielecki, Filipe R N C Maia
Imaging the structure and observing the dynamics of isolated proteins using single-particle X-ray diffractive imaging (SPI) is one of the potential applications of X-ray free-electron lasers (XFELs). Currently, SPI experiments on isolated proteins are limited by three factors: low signal strength, limited data and high background from gas scattering. The last two factors are largely due to the shortcomings of the aerosol sample delivery methods in use. Here we present our modified electrospray ionization (ESI) source, which we dubbed helium-ESI (He-ESI)...
February 22, 2024: Scientific Reports
#28
JOURNAL ARTICLE
Arthur Popkowski, S Craig Rhodes, John F Hatton
INTRODUCTION: Diagnostic reference levels (DRLs) are intended to improve patient safety and ensure that patient ionizing radiation doses are as low as reasonably achievable. PURPOSE: The purpose of this dosimetry study was to establish regional DRL levels for CBCT imaging for specialty endodontics. Another aim was to compare phantom-measured ionizing radiation DI1 index doses to the manufacturer-provided DAP radiation output valuesfor each of the CBCT machines studied, to ascertain their degree of correlation...
February 19, 2024: Journal of Endodontics
#29
JOURNAL ARTICLE
Jiří Valenta, Manfred Schmidt, Christoph Bert
PURPOSE: In medical linac quality assurance (QA), to replace film dosimetry with low-resolution 2-D ionization chamber array measurements, to validate the procedures, and to perform a comprehensive sensitivity analysis. METHODS: A 2-D ionization chamber array with a spatial resolution of 7.62 mm was deployed to perform the following tests: Junction tests, MLC transmission test, beam profile constancy vs. gantry angle test, beam profile constancy vs. low dose delivery test, and beam energy constancy vs...
February 16, 2024: Zeitschrift Für Medizinische Physik
#30
JOURNAL ARTICLE
S Rakshit, M S Kulkarni
A parallel-plate ionization chamber (PPC) with a nominal volume of 8.16 cm³ was developed based on theoretically simulated design parameters. Its purpose is to serve as a transfer standard for dosimetry in a beta radiation field. The entrance window of the PPC consists of an aluminized Mylar sheet with a thickness of 1.4 mg/cm2 . The collecting and guard electrodes are created by applying a graphite coating on a Poly Methyl Methacrylate (PMMA) substrate with a thickness of 5 mm. The nominal sheet resistance of the graphite-coated PMMA substrate was measured using a four-probe technique and found to be approximately 800 Ω per square (Ω/□)...
January 28, 2024: Applied Radiation and Isotopes
#31
JOURNAL ARTICLE
Ahtesham Ullah Khan, Larry A DeWerd, Poonam Yadav
PURPOSE: The purpose of this study was to directly calculate [Formula: see text] correction factors for four cylindrical ICs for a 0.35 T MR-linac using the Monte Carlo (MC) method. METHODS: A previously-validated TOPAS/GEANT4 MC head model of the 0.35 T MR-linac was employed. The MR-compatible Exradin A12, A1SL, A26, and A28 cylindrical ICs were modeled considering the dead volume in the air cavity. The [Formula: see text] correction factor was determined for initial electron energies of 5-7 MeV...
February 8, 2024: Physica Medica: PM
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JOURNAL ARTICLE
Elise Konradsson, Rebecka Ericsson Szecsenyi, Pontus Wahlqvist, Andreas Toft, Börje Blad, Sven Åj Bäck, Crister Ceberg, Kristoffer Petersson
This study aims to investigate the feasibility of enhancing the charge collection efficiency (CCE) of a transmission chamber by reconfiguring its design and operation. The goal was to extend the range of dose-per-pulse (DPP) values with no or minimal recombination effects up to the ultra-high dose rate (UHDR) regime. The response of two transmission chambers, with electrode distance of 1 mm and 0.6 mm, respectively, was investigated as a function of applied voltage. The chambers were mounted one-by-one in the electron applicator of a 10 MeV FLASH-modified clinical linear accelerator...
February 3, 2024: Radiation Research
#33
JOURNAL ARTICLE
Safi Rafie-Zinedine, Tej Varma Yenupuri, Lena Worbs, Filipe R N C Maia, Michael Heymann, Joachim Schulz, Johan Bielecki
This work investigates the performance of the electrospray aerosol generator at the European X-ray Free Electron Laser (EuXFEL). This generator is, together with an aerodynamic lens stack that transports the particles into the X-ray interaction vacuum chamber, the method of choice to deliver particles for single-particle coherent diffractive imaging (SPI) experiments at the EuXFEL. For these experiments to be successful, it is necessary to achieve high transmission of particles from solution into the vacuum interaction region...
March 1, 2024: Journal of Synchrotron Radiation
#34
JOURNAL ARTICLE
Graysen Vigneux, Taylor Laframboise, Sujeenthar Tharmalingam, Christopher Thome
PURPOSE: Exposure to ionizing radiation is one of the known risk factors for the development of lens opacities. It is believed that radiation interactions with lens epithelial cells (LEC) are the underlying cause of cataract development, however, the exact mechanisms have yet to be identified. The aim of this study was to investigate how different radiation dose and fractionation impact normal LEC function. MATERIALS AND METHODS: A human derived LEC cell line (HLE-B3) was exposed to a single acute x-ray dose (0...
January 30, 2024: International Journal of Radiation Biology
#35
JOURNAL ARTICLE
Jiahao Chang, Zhentao Wang
The response time of a detector stands as a critical parameter in radiation imaging systems. However, the existing parallel plate ionization chamber detector manifests a noteworthy delay in response time, leading to the production of blurred radiation images. To enhance the image quality of radiation imaging systems, it becomes imperative to modify the electrode structure of the detector and consequently reduce the response time. We propose a gas ionization chamber detector incorporating a glass plate, resulting in a notably swift response time...
January 23, 2024: Applied Radiation and Isotopes
#36
JOURNAL ARTICLE
Julien Jurczak, Benjamin Rapp, Jean-Marc Bordy, Stephanie Josset, Stephane Dufreneix
BACKGROUND: Dose area product in water (DAPw ) in small fields relies on the use of detectors with a sensitive area larger than the irradiation field. This quantity has recently been used to establish primary standards down to 5 mm field size, with an uncertainty smaller than 0.7%. It has the potential to decrease the uncertainty related to field output factors, but is not currently integrated into treatment planning systems. PURPOSE: This study aimed to explore the feasibility of converting DAPw into a point dose in small fields by determining the volume averaging correction factor...
January 24, 2024: Medical Physics
#37
JOURNAL ARTICLE
Yuya Nagake, Keisuke Yasui, Hiromu Ooe, Masaya Ichihara, Kaito Iwase, Toshiyuki Toshito, Naoki Hayashi
The reference dose for clinical proton beam therapy is based on ionization chamber dosimetry. However, data on uncertainties in proton dosimetry are lacking, and multifaceted studies are required. Monte Carlo simulations are useful tools for calculating ionization chamber dosimetry in radiation fields and are sensitive to the transport algorithm parameters when particles are transported in a heterogeneous region. We aimed to evaluate the proton transport algorithm of the Particle and Heavy Ion Transport Code System (PHITS) using the Fano test...
March 2024: Radiological Physics and Technology
#38
JOURNAL ARTICLE
Marie Vidal, Anaïs Gérard, Vincent Floquet, Julien Forthomme, Jeppe Brage Christensen, Erik Almhagen, Erik Grusell, Vincent Heymans, Severine Rossomme, Serge Dumas, Richard Trimaud, Joel Herault
Ionization chambers, mostly used for beam calibration and for reference dosimetry, can show high recombination effects in pulsed high dose rate proton beams. The aims of this paper are: first, to characterize the linearity response of newly designed Asymmetrical Beam Monitor Chambers (ABMC) in a 100 to 226 MeV pulsed high dose rate per pulse scanned proton beam; and secondly, to calibrate the ABMC with a PPC05 (IBA Dosimetry) plane parallel ionization chamber and compare to calibration with a home-made Faraday Cup (FC)...
January 22, 2024: Physics in Medicine and Biology
#39
JOURNAL ARTICLE
Måns Lundberg, Arturs Meijers, Kevin Souris, Sylvain Deffet, Damien Charles Weber, Antony John Lomax, Antje Knopf
Range uncertainties remain a limitation for the confined dose distribution that proton therapy can offer. The uncertainty stems from the ambiguity when translating CT Hounsfield Units (HU) into proton stopping powers. Proton Radiography (PR) can be used to verify the proton range. Specifically, PR can be used as a quality-control tool for CBCT-based synthetic CTs. An essential part of the work illustrating the potential of PR has been conducted using multi-layer ionization chamber (MLIC) detectors and mono-energetic PR...
January 19, 2024: Biomedical Physics & Engineering Express
#40
JOURNAL ARTICLE
Izabela Junis, Yousif Yousif, Rachel Stensmyr, Jeffrey Barber
The myQA SRS (IBA) is a new to market 2D complementary metal oxide semiconductor detector array with an active area 140 × 120 mm2 and 0.4 mm resolution, making it a potential real-time dosimetry alternative to radiochromic film for stereotactic plan verification. Characterisation of the device was completed to assess performance. The dosimetric properties of the device were assessed for 6FF and 6FFF beams from a Varian TrueBeam STx with high definition multileaf collimator. Clinical suitability of the device for Patient Specific Quality Assurance was verified using ten SRS/SBRT plans, compared against other detectors, as well as multi leaf collimator (MLC) tests including picket fence and chair...
January 18, 2024: Physical and engineering sciences in medicine
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