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https://www.readbyqxmd.com/read/28541190/benchmarking-for-on-scalp-meg-sensors
#1
Minshu Xie, Justin F Schneiderman, Maxim L Chukharkin, Alexei Kalabukhov, Bushra Riaz, Daniel Lundqvist, Stephen Whitmarsh, Matti Hamalainen, Veikko Jousmaki, Robert Oostenveld, Dag Winkler
OBJECTIVE: We present a benchmarking protocol for quantitatively comparing emerging on-scalp magnetoencephalography (MEG) sensor technologies to their counterparts in state-of-the-art MEG systems. METHODS: As a means of validation, we compare a high-critical-temperature superconducting quantum interference device (high Tc SQUID) with the low- Tc SQUIDs of an Elekta Neuromag TRIUX system in MEG recordings of auditory and somatosensory evoked fields (SEFs) on one human subject...
June 2017: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/28536486/emerging-indications-for-fractionated-gamma-knife-radiosurgery
#2
Emory McTyre, Corbin A Helis, Michael Farris, Lisa Wilkins, Darrell Sloan, William H Hinson, J Daniel Bourland, William A Dezarn, Michael T Munley, Kounosuke Watabe, Fei Xing, Adrian W Laxton, Stephen B Tatter, Michael D Chan
BACKGROUND: Gamma Knife radiosurgery (GKRS) allows for the treatment of intracranial tumors with a high degree of dose conformality and precision. There are, however, certain situations wherein the dose conformality of GKRS is desired, but single session treatment is contraindicated. In these situations, a traditional pin-based GKRS head frame cannot be used, as it precludes fractionated treatment. OBJECTIVE: To report our experience in treating patients with fractionated GKRS using a relocatable, noninvasive immobilization system...
February 1, 2017: Neurosurgery
https://www.readbyqxmd.com/read/28514899/clinical-positioning-accuracy-for-multisession-stereotactic-radiotherapy-with-the-gamma-knife-perfexion
#3
Wade P Smith, Lori A Young, Mark H Phillips, Michael Cheung, Lia M Halasz, Jason K Rockhill
Multisession stereotactic radiation therapy is increasingly being seen as a preferred option for intracranial diseases in close proximity to critical structures and for larger target volumes. The objective of this study is to investigate the reproducibility of the Extend system from Elekta. A retrospective review was conducted for all patients treated with multisession Gamma Knife between July 2010 and June 2015, including both malignant and benign lesions. Eighty-four patients were treated in this 5-year span...
January 1, 2017: Technology in Cancer Research & Treatment
https://www.readbyqxmd.com/read/28508836/tabulated-square-shaped-source-model-for-linear-accelerator-electron-beam-simulation
#4
Navid Khaledi, Mahmood Reza Aghamiri, Hossein Aslian, Ahmad Ameri
CONTEXT: Using this source model, the Monte Carlo (MC) computation becomes much faster for electron beams. AIMS: The aim of this study was to present a source model that makes linear accelerator (LINAC) electron beam geometry simulation less complex. SETTINGS AND DESIGN: In this study, a tabulated square-shaped source with transversal and axial distribution biasing and semi-Gaussian spectrum was investigated. SUBJECTS AND METHODS: A low energy photon spectrum was added to the semi-Gaussian beam to correct the bremsstrahlung X-ray contamination...
January 2017: Journal of Cancer Research and Therapeutics
https://www.readbyqxmd.com/read/28503898/evaluation-of-initial-setup-errors-of-two-immobilization-devices-for-lung-stereotactic-body-radiation-therapy-sbrt
#5
Yoshihiro Ueda, Teruki Teshima, Higinia Cárdenes, Indra J Das
The aim of this study was to investigate the accuracy and efficacy of two commonly used commercial immobilization systems for stereotactic body radiation therapy (SBRT) in lung cancer. This retrospective study assessed the efficacy and setup accuracy of two immobilization systems: the Elekta Body Frame (EBF) and the Civco Body Pro-Lok (CBP) in 80 patients evenly divided for each system. A cone beam CT (CBCT) was used before each treatment fraction for setup correction in both devices. Analyzed shifts were applied for setup correction and CBCT was repeated...
May 14, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28493295/towards-ultrasound-guided-adaptive-radiotherapy-for-cervical-cancer-evaluation-of-elekta-s-semi-automated-uterine-segmentation-method-on-3d-ultrasound-images
#6
Sarah A Mason, Tuathan P O'Shea, Ingrid M White, Susan Lalondrelle, Kate Downey, Mariwan Baker, Claus F Behrens, Jeffrey C Bamber, Emma J Harris
PURPOSE: 3D ultrasound (US) images of the uterus may be used to adapt radiotherapy (RT) for cervical cancer patients based on changes in daily anatomy. This requires accurate on-line segmentation of the uterus. The aim of this work was to assess the accuracy of Elekta's "Assisted Gyne Segmentation" (AGS) algorithm in semi-automatically segmenting the uterus on 3D transabdominal ultrasound images by comparison with manual contours. MATERIALS & METHODS: Nine patients receiving RT for cervical cancer were imaged with the 3D Clarity(®) transabdominal probe at RT planning, and 1 to 7 times during treatment...
May 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28477339/dose-discrepancy-between-planning-system-estimation-and-measurement-in-spine-stereotactic-body-radiation-therapy-a-case-report
#7
Sankar Arumugam, Megan Berry, Cesar Ochoa, Aitang Xing, Bradley Beeksma, Philip Vial
Stereotactic body radiation therapy (SBRT) to treat spinal metastases has shown excellent clinical outcomes for local control. High dose gradients wrapping around spinal cord make this treatment technically challenging. In this work, we present a spine SBRT case where a dosimetric error was identified during pre-treatment dosimetric quality assurance (QA). A patient with metastasis in T7 vertebral body consented to undergo SBRT. A dual arc volumetric modulated arc therapy plan was generated on the Pinnacle treatment planning system (TPS) with a 6 MV Elekta machine using gantry control point spacing of 4°...
May 6, 2017: Journal of Medical Imaging and Radiation Oncology
https://www.readbyqxmd.com/read/28475490/reducing-4dcbct-imaging-time-and-dose-the-first-implementation-of-variable-gantry-speed-4dcbct-on-a-linear-accelerator
#8
Ricky T O'Brien, Uros Stankovic, Jan-Jakob Sonke, Paul J Keall
Four dimensional cone beam computed tomography (4DCBCT) uses a constant gantry speed and imaging frequency that are independent of the patient's breathing rate. Using a technique called respiratory motion guided 4DCBCT (RMG-4DCBCT), we have previously demonstrated that by varying the gantry speed and imaging frequency, in response to changes in the patient's real-time respiratory signal, the imaging dose can be reduced by 50-70%. RMG-4DCBCT optimally computes a patient specific gantry trajectory to eliminate streaking artefacts and projection clustering that is inherent in 4DCBCT imaging...
May 5, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28454327/stereotactic-radiotherapy-in-the-treatment-of-local-recurrences-of-esophageal-cancer
#9
Marcel Matzenauer, David Vrána, Zuzana Vlachová, Rene Aujesky, Radek Vrba, Cestmir Neoral, Bohuslav Melichar
Esophageal cancer (EC) consists of tumors with a generally poor prognosis, and treatment options for patients with disease recurrence are extremely limited. Due to this poor patient prognosis, the possible treatment toxicity should be carefully balanced against its potential benefit and patient quality of life. Stereotactic body radiotherapy (SBRT) is a rapidly expanding novel technique combining a short treatment time together with high local efficacy and an acceptable toxicity profile. There are no publications thus far presenting data regarding the usage of SBRT utilizing a conventional linear accelerator in locally recurrent EC patients...
March 2017: Oncology Letters
https://www.readbyqxmd.com/read/28410679/dual-energy-imaging-method-to-improve-the-image-quality-and-the-accuracy-of-dose-calculation-for-cone-beam-computed-tomography
#10
Kuo Men, Jianrong Dai, Xinyuan Chen, Minghui Li, Ke Zhang, Peng Huang
PURPOSE: To improve the image quality and accuracy of dose calculation for cone-beam computed tomography (CT) images through implementation of a dual-energy cone-beam computed tomography method (DE-CBCT), and evaluate the improvement quantitatively. METHODS: Two sets of CBCT projections were acquired using the X-ray volumetric imaging (XVI) system on a Synergy (Elekta, Stockholm, Sweden) system with 120kV (high) and 70kV (low) X-rays, respectively. Then, the electron density relative to water (relative electron density (RED)) of each voxel was calculated using a projection-based dual-energy decomposition method...
April 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28410678/novel-6mv-x-ray-photoneutron-detection-and-dosimetry-of-medical-accelerators
#11
Mehdi Sohrabi, Amir Hakimi
PURPOSE: Dosimetry of fast, epithermal and thermal photoneutrons in 6MV X-ray beams of two medical accelerators were studied by novel dosimetry methods. METHODS: A Siemens ONCOR and an Elekta COMPACT medical accelerators were used. Fast, epithermal and thermal photoneutron dose equivalents in 10cm×10cm 6MV X-rays fields were determined in air and on surface of a polyethylene phantom in X and Y directions. Polycarbonate dosimeters as bare or with enriched (10)B convertors (with or without cadmium covers) were used applying a 50Hz-HV electrochemical etching method...
April 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28391596/technical-note-is-bulk-electron-density-assignment-appropriate-for-mri-only-based-treatment-planning-for-lung-cancer
#12
Phil Prior, Xinfeng Chen, Elizabeth Gore, Candice Johnstone, X Allen Li
PURPOSE: MRI-based treatment planning in radiation therapy (RT) is prohibitive, in part, due to the lack of electron density (ED) information within the image. The dosimetric differences between MRI- and CT-based planning for intensity modulated RT (IMRT) of lung cancer were investigated to assess the appropriateness of bulk ED assignment. METHODS: Planning CTs acquired for six representative lung cancer patients were used to generate bulk ED IMRT plans. To avoid the effect of anatomic differences between CT and MRI, "simulated MRI-based plans" were generated by forcing the relative ED (rED) to water on CT-delineated structures using organ specific values from the ICRU Report 46 and using the mean rED value of the internal target volume (ITV) from the planning CT...
April 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/28385495/dosimetric-characterization-of-small-fields-using-a-plastic-scintillator-detector-a-large-multicenter-study
#13
Pietro Mancosu, Massimo Pasquino, Giacomo Reggiori, Laura Masi, Serenella Russo, Michele Stasi
PURPOSE: In modern radiation therapy accurate small fields dosimetry is a challenge and its standardization is fundamental to harmonize delivered dose in different institutions. This study presents a multicenter characterization of MLC-defined small field for Elekta and Varian linear accelerators. Measurements were performed using the Exradin W1 plastic scintillator detector. MATERIALS AND METHODS: The project enrolled 24 Italian centers. Each center performed Tissue Phantom Ratio (TPR), in-plane and cross-plane dose profiles of 0...
April 3, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28370918/effect-of-beam-profile-measurement-on-arc-therapy-plan-quality-assurance-a-case-study
#14
Leonard H Kim, Irina Malajovich, Meral L Reyhan, Jinyu Xue, Joo Han Park
We present an example when profile measurement and modeling of an Elekta Agility multileaf collimator (MLC) had a large effect specifically on arc therapy plan quality assurance (QA) results using ArcCheck. ArcCheck absolute dose measurements of these plans were systematically lower than planned by 3-10%. Failing QA results were seen even with unmodulated static and conformal arcs. Furthermore, the effect was found to be dependent on collimator angle, with worse results associated with near-zero collimator angles...
March 29, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28368501/cystic-vestibular-schwannomas-respond-best-to-radiosurgery
#15
Greg Bowden, Jonathon Cavaleri, Edward Monaco Iii, Ajay Niranjan, John Flickinger, L Dade Lunsford
BACKGROUND: Vestibular schwannomas (VS) have a well-documented response to Gamma Knife® (Elekta AB, Stockholm, Sweden) Stereotactic radiosurgery (SRS). However, there are limited data available regarding the volumetric response of cystic tumors. OBJECTIVE: This report correlates the radiographic appearance of VS before radiosurgery with the delayed volumetric response. METHODS: This study reviewed our SRS experience with 219 VS patients between 2003 and 2013...
March 28, 2017: Neurosurgery
https://www.readbyqxmd.com/read/28342596/the-practical-application-of-scintillation-dosimetry-in-small-field-photon-beam-radiotherapy
#16
Elisa Burke, Daniela Poppinga, Andreas A Schönfeld, Dietrich Harder, Björn Poppe, Hui Khee Looe
Plastic scintillation detectors are a new instrument of stereotactic photon-beam dosimetry. The clinical application of the plastic scintillation detector Exradin W1 at the Siemens Artiste and Elekta Synergy accelerators is a matter of current interest. In order to reduce the measurement uncertainty, precautions have to be taken with regard to the geometrical arrangement of the scintillator, the light-guide fiber and the photodiode in the radiation field. To determine the "Cerenkov light ratio" CLR with a type A uncertainty below 1%, the Cerenkov calibration procedure for small-field measurements based on the two-channel spectral method was used...
March 22, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28297462/surface-dose-variations-in-6-and-10-mv-flattened-and-flattening-filter-free-fff-photon-beams
#17
Jason Cashmore
As the use of linear accelerators operating in flattening filter-free (FFF) modes becomes more widespread, it is important to have an understanding of the surface doses delivered to patients with these beams. Flattening filter removal alters the beam quality and relative contributions of low-energy X-rays and contamination electrons in the beam. Having dosimetric data to describe the surface dose and buildup regions under a range of conditions for FFF beams is important if clinical decisions are to be made...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297443/comparison-of-automatic-image-registration-uncertainty-for-three-igrt-systems-using-a-male-pelvis-phantom
#18
Jeffrey Barber, Jonathan R Sykes, Lois Holloway, David I Thwaites
A series of phantom images using the CIRS Virtual Human Male Pelvis was acquired across available dose ranges for three image-guided radiotherapy (IGRT) imaging systems: Elekta XVI CBCT, Varian TrueBeam CBCT, and TomoTherapy MV CT. Each image was registered to a fan-beam CT within the XVI software 100 times with random initial offsets. The residual registration error was analyzed to assess the role of imaging hardware and reconstruction in the uncertainty of the IGRT process. Residual translation errors were similar for all systems and <0...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297419/radiation-leakage-dose-from-elekta-electron-collimation-system
#19
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
This study provided baseline data required for a greater project, whose objective was to design a new Elekta electron collimation system having significantly lighter electron applicators with equally low out-of field leakage dose. Specifically, off-axis dose profiles for the electron collimation system of our uniquely configured Elekta Infinity accelerator with the MLCi2 treatment head were measured and calculated for two primary purposes: 1) to evaluate and document the out-of-field leakage dose in the patient plane and 2) to validate the dose distributions calculated using a BEAMnrc Monte Carlo (MC) model for out-of-field dose profiles...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297340/dosimetric-properties-of-equivalent-quality-flattening-filter-free-fff-and-flattened-photon-beams-of-versa-hd-linear-accelerator
#20
Mukesh N Meshram, Srimanta Pramanik, C P Ranjith, Saravana K Gopal, Rishabh Dobhal
This study presents the basic dosimetric properties of photon beams of a Versa HD linear accelerator (linac), which is capable of delivering flattening filter-free (FFF) beams with a beam quality equivalent to the corresponding flattened beams based on comprehensive beam data measurement. The analyzed data included the PDDs, profiles, penumbra, out-of-field doses, surface doses, output factors, head and phantom scatter factors, and MLC transmissions for both FFF and flattened beams of 6 MV and 10 MV energy from an Elekta Versa HD linac...
May 2016: Journal of Applied Clinical Medical Physics
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