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https://www.readbyqxmd.com/read/29130896/characterisation-of-flattening-filter-free-fff-beam-properties-for-initial-beam-set-up-and-routine-qa-independent-of-flattened-beams
#1
David Paynter, Steve J Weston, Vivian P Cosgrove, David I Thwaites
Objectives Flattening filter free beams have reached widespread use for clinical treatment deliveries. The usual methods for FFF beam characterisation for their quality assurance require the use of associated conventional flattened beams (cFF). Methods for QA of FFF without the need to use an associated cFF beams are presented and evaluated against current methods for both FFF and cFF beams. Methods Inflection point normalisation is evaluated against conventional methods for the determination of field size and penumbra for field sizes from 3cm x 3cm to 40cm x40cm at depths from dmax to 20cm in water for matched and unmatched FFF beams and for cFF beams...
November 13, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29091675/fast-wide-field-and-distortion-free-telescope-with-curved-detectors-for-surveys-at-ultralow-surface-brightness
#2
Eduard Muslimov, David Valls-Gabaud, Gérard Lemaître, Emmanuel Hugot, Wilfred Jahn, Simona Lombardo, Xin Wang, Pascal Vola, Marc Ferrari
We present the design of an all-reflective, bifolded Schmidt telescope aimed at surveys of extended astronomical objects with extremely low surface brightness. The design leads to a high image quality without any diffracting spider, a large aperture and field of view (FoV), and a small central obstruction that barely alters the point spread function (PSF). As an example, we design a high-quality, 36 cm diameter, fast (f/2.5) telescope working in the visible with a large FoV (1.6°×2.6°). The telescope can operate with a curved detector (or with a flat detector with a field flattener) and a set of filters...
November 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/29053107/spectral-imaging-using-clinical-megavoltage-beams-and-a-novel-multi-layer-imager
#3
Marios E Myronakis, Rony Fueglistaller, Joerg Rottmann, Yue-Houng Hu, Adam Wang, Paul Baturin, Pascal Huber, Daniel Morf, Josh M Star-Lack, Ross I Berbeco
We assess the feasibility of clinical megavoltage (MV) spectral imaging for material and bone separation with a novel multi-layer imager (MLI) prototype. The MLI provides higher detective quantum efficiency and lower noise than conventional electronic portal imagers. Simulated experiments were performed using a validated Monte Carlo model of the MLI to estimate energy absorption and energy separation between the MLI components. Material separation was evaluated experimentally using solid water and aluminum (Al), copper (Cu) and gold (Au) for 2...
October 20, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29048329/measurement-and-modeling-of-out-of-field-doses-from-various-advanced-post-mastectomy-radiotherapy-techniques
#4
Jihyung Yoon, David Heins, Xiaodong Zhao, Mary Sanders, Rui Zhang
More and more advanced radiotherapy techniques have been adopted for post-mastectomy radiotherapies (PMRT). Patient dose reconstruction is challenging for these advanced techniques because they increase the low out-of-field dose area while the accuracy of out-of-field dose calculations by current commercial treatment planning systems (TPSs) is poor. We aim to measure and model the out-of-field radiation doses from various advanced PMRT techniques. PMRT treatment plans for an anthropomorphic phantom were generated, including volumetric modulated arc therapy (VMAT) with standard and flattening-filter-free (FFF) photon beams, mixed beam therapy, 4-field intensity modulated radiation therapy (IMRT), and Tomotherapy...
October 19, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29031915/experimental-and-monte-carlo-based-determination-of-the-beam-quality-specifier-for-tomotherapyhd-treatment-units
#5
S Howitz, M Schwedas, T Wiezorek, K Zink
Reference dosimetry by means of clinical linear accelerators in high-energy photon fields requires the determination of the beam quality specifier TPR20,10, which characterizes the relative particle flux density of the photon beam. The measurement of TPR20,10 has to be performed in homogenous photon beams of size 10×10cm(2) with a focus-detector distance of 100cm. These requirements cannot be fulfilled by TomoTherapy treatment units from Accuray. The TomoTherapy unit provides a flattening-filter-free photon fan beam with a maximum field width of 40cm and field lengths of 1...
October 11, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29031610/characteristics-of-2-5%C3%A2-mv-beam-and-imaging-dose-to-patients
#6
George X Ding, Peter Munro
PURPOSE: This work provides the beam characteristics and evaluates the imaging dose to patients for a 2.5 MV portal imaging beam. METHOD AND MATERIALS: The Monte Carlo technique has been used to simulate the 2.5 MV imaging beam. Beam characteristics have been analyzed including the energy spectra and the fluence distributions as a function of position away from the beam central axis. The accuracy of a simulated beam was validated through comparisons between the Monte Carlo calculated and measured dose distributions in a water phantom...
October 11, 2017: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
https://www.readbyqxmd.com/read/29030203/characterization-and-clinical-evaluation-of-a-novel-2d-detector-array-for-conventional-and-flattening-filter-free-fff-imrt-pre-treatment-verification
#7
Yuvaraj Sekar, Johannes Thoelking, Miriam Eckl, Irakli Kalichava, Dwi Seno Kuncoro Sihono, Frank Lohr, Frederik Wenz, Hansjoerg Wertz
BACKGROUND AND PURPOSE: The novel MatriXX(FFF) (IBA Dosimetry, Germany) detector is a new 2D ionization chamber detector array designed for patient specific IMRT-plan verification including flattening-filter-free (FFF) beams. This study provides a detailed analysis of the characterization and clinical evaluation of the new detector array. MATERIAL AND METHODS: The verification of the MatriXX(FFF) was subdivided into (i) physical dosimetric tests including dose linearity, dose rate dependency and output factor measurements and (ii) patient specific IMRT pre-treatment plan verifications...
October 10, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28974859/choice-of-a-suitable-dosimeter-for-photon-percentage-depth-dose-measurements-in-flattening-filter-free-beams
#8
Silvia Vargas Castrillón, Francisco Cutanda Henríquez
The International Atomic Energy Agency Technical Reports Series-398 code of practice for dosimetry recommends measuring photon percentage depth dose (PDD) curves with parallel-plate chambers. This code of practice was published before flattening filter-free (FFF) beams were widely used in clinical linear accelerators. The choice of detector for PDD measurements needs to be reassessed for FFF beams given the physical differences between FFF beams and flattened ones. The present study compares PDD curves for FFF beams of nominal energies 6 MV, 6 FFF, 10 MV, and 10 FFF from a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, USA) acquired with Scanditronix photon diodes, two scanning type chambers (both PTW 31010 Semiflex), two small volume chambers (Wellhofer CC04 and PTW 31016 PinPoint 3D), PTW 34001 Roos, Scanditronix Roos, and NACP 02 parallel-plate chambers...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28971344/the-effect-of-beam-interruption-during-fff-vmat-plans-for-sbrt
#9
Seongjong Oh, Benjamin Lewis, Amy Watson, Siyong Kim, Taeho Kim
To investigate the dosimetric effect of intended beam interruption during volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beam for exploring the possibility of deep inspiration breath hold stereotactic body radiation therapy (SBRT). A total of ten SBRT plans with 6 and 10 MV FFF beams were retrospectively selected. All plans consisted of four partial arcs, except one plan with six partial arcs. We delivered the plans using a Varian Truebeam™ with three different scenarios; without interruption (0int), with one intentional interruption (1int), or with two intentional interruptions (2int), per each partial arc...
October 2, 2017: Australasian Physical & Engineering Sciences in Medicine
https://www.readbyqxmd.com/read/28951047/hippocampal-dose-during-linac-based-stereotactic-radiotherapy-for-brain-metastases-an-observational-study
#10
Alba Fiorentino, Umberto Tebano, Gianluisa Sicignano, Francesco Ricchetti, Gioacchino Di Paola, Dario Aiello, Niccolò Giaj-Levra, Rosario Mazzola, Sergio Fersino, Ruggero Ruggieri, Filippo Alongi
INTRODUCTION: Aim of the present study is to evaluate homolateral and contralateral hippocampus (H-H, C-H, respectively) dose during Fractionated Stereotactic Radiotherapy (FSRT) or Radiosurgery (SRS) for brain metastases (BM). MATERIALS & METHODS: Patients with BM<5, size≤30mm, KPS≥80 and a life expectancy>3months, were considered for SRS/FSRT (total dose 15-30Gy, 1-5 fractions). For each BM, a Flattening Filter Free (FFF) Volumetric Modulated Arc Therapy (VMAT) plan was generated with one or two arcs...
September 23, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28944979/dosimetric-validation-of-monaco-treatment-planning-system-on-an-elekta-versahd-linear-accelerator
#11
Ganesh Narayanasamy, Daniel L Saenz, Dewayne Defoor, Niko Papanikolaou, Sotirios Stathakis
The purpose of this study is to perform dosimetric validation of Monaco treatment planning system version 5.1. The Elekta VersaHD linear accelerator with high dose rate flattening filter-free photon modes and electron energies was used in this study. The dosimetric output of the new Agility head combined with the FFF photon modes warranted this investigation into the dosimetric accuracy prior to clinical usage. A model of the VersaHD linac was created in Monaco TPS by Elekta using commissioned beam data including percent depth dose curves, beam profiles, and output factors...
September 25, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28915893/dosimetric-comparison-of-different-treatment-modalities-for-stereotactic-radiotherapy
#12
Shih-Ming Hsu, Yuan-Chun Lai, Chien-Chung Jeng, Chia-Ying Tseng
BACKGROUND: The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and experimentally assessing the accuracy of the output radiation doses through clinical measurements...
September 16, 2017: Radiation Oncology
https://www.readbyqxmd.com/read/28899649/small-field-characterization-of-a-nanochamber-prototype-under-flattening-filter-free-photon-beams
#13
G Reggiori, A Stravato, P Mancosu, F Lobefalo, L Paganini, F Zucconi, V Palumbo, A Gaudino, M Scorsetti, S Tomatis
INTRODUCTION: Nanochambers present some advantages in terms of energy independence and absolute dose measurement for small field dosimetry in the SBRT scenario. Characterization of a micro-chamber prototype was carried out both under flattened and flattening-filter-free (FFF) beams with particular focus on stem effect. METHODS: The study included characterization of leakage and stem effects, dose rate and dose per pulse dependence, measurement of profiles, and percentage depth doses (PDDs)...
September 9, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28887827/a-universal-parameterized-gradient-based-method-for-photon-beam-field-size-determination
#14
Sharon Lebron, Guanghua Yan, Jonathan Li, Bo Lu, Chihray Liu
PURPOSE: To propose a universal, parameterized gradient-based method (PGM) for radiation field size determination. METHODS: The PGM locates the beam profile's edge by parameterizing its penumbra region with a modified sigmoid function where the inflection point can be determined in a closed form. The parametrization was validated with filter-flattened (FF), flattening-filter-free (FFF) and wedged profiles measured on two Elekta linac models (Synergy and Versa HD)...
September 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/28870945/flattening-filter-free-vs-flattened-beams-for-lung-stereotactic-body-radiation-therapy
#15
Pierre Annede, Julien Darreon, Ahcene Benkemouche, Simon Valdenaire, Marguerite Tyran, Bertrand Kaeppelin, Alban Macagno, Julien Barrou, Leonel Varela Cagetti, Veronique Favrel, Laurence Moureau-Zabotto, Laurence Gonzague, Pierre Fau, Cyrus Chargari, Agnes Tallet, Naji Salem
BACKGROUND/AIM: To assess the clinical impact of high dose rate stereotactic body radiation therapy (SBRT) in patients with lung neoplastic lesions. PATIENTS AND METHODS: From January 2014 to June 2016, a single-center retrospective analysis was performed including all patients treated by either flattening filter free (FFF) beams or flattening filter beams (FF) three-dimensional (3D) SBRT for lung neoplastic lesions. RESULTS: A total of 99 SBRT were performed on 75 patients...
September 2017: Anticancer Research
https://www.readbyqxmd.com/read/28857432/volumetric-modulated-arc-therapy-and-intensity-modulated-radiation-therapy-treatment-planning-for-prostate-cancer-with-flattened-beam-and-flattening-filter-free-linear-accelerators
#16
Marius Treutwein, Matthias Hipp, Oliver Koelbl, Barbara Dobler
This study on patients with localized prostate cancer was set up to investigate valuable differences using flattened beam (FB) and flattening filter free (FFF) mode in the application of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT). For ten patients, four different plans were calculated with Oncentra planning system of Elekta, using Synergy machines: IMRT and VMAT, with and without flattening filter. Homogeneity and conformity indexes, dose to the organs at risk, and measurements of peripheral dose and dosimetric plan verification including record of the delivery times were analyzed and statistically evaluated...
August 30, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28771143/equivalent-uniform-square-field-sizes-of-flattening-filter-free-photon-beams
#17
Wolfgang Lechner, Peter Kuess, Dietmar Georg, Hugo Palmans
Various types of treatment units, such as CyberKnife, TomoTherapy and C-arm linear accelerators (LINACs) are operated using flattening filter free (FFF) photon beams. Their reference dosimetry, however, is currently based on codes of practice that provide data which were primarily developed and tested for high-energy photon beams with flattening filter (WFF). The aim of this work was to introduce equivalent uniform square field sizes of FFF beams to serve as a basis of a unified reference dosimetry procedure applicable to all aforementioned FFF machines...
September 15, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28736809/dose-evaluation-of-grid-therapy-using-a-6-mv-flattening-filter-free-fff-photon-beam-a-monte-carlo-study
#18
Immaculada Martínez-Rovira, Josep Puxeu-Vaqué, Yolanda Prezado
PURPOSE: Spatially fractionated radiotherapy is a strategy to overcome the main limitation of radiotherapy, i.e., the restrained normal tissue tolerances. A well-known example is Grid Therapy, which is currently performed at some hospitals using megavoltage photon beams delivered by Linacs. Grid Therapy has been successfully used in the management of bulky abdominal tumors with low toxicity. The aim of this work was to evaluate whether an improvement in therapeutic index in Grid Therapy can be obtained by implementing it in a flattening filter-free (FFF) Linac...
October 2017: Medical Physics
https://www.readbyqxmd.com/read/28714067/technical-note-evaluation-of-plastic-scintillator-detector-for-small-field-stereotactic-patient-specific-quality-assurance
#19
Yujiao Qin, Stephen J Gardner, Joshua Kim, Yimei Huang, Ning Wen, Anthony Doemer, Indrin J Chetty
PURPOSE: To evaluate the performance of a commercial plastic scintillator detector (PSD) for small-field stereotactic patient-specific quality assurance (QA) measurements using flattening-filter-free beam. METHODS: A total of 10 spherical targets [volume range: (0.03 cc-2 cc)] were planned with two techniques: (a) dynamic conformal arc (DCA-10 plans) and (b) volumetric modulated arc therapy (VMAT-10 plans). All plans were generated using Varian Eclipse treatment planning system, and AcurosXB v...
October 2017: Medical Physics
https://www.readbyqxmd.com/read/28711480/commissioning-of-small-field-size-radiosurgery-cones-in-a-6-mv-flattening-filter-free-beam
#20
Juan Diego Azcona, Benigno Barbés, Verónica Morán, Javier Burguete
This study aimed to describe the commissioning of small field size radiosurgery cones in a 6-MV flattening filter free (FFF) beam and report our measured values. Four radiosurgery cones of diameters 5, 10, 12.5, and 15 mm supplied by Elekta Medical were commissioned in a 6-MV FFF beam from an Elekta Versa linear accelerator. The extraction of a reference signal for measuring small fields in scanning mode is challenging. A transmission chamber was attached to the lower part of the collimators and used for percentage depth dose (PDD) and profile measurements in scanning mode with a stereotactic diode...
July 12, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
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