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https://www.readbyqxmd.com/read/29776740/development-of-a-deformable-phantom-for-experimental-verification-of-4d-monte-carlo-simulations-in-a-deforming-anatomy
#1
Sara Gholampourkashi, Joanna E Cygler, Bernie Lavigne, Emily Heath
PURPOSE: To verify the accuracy of 4D Monte Carlo (MC) simulations, using the 4DdefDOSXYZnrc user code, in a deforming anatomy. We developed a tissue-equivalent and reproducible deformable lung phantom and evaluated 4D simulations of delivered dose to the phantom by comparing calculations against measurements. METHODS: A novel deformable phantom consisting of flexible foam, emulating lung tissue, inside a Lucite external body was constructed. A removable plug, containing an elastic tumor that can hold film and other dosimeters, was inserted in the phantom...
May 15, 2018: Physica Medica: PM
https://www.readbyqxmd.com/read/29765297/group-analysis-in-fieldtrip-of-time-frequency-responses-a-pipeline-for-reproducibility-at-every-step-of-processing-going-from-individual-sensor-space-representations-to-an-across-group-source-space-representation
#2
Lau M Andersen
An important aim of an analysis pipeline for magnetoencephalographic (MEG) data is that it allows for the researcher spending maximal effort on making the statistical comparisons that will answer his or her questions. The example question being answered here is whether the so-called beta rebound differs between novel and repeated stimulations. Two analyses are presented: going from individual sensor space representations to, respectively, an across-group sensor space representation and an across-group source space representation...
2018: Frontiers in Neuroscience
https://www.readbyqxmd.com/read/29762130/ionization-chamber-correction-factors-for-mr-linacs
#3
Stefan Pojtinger, Oliver Steffen Dohm, Ralf-Peter Kapsch, Daniela Thorwarth

 Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor kB.
 The purpose of this study is to systematically investigate kB for a typical reference setup for commercially available ionization chambers with different magnetic field strengths.
 
 Material and Methods:
 The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0 to 2...
May 15, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29761625/beam-focal-spot-position-determination-for-an-elekta-linac-with-the-agility-%C3%A2-head-practical-guide-with-a-ready-to-go-procedure
#4
Jacek M Chojnowski, Lee M Taylor, Jonathan R Sykes, David I Thwaites
A novel phantomless, EPID-based method of measuring the beam focal spot offset of a linear accelerator was proposed and validated for Varian machines. In this method, one set of jaws and the MLC were utilized to form a symmetric field and then a 180o collimator rotation was utilized to determine the radiation isocenter defined by the jaws and the MLC, respectively. The difference between these two isocentres is directly correlated with the beam focal spot offset of the linear accelerator. In the current work, the method has been considered for Elekta linacs...
May 14, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29760593/dosimetric-effect-of-limited-aperture-multileaf-collimator-on-vmat-plan-quality-a-study-of-prostate-and-head-and-neck-cancers
#5
Ghulam Murtaza, Shahid Mehmood, Shahid Rasul, Imran Murtaza, Ehsan Ullah Khan
Aim: The aim of study was to evaluate the dosimetric effect of collimator-rotation on VMAT plan quality, when using limited aperture multileaf collimator of Elekta Beam Modulator™ providing a maximum aperture of 21 cm × 16 cm. Background: The increased use of VMAT technique to deliver IMRT from conventional to very specialized treatments present a challenge in plan optimization. In this study VMAT plans were optimized for prostate and head and neck cancers using Elekta Beam-ModulatorTM , whereas previous studies were reported for conventional Linac aperture...
May 2018: Reports of Practical Oncology and Radiotherapy
https://www.readbyqxmd.com/read/29756267/evaluation-of-prototype-of-improved-electron-collimation-system-for-elekta-linear-accelerators
#6
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
PURPOSE: This study evaluated a new electron collimation system design for Elekta 6-20 MeV beams, which should reduce applicator weights by 25%-30%. Such reductions, as great as 3.9 kg for the largest applicator, should result in considerably easier handling by members of the radiotherapy team. METHODS: Prototype 10 × 10 and 20 × 20-cm2 applicators, used to measure weight, in-field flatness, and out-of-field leakage dose, were constructed according to the previously published design with two minor modifications: (a) rather than tungsten, lead was used for trimmer material; and (b) continuous trimmer outer-edge bevel was approximated by three steps...
May 13, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29745100/comparative-performance-evaluation-of-a-new-a-si-epid-that-exceeds-quad-high-definition-resolution
#7
Kristen A McConnell, Ara Alexandrian, Niko Papanikolaou, Sotiri Stathakis
PURPOSE: Electronic portal imaging devices (EPIDs) are an integral part of the radiation oncology workflow for treatment setup verification. Several commercial EPID implementations are currently available, each with varying capabilities. To standardize performance evaluation, Task Group Report 58 (TG-58) and TG-142 outline specific image quality metrics to be measured. A LinaTech Image Viewing System (IVS), with the highest commercially available pixel matrix (2688x2688 pixels), was independently evaluated and compared to an Elekta iViewGT (1024x1024 pixels) and a Varian aSi-1000 (1024x768 pixels) using a PTW EPID QC Phantom...
January 2018: Journal of B.U.ON.: Official Journal of the Balkan Union of Oncology
https://www.readbyqxmd.com/read/29660047/trigeminal-nerve-atrophy-predicts-pain-recurrence-after-gamma-knife-stereotactic-radiosurgery-for-classical-trigeminal-neuralgia
#8
Yong-Sin Hu, Cheng-Chia Lee, Wan-Yuo Guo, Chung-Jung Lin, Huai-Che Yang, Hsiu-Mei Wu, Kang-Du Liu, Wen-Yuh Chung
BACKGROUND: Trigeminal nerve atrophy and neurovascular compression (NVC) are frequently observed in classical trigeminal neuralgia (CTN). OBJECTIVE: To determine whether nerve characteristics contribute to Gamma Knife (Elekta AB, Stockholm, Sweden) surgery (GKS) outcomes in unilateral CTN without previous surgery. METHODS: From 2006 to 2012, 67 patients with unilateral CTN without previous surgery received GKS with a maximal dose of 90 Gy delivered to the trigeminal nerve juxta brainstem...
April 11, 2018: Neurosurgery
https://www.readbyqxmd.com/read/29643777/a-case-of-retinal-detachment-with-unique-optical-coherence-tomography-findings-after-gamma-knife%C3%A2-radiosurgery-treatment-for-choroidal-melanoma
#9
Daisaku Kimura, Teruyo Kida, Takaki Sato, Masanori Fukumoto, Ryohsuke Kohmoto, Shota Kojima, Hiroshi Mizuno, Hitoshi Sakaguchi, Jun Sugasawa, Tsunehiko Ikeda
Purpose: To report a case of retinal detachment with unique optical coherence tomography (OCT) findings after Gamma Knife® (GK; Elekta Instrument AB, Stockholm, Sweden) treatment for choroidal melanoma (CM). Case Report: A 48-year-old woman underwent GK therapy for CM in her right eye from the macula to the temporal side. While the tumor subsequently shrank, the patient developed radiation retinopathy, which was treated with laser photocoagulation. The tumor lesions later subsided; however, her visual acuity (VA) decreased 8 years after the initial treatment...
January 2018: Case Reports in Ophthalmology
https://www.readbyqxmd.com/read/29611866/gamma-knife-radiosurgery-for-arteriovenous-malformations-general-principles-and-preliminary-results-in-a-swiss-cohort
#10
Matthieu Raboud, Constantin Tuleasca, Philippe Maeder, Luis Schiappacasse, Maud Marguet, Roy Thomas Daniel, Marc Levivier
INTRODUCTION: Arteriovenous malformations (AVMs) are a type of vascular malformation characterised by an abnormal connection between arteries and veins, bypassing the capillary system. This absence of capillaries generates an elevated pressure (hyperdebit), in both the AVM and the venous drainage, increasing the risk of rupture. Management modalities are: observation, microsurgical clipping, endovascular treatment and radiosurgery. The former can be used alone or in the frame of a multidisciplinary approach...
April 3, 2018: Swiss Medical Weekly
https://www.readbyqxmd.com/read/29603874/comparison-of-measured-electron-energy-spectra-for-six-matched-radiotherapy-accelerators
#11
David J McLaughlin, Kenneth R Hogstrom, Daniel W Neck, John P Gibbons
This study compares energy spectra of the multiple electron beams of individual radiotherapy machines, as well as the sets of spectra across multiple matched machines. Also, energy spectrum metrics are compared with central-axis percent depth-dose (PDD) metrics. METHODS: A lightweight, permanent magnet spectrometer was used to measure energy spectra for seven electron beams (7-20 MeV) on six matched Elekta Infinity accelerators with the MLCi2 treatment head. PDD measurements in the distal falloff region provided R50 and R80-20 metrics in Plastic Water® , which correlated with energy spectrum metrics, peak mean energy (PME) and full-width at half maximum (FWHM)...
March 30, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29598924/oncentra-brachytherapy-planning-system
#12
REVIEW
Jack Yang
In modern cancer management, treatment planning has progressed as a contemporary tool with all the advances in computing power in recent years. One of the advanced planning tools uses 3-dimensional (3D) data sets for accurate dose distributions in patient prescription. Among these planning processes, brachytherapy has been a very important part of a successful cancer management program, offering clinical benefits with specific or combined treatments with external beam therapy. In this chapter, we mainly discussed the Elekta Oncentra planning system, which is the main treatment planning tool for high-dose rate (HDR) modality in our facility and in many other facilities in the United States...
March 27, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/29573923/a-comprehensive-evaluation-of-angular-range-and-separation-on-image-quality-image-registration-and-imaging-dose-for-cone-beam-computed-tomography-in-radiotherapy
#13
Kuo Men, Jianrong Dai
We aimed to comprehensively evaluate the quality, dose, and registration of cone beam computed tomography (CBCT) images acquired with different angular range (θ) and angular separation (Δθ). Elekta XVI volumetric imaging system was used in this study. CBCT images of a Catphan 503 phantom were reconstructed with projections that were acquired under 17 × 8 different combinations of θ (200° to 360°) and Δθ (0.27° to 3.24°). The evaluation indices were contrast-to-noise ratio (CNR), spatial resolution (modulation transfer function [MTF50% ]), uniformity, and registration accuracy...
March 21, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/29553478/validation-of-a-virtual-source-model-of-medical-linac-for-monte-carlo-dose-calculation-using-multi-threaded-geant4
#14
Zakaria Aboulbanine, Naïma El Khayati
The use of phase space in medical linear accelerator Monte Carlo (MC) simulations significantly improves the execution time and leads to results comparable to those obtained from full calculations. The classical representation of phase space stores directly the information of millions of particles, producing bulky files. This paper presents a virtual source model (VSM) based on a reconstruction algorithm, taking as input a compressed file of roughly 800 kb derived from phase space data freely available in the International Atomic Energy Agency (IAEA) database...
March 19, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29537634/reference-dosimetry-data-and-modeling-challenges-for-elekta-accelerators-based-on-iroc-houston-site-visit-data
#15
James R Kerns, David S Followill, Jessica Lowenstein, Andrea Molineu, Paola Alvarez, Paige A Taylor, Stephen F Kry
PURPOSE: Reference dosimetry data can provide an independent second check of acquired values when commissioning or validating a treatment planning system (TPS). The Imaging and Radiation Oncology Core at Houston (IROC-Houston) has measured numerous linear accelerators throughout its existence. The results of those measurements are given here, comparing accelerators and the agreement of measurement versus institutional TPS calculations. METHODS: Data from IROC-Houston on-site reviews from 2000 through 2014 were analyzed for all Elekta accelerators, approximately 50...
May 2018: Medical Physics
https://www.readbyqxmd.com/read/29536664/low-cost-kinect-version-2-imaging-system-for-breath-hold-monitoring-and-gating-proof-of-concept-study-for-breast-cancer-vmat-radiotherapy
#16
David M Edmunds, Lone Gothard, Komel Khabra, Anna Kirby, Poonam Madhale, Helen McNair, David Roberts, K K Tang, Richard Symonds-Tayler, Fatemeh Tahavori, Kevin Wells, Ellen Donovan
Voluntary inspiration breath hold (VIBH) for left breast cancer patients has been shown to be a safe and effective method of reducing radiation dose to the heart. Currently, VIBH protocol compliance is monitored visually. In this work, we establish whether it is possible to gate the delivery of radiation from an Elekta linac using the Microsoft Kinect version 2 (Kinect v2) depth sensor to measure a patient breathing signal. This would allow contactless monitoring during VMAT treatment, as an alternative to equipment-assisted methods such as active breathing control (ABC)...
March 13, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29521280/beam-characterisation-of-the-1-5-t-mri-linac
#17
S J Woodings, J J Bluemink, J H W de Vries, Y Niatsetski, B van Veelen, J Schillings, J G M Kok, J W H Wolthaus, S L Hackett, B van Asselen, H M van Zijp, S Pencea, D A Roberts, J J W Lagendijk, B W Raaymakers
As a prerequisite for clinical treatments it was necessary to characterize the Elekta 1.5 T MRI-linac 7 MV FFF radiation beam. Following acceptance testing, beam characterization data were acquired with Semiflex 3D (PTW 31021), microDiamond (PTW 60019), and Farmer-type (PTW 30013 and IBA FC65-G) detectors in an Elekta 3D scanning water phantom and a PTW 1D water phantom. EBT3 Gafchromic film and ion chamber measurements in a buildup cap were also used. Special consideration was given to scan offsets, detector effective points of measurement and avoiding air gaps...
April 19, 2018: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29520938/an-evaluation-of-the-stability-of-image-quality-parameters-of-elekta-x-ray-volume-imager-and-iviewgt-imaging-systems
#18
Dennis N Stanley, Karl Rasmussen, Neil Kirby, Nikos Papanikolaou, Alonso N Gutiérrez
INTRODUCTION: A robust image quality assurance and analysis methodology for image-guided localization systems is crucial to ensure the accurate localization and visualization of target tumors. In this study, the long-term stability of selected image parameters was assessed and evaluated for the cone-beam computed tomography (CBCT) mode, planar radiographic kV mode, and the radiographic MV mode of an Elekta VersaHD. MATERIALS AND METHODS: The CATPHAN, QckV-1, and QC-3 phantoms were used to evaluate the image quality parameters...
March 9, 2018: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/29507849/exceptional-eight-year-response-to-stereotactic-radiosurgery-monotherapy-for-multiple-brain-metastases
#19
Ronny Kalash, Phillip M Pifer, Sushil Beriwal, Scott M Glaser, John A Vargo, Dwight E Heron
Breast cancer represents the second leading cause of brain metastases in women. Once diagnosed, brain metastases have been associated with a rapidly progressive and universally poor prognosis. Breast cancer patients, particularly those with advantageous disease characteristics, may achieve extended survival. This extended life expectancy highlights the importance of effective intracranial treatments that minimize treatment-related late toxicity. Whole brain radiation therapy (WBRT) remains a standard of care palliative option; however, concerns remain regarding the late neurocognitive effects...
December 29, 2017: Curēus
https://www.readbyqxmd.com/read/29493101/dosimetric-assessment-of-an-air-filled-balloon-applicator-in-hdr-vaginal-cuff-brachytherapy-using-the-monte-carlo-method
#20
Hongyu Jiang, Rajeev Badkul, Damodar Pokhrel
PURPOSE: As an alternative to cylindrical applicators, air-inflated balloon applicators have been introduced into high-dose-rate (HDR) vaginal cuff brachytherapy to achieve sufficient dose to the vagina mucosa as well as to spare organs at risk, mainly the rectum and bladder. Commercial treatment planning systems which employ formulae in the AAPM Task Group No. 43 (TG 43) report do not take into account tissue inhomogeneity. Consequently, the low-density air in a balloon applicator induces different doses delivered to the mucosa from planned by these planning systems...
March 1, 2018: Journal of Applied Clinical Medical Physics
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