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TU-D-330A-08: Information-Theoretic CAD System in Mammography: Investigation of An Entropy-Based Indexing Scheme for Improved Computational Efficiency and Robust Performance

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Medical Physics 2006年第6PART17期33卷 2197-2197页

作者： G Tourassi B Harrawood C Floyd Duke University Medical Center Durham NC

Purpose: We previously presented a Knowledge-Based computer Assisted Detection (KB-CAD) system for the detection of mammographic masses based on information theoretic similarity measures. The purpose of this study is to integrate an entropy-based indexing strategy that improves the speed of analysis without compromising the diagnostic performance of the system. Materials and Methods: The KB-CAD system is designed to compare a query mammographic region with mammographic templates of known ground truth stored in the knowledge databank. The system utilizes normalized mutual information (NMI) as the similarity measure. Previous studies showed that the system's diagnostic performance consistently improves as the knowledge databank increases. However, comparing each query to every template stored in the databank becomes computationally impractical. To address this concern, we implemented an entropy-based indexing scheme. Instead of comparing the query with the whole knowledge databank, we restrict the comparisons to those stored templates that are most relevant or informative. Only those templates are retrieved for more detailed analysis using the NMI similarity measure. Image entropy was used to determine the level of information or relevance for each available template. Results: We used a database of 2,318 mammographic regions (905 masses, 1,413 normal) extracted from the Digital Database of Screening Mammography (DDSM). Based on a leaveone- out sampling scheme, different clustering implementations of the entropy-based indexing scheme were investigated. Using entropy-based indexing, the KB-CAD system achieved the same performance (ROC area index Az=0.91±0.01 for malignant masses) using only a subset of 600 templates from the knowledge databank (compared to the full set of 2,317 available templates). Conclusion: This study showed that to sustain detection performance while maintaining computational efficiency, an optimized subset of relevant templates could be determined

关键词： Mammography Databases Digital mammography computer systems Entropy computer science and technology Cluster analysis Information theory entropy Cancer Medical imaging

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SU-FF-P-02: Live Webcast and Video Archiving of Physics Seminars

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Medical Physics 2006年第6PART14期33卷 2152-2152页

作者： M Woo Toronto Sunnybrook Regional Cancer Ctr Toronto ON CA

This presentation is to report and promote a webcasting and video archiving project at our cancer centre. We use a commercial system that requires special hardware to be installed in the presentation room, although a portable system is also available to videotape lectures but not for live webcast. The process begins with an email to the invited speaker, explaining the process and requesting his or her permission for the videotaping. Once the speaker agrees to it, the hospital's IS department is notified. All that is required of the IS staff is to enter the basic information on their computer, and then, at the actual time of the seminar, observe the speaker remotely on their TV monitor and adjust the video camera. The speaker image, the audio, together with the screen image of the speaker's presentation computer, will then be broadcast live on the web. To view the broadcast, intended audience will be sent a link in advance. The same link can be used to view the archived seminar afterwards. The archiving is done automatically, with no extra step for the IS staff. For the live webcast, some electronic form of remote audience participation, such as polling and sending questions by email, is available. We have decided that a speaker phone for audience to phone in would be most effective. The whole process is extremely easy to implement and also transparent to speakers, and the feedback has been highly positive. We are in the process of setting up an announcement for upcoming talks, as well as a catalog of archived talks. We encourage the Medical Physics community to participate in the project as audience. We would also like to promote this concept for other centres to set up similar facilities so that information and knowledge could be shared widely.

关键词： Medical imaging Cancer Announcements Lectures Cameras computer science and technology Medical physics

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SU-FF-T-308: ITC Assists Developers of ATC Compliant DICOM Export for Clinical Trials

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Medical Physics 2006年第6PART11期33卷 2117-2117页

作者： J Matthews W Bosch W Straube J Purdy Washington University School of Medicine St. Louis MO UC Davis Medical Center Sacramento CA

Purpose: The Image-guided Therapy QA Center (ITC) as part of the Advanced technology QA Consortium (ATC) has played a key role in assisting treatment planning system (TPS) developers in verifying that their DICOM implementations (CT, RT Structure Set, RT Dose, RT Plan, and RT Image) match ATC's conformance statement. This presentation will review lessons learned in this important effort. Methods and Materials: ITC hosted a series of DICOM Implementers' Workshops to assist TPS vendors in implementing RT objects needed for clinical trials. A system of software (“ATC Method 1”) developed at ITC to receive, process, and review volumetric treatment planning data for advanced technology clinical trials was used to assist vendors in their implementation of DICOM export. ATC's DICOM conformance statement specifies requirements for using DICOM RT objects in these clinical trials. ITC's DICOM fileset reader converts incoming data to an internal format for efficient display and review using the ITC web-based Remote Review Tool (RRT). The RRT was used by TPS developers to visualize/compare submitted images, structure sets, and dose distributions, thus greatly facilitating their DICOM implementations. Results: Interactions with developers have exposed several problems in interpretation and implementation of the DICOM standard resulting from the complexity of DICOM RT objects and differences in design/capabilities of TPSs. Examples of problems seen include CT/Structure/Dose miss-registration and DVH-calculation discrepancies. To date, 6 TPSs have released ATC-compliant DICOM export software. ITC has received DICOM data matching the ATC conformance statement from a total of 15 TPSs. ITC has worked with 8 additional TPS developers. Conclusions: The ITC web-based Remote Review Tool has proven to be of great help to vendors in developing and verifying implementations. More effort is needed by vendors to make digital data submission for clinical trials a simpler process. Support: NIH

关键词： Medical imaging Medical treatment planning computer software Computed tomography computer science and technology Visualization

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SU-FF-T-449: Validation of a Plan-Based Calibration Method for Relative Dosimetry of IMRT

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Medical Physics 2006年第6PART14期33卷 2149-2149页

作者： A Olch University of Southern California Keck School of Medicine and Childrens Hospital Los Angeles Los Angeles CA

Purpose: Validation of a new “plan-based” image calibration method for IMRT relative dosimetry comparisons. Method and Materials: Radiological Imaging technology image analysis software (version 4.2) contains a new calibration routine called plan-based calibration (patent pending). After registration of a 2-D dose image from the planning system with a measured but uncalibrated dose image, the routine then maps the planning system doses to each film or CR image pixel value and constructs a calibration curve. This calibration curve is then applied throughout measurement image to convert all pixels to dose. Because it does not use an independent dose vs. pixel calibration, it can be used for relative dosimetry only. Ten IMRT cases were studied for which both conventional dose calibration using parallel irradiation of film and the plan-based calibration were used. The Gamma value was used as a measure of agreement where 3% dose and 3 mm distance to agreement were set as tolerances. For these same cases, a 5 mm registration error was introduced and the comparison repeated. Results: In all properly registered cases, the plan-based calibration had fewer pixels with Gamma >1 than did the conventional calibration. Overall, the plan-based method gave 50% fewer pixels with Gamma > 1 than did the film-based calibration. This may be due to additional errors of the film calibration process convolving with intrinsic planning system, phantom setup, and film processing and scanning errors. The plan-based calibration was equally able to detect the registration error by giving a similarly large increase in percentage of pixels with Gamma >1. Conclusion: These data suggest that the plan-based calibration method provides a more accurate comparison of the measured vs. calculated dose distribution than conventional calibration methods using less time and materials. Conflict of Interest: This research was supported by Radiological Imaging technology.

关键词： Calibration Dosimetry Medical imaging Intensity modulated radiation therapy Image analysis computer science and technology Materials analysis computer software Computed radiography Patents

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MO-D-330D-01: Molecular Imaging I: The Physics of Molecular Imaging

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Medical Physics 2006年第6PART14期33卷 2160-2160页

作者： D Cody J Stickel G Johnson J Boone U.T.M.D Anderson Cancer Center Houston TX University California - Davis Sacramento CA Duke University Medical Center Durham NC

The first day of the Molecular Imaging Symposium (MI-1) will focus on the technology aspects of molecular, functional, and small animal imaging. Modalities which will be discussed include micro-CT, micro-PET, and high resolution MRI for small animal imaging. The presentation on micro-CT technology will include an introduction to the basic requirements of the scanner hardware, examples of the images and biological applications in which micro-CT is useful, and the radiation dose to the small animal undergoing micro-CT will also be discussed. Micro-CT techniques require longer acquisition times than human scanners, and thus maintaining the animal in a viable but motionless state is of clear importance. Therefore, issues surrounding animal support including anesthesia and respiratory gating will also be presented. Micro-PET systems are widely used in small animal imaging for genome research, and represent probably the mainstay of truly molecular imaging modalities at this point in time. The presentation on micro-PET will include a description of micro-PET scanner hardware, a discussion of PET-radiotracers, and an overview of current small animal PET systems. The limitation of current micro-PET system design will be discussed, and ideas for overcoming some of these limitations will be presented. High resolution MRI systems have the benefit of delivering exquisite contrast with excellent spatial resolution, with no ionizing radiation. The presentation on micro-MRI techniques for phenotype imaging will describe the integration of physics, biology, chemistry, engineering, and computer science which is necessary to achieve state-of-the-art small animal MRI imaging. The use of hyperpolarized gases for lung imaging and MR histology will be discussed as well. The availability of small animal imaging systems across a number of modalities has proved essential for a large number of research applications. The primary goal of MI-1 is to help familiarize medical physicists with the t

关键词： Medical imaging Image scanners Magnetic resonance imaging Dosimetry Spatial resolution Positron emission tomography Genomics Medical image contrast Ionizing radiation computer science and technology

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TH-A-ValA-01: The Value Proposition of the Physicist in Informatics

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Medical Physics 2006年第6PART21期33卷 2260-2260页

作者： P Nagy Univ Maryland School of Medicine Baltimore MD

There exists today a vacuum in the knowledge to transform medicine with information technology (informatics). Many diagnostic physicists today get pulled into their institution's PACS implementation willingly or not and find themselves trying to provide informatics leadership. For those physicists who are interested, aiding a facility with informatics can be very rewarding. There is a strong affinity between the informatics skill set and the role of diagnostic physics in the way we bridge the worlds of science and technology with medicine. Many of the leaders of the Society of Imaging Informatics in Medicine (SIIM, formerly SCAR), are diagnostic physicists. There is an opportunity of growth for the profession to provide leadership in the changing face of medicine. A subcommittee on Imaging Informatics has been established by the AAPM to understand this opportunity. The views expressed in this talk are my own and do not necessarily reflect the opinions of the committee. We will try and present a roadmap for those physicists who are being called in to fill the informatics roles of their department or are interested in expanding their clinical tool set to include informatics. Most physicists trained today have a solid grounding in computer science. In addition to a good comprehension in computer science, an informaticist needs to know about systems management, systems integration, and project management. Systems management includes the information technology principles needed to ensure smooth operations of a large IT service such as PACS. This includes availability monitoring, change management, failure mode effects analysis, problem management, performance monitoring, disaster recovery, and continuity management to name a few. A physicist should not be a PACS administrator, but instead be the person to train the PACS administrators and provide the oversight and strategy to allow the facility take advantage of information technology. This is identical to our role in wo

关键词： Informatics Physicists Medical imaging Medical diagnosis Medical image quality computer science and technology Quality assurance Calibration Failure analysis computer systems

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SU-FF-T-327: Monte Carlo Dose Calculations in Homogeneous and Heterogeneous Media: A Comparison Between the PMCEPT Code and the MCNP5, EGS4, DPM Codes and Measurements

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Medical Physics 2006年第6PART12期33卷 2122-2122页

作者： O Kum Pohang Univseristy of Science and Technology Pohang Kyungbook KR

The Monte Carlo method for high-energy photon and charged particle transport is the most accurate means for predicting dose distributions in radiation treatment of patients. Owing to rapid development of computer hardware and network technologies the use of this method is not restricted only to big research centers any more. A new parallel Monte Carlo electron and photon transport (PMCEPT) code [Kum and Lee, J. Kor. Phys. Soc. 47 (2005) 716] for calculating electron and photon beam doses has been developed based on a three dimensional geometry defined by computerized tomography (CT) images and implemented on the Beowulf PC cluster. The PMCEPT code was validated on the homogeneous and multi-layered targets for megavoltage electron beams by comparing with the results of experiments and calculations from conventional Monte Carlo codes of the MCNP5, EGS4, and DPM. The computing time of the PMCEPT code was approximately twenty times faster than that of MCNP5 on the IBM ThinkPad X40 (laptop) with 1.2-GHz CPU and 512-MB ram memory operated by RedHat Linux 9. The PMCEPT results in general agreed well with others in homogeneous and heterogeneous media within a maximum of 2–3 % error. At the conference, we will show various benchmark results for the PMCEPT. This work was supported, in part, by the SRC/ERC program of MOST/KOSEF (grant number: R11-1999-054).

关键词： Photons Dosimetry Computed tomography Electron beams Monte Carlo methods Electronic transport computer science and technology Radiation treatment computer hardware Tomography

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SU-FF-T-397: Stereotactic Radiotherapy: Varian 120-Leaf MLC Verses Radionics' MMLC

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Medical Physics 2006年第6PART13期33卷 2137-2137页

作者： S Jaywant E Kagan Cancer Institute of New Jersey New Brunswick NJ

Purpose: With the continuing rapid development of technology, more options are becoming available for the clinician. However, this is bringing forth technical challenges to the Physicist, especially in the integration of these technologies. The most commonly used Varian linear accelerator that has the 120 leaf MLC attached to its head prohibits the use of an additional Radionics' MMLC. Hence the 120 leaf MLC was integrated into the Radionics' XKnifeRT system to be used in both cranial and extracranial applications. This presentation provides technical information and clinical experience using this combination. Methods and Materials: The stereotactic technology utilizes the Radionics' XKnifeRT system consisting of a) treatment planning software capable of both 3D conformal as well as step and shoot IMRT; b) stereotactic frames for cranial and extracranial applications. The Varian 120 leaf MLC with an inner leaf width of 5 mm was integrated into the XKnifeRT system so that either the 120MLC or the MMLC could be used clinically. The limitations in the use of the MMLC in this configuration include reduced clearance, especially for extracranial applications, and a reduced maximum field size of 9 × 11 cm. Thus far nearly 40 patients have been treated, mostly using the IMRT component, and include GTC/TLC for cranial sites, and, Head & Neck Localizer(HNL)/Body Localizer(BL) for extracranial sites. Results: A comparison of dose distributions/DVHs of the 120 MLC and the MMLC indicate only marginal improvement if the MMLC were to be used. Not only is the setup time at the linac reduced, the actual IMRT delivery is only a few seconds more than a corresponding dynamic delivery. A cranial and a C-spine application of the technology validates this integration. Conclusions: We continue to utilize the 120 leaf MLC successfully for all stereotactic applications with XKnifeRT.

关键词： Multileaf collimators Intensity modulated radiation therapy Linear accelerators Therapeutics computer science and technology Radiosurgery Physicists Field size computer software Medical treatment planning

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Complex grid computing

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EUROPEAN PHYSICAL JOURNAL B 2005年第1期44卷 119-128页

作者： Costa, LD Travieso, G Ruggiero, CA Univ Sao Paulo Inst Fis Sao Carlos BR-13560970 Sao Carlos SP Brazil

This article investigates the functional properties of complex networks used as grid computing systems. Complex networks following the Erdos-Renyi model and other models with a preferential attachment rule ( with and without growth) or priority to the connection of isolated nodes are studied. Regular networks are also considered for comparison. The processing load of the parallel program executed on the grid is assigned to the nodes on demand, and the efficiency of the overall computation is quantified in terms of the parallel speedup. It is found that networks with preferential attachment allow lower computing efficiency than networks with uniform link attachment. At the same time, considering only node clusters of the same size, preferential attachment networks display better efficiencies. The regular networks, on the other hand, display a poor efficiency, due to their implied larger internode distances. A correlation is observed between the topological properties of the network, specially average cluster size, and their respective computing efficiency.

关键词： Structures and organization in complex systems computer science and technology World Wide Web, Internet Combinatorics, graph theory Networks and genealogical trees

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Evolving network - Simulation study - From regular lattice to scale free network

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EUROPEAN PHYSICAL JOURNAL B 2005年第4期48卷 547-555页

作者： Makowiec, D Univ Gdansk Inst Theoret Phys & Astrophys PL-80952 Gdansk Poland

The Watts-Strogatz algorithm of transferring the square lattice to a small world network is modified by introducing preferential rewiring constrained by connectivity demand. The evolution of the network is two-step: sequential preferential rewiring of edges controlled by p and updating the information about changes done. The evolving system self-organizes into stationary states. The topological transition in the graph structure is noticed with respect to p. Leafy phase - a graph formed by multiple connected vertices (graph skeleton) with plenty of leaves attached to each skeleton vertex emerges when p is small enough to pretend asynchronous evolution. Tangling phase where edges of a graph circulate frequently among low degree vertices occurs when p is large. There exist conditions at which the resulting stationary network ensemble provides networks which degree distribution exhibit power-law decay in large interval of degrees.

关键词： Stochastic processes Structures and organization in complex systems computer science and technology

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