Future photonic networks will perform routing and switching in the optical layer by use of ultrafast photonic processing. An ultra-wideband hierarchical hybrid optical time division multiplexing/wavelength division multiplexing (OTDM/WDM) network is proposed for the future core photonic network. As its enabling technologies, continuous C- and L-wavelength-band signal generation, OTDM-WDM multiplexing format conversions, and OTDM wavelength-band conversions are demonstrated.
Future photonic networks will perform routing and switching in the optical layer based upon ultrafast photonic processing. An ultra-wideband hierarchical hybrid optical time division multiplexing/wavelength division multiplexing (OTDM/WDM) network is proposed for the future core photonic network. As its enabling technologies, continuous C- and L- wavelength-band signal generation, OTDM-WDM multiplexing format conversions, and OTDM wavelength-band conversions are demonstrated.
In a radiological examination reading, radiologists usually compare a newly generated examination with previous examinations of the same patient. For this reason, the retrieval of old images is a critical design requirement of totally digital radiology using Picture Archiving and Communication Systems (PACS). To achieve the required performance in a PACS with a hierarchical and possibly distributed image archival system, pre-fetching of images from slower or remote storage devices to the local buffers of workstations is proposed. Image Retrieval Expert System (IRES) is a knowledge-based image retrieval system which will predict and then pre-fetch relevant old images. Previous work on IRES design focused on the knowledge acquisition phase and the development of an efficient modeling methodology and architecture. The goal of this paper is to evaluate the effectiveness of the current IRES design and to identify appropriate directions for exploring other design features and alternatives by means of a cognitive study and an associated survey study.
Proc. SPIE. 1446, Medical Imaging V: PACS Design and Evaluation
KEYWORDS: Imaging systems, Databases, Interfaces, Medical imaging, Digital imaging, Radiology, Data communications, Information security, Standards development, Picture Archiving and Communication System
During the last decade, the concept of picture archiving and communication systems (PACS) has evolved and matured to integrate digital image information in a hospital. PACS integrates various imaging devices, database archive systems, and image viewing workstations. One of the most difficult problems for integration is the standardization of communication protocols required to connect devices from different vendors. When the ACR-NEMA standard was announced for communications in digital radiology in 1985, it solved some of the problems for PACS with a hardware interface, a set of software commands, and a consistent set of data formats. However, it has been found to be inadequate for networked PACS environments, not only because of its point-to-point nature and lack of a network layer, but also because of its inflexibility to allow other services and protocols to be added in the future. Based on previous experience, the case is made for a new standard for PACS networks and a suggested approach for new protocol is presented. This paper addresses the development of a new standard for PACS protocol layers and attempts to define the protocols from a layered-systems approach. The basis for the new protocol definition is primarily the International Organization for Standardization/Open Systems Interconnection (ISO/OSI) protocols and the data format portion of ACR-NEMA standard. The scope and rationale of the proposed protocol, background, and relationship to PACS technology are discussed. The proposed PACS protocol covers the protocol service definition and specification for the application, presentation, session, transport, and network layers. The proposed PACS protocol is intended to facilitate the development of PACSs by several vendors capable of interfacing with each other. The new PACS protocols will also support a global PACS environment.
The sound design of any system begins with a full understanding of user requirements and the environment
in which the system is to operate. The process of obtaining this understanding is called requirement
analysis. The design of a Picture Archiving and Communication System (PACS) Database (DB) also
starts with a requirement analysis, following a systematic top-down DB design approach. The purpose of
a DB requirement analysis is to provide the information necessary for deriving DB design specifications.
This paper presents the results and implications of a year long intensive requirement analysis for a PACS
DB at the University Medical Center (UMC) of the University of Arizona (U of A).
In this paper, the PACS network data rate requirement in a
radiology department is discussed. The network data transmission
rate under real data traffic in a medium-size hospital is
evaluated using a simulation study. The network is assumed to be
a circuit switching network. A preloading system, in which each
workstation has local storage to store the next procedure, is
assumed, and the network transmission rate which satisfies the
response time of this system is obtained.
The delivery of an operable Picture Archiving and Communication System (PACS) that will meet a
hospital's high performance requirements is hampered by severe bottlenecks encountered in the database
(DB) and communication systems of a centralized architecture. As an alternative to a centralized design,
a distributed DB design that physically allocates and potentially replicates data across a hospital has
been modeled and evaluated for PACS at the University of Arizona. Because of geographic dispersion of
image generation and "local interest" in image retrieval, a distributed DB design approach has a liatural
appeal to PACS. This paper examines the issues of a distributed PACS DB design, describes our modeling
approach, and presents the results of a preliminary performance evaluation of two distributed DB designs
vs. a centralized design for PACS The results of our simulation experiments show that there is a significant
improvement of response time in a distributed architecture due to the effects of "local reference" and "load
The concept of picture archiving and communication systems (PACS) is now widely accepted in the medical
community. In order to bring the concept to reality, however, innovative designs and implementations are needed.
One such design is a fiber optic star based PACS, conceived by the University of Arizona and Toshiba corporation.
This PACS network is based on a multiplexed passive star local area network with wavelength-division multiplexing
to provide separate logical channels for transfer of control and image data. The system consists of an Image-Network
(INET), for image transfer at a rate of 140 Mbps, and a Control-network (CNET), operating at 10 Mbps, for
mediating the flow of image transfers. INET is a circuit switched network where a network supervisor grants users
permission to transfer images over it, while CNET employs the CSMA/CD protocol for bus arbitration. Before such a
system can be deployed, an accurate evaluation study must be carried out to estimate its performance characteristics.
Such evaluations are complicated both by the complexity of the PACS itself and the varied demands that are placed
on such a system. An novel approach based on siochastic aciiviiy neiworks, a stochastic extension of Petri nets, is
useful in this regard. Stochastic activity networks were used to develop a detailed model of the command and image
channels. The performance of the system was then evaluated under realistic workload conditions. In particular, we
were able to estimate a number of important performance variables including the image response time, command
channel delay, and queue length each type of node and the network supervisor. The results 1) show that stochastic
activity networks are an appropriate model type for evaluating picture archiving and communication systems, 2)
delineate the workload conditions under which PACS may effectively operate, and 3) show that even when these
conditions are exceeded, the command channel load remains extremely light. Results of this type are useful both to
designers of other PACS networks and those interested in this particular PACS design.