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https://www.readbyqxmd.com/read/28338948/comparing-measured-and-calculated-doses-in-interventional-cardiology-procedures
#1
M W Oliveira da Silva, L V Canevaro, J Hunt, B B D Rodrigues
Interventional cardiology requires complex procedures and can result in high doses and dose rates to the patient and medical staff. The many variables that influence the dose to the patient and staff include the beam position and angle, beam size, kVp, filtration, kerma-area product and focus-skin distance. A number of studies using the Monte Carlo method have been undertaken to obtain prospective dose assessments. In this paper, detailed irradiation scenarios were simulated mathematically and the resulting dose estimates were compared with real measurements made previously under very similar irradiation conditions and geometries...
March 16, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28335335/contact-resistance-and-channel-conductance-of-graphene-field-effect-transistors-under-low-energy-electron-irradiation
#2
Filippo Giubileo, Antonio Di Bartolomeo, Nadia Martucciello, Francesco Romeo, Laura Iemmo, Paola Romano, Maurizio Passacantando
We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono- and bi-layer graphene flakes on SiO₂, obtaining specific contact resistivity ρ c ≈ 19 k Ω · µ m 2 and carrier mobility as high as 4000 cm²·V(-1)·s(-1). By using a highly doped p-Si/SiO₂ substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment...
November 10, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28334532/an-ultrafast-switchable-terahertz-polarization-modulator-based-on-iii-v-semiconductor-nanowires
#3
Sarwat A Baig, Jessica L Boland, Djamshid A Damry, Hark Hoe Tan, Chennupati Jagadish, Hannah J Joyce, Michael B Johnston
Progress in the terahertz (THz) region of the electromagnetic spectrum is undergoing major advances, with advanced THz sources and detectors being developed at a rapid pace. Yet, ultrafast THz communication is still to be realised, owing to the lack of practical and effective THz modulators. Here, we present a novel ultrafast active THz polarization modulator based on GaAs semiconductor nanowires arranged in a wire-grid configuration. We utilise an optical pump--terahertz probe spectroscopy system and vary the polarization of the optical pump beam to demonstrate ultrafast THz modulation with a switching time of less than 5\,ps and a modulation depth of -8dB...
March 23, 2017: Nano Letters
https://www.readbyqxmd.com/read/28333640/integrated-hifu-drive-system-on-a-chip-for-cmut-based-catheter-ablation-system
#4
Omid Farhanieh, Ali Sahafi, Rupak Bardhan Roy, Arif Sanli Ergun, Ayhan Bozkurt
Conventional High Intensity Focused Ultrasound (HIFU) is a therapeutic modality which is extracorporeally administered. In applications where a relatively small HIFU lesion is required, an intravascular HIFU probe can be deployed to the ablation site. In this paper, we demonstrate the design and implementation a fully integrated HIFU drive system on a chip to be placed on a 6 Fr catheter probe. An 8-element capacitive micromachined ultrasound transducer (CMUT) ring array of 2 mm diameter has been used as the ultrasound source...
March 20, 2017: IEEE Transactions on Biomedical Circuits and Systems
https://www.readbyqxmd.com/read/28332994/predicting-patient-specific-dosimetric-benefits-of-proton-therapy-for-skull-base-tumors-using-a-geometric-knowledge-based-method
#5
David C Hall, Alexei V Trofimov, Brian A Winey, Norbert J Liebsch, Harald Paganetti
PURPOSE: To predict the organ at risk (OAR) dose levels achievable with proton beam therapy (PBT), solely based on the geometric arrangement of the target volume in relation to the OARs. A comparison with an alternative therapy yields a prediction of the patient-specific benefits offered by PBT. This could enable physicians at hospitals without proton capabilities to make a better-informed referral decision or aid patient selection in model-based clinical trials. METHODS AND MATERIALS: Skull-base tumors were chosen to test the method, owing to their geometric complexity and multitude of nearby OARs...
April 1, 2017: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/28325906/electric-field-driven-magnetic-domain-wall-as-a-microscale-magneto-optical-shutter
#6
Nikolai E Khokhlov, Anastasiya E Khramova, Elena P Nikolaeva, Tatyana B Kosykh, Alexey V Nikolaev, Anatoly K Zvezdin, Alexander P Pyatakov, Vladimir I Belotelov
Nowadays, spintronics considers magnetic domain walls as a kind of nanodeviсe that demands for switching much less energy in comparison to homogeneous process. We propose and demonstrate a new concept for the light control via electric field applied locally to a magnetic domain wall playing the role of nanodevice. In detail, we charged a 15-μm-thick metallic tip to generate strong non-uniform electric field in the vicinity of the domain wall in the iron garnet film. The electric field influences the domain wall due to flexomagnetoelectric effect and causes the domain wall shift...
March 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28319381/effects-of-second-metal-al-v-co-doping-on-the-no-reactivity-of-small-rhodium-cluster-cations
#7
Shinichi Hirabayashi, Masahiko Ichihashi
Reactions of pure and doped rhodium cluster cations, RhnX(+) (n = 2-6; X = Al, V, Co, Rh), with NO molecules were investigated at near-thermal energy using a guided ion beam tandem mass spectrometer. We found that the doping with Al and V increases the total reaction cross section mostly. Under single collision conditions, Rh2X(+) react with NO to produce Rh2N(+) with releasing metal monoxide, XO, while RhnX(+) (n = 3-6) adsorb NO. For the specific clusters, RhnAl(+) (n = 3 and 4) and RhnV(+) (n = 4-6), the NO adsorption is often accompanied with the release of one Rh atom...
March 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28318881/targeted-therapy-in-thyroid-cancer-state-of-the-art
#8
L Valerio, L Pieruzzi, C Giani, L Agate, V Bottici, L Lorusso, V Cappagli, L Puleo, A Matrone, D Viola, C Romei, R Ciampi, E Molinaro, R Elisei
Thyroid cancer typically has a good outcome following standard treatments, which include surgery, radioactive iodine ablation for differentiated tumours and treatment with thyrotropine hormone-suppressive levothyroxine. Thyroid cancers that persist or recur following these therapies have a poorer prognosis. Cytotoxic chemotherapy or external beam radiotherapy has a low efficacy in these patients. 'Target therapy' with tyrosine kinase inhibitors (TKIs) represent an important therapeutic option for the treatment of advanced cases of radioiodine refractory (RAI-R) differentiated thyroid cancer (DTC), medullary thyroid cancer (MTC) and possibly for cases of poorly differentiated (PDTC) and anaplastic thyroid cancer (ATC)...
March 16, 2017: Clinical Oncology: a Journal of the Royal College of Radiologists
https://www.readbyqxmd.com/read/28306315/hard-two-photon-contribution-to-elastic-lepton-proton-scattering-determined-by-the-olympus-experiment
#9
B S Henderson, L D Ice, D Khaneft, C O'Connor, R Russell, A Schmidt, J C Bernauer, M Kohl, N Akopov, R Alarcon, O Ates, A Avetisyan, R Beck, S Belostotski, J Bessuille, F Brinker, J R Calarco, V Carassiti, E Cisbani, G Ciullo, M Contalbrigo, R De Leo, J Diefenbach, T W Donnelly, K Dow, G Elbakian, P D Eversheim, S Frullani, Ch Funke, G Gavrilov, B Gläser, N Görrissen, D K Hasell, J Hauschildt, Ph Hoffmeister, Y Holler, E Ihloff, A Izotov, R Kaiser, G Karyan, J Kelsey, A Kiselev, P Klassen, A Krivshich, I Lehmann, P Lenisa, D Lenz, S Lumsden, Y Ma, F Maas, H Marukyan, O Miklukho, R G Milner, A Movsisyan, M Murray, Y Naryshkin, R Perez Benito, R Perrino, R P Redwine, D Rodríguez Piñeiro, G Rosner, U Schneekloth, B Seitz, M Statera, A Thiel, H Vardanyan, D Veretennikov, C Vidal, A Winnebeck, V Yeganov
The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°...
March 3, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28300370/linac-based-stereotactic-radiosurgery-srs-in-the-treatment-of-refractory-trigeminal-neuralgia-detailed-description-of-srs-procedure-and-reported-clinical-outcomes
#10
Damodar Pokhrel, Sumit Sood, Christopher McClinton, Habeeb Saleh, Rajeev Badkul, Hongyu Jiang, Timothy Stepp, Paul Camarata, Fen Wang
PURPOSE/OBJECTIVES: To present our linac-based SRS procedural technique for medically and/or surgically refractory trigeminal neuralgia (TN) treatment and simultaneously report our clinical outcomes. MATERIALS AND METHODS: Twenty-seven refractory TN patients who were treated with a single fraction of 80 Gy to TN. Treatment delivery was performed with a 4 mm cone size using 7-arc arrangement with differential-weighting for Novalis-TX with six MV-SRS (1000 MU/min) beam and minimized dose to the brainstem...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28300363/activation-of-hip-prostheses-in-high-energy-radiotherapy-and-resultant-dose-to-nearby-tissue
#11
Stephanie Keehan, Ryan L Smith, Jeremy Millar, Max Esser, Michael L Taylor, Peta Lonski, Tomas Kron, Rick D Franich
High energy radiotherapy can produce contaminant neutrons through the photonuclear effect. Patients receiving external beam radiation therapy to the pelvis may have high-density hip prostheses. Metallic materials such as those in hip prostheses, often have high cross-sections for neutron interaction. In this study, Thackray (UK) prosthetic hips have been irradiated by 18 MV radiotherapy beams to evaluate the additional dose to patients from the activation products. Hips were irradiated in- and out-of field at various distances from the beam isocenter to assess activation caused in-field by photo-activation, and neutron activation which occurs both in and out-of-field...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297441/comprehensive-dosimetric-planning-comparison-for-early-stage-non-small-cell-lung-cancer-with-sabr-fixed-beam-imrt-versus-vmat-versus-tomotherapy
#12
Ilma Xhaferllari, Omar El-Sherif, Stewart Gaede
Volumetric-modulated arc therapy (VMAT) is emerging as a leading technology in treating early-stage, non-small cell lung cancer (NSCLC) with stereotactic ablative radiotherapy (SABR). However, two other modalities capable of delivering intensity-modulated radiation therapy (IMRT) include fixed-beam and helical TomoTherapy (HT). This study aims to provide an extensive dosimetric comparison among these various IMRT techniques for treating early-stage NSCLC with SABR. Ten early-stage NSCLC patients were retrospectively optimized using three fixed-beam techniques via nine to eleven beams (high and low modulation step-and-shoot (SS), and sliding window (SW)), two VMAT techniques via two partial arcs (SmartArc (SA) and RapidArc (RA)), and three HT techniques via three different fan beam widths (1 cm, 2...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297425/investigation-on-using-high-energy-proton-beam-for-total-body-irradiation-tbi
#13
Miao Zhang, Nan Qin, Xun Jia, Wei J Zou, Atif Khan, Ning J Yue
This work investigated the possibility of using proton beam for total body irradiation (TBI). We hypothesized the broad-slow-rising entrance dose from a monoenergetic proton beam can deliver a uniform dose to patient with varied thickness. Comparing to photon-based TBI, it would not require any patient-specific compensator or beam spoiler. The hypothesis was first tested by simulating 250 MeV, 275 MeV, and 300 MeV protons irradiating a wedge-shaped water phantom in a paired opposing arrangement using Monte Carlo (MC) method...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297342/in-house-quality-check-of-external-beam-plans-using-3d-treatment-planning-systems-a-dvh-comparison
#14
Ayyalasomayajula Anil Kumar, Roopa Rani Akula, Komanduri Ayyangar, Reddy P Krishna, Srinivas Vuppu, P V Lakshmi Narayana, A Durga Prasada Rao
This paper presents a new approach towards the quality assurance of external beam plans using in-house-developed DICOM import and export software in a clinical setup. The new approach is different from what is currently used in most clinics, viz., only MU and point dose are verified. The DICOM-RT software generates ASCII files to import/export structure sets, treatment beam data, and dose-volume histograms (DVH) from one treatment planning system (TPS) to the other. An efficient and reliable 3D planning system, ROPS, was used for verifying the accuracy of treatment plans and treatment plan parameters...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297328/a-preplanning-method-for-stereotactic-radiosurgery-to-improve-treatment-workflow
#15
Kang-Hyun Ahn, Naim Ozturk, Brett Smith, Konstantin V Slavin, Matthew Koshy, Bulent Aydogan
Frame-based stereotactic radiosurgery (SRS) requires fixation of an invasive head ring to ensure accurate targeting. Minimizing waiting time with a fixed head ring is important for patient comfort and satisfaction. We report a practical preplanning solution for the Brainlab iPlan treatment planning system that reduces waiting time by expediting the planning process on treatment day. A water-filled anthropomorphic head phantom was used to acquire a surrogate CT image set for preplanning and fused with patient's MRI, which was obtained before the day of treatment...
May 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28297304/evaluation-of-kidney-motion-and-target-localization-in-abdominal-sbrt-patients
#16
Marcus Sonier, William Chu, Nafisha Lalani, Darby Erler, Patrick Cheung, Renee Korol
The purpose of this study was to evaluate bilateral kidney and target translational/rotational intrafraction motion during stereotactic body radiation therapy treatment delivery of primary renal cell carcinoma and oligometastatic adrenal lesions for patients immobilized in the Elekta BodyFIX system. Bilateral kidney motion was assessed at midplane for 30 patients immobilized in a full-body dual-vacuum-cushion system with two patients immobilized via abdominal compression. Intrafraction motion was assessed for 15 patients using kilovoltage cone-beam computed tomography (kV-CBCT) datasets (n=151) correlated to the planning CT...
November 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28295647/solid-state-electrolyte-gated-graphene-in-optical-modulators
#17
Francisco J Rodriguez, Diana E Aznakayeva, Owen P Marshall, Vasyl G Kravets, Alexander N Grigorenko
The gate-tunable wide-band absorption of graphene makes it suitable for light modulation from terahertz to visible light. The realization of graphene-based modulators, however, faces challenges connected with graphene's low absorption and the high electric fields necessary to change graphene's optical conductivity. Here, a solid-state supercapacitor effect with the high-k dielectric hafnium oxide is demonstrated that allows modulation from the near-infrared to shorter wavelengths close to the visible spectrum with remarkably low voltages (≈3 V)...
March 15, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28294104/top-down-design-of-magnonic-crystals-from-bottom-up-magnetic-nanoparticles-through-protein-arrays
#18
M Okuda, T Schwarze, J-C Eloi, S E Ward Jones, P J Heard, A Sarua, E Ahmad, V V Kruglyak, D Grundler, W Schwarzacher
We show that chemical fixation enables top-down micro-machining of large periodic 3D arrays of protein-encapsulated magnetic nanoparticles (NPs) without loss of order. We machined 3D micro-cubes containing a superlattice of NPs by means of focused ion beam etching, integrated an individual micro-cube to a thin-film coplanar waveguide and measured the resonant microwave response. Our work represents a major step towards well-defined magnonic metamaterials created from the self-assembly of magnetic nanoparticles...
April 18, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28287564/feeding-experimentation-device-fed-construction-and-validation-of-an-open-source-device-for-measuring-food-intake-in-rodents
#19
Katrina P Nguyen, Mohamed A Ali, Timothy J O'Neal, Ilona Szczot, Julia A Licholai, Alexxai V Kravitz
Food intake measurements are essential for many research studies. Here, we provide a detailed description of a novel solution for measuring food intake in mice: the Feeding Experimentation Device (FED). FED is an open-source system that was designed to facilitate flexibility in food intake studies. Due to its compact and battery powered design, FED can be placed within standard home cages or other experimental equipment. Food intake measurements can also be synchronized with other equipment in real-time via FED's transistor-transistor logic (TTL) digital output, or in post-acquisition processing as FED timestamps every event with a real-time clock...
February 21, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28286895/magnetic-trapping-of-sh-radicals
#20
J S Eardley, N Warner, L Z Deng, D Carty, E Wrede
Magnetic trapping of SH radicals, produced via the photostop technique, has been demonstrated. H2S in a skimmed, supersonic molecular beam was photodissociated at 212.8 nm to produce SH inside a 330 mK deep static magnetic trap. The molecular-beam speed was controlled by the mixing ratio of H2S in Kr to match the recoil velocity of the SH photofragments such that some SH radicals were produced with near-zero laboratory-frame velocity. The density of SH radicals in the (2)Π3/2, v = 0, J = 3/2 state was followed by (2 + 1) REMPI over seven orders of magnitude of signal intensity...
March 13, 2017: Physical Chemistry Chemical Physics: PCCP
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