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https://www.readbyqxmd.com/read/28640950/development-of-a-monte-carlo-multiple-source-model-for-inclusion-in-a-dose-calculation-auditing-tool
#1
Austin M Faught, Scott E Davidson, Jonas Fontenot, Stephen F Kry, Carol Etzel, Geoffrey S Ibbott, David S Followill
PURPOSE: The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms and heterogeneity corrections used. To audit this component of the radiotherapy treatment process an independent dose calculation tool is needed. METHODS: Monte Carlo multiple source models for Elekta 6MV and 10MV therapeutic x-ray beams were commissioned based on measurement of central axis depth dose data for a 10 x 10 cm(2) field size and dose profiles for a 40 x 40 cm(2) field size...
June 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28636763/sensitive-volume-effects-on-monte-carlo-calculated-ion-chamber-response-in-magnetic-fields
#2
Victor N Malkov, David W O Rogers
PURPOSE: The development of magnetic resonance guided radiation therapy (MR-gRT) necessitates accurate Monte Carlo (MC) models of ion chambers for computing ion chamber corrections to compensate for the presence of the magnetic field. This study evaluates the sensitivity of the ion chamber dose response in a magnetic field on the collection volume used in the MC simulation METHODS: The EGSnrc system's egs_chamber application is used with a recently developed and validated magnetic field transport code...
June 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28635617/the-dosimetric-impact-of-gadolinium-based-contrast-media-in-gbm-brain-patient-plans-for-a-mri-linac
#3
Syed Bilal Ahmad, Moti Raj Paudel, Arman Sarfehnia, Anthony Kim, Geordi Pang, Mark Ruschin, Arjun Sahgal, Brian M Keller
Dosimetric effects of gadolinium based contrast media (Gadovist) were evaluated for the Elekta MRI Linear accelerator (MRL) using the research version of Monaco treatment planning system (TPS). In order to represent a gadolinium uptake it was manually assigned to a phantom as well as to the Gross Tumour Volume (GTV) of 6 Glioblastoma Multiforme (GBM) patients. A preliminary estimate of dose enhancement, due to gadolinium, was performed using the phantom irradiated with a single beam. More complicated assessment was performed for the GBM patients using a 7 field IMRT technique...
June 21, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28624329/the-bebig-valencia-type-skin-applicators-dosimetric-study-and-implementation-of-a-dosimetric-hybrid-technique
#4
Georgios Anagnostopoulos, Michael Andrássy, Dimos Baltas
PURPOSE: To determine the relative dose rate distribution in water for the Bebig 20 mm and 30 mm skin applicators and report results in a form suitable for potential clinical use. Results for both skin applicators are also provided in the form of a hybrid Task Group 43 (TG-43) dosimetry technique. Furthermore, the radiation leakage around both skin applicators from the radiation protection point of view and the impact of the geometrical source position uncertainties are studied and reported...
June 14, 2017: Brachytherapy
https://www.readbyqxmd.com/read/28597229/couch-modelling-for-volumetric-modulated-arc-therapy-vmat
#5
Te-Yu Chyou, Friedlieb Lorenz
The aim of this work was to investigate the impact of the accuracy of a certain couch model on the overall accuracy of the dose calculation. For this purpose two models of the Varian Exact Couch (Varian Medical Systems, Palo Alto, CA, USA) for use in the planning of volumetric modulated arc therapy (VMAT) were created in Monaco 5.1 (Elekta, Stockholm, Sweden). The first was a simplistic model, with the relative electron densities (ED) of structures based entirely on CT Hounsfield units (HU). The second couch model was obtained by assigning the appropriate EDs to the relevant couch structures...
June 8, 2017: Australasian Physical & Engineering Sciences in Medicine
https://www.readbyqxmd.com/read/28541190/benchmarking-for-on-scalp-meg-sensors
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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