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https://www.readbyqxmd.com/read/29781165/dose-rate-response-of-digital-megavolt-imager-detector-for-flattening-filter-free-beams
#1
Zhigang Xu, Jinkoo Kim, James Han, An Ting Hsia, Samuel Ryu
In this study we investigated the dose rate response characteristics of the Digital Megavolt Imager (DMI) detector, including panel saturation, linearity, and imager ghosting effects for flattening filter-free (FFF) beams. The DMI detector dose rate response characteristics were measured as a function of dose rate on a Varian TrueBeam machine. Images were acquired at dose rates ranging from 400 to 1400 MU/min for 6XFFF and 400 to 2400 MU/min for 10XFFF. Line profiles and central portal doses derived from the images were analyzed and compared...
May 21, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29780047/-evaluation-of-a-2d-diode-array-corresponding-to-flattening-filter-free-x-ray-beams
#2
Tomoko Kimura, Jun-Ichi Fukunaga, Taka-Aki Hirose, Ryota Hirayama
Recently, a medical linear accelerator with a flattening filter free (FFF) mode has led to the use of FFF X-ray beams at clinical sites. The usefulness of FFF X-ray beams in high-precision radiation therapy has been reported. Therefore, the quality assurance and quality control for FFF X-ray beams have become necessary. In this study, the characteristics of the detectors of a newly developed 2-D diode array (MapCHECK2, Sun Nuclear Corporation) for FFF X-ray beams, i.e., dose reproducibility, dose rate dependence, dose linearity, and output factor, were evaluated...
2018: Nihon Hoshasen Gijutsu Gakkai Zasshi
https://www.readbyqxmd.com/read/29772081/a-photon-source-model-based-on-particle-transport-in-a-parameterized-accelerator-structure-for-monte-carlo-dose-calculations
#3
Yoshiki Ishizawa, Suguru Dobashi, Noriyuki Kadoya, Kengo Ito, Takahito Chiba, Yoshiki Takayama, Kiyokazu Sato, Ken Takeda
PURPOSE: An accurate source model of a medical linear accelerator is essential for Monte Carlo (MC) dose calculations. This study aims to propose an analytical photon source model based on particle transport in parameterized accelerator structures, focusing on a more realistic determination of linac photon spectra compared to existing approaches. METHODS: We designed the primary and secondary photon sources based on the photons attenuated and scattered by a parameterized flattening filter...
May 17, 2018: Medical Physics
https://www.readbyqxmd.com/read/29696321/linac-based-stereotactic-body-radiation-therapy-for-unresectable-locally-advanced-pancreatic-cancer-risk-adapted-dose-prescription-and-image-guided-delivery
#4
Rosario Mazzola, Sergio Fersino, Dario Aiello, Fabiana Gregucci, Umberto Tebano, Stefanie Corradini, Gioacchino Di Paola, Massimo Cirillo, Luca Tondulli, Giacomo Ruffo, Ruggero Ruggieri, Filippo Alongi
BACKGROUND: Stereotactic body radiation therapy (SBRT) represents a new treatment option for locally advanced pancreatic cancer (LAPC). An accurate treatment planning with risk-adapted dose prescription with adherence to specific dose constraints for organs at risk (OARs) and the use of daily cone beam CT (CBCT) for image guidance could allow an effective and safe treatment delivery. Here, feasibility and efficacy of SBRT in LAPC treated in our cancer care center are reported. PATIENTS AND METHODS: 33 unresectable LAPC patients underwent SBRT...
April 25, 2018: Strahlentherapie und Onkologie: Organ der Deutschen Röntgengesellschaft ... [et Al]
https://www.readbyqxmd.com/read/29671410/motion-induced-interplay-effects-for-vmat-radiotherapy
#5
Anneli Edvardsson, Fredrik Nordström, Crister Ceberg, Sofie Ceberg
The purpose of this study was to develop a method to simulate breathing motion induced interplay effects for volumetric modulated arc therapy (VMAT), to verify the proposed method with measurements, and to use the method to investigate how interplay effects vary with different patient- and machine specific parameters. VMAT treatment plans were created on a virtual phantom in a treatment planning system (TPS). Interplay effects were simulated by dividing each plan into smaller sub-arcs using an in-house developed software and shifting the isocenter for each sub-arc to simulate a sin6 breathing motion in the superior-inferior direction...
April 19, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29611210/interplay-effect-on-a-6-mv-flattening-filter-free-linear-accelerator-with-high-dose-rate-and-fast-multi-leaf-collimator-motion-treating-breast-and-lung-phantoms
#6
Tucker Netherton, Yuting Li, Paige Nitsch, Simona Shaitelman, Peter Balter, Song Gao, Ann Klopp, Manickam Muruganandham, Laurence Court
PURPOSE: Using a new linear accelerator with high dose rate (800 MU/min), fast MLC motions (5.0cm/s), fast gantry rotation (15sec/rotation), and 1cm wide MLCs, we aimed to quantify the effects of complexity, arc number, and fractionation on interplay for breast and lung treatments under target motion. METHODS: To study lung interplay, eight VMAT plans (one to six arcs) and four nine-field sliding-window IMRT plans varying in complexity were created. For the breast plans, four four-field sliding-window IMRT plans were created...
April 2, 2018: Medical Physics
https://www.readbyqxmd.com/read/29580032/comparative-evaluation-of-a-6mv-flattened-beam-and-a-flattening-filter-free-beam-for-carcinoma-of-cervix-%C3%A2-imrt-planning-study
#7
Suresh Tamilarasu, Madeswaran Saminathan, S K Sharma, Anjali Pahuja, Abhinav Dewan
Purpose: Intensity modulated radiotherapy (IMRT) plan quality, beam on time and integral dose were compared using 6MV FB (Flattened Beam) and FFFB (Flattening filter free beam) for carcinoma of cervix. Materials and Methods: Ten patients with stage II–IIIB cervix cancer (Ca.Cx) were retrospectively identified from the department database. Target volume (TV) and organ at risk (OAR) were delineated as per Radiation Therapy Oncology Group (RTOG) cancer guidelines. Dose prescribed to planning target volume (PTV) was 50...
March 27, 2018: Asian Pacific Journal of Cancer Prevention: APJCP
https://www.readbyqxmd.com/read/29575596/verification-of-acuros-xb-dose-algorithm-using-3d-printed-low-density-phantoms-for-clinical-photon-beams
#8
Rodolfo Zavan, Philip McGeachy, Joseph Madamesila, Jose-Eduardo Villarreal-Barajas, Rao Khan
The transport-based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities primarily through comparisons with Monte Carlo simulations. This study aims to provide additional experimental verification of AXB for clinically relevant flattened and unflattened beam energies in low density phantoms of the same material. Polystyrene slabs were created using a bench-top 3D printer. Six slabs were printed at varying densities from 0.23 to 0.68 g/cm3 , corresponding to different density humanoid tissues...
March 25, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29563993/flattening-filter-free-technique-in-volumetric-modulated-arc-therapy-for-lung-stereotactic-body-radiotherapy-a-clinical-comparison-with-the-flattening-filter-technique
#9
Shuri Aoki, Hideomi Yamashita, Akihiro Haga, Kanabu Nawa, Toshikazu Imae, Wataru Takahashi, Osamu Abe, Keiichi Nakagawa
The present study sought to evaluate the impact of the flattening filter-free (FFF) technique in volumetric modulated arc therapy for lung stereotactic body radiotherapy. Its clinical safety and availability were compared with the flattening filter (FF) method. The cases of 65 patients who underwent lung volumetric modulated arc therapy-stereotactic body radiotherapy (VMAT-SBRT) using FF or FFF techniques were reviewed. A total of 55 Gy/4 fractions (fr) was prescribed for peripheral lesions or 56 Gy/7 fr for central lesions...
March 2018: Oncology Letters
https://www.readbyqxmd.com/read/29562568/monte-carlo-evaluation-of-the-potential-benefits-of-flattening-filter-free-beams-from-the-oncor%C3%A2-clinical-linear-accelerator
#10
Amin Asadi, Seid Kazem Razavi-Ratki, Keyvan Jabbari, Milad Najafzadeh, Abolfazl Nickfarjam
OBJECTIVES: To evaluate the potential privileges of flattening filter-free (FFF) photon beams from Oncor® linac for 6 MV and 18 MV energies. METHODS: A Monte Carlo (MC) model of Oncor® linac was built using BEAMnrc MCCode and verified by the measured data using 6 MV and 18 MV energies. A comprehensive set of data was also characterized for MC model of Oncor® machine running with and without flattening filter (FF) for 6 MV and 18 MV beams in six field sizes...
2018: Journal of X-ray Science and Technology
https://www.readbyqxmd.com/read/29528035/the-impact-of-the-oxygen-scavenger-on-the-dose-rate-dependence-and-dose-sensitivity-of-magic-type-polymer-gels
#11
Muzafar Khan, Gerd Heilemann, Peter Kuess, Dietmar Georg, Andreas Berg
Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D) , which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates...
March 12, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29527816/commissioning-of-a-dedicated-commercial-co-60-total-body-irradiation-unit
#12
Jay Burmeister, Adrian Nalichowski, Michael Snyder, Robert Halford, Geoff Baran, Brian Loughery, Ahmad Hammoud, Joe Rakowski, Todd Bossenberger
We describe the commissioning of the first dedicated commercial total body irradiation (TBI) unit in clinical operation. The Best Theratronics GammaBeam 500 is a Co-60 teletherapy unit with extended field size and imaging capabilities. Radiation safety, mechanical and imaging systems, and radiation output are characterized. Beam data collection, calibration, and external dosimetric validation are described. All radiation safety and mechanical tests satisfied relevant requirements and measured dose distributions meet recommendations of American Association of Physicists in Medicine (AAPM) Report #17...
March 11, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29520733/dosimetric-analysis-of-unflattened-fffb-and-flattened-fb-photon-beam-energy-for-gastric-cancers-using-imrt-and-vmat-a-comparative-study
#13
Manindra Bhushan, Girigesh Yadav, Deepak Tripathi, Lalit Kumar, Vimal Kishore, Abhinav Dewan, Gourav Kumar, Inderjit Kaur Wahi, Munish Gairola
PURPOSE: To evaluate the feasibility of flattening filter free beam (FFFB) for the treatment of gastric tumors and to review their benefits over 6MV flatten beam (6MV_FFB). METHODS: Fifteen patients with histologically proven gastric carcinoma were selected. CT scans with slice thickness of 0.3 cm were acquired and planning target volume (PTV) and organ at risk (OAR) were delineated. Plans were made retrospectively for each patient for the prescription dose of 45 Gy/25 fractions to the PTV...
March 8, 2018: Journal of Gastrointestinal Cancer
https://www.readbyqxmd.com/read/29519415/relative-biological-effectiveness-study-of-lipiodol-based-on-microdosimetric-kinetic-model
#14
Daisuke Kawahara, Hisashi Nakano, Shuichi Ozawa, Akito Saito, Tomoki Kimura, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
OBJECTIVES: We examine the contrast agent Lipiodol effect on the relative biological effectiveness (RBE) values for flattening filter free (FFF) and flattening filter (FF) beams of 6 MV-Xray (6 MVX) and 10 MVX. METHODS: Lipiodol was placed at 5 cm depth in water. According to the microdosimetric kinetic model, the RBE values for killing the human liver hepatocellular cells were calculated from dose and lineal energy (yd(y)) from Monte Carlo simulations. RBE200kVX and RBECo were defined as the ratios of dose using reference radiation (200 kVX, Co-ɤ) to the dose of test radiation (FFF and FF beams for 6 MV and 10 MV) to produce the same biological effects...
February 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29516908/dose-rate-and-energy-dependence-study-of-methacrylic-acid-gelatin-tetrakis-hydroxymethyl-phosphonium-chloride-gel-with-flattened-and-unflattened-photon-beams
#15
P Sathiyaraj, James Jebaseelan Samuel
Aims: The aim of this study is to evaluate the dose rate and energy dependency of methacrylic acid gelatin tetrakis (hydroxymethyl) phosphonium chloride (MAGAT) gel in unflattened photon beam using X-ray computed tomography (CT) and ultraviolet (UV)-visible spectroscopy. Materials and Methods: MAGAT gel was prepared and it was exposed to 6 MV flattened and unflattened beams. The dose selected for irradiation was ranging from 3 to 15 Gy with an increment of 3 Gy...
January 2018: Journal of Cancer Research and Therapeutics
https://www.readbyqxmd.com/read/29472075/a-novel-high-resolution-2d-silicon-array-detector-for-small-field-dosimetry-with-fff-photon-beams
#16
G Biasi, M Petasecca, S Guatelli, N Hardcastle, M Carolan, V Perevertaylo, T Kron, A B Rosenfeld
PURPOSE: Flattening filter free (FFF) beams are increasingly being considered for stereotactic radiotherapy (SRT). For the first time, the performance of a monolithic silicon array detector under 6 and 10 MV FFF beams was evaluated. The dosimeter, named "Octa" and designed by the Centre for Medical Radiation Physics (CMRP), was tested also under flattened beams for comparison. METHODS: Output factors (OFs), percentage depth-dose (PDD), dose profiles (DPs) and dose per pulse (DPP) dependence were investigated...
January 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29461974/comparison-of-k-q-factors-measured-with-a-water-calorimeter-in-flattening-filter-free-fff-and-conventional-flattening-filter-cff-photon-beams
#17
Leon de Prez, Jacco de Pooter, Bartel Jansen, Thijs Perik, Frits Wittkämper
Recently flattening filter free (FFF) beams became available for application in modern radiotherapy. There are several advantages of FFF beams over conventional flattening filtered (cFF) beams, however differences in beam spectra at the point of interest in a phantom potentially affect the ion chamber response. Beams are also non-uniform over the length of a typical reference ion chamber and recombination is usually larger. Despite several studies describing FFF beam characteristics, only a limited number of studies investigated their effect on k Q factors...
February 20, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29450985/effect-of-secondary-electron-generation-on-dose-enhancement-in-lipiodol-with-and-without-a-flattening-filter
#18
Daisuke Kawahara, Shuichi Ozawa, Akito Saito, Tomoki Kimura, Tatsuhiko Suzuki, Masato Tsuneda, Sodai Tanaka, Takeo Nakashima, Yoshimi Ohno, Yuji Murakami, Yasushi Nagata
PURPOSE: Lipiodol, which was used in transcatheter arterial chemoembolization before liver stereotactic body radiation therapy (SBRT), remains in SBRT. Previous we reported the dose enhancement in Lipiodol using 10 MV (10×) FFF beam. In this study, we compared the dose enhancement in Lipiodol and evaluated the probability of electron generation (PEG) for the dose enhancement using flattening filter (FF) and flattening filter free (FFF) beams. METHODS: FF and FFF for 6 MV (6×) and 10× beams were delivered by TrueBeam...
March 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29431865/refinement-of-mlc-modeling-improves-commercial-qa-dosimetry-system-for-srs-and-sbrt-patient-specific-qa
#19
Yair Hillman, Josh Kim, Indrin Chetty, Ning Wen
PURPOSE: Mobius 3D (M3D) provides a volumetric dose verification of the treatment planning system's calculated dose using an independent beam model and a collapsed cone convolution superposition algorithm. However, there is a lack of investigation into M3D's accuracy and effectiveness for stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) quality assurance (QA). Here, we collaborated with the vendor to develop a revised M3D beam model for SRS/SBRT cases treated with a 6X flattening filter-free (FFF) beam and high-definition multiple leaf collimator (HDMLC) on an Edge linear accelerator...
April 2018: Medical Physics
https://www.readbyqxmd.com/read/29373670/general-ion-recombination-effect-in-a-liquid-ionization-chamber-in-high-dose-rate-pulsed-photon-and-electron-beams
#20
Hideyuki Takei, Tomonori Isobe, Nozomi Kitamura, Yutaro Mori, Tetsuya Tomita, Daisuke Kobayashi, Satoshi Kamizawa, Tomoharu Sato, Hideyuki Sakurai, Takeji Sakae
Liquid ionization chambers (LICs) are highly sensitive to dose irradiation and have small perturbations because of their liquid-filled sensitive volume. They require a sensitive volume much smaller than conventional air-filled chambers. However, it has been reported that the collection efficiency has dependencies on the dose per pulse and the pulse repetition frequency of a pulsed beam. The purpose of this study was to evaluate in detail the dependency of the ion collection efficiency on the pulse repetition frequency...
January 24, 2018: Journal of Radiation Research
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