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https://www.readbyqxmd.com/read/27908162/an-efficient-method-to-determine-double-gaussian-fluence-parameters-in-the-eclipse%C3%A2-proton-pencil-beam-model
#1
Jiajian Shen, Wei Liu, Joshua Stoker, Xiaoning Ding, Aman Anand, Yanle Hu, Michael G Herman, Martin Bues
PURPOSE: To find an efficient method to configure the proton fluence for a commercial proton pencil beam scanning (PBS) treatment planning system (TPS). METHODS: An in-water dose kernel was developed to mimic the dose kernel of the pencil beam convolution superposition algorithm, which is part of the commercial proton beam therapy planning software, eclipse™ (Varian Medical Systems, Palo Alto, CA). The field size factor (FSF) was calculated based on the spot profile reconstructed by the in-house dose kernel...
December 2016: Medical Physics
https://www.readbyqxmd.com/read/27905521/evaluation-of-a-silicon-90-sr-betavoltaic-power-source
#2
Jefferson Dixon, Aravindh Rajan, Steven Bohlemann, Dusan Coso, Ajay D Upadhyaya, Ajeet Rohatgi, Steven Chu, Arun Majumdar, Shannon Yee
Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from (90)Sr as a power source is investigated...
December 1, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27903198/dosimetric-characterization-of-hypofractionated-gamma-knife-radiosurgery-of-large-or-complex-brain-tumors-versus-linear-accelerator-based-treatments
#3
Peng Dong, Angélica Pérez-Andújar, Dilini Pinnaduwage, Steve Braunstein, Philip Theodosopoulos, Michael McDermott, Penny Sneed, Lijun Ma
OBJECTIVE Noninvasive Gamma Knife (GK) platforms, such as the relocatable frame and on-board imaging, have enabled hypofractionated GK radiosurgery of large or complex brain lesions. This study aimed to characterize the dosimetric quality of such treatments against linear accelerator-based delivery systems that include the CyberKnife (CK) and volumetric modulated arc therapy (VMAT). METHODS Ten patients treated with VMAT at the authors' institution for large brain tumors (> 3 cm in maximum diameter) were selected for the study...
December 2016: Journal of Neurosurgery
https://www.readbyqxmd.com/read/27897141/measured-and-monte-carlo-simulated-electron-backscatter-to-the-monitor-chamber-for-the-varian-truebeam-linac
#4
Samantha A M Lloyd, Isabelle M Gagne, Magdalena Bazalova-Carter, Sergei Zavgorodni
To accurately simulate therapeutic electron beams using Monte Carlo methods, backscatter from jaws into the monitor chamber must be accounted for via the backscatter factor, S b. Measured and simulated values of S b for the TrueBeam are investigated. Two approaches for measuring S b are presented. Both require service mode operation with the dose and pulse forming networking servos turned off in order to assess changes in dose rate with field size. The first approach samples an instantaneous dose rate, while the second approach times the delivery of a fixed number of monitor units to assess dose rate...
December 21, 2016: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/27896625/mri-characterization-in-the-acute-phase-of-experimental-subarachnoid-hemorrhage
#5
Dewei Guo, D Andrew Wilkinson, B Gregory Thompson, Aditya S Pandey, Richard F Keep, Guohua Xi, Ya Hua
A number of mechanisms have been proposed for the early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated the radiographic characteristics and influence of gender on early brain injury after experimental SAH. SAH was induced by endovascular perforation in male and female rats. Magnetic resonance imaging was performed in a 7.0-T Varian MR scanner at 24 h after SAH. The occurrence and size of T2 lesions, ventricular dilation, and white matter injury (WMI) were determined on T2-weighted images (T2WI)...
November 28, 2016: Translational Stroke Research
https://www.readbyqxmd.com/read/27872879/data-on-fe-ii-biosorption-onto-sargassum-hystrix-algae-obtained-from-the-persian-gulf-in-bushehr-port-iran
#6
Fatemeh Faraji Ghasemi, Sina Dobaradaran, Alireza Raeisi, Abdolhamid Esmaili, Mohammad Javad Mohammadi, Mozhgan Keshtkar, Sara Ghaderi Nasab, Farshid Soleimani
In this article, we used Sargassum hystrix algae as biosorbent for removal of Fe (II) from aqueous solutions that was collected along the Persian Gulf coastline, Bushehr, Iran. The concentration level of remaining Fe (II) in the samples was measured by using flame atomic absorption spectrometry (FAAS, Varian AA240, Australia). The isotherms, kinetics and modeling data of Fe (II) biosorption onto Sargassum hystrix were also presented.
December 2016: Data in Brief
https://www.readbyqxmd.com/read/27866896/performance-of-the-irregular-surface-compensator-compared-with-four-field-box-and-intensity-modulated-radiation-therapy-for-gynecologic-cancer
#7
Wonmo Sung, Jung-In Kim, Hyun Suk Kim, Hak Jae Kim, Yang Hoon Lee, Sung-Joon Ye
PURPOSE: A retrospective planning study was undertaken to evaluate the dosimetric advantages of the irregular surface compensator (ISC) technique, a forward planning technique with electronic compensation algorithm available on Varian Eclipse treatment planning system. This was extensively compared to the conventional four-field box (4FB) and intensity modulated radiation therapy using 5 fields (IMRT5F) on gynecologic cancer patients. METHODS: Twenty-two patients were enrolled...
November 17, 2016: Physica Medica: PM
https://www.readbyqxmd.com/read/27825953/microbial-lysate-upregulates-host-oxytocin
#8
Bernard J Varian, Theofilos Poutahidis, Brett T DiBenedictis, Tatiana Levkovich, Yassin Ibrahim, Eliska Didyk, Lana Shikhman, Harry K Cheung, Alexandros Hardas, Catherine E Ricciardi, Kumaran Kolandaivelu, Alexa H Veenema, Eric J Alm, Susan E Erdman
Neuropeptide hormone oxytocin has roles in social bonding, energy metabolism, and wound healing contributing to good physical, mental and social health. It was previously shown that feeding of a human commensal microbe Lactobacillus reuteri (L. reuteri) is sufficient to up-regulate endogenous oxytocin levels and improve wound healing capacity in mice. Here we show that oral L. reuteri-induced skin wound repair benefits extend to human subjects. Further, dietary supplementation with a sterile lysate of this microbe alone is sufficient to boost systemic oxytocin levels and improve wound repair capacity...
November 5, 2016: Brain, Behavior, and Immunity
https://www.readbyqxmd.com/read/27816362/experimental-platform-for-ultra-high-dose-rate-flash-irradiation-of-small-animals-using-a-clinical-linear-accelerator
#9
Emil Schüler, Stefania Trovati, Gregory King, Frederick Lartey, Marjan Rafat, Manuel Villegas, A Joe Praxel, Billy W Loo, Peter G Maxim
PURPOSE: A key factor limiting the effectiveness of radiation therapy is normal tissue toxicity, and recent preclinical data have shown that ultra-high dose rate irradiation (>50 Gy/s, "FLASH") potentially mitigates this effect. However, research in this field has been strongly limited by the availability of FLASH irradiators suitable for small animal experiments. We present a simple methodologic approach for FLASH electron small animal irradiation with a clinically available linear accelerator (LINAC)...
September 20, 2016: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/27811709/cliona-acephala-porifera-demospongiae-clionaida-a-new-encrusting-excavating-reef-sponge-from-the-colombian-caribbean-belonging-to-the-cliona-viridis-species-complex
#10
Sven Zea, Mateo López-Victoria
Several groups of sponges are able to excavate galleries and tunnels in calcareous substrata such as limestone rock, shells, calcareous algae and coral skeletons. Within the genus Cliona, some species share the common traits of being brown to olive-green in color, and harboring photosynthetic, unicellular dinoflagellates (zooxanthellae). These Cliona spp. have been grouped as the Cliona viridis species complex. Several species of this complex completely encrust the excavated substratum with a thin veneer of tissue and, when colonizing dead exposed parts of live coral colonies, they are able to undermine or overgrow and thus kill live coral tissue as they advance predominantly laterally...
October 26, 2016: Zootaxa
https://www.readbyqxmd.com/read/27811392/automatic-detection-of-mlc-relative-position-errors-for-vmat-using-the-epid-based-picket-fence-test
#11
Damianos Christophides, Alex Davies, Mark Fleckney
Multi-leaf collimators (MLCs) ensure the accurate delivery of treatments requiring complex beam fluences like intensity modulated radiotherapy and volumetric modulated arc therapy. The purpose of this work is to automate the detection of MLC relative position errors  ⩾0.5 mm using electronic portal imaging device-based picket fence tests and compare the results to the qualitative assessment currently in use. Picket fence tests with and without intentional MLC errors were measured weekly on three Varian linacs...
December 7, 2016: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/27806611/accuracy-of-dose-calculations-on-kv-cone-beam-ct-images-of-lung-cancer-patients
#12
Mariska de Smet, Danny Schuring, Sebastiaan Nijsten, Frank Verhaegen
PURPOSE: To develop a clinically feasible method for dose calculations on cone beam CT (CBCT) images of two different vendors, and to determine the accuracy of these dose calculations for lung cancer patients. METHODS: Lung cancer patients with CBCT imaging (n = 10 for Elekta, n = 6 for Varian) and a repeated planning CT scan on the same day were selected. For CBCT dose calculations, an adapted Hounsfield units-to-mass density table (HU table) was used which was obtained by comparing CT values of corresponding points on the CBCT and the repeated planning CT scan...
November 2016: Medical Physics
https://www.readbyqxmd.com/read/27806597/influence-of-standard-rf-coil-materials-on-surface-and-buildup-dose-from-a-6-mv-photon-beam-in-magnetic-field
#13
A Ghila, B G Fallone, S Rathee
PURPOSE: Magnetic resonance guided teletherapy systems aspire to image the patient concurrently with the radiation delivery. Thus, the radiofrequency (RF) coils used for magnetic resonance imaging, placed on or close to patient skin and in close proximity to the treatment volume, would be irradiated leading to modifications of radiation dose to the skin and in the buildup region. The purpose of this work is to measure and assess these dose modifications due to standard off-the-shelf RF coil materials...
November 2016: Medical Physics
https://www.readbyqxmd.com/read/27806583/performance-of-a-clinical-gridded-electron-gun-in-magnetic-fields-implications-for-mri-linac-therapy
#14
Brendan Whelan, Lois Holloway, Dragos Constantin, Brad Oborn, Magdalena Bazalova-Carter, Rebecca Fahrig, Paul Keall
PURPOSE: MRI-linac therapy is a rapidly growing field, and requires that conventional linear accelerators are operated with the fringe field of MRI magnets. One of the most sensitive accelerator components is the electron gun, which serves as the source of the beam. The purpose of this work was to develop a validated finite element model (FEM) model of a clinical triode (or gridded) electron gun, based on accurate geometric and electrical measurements, and to characterize the performance of this gun in magnetic fields...
November 2016: Medical Physics
https://www.readbyqxmd.com/read/27785640/can-mri-t1-be-used-to-detect-early-changes-in-5xfad-alzheimer-s-mouse-brain
#15
Nicholas G Spencer, David P Lovell, Kay Elderfield, Brian Austen, Franklyn A Howe
OBJECTIVES: In the present study, we have tested whether MRI T1 relaxation time is a sensitive marker to detect early stages of amyloidosis and gliosis in the young 5xFAD transgenic mouse, a well-established animal model for Alzheimer's disease. MATERIALS AND METHODS: 5xFAD and wild-type mice were imaged in a 4.7 T Varian horizontal bore MRI system to generate T1 quantitative maps using the spin-echo multi-slice sequence. Following immunostaining for glial fibrillary acidic protein, Iba-1, and amyloid-β, T1 and area fraction of staining were quantified in the posterior parietal and primary somatosensory cortex and corpus callosum...
October 26, 2016: Magma
https://www.readbyqxmd.com/read/27782735/evaluation-of-the-dose-calculation-accuracy-for-small-fields-defined-by-jaw-or-mlc-for-aaa-and-acuros-xb-algorithms
#16
Antonella Fogliata, Francesca Lobefalo, Giacomo Reggiori, Antonella Stravato, Stefano Tomatis, Marta Scorsetti, Luca Cozzi
PURPOSE: Small field measurements are challenging, due to the physical characteristics coming from the lack of charged particle equilibrium, the partial occlusion of the finite radiation source, and to the detector response. These characteristics can be modeled in the dose calculations in the treatment planning systems. Aim of the present work is to evaluate the MU calculation accuracy for small fields, defined by jaw or MLC, for anisotropic analytical algorithm (AAA) and Acuros XB algorithms, relative to output measurements on the beam central axis...
October 2016: Medical Physics
https://www.readbyqxmd.com/read/27751617/single-fraction-flattening-filter-free-volumetric-modulated-arc-therapy-for-lung-cancer-dosimetric-results-and-comparison-with-flattened-beams-technique
#17
Sara Barbiero, Alexandra Rink, Fabrizio Matteucci, David Fedele, Fabiola Paiar, Francesco Pasqualetti, Michele Avanzo
PURPOSE: To report on single-fraction stereotactic body radiotherapy (RT) (SBRT) with flattening filter (FF)-free (FFF) volumetric modulated arc therapy (VMAT) for lung cancer and to compare dosimetric results with VMAT with FF. METHODS AND MATERIALS: Overall, 25 patients were treated with 6-MV FFF VMAT (Varian TrueBeam STx LINAC) to a prescribed dose of 24Gy in a single fraction. Treatment plans were recreated using FF VMAT. Dose-volume indices, monitor units (MU), and treatment times were compared between FFF and FF VMAT techniques...
October 14, 2016: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/27740944/range-optimization-for-mono-and-bi-energetic-proton-modulated-arc-therapy-with-pencil-beam-scanning
#18
Daniel Sanchez-Parcerisa, Maura Kirk, Marcus Fager, Brendan Burgdorf, Malorie Stowe, Tim Solberg, Alejandro Carabe
The development of rotational proton therapy plans based on a pencil-beam-scanning (PBS) system has been limited, among several other factors, by the energy-switching time between layers, a system-dependent parameter that ranges between a fraction of a second and several seconds. We are investigating mono- and bi-energetic rotational proton modulated arc therapy (PMAT) solutions that would not be affected by long energy switching times. In this context, a systematic selection of the optimal proton energy for each arc is vital...
October 14, 2016: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/27709851/comparison-of-dosimetric-performance-among-commercial-quality-assurance-systems-for-verifying-pretreatment-plans-of-stereotactic-body-radiotherapy-using-flattening-filter-free-beams
#19
Jin Beom Chung, Sang Won Kang, Keun Yong Eom, Changhoon Song, Kyoung Sik Choi, Tae Suk Suh
The purpose of this study was to compare the performance of different commercial quality assurance (QA) systems for the pretreatment verification plan of stereotactic body radiotherapy (SBRT) with volumetric arc therapy (VMAT) technique using a flattening-filter-free beam. The verification for 20 pretreatment cancer patients (seven lung, six spine, and seven prostate cancers) were tested using three QA systems (EBT3 film, I'mRT MatriXX array, and MapCHECK). All the SBRT-VMAT plans were optimized in the Eclipse (version 11...
November 2016: Journal of Korean Medical Science
https://www.readbyqxmd.com/read/27685137/comparison-of-automatic-image-registration-uncertainty-for-three-igrt-systems-using-a-male-pelvis-phantom
#20
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...
2016: Journal of Applied Clinical Medical Physics
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