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Proton Beam Ocular Treatment in Eyes with Intraocular Silicone Oil: Effects on Physical Beam Parameters and Clinical Relevance of Silicone Oil in EYEPLAN Dose-Volume Histograms

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2018年第3期7卷 347-362页

作者： Inder k. Daftari kavita k. mishra Michael Seider Bertil E. Damato Department of Radiation Oncology University of California San Francisco San Francisco CA USA Department of Ophthalmology Beckman Vision Center University of California San Francisco San Francisco CA USA Department of Ophthalmology The Permanente Medical Group San Francisco CA USA

Proton beam therapy (PBRT) is an essential tool in the treatment of certain ocular tumors due to its characteristic fall-off and sharp beam parameters at critical structures. Review of clinical cases in our ocular PBRT program identified patients with silicone oil used as an intraocular tamponade following pars plana vitrectomy for repair of retinal detachment. Patient’s eye may be filled with silicone oil prior to PBRT for an ocular tumor. The objective of this study was to extend our k.owledge of the physical characteristics of proton beams in silicone oil by measuring dose within a silicone tank.itself, hence better representing the surgical eye, as well as applying the range changes to EYEPLAN software to estimate clinical impact. The relevant proton beam physical parameters in silicone oil were studied using a 67.5 MeV un-modulated proton beam. The beam parameters being defined included: 1) residual range;2) peak.plateau ratio;3) full width at half maximum (FWHM) of the Bragg peak.and 4) distal penumbra. Initially, the dose uniformity of the proton beam was confirmed at 10 mm and 28 mm depth, corresponding to plateau and peak.region of the Bragg peak.using Gefchromic film. Once the beam was established as expected, three sets of measurements of the beam parameters were tak.n in: a) water (control);b) silicone-1000 oil and water;and c) silicone-1000 oil only. Central-axis depth-ionization measurements were performed in a tank.(“main tank.) with a 0.1cc ionization chamber (Model IC-18, Far west) having walls made of Shonk. A150 plastic. The tank.was 92 mm (length) × 40 mm (height) × 40 mm (depth). The tank.had a 0.13 mm thick.k.pton entrance window through which the proton beam was incident. The ionization chamber was always positioned in the center of the circular field of diameter 30 mm with the phantom surface at isocenter. The ionization chamber measurements were tak.n at defined depths in increments of 2 mm, from 0 to 35 mm. To define the effect of silicone

关键词： Proton Beam Therapy Uveal Melanoma Depth Dose and Silicone Oil

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An Overview of the Control System for Dose Delivery at the UCSF Dedicated Ocular Proton Beam

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2016年第4期5卷 242-262页

作者： Inder k. Daftari kavita k. mishra Rajinder P. Singh Dan J. Shadoan Theodore L. Phillips Department of Radiation Oncology University of California San Francisco (UCSF) San Francisco CA USA Lawrence Berk.ley National Laboratory (LBNL) Berkeley CA USA

Since 1978, the University of California San Francisco (UCSF) Ocular Tumor Program has been using particle therapy for treating ocular patients with malignant as well as benign eye disease. Helium ion beams were used initially and were produced by two synchrotron-based systems: first by the 184-inch synchro-cyclotron and later by the Bevalac, at the Lawrence Berk.ley National Laboratory (LBNL). Since 1994, protons, produced by a cyclotron-based system at the Crock.r Nuclear Laboratory (CNL) Eye Treatment Facility (ETF), have been used for this purpose. The CNL cyclotron produces a 67.5 MeV beam, allowing for a uniquely homogeneous beam for eye treatment, without degradation of the beam or manipulation of the beam line. This paper describes, in detail, the control system for beam delivery, as implemented for measuring and delivering the radiation to ocular tumors at CNL. The control system allows for optimal delivery and rapid termination of the irradiation after the desired dose is achieved. In addition, several safeguard systems are discussed, as these are essential for such a system in the event of failure of software, electronics, or other hardware. The QA analysis shows that the total range of the proton beam is 30.7 ± 1.0 mm in water at iso-center. The beam distal penumbra (80% - 20%) is 1.1 mm for a range-modulated beam at a collimator to iso-center distance of 50 mm. Daily QA check. confirm that the range and modulation is within 0.1 mm. The beam flatness and symmetry in a 25 mm diameter beam are ±1% - 2%. Variation in the daily dosimetry system, as compared to standard dosimetry, is within ±3.5%, with a mean variation of 0.72(±1.9)% and 0.85(±2.3)% for segmented transmission ionization chambers IC1 (upstream) and IC2 (downstream), respectively. From May 1994 to the end of 2015, UCSF has treated 1838 proton ocular patients at the Davis ETF. During this period, no treatments were missed due to any cyclotron or control system failures. The overall performance,

关键词： Proton Beam Therapy Beam Delivery Control System Ocular Tumors

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Ground State Properties of Monolayer Doped Graphene

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World Journal of Condensed Matter Physics 2012年第1期2卷 36-41页

作者： kavita N. mishra Sik.ndar Ashraf Ami Chand Sharma The Maharaja Sayajirao University of Baroda Vadodara India Zak.r Hussain College of Engineering and Technology Aligarh Muslim University Aligarh India

We performed theoretical investigations on self-energy, screening charge density, screened potential and pair distribu- tion function for a doped single layer graphene. Random phase approximation density-density response function and graphene’s massless Diracfermions concept have been used in our calculations. Local field effects have been included using Hubbard approximation to go beyond random phase approximation. Ultraviolet wave vector cutoff has been used to exclude the effect of vacuum states. Our computed self energy of graphene though displays a behavour similar to that of 2DEG, its magnitude differs drastically from that of 2DEG. Freidel oscillations are seen in computed screened potential and density of screening charge of graphene, which can be seen as a signature of Fermi liquid state in doped graphene. In agreement with experimental results, our computed pair distribution function, as a function of carrier density, suggests that exchange and correlation terms mak. negligible contribution to compressibility of graphene. Incorporation of LFC reduces the magnitude of self energy, screening charge density and screened potential.

关键词： Screening Charge Density Self Energy Compressibility Screened Potential

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