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Informatics in Medical Imaging

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Medical Physics 2012年第3期39卷 1681-1681页

作者： Yu Liu Ph.D. DABR

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Sustainable growth in complex networks

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EPL 2011年第5期96卷

作者： Tessone, C. J. Geipel, M. M. Schweitzer, F. Swiss Fed Inst Technol Chair Syst Design D MTEC CH-8032 Zurich Switzerland

Based on the analysis of the dependency network in 18 Java projects, we develop a novel model of network growth which considers both preferential attachment and the addition of new nodes with a heterogeneous distribution of their initial degree, k(0). Empirically we find that the cumulative distributions of initial and final degrees in the network follow power law behaviours: 1-P(k(0)) proportional to k(0)(1-alpha), and 1-P(k) proportional to k(1-gamma), respectively. For the total number of links as a function of the network size, we find empirically K(N) proportional to N-beta, where beta is an element of [1.25, 2] (for small N), while converging to beta similar to 1 for large N. This indicates a transition from a growth regime with increasing network density towards a sustainable regime, which prevents a collapse due to ever increasing dependencies. Our theoretical framework allows us to predict relations between the exponents alpha, beta, gamma, which also link issues of software engineering and developer activity. These relations are verified by means of computer simulations and empirical investigations. They indicate that the growth of real Open Source Software networks occurs on the edge between two regimes, which are dominated either by the initial degree distribution of added nodes, or by the preferential attachment mechanism. Hence, the heterogeneous degree distribution of newly added nodes, found empirically, is essential to describe the laws of sustainable growth in networks. Copyright (C) EPLA, 2011

关键词： Networks and genealogical trees Fluctuation phenomena, random processes, noise, and Brownian motion computer science and technology

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Link prediction in complex networks: A local naive Bayes model

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EPL 2011年第4期96卷

作者： Liu, Zhen Zhang, Qian-Ming Lu, Linyuan Zhou, Tao Univ Elect Sci & Technol China Web Sci Ctr Chengdu 610054 Peoples R China Univ Fribourg Dept Phys CH-1700 Fribourg Switzerland

The common-neighbor-based method is simple yet effective to predict missing links, which assume that two nodes are more likely to be connected if they have more common neighbors. In the traditional method, each common neighbor of two nodes contributes equally to the connection likelihood. In this letter, we argue that different common neighbors may play different roles and thus contributes differently, and propose a local naive Bayes model. Extensive experiments were carried out on nine real networks. Compared with the traditional method, the present method can provide more accurate predictions. Copyright (C) EPLA, 2011

关键词： Networks and genealogical trees computer science and technology Social and economic systems

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WE-G-224-01: History Symposium - Historical Aspects of Brachytherapy

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Medical Physics 2011年第6PART33期38卷 3825-3826页

作者： L Rothenberg B Hilaris J St. Germain Memorial Sloan-Kettering Cancer Center New York NY New York Medical College Mem Sloan-Kettering Cancer Ctr New York NY

This presentation will review some of the historic developments in brachytherapy treatment. The early history of brachytherapy is primarily the history of radium and its daughter products, particularly 222 Rn. Much of this history is interwoven with the histories of institutions in North America and Europe, such as the Memorial Hospital, Harvard Medical School, the Huntington Memorial Hospital, closed in 1941, with its activities transferred to the Massachusetts General Hospital, M.D. Anderson Hospital, the Mayo Clinic, the Radium Institute of Paris, the Radium Hemmet in Stockholm and the Holt Radium Institute in Manchester. Noted personalities such as William Duane, Gioacchino Failla, Robert Abbe, Henry Janeway, Victor Hess and Enrico Fermi all worked with “radium cows” which supplied radon gas in seeds and tubes for treatment. Edith Quimby and Herbert Parker made significant advances in dosimetry, developing systems for planar implants and more complex geometries. Noted physicians such as Gilbert Fletcher, Ulrich Henschke, Luis Delclos and Nisar Syed developed applicators and procedures for using radioactive sources for treatment. Modern brachytherapy techniques were developed in the 1960ˈs with the search for radium-substitute materials including 125 I and 192 Ir. This time period also saw the development of remote afterloading by Henschke and his associates and the adaptation of computer technology which facilitated the development of more accurate, user friendly techniques of dosimetry. In the modern era, remote afterloading in conjunction with high dose rate radioactive sources (HDR) and the use of 125 I and 103 Pd seeds have become staples of modern treatment.

关键词： Brachytherapy Radium Dosimetry Radioactive sources computer science and technology North America Europe

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Effective privacy amplification for secure classical communications

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EPL 2011年第2期94卷 28002-28002页

作者： Horvath, T. Kish, L. B. Scheuer, J. Univ Bonn Dept Comp Sci D-5300 Bonn Germany Fraunhofer IAIS D-53754 Schloss Birlinghoven Sankt Augustin Germany Texas A&M Univ Dept Elect & Comp Engn College Stn TX 77843 USA Tel Aviv Univ Sch Elect Engn Ramat Aviv Israel Tel Aviv Univ Ctr Nanosci & Nanotechnol Ramat Aviv Israel

We study the practical effectiveness of privacy amplification for classical key distribution schemes. We find that in contrast to quantum key distribution schemes, the high fidelity of the raw key generated in classical systems allow the users to always sift a secure shorter key if they have an upper bound on the eavesdropper probability to correctly guess the exchanged key bits. The number of privacy amplification iterations needed to achieve information leak of 10(-8) in existing classical communicators is 2 or 3 resulting in a corresponding slowdown 4 to 8. We analyze the inherent tradeoff between the number of iterations and the security of the raw key. This property which is unique to classical key distribution systems render them highly useful for practical, especially for noisy channels where sufficiently low quantum bit error ratios are difficult to achieve. Copyright (C) EPLA, 2011

关键词： Other topics in areas of applied and interdisciplinary physics (restricted to new topics in section 89) computer science and technology

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Enabling a high throughput real time data pipeline for a large radio telescope array with GPUs

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computer PHYSICS COMMUNICATIONS 2010年第10期181卷 1707-1714页

作者： Edgar, R. G. Clark, M. A. Dale, K. Mitchell, D. A. Ord, S. M. Wayth, R. B. Pfister, H. Greenhill, L. J. Initiat Innovat Comp Cambridge MA 02138 USA Harvard Smithsonian Ctr Astrophys Cambridge MA 02138 USA Sch Engn & Appl Sci Cambridge MA 02138 USA

The Murchison Widefield Array (MWA) is a next-generation radio telescope currently under construction in the remote Western Australia Outback. Raw data will be generated continuously at 5 GiBs(-1), grouped into 8 s cadences. This high throughput motivates the development of on-site, real time processing and reduction in preference to archiving, transport and off-line processing. Each batch of 8 s data must be completely reduced before the next batch arrives. Maintaining real time operation will require a sustained performance of around 2.5 TFLOPs(-1) (including convolutions, FFTs, interpolations and matrix multiplications). We describe a scalable heterogeneous computing pipeline implementation, exploiting both the high computing density and FLOP-per-Watt ratio of modern GPUs. The architecture is highly parallel within and across nodes, with all major processing elements performed by GPUs. Necessary scatter-gather operations along the pipeline are loosely synchronized between the nodes hosting the GPUs. The MWA will be a frontier scientific instrument and a pathfinder for planned peta- and exa-scale facilities. (c) 2010 Elsevier B.V. All rights reserved.

关键词： Radio telescopes and instrumentation Heterodyne receivers Mathematical procedures and computer techniques computer science and technology

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Prose and Poetry Classification and Boundary Detection Using Word Adjacency Network Analysis

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INTERNATIONAL JOURNAL OF MODERN PHYSICS C 2010年第4期21卷 513-522页

作者： Mrowinski, Maciej J. Kosinski, Robert A. Warsaw Univ Technol Fac Phys PL-00662 Warsaw Poland Natl Res Inst Cent Inst Labour Protect PL-00701 Warsaw Poland

Word adjacency networks constructed from written works reflect differences in the structure of prose and poetry. We present a method to disambiguate prose and poetry by analyzing network parameters of word adjacency networks, such as the clustering coefficient, average path length and average degree. We determine the relevant parameters for disambiguation using linear discriminant analysis (LDA) and the effect size criterion. The accuracy of the method is 74.9 +/- 2.9% for the training set and 73.7 +/- 6.4% for the test set which are greater than the acceptable classifier requirement of 67.3%. This approach is also useful in locating text boundaries within a single article which falls within a window size where the significant change in clustering coefficient is observed. Results indicate that an optimal window size of 75 words can detect the text boundaries.

关键词： Text genre classification word adjacency networks LDA Structures and organization in complex systems Complex systems computer science and technology

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TH-B-110-01: Informatics in Radiation Oncology

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Medical Physics 2011年第6PART34期38卷 3850-3850页

作者： R Siochi University Of Iowa Iowa City IA

Informatics covers not only the information technology (IT) and infrastructure required to support data collection and management but also the computer science concepts that turn data into knowledge. In radiation oncology, medical physicists need to be familiar with the basic IT infrastructure that makes it possible to transfer and transform data through clinical processes that ultimately control radiation treatment delivery. The application of informatics continues with patient outcomes. Typically, this happens through participation in national protocols (e.g. RTOG). While they provide a framework for evidence-based medicine, the data are often limited to parameters that were designed to test a pre-defined hypothesis. As the ability to acquire and distribute data increases, we may be able to adopt data mining approaches to discover knowledge, even without asking specific questions. While simple database queries can efficiently provide statistical information (e.g. the NCI Surveillance, Epidemiology and End Results, SEER), data mining seeks hidden patterns through clustering, classification, regression and association. These principles can be applied to large volumes of concisely described data sets, similar to what can be found in clinical trials. Researchers in radiation oncology informatics are developing the infrastructure to acquire large data sets. The Radiation Oncology Data Alliance (RODA) initiative aims to provide online aggregate de-identified data from participating users of the MOSAIQ EMR. Borrowing from the field of astronomy, researchers from Johns Hopkins used the SkyServer framework to build the OncoSpace project. The NCI caBIG (Cancer Bioinformatics Grid) also provides infrastructure support. Data analytics have also been developing in parallel, with researchers structuring the data collection phases to answer questions in Comparative Effectiveness Research (CER). While a majority of researchers look for links between treatment and outcome, others

关键词： Informatics Cancer Researchers Data mining Radiation treatment computer science and technology Radiation therapy Data sets Medical physicists computer aided diagnosis

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TU-A-301-03: A Multi-Dimensional Description of Breast Anatomy Using Breast CT

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Medical Physics 2011年第6PART28期38卷 3745-3745页

作者： S Huang J Boone K Yang N Packard S McKenney N Prionas M Yaffe K Lindfors University of California Davis Davis CA Carestream Health Inc. Rochester NY University Toronto Toronto ON CA

Purpose: Accurate anatomical characterization of the breast is useful in breast phantom development, computer modeling of breast imaging technologies, and computer-aided diagnosis of various imaging tasks. Using the breast CT (bCT) data sets of women from a clinical trial, a number of two-dimensional (2D) and three-dimensional (3D) parameters which describe breast shape and composition are presented. Methods: The diameter, length, and volume of the pendant breast were measured for 219 bCT data sets, grouped by bra cup size. Segmented bCT data sets were used to determine the volume glandular fraction (VGF). VGF was found as a function of patient age, BIRADS density, and bra cup size. The glandular fraction was examined in coronal (GFcoronal and sagittal (GFsagittal) planes of the breast, and the radial distribution of breast glandular fraction (RGFn) within a coronal bCT image was examined for three breast regions. The areal glandular fraction (AGF) was estimated from 2D projections of the breast (simulated by linear integration of bCT data sets) and was compared to the corresponding VGF. A 3D probability map of fibroglandular distribution was simulated using the breast metrics found in this study. Results: Breast diameter, length, and volume increase with increasing bra cup size. VGF was lower among older women and those with larger bra cup size. For each increasing BIRADS category, VGF increased by 5.62% (p < 0.001). VGF was also found to increase with AGF following a power function. Most fibroglandular tissue was distributed mainly in the central portion of the breast. Conclusions: Breast anatomy was examined and a number of parameters were described. The reported data may provide useful information for breast modeling in various imaging or dosimetry tasks.

关键词： Medical imaging Data sets Computed tomography Anatomy computer science and technology computer modeling Tissues Dosimetry

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WE-C-BRB-09: Volumetric Modulated Arc Therapy Based Total Marrow Irradiation and Dosimetry Verification

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Medical Physics 2011年第6PART32期38卷 3806-3806页

作者： Y Liang L Mell G Kim Center for Advanced Radiotherapy Technologies University of California San Diego La Jolla CA University of California San Diego La Jolla CA

Purpose: This study develops treatment planning and a comprehensive dosimetry verification procedure for volumetric modulated arc therapy(VMAT) based total marrow irradiation(TMI), a form of targeted total body irradiation(TBI). Methods: The simulation CT of 3 patients treated with TBI were used. Planning was done with Eclipse treatment planning system(Varian Medical Systems, CA). Planning volume(PTV) was defined as skeletal bone, rib, and sternum, with 3mm margin, from head to mid-femur. In total marrow and lymphoid irradiation(TMLI), PTV is expanded to include spleen and major lymph nodes. The mandible, maxillary bones and forearms were excluded. The dose prescription was 12Gy in 6 fractions. The PTV is divided into head-and-neck(H&N), chest and pelvis regions. Correspondingly, there is separate plan for each region, composed of 2∼3 arcs/fields with multiple isocenters along patient axial direction. The 2D dosimetry verification was conducted with EBT2 Gafchromic film(International Specialty Products, NJ) for gamma evaluation and ion chamber for absolute point dose measurement, using a IMRT phantom(computerized Imaging Reference Systems, VA) and RIT software(Radiological Imaging technology, CO), with emphasis of junction area between neighboring plans for hot/cold spots. We further conduct volumetric dose verification with electronic portal imaging devices and DosimetryCheck program(Math resolutions, MD). The gamma evaluation criteria were 5% absolute point dose difference and 3mm distance to agreement. Results: More than 90% of PTV is covered by 100% of prescribed dose. Compared to TBI, average dose reduction on critical organs are: lung(10%), kidney(53%), liver(48%), Eyes(69%), and heart(51%). Junction areas show average 98% gamma passing rate and 3% absolute dose difference; volumetric portal dosimetry show average 91% gamma passing rate and 2% absolute dose difference, compared to plan dose. Conclusions: Adequate target dose coverage and reduced normal organ d

关键词： Dosimetry Medical treatment planning Medical imaging Anatomy Computed tomography Ionization chambers computer science and technology Intensity modulated radiation therapy Therapeutics Ionic conduction

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