Monte Carlo simulations of out-of-field surface doses due to the electron streaming effect in orthogonal magnetic fields.

Monte Carlo simulations of out-of-field surface doses due to the electron streaming effect in orthogonal magnetic fields. Phys Med Biol. 2019 Feb 26;: Authors: Malkov VN, Hackett SL, Wolthaus JWH, Raaymakers BW, van Asselen B Abstract The out-of-field surface dose contribution due to backscattered or ejected electrons, contained by the magnetic field, is evaluated in this work. This electron streaming effect (ESE) can contribute to out-of-field skin doses and toxicity in orthogonal magnetic resonance guided radiation therapy machines. Using the EGSnrc Monte Carlo package, a central phantom is set-up with an incident 10X10cm<sup>2</sup> 7MV FFF photon beam. The phantom exit or entry surface is inclined with respect to the magnetic field, and an out-of-field water panel is positioned 10cm away from, and centered on, isocenter. The doses from streaming backscattered or ejected electrons, for either a 0.35T or 1.5T magnetic fied, are evaluated in the out-of-field water panel for surface inclines of 10, 30 and 45<sup>o<\sup>. The magnetic field focuses the electrons emitted from the central inclined phantom. Dose distributions at the surface of the out-of-field panel are sharper in the 1.5T magnetic field as compared to 0.35T. The maximum doses for the 0.35T simulations are 23.2%, 37.8%, and 39.0% for the respective 10, 30, and 45<sup>o</sup> simulations. For 1.5T, for the same angles, the maximum val...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research

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Source: AuntMinnie.com Headlines - Category: Radiology Source Type: news
Publication date: Available online 12 September 2019Source: Radiation Physics and ChemistryAuthor(s): James Archer, Levi Madden, Enbang Li, Dean Wilkinson, Anatoly RosenfeldAbstractAs part of clinical safety for radiation therapy, quality assurance is vital for ensure that the delivered dose matches the prescribed dose for any targeted volumes and surrounding healthy tissue. A challenge when measuring the beam quality, especially for smaller sized beams, is having a water equivalent dosimeter with a high spatial resolution and the ability to perform accurate 2D mapping. In this work we use a plastic scintillator fibre opti...
Source: Radiation Physics and Chemistry - Category: Physics Source Type: research
Publication date: Available online 11 September 2019Source: Radiation Physics and ChemistryAuthor(s): Ali Pashazadeh, Eduardo de Paiva, Naghmeh Mahmoodian, Michael FriebeAbstractBeta radiation therapy of superficial thin skin tumors using a radioactive patch is an interesting treatment, mainly when the lesion is near sensitive targets, for example, close to the eyes or bone structures. Due to their short range and rapid dose fall-off, beta radiation from a skin patch deposits its energy within the first layers of the skin. This property may lead to the protection of sensitive structures located right beneath the skin lesio...
Source: Radiation Physics and Chemistry - Category: Physics Source Type: research
Conclusion: Radiation therapy and pelvic operation for cancer were more common causes than birth injury, and these causes of rectovaginal fistula were the most important prognostic factors. An individualized approach and repeated surgeries with complex or newly developed procedures, even among high-risk causes of fistula, may be necessary to achieve successful closure. PMID: 31508396 [PubMed]
Source: Annals of Surgical Treatment and Research - Category: Surgery Tags: Ann Surg Treat Res Source Type: research
The purpose of this study was to assess the feasibility, efficacy and toxicity of fiducial marker implantation and tracking in CyberKnife ® stereotactic radiation therapy (SBRT) applied to extracranial locations.
Source: Radiation Oncology - Category: Cancer & Oncology Authors: Tags: Research Source Type: research
Bone metastases frequently occur in metastatic cancer patients and the spine is a common site of tumor spread [1]. Palliative radiation therapy (RT) is an effective therapy for painful spinal metastases [2]. Stereotactic body radiation therapy (SBRT) to the spine has been implemented in the last decade as a highly efficient approach [3,4]. By multimodality imaging for target volume definition, modern intensity-modulated treatment planning, radiotherapy delivery with image-guidance and nearly rigid patient immobilization, SBRT enables safe treatment with escalated doses to the affected parts of the vertebra whilst sparing the spinal cord.
Source: Radiotherapy and Oncology - Category: Radiology Authors: Tags: Original Article Source Type: research
This study aimed to evaluate risk factors pertinent to OS and to propose an optimal treatment strategy. METHODS: Clinical data of patients with PIRMS treated at Beijing Tiantan Hospital and from the English-language literature between 1946 and 2018 were reviewed. A literature review was performed via Ovid, MEDLINE, Embase, PubMed, Web of Science, and Cochrane databases using the terms "rhabdomyosarcoma," "intracranial," "cerebral," and "brain." Previously published data were processed and used according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidel...
Source: Journal of Neurosurgery - Category: Neurosurgery Authors: Tags: J Neurosurg Source Type: research
Abstract Benign notochordal cell tumors (BNCTs) are considered to be benign intraosseous lesions of notochord origin; however, recent spine studies have suggested the possibility that some chordomas arise from BNCTs. Here, the authors describe two cases demonstrating histological features of BNCT and concomitant chordoma involving the clivus, which, to the best of the authors' knowledge, have not been previously documented at this anatomical site.An 18-year-old female presented with an incidentally discovered clival mass. Magnetic resonance imaging revealed a 2.8-cm nonenhancing lesion in the upper clivus that was...
Source: Journal of Neurosurgery - Category: Neurosurgery Authors: Tags: J Neurosurg Source Type: research
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Source: Journal of Medical Physics - Category: Physics Authors: Source Type: research
N V. N Madhusudhana Sresty, A Krishnam Raju, B Nagarjuna Reddy, VC Sahithya, Yakub Mohmd, G Deleep Kumar, T Anil Kumar, Tasneem Rushdi, S Aparna, G Durga Prasad, Harjot Kaur BajwaJournal of Medical Physics 2019 44(3):222-227TomoTherapy® is a modern radiation treatment technique in which intensity-modulated radiation therapy (IMRT) is delivered in helical fashion. A two-dimensional (2D) array which has been existing for IMRT patient-specific quality assurance (PSQA) verifications for many years is I'MatriXX. Our objectives were to validate this I'MatriXX and to evaluate it for different patient sites and fracti...
Source: Journal of Medical Physics - Category: Physics Authors: Source Type: research
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