Ursula M. Maydell

Simulation Of A PACS In A Hospital Environment

This paper presents a simulation of a distributed imaging system used for storing and retrieving digitally formatted medical images. The simulation model includes a one segment Ethernet local area network (LAN) as its communication system. This segment connects three image input devices, an image processor, an active storage device, an archival storage device, and one or more display devices (workstations). The simulated model is driven by a medical imaging workload similar to a hospital radiology department, and consists of a mix of user activities such as display, edit, manipulate and browse. These operations are performed interactively at a workstation. Performance measures such as response times, channel utilization and number of collisions were tabulated and are presented in graphs for different numbers of workstations connected to a system with different channel capacities and different image sizes. Conclusions are drawn with regard to necessary channel capacity and the viability of Ethernet for PACS.

The self-traffic-engineering network

Characterizes several techniques for the distributed, dynamic management of telecommunications network transmission facilities. Several methods are presented for changing trunk-group sizes in order to respond to extraordinary network loads. These methods are given the generic title of self-traffic-engineering (STE), because the network effectively reengineers itself to adapt to unforeseen circumstances. Self-traffic-engineering is a new network management application for telecommunication facilities networks. One of these methods is based on a new interpretation of network reliability, which is embodied in a metric called connectability. The paper reports the results of a simulation study in which self-traffic-engineering is used to enable the Telecom Canada network to adapt to a focused overload.

A Survey Of Current Lan Technology And Performance

AbstractA variety of methods has been used to construct commercially available local area networks (LANS). This paper describes various aspects of LAN technology and summarizes recent comparative performance studies. The design factors that are addressed are the choice of network configuration, transmission techniques, transmission medium, and medium-access protocols. Standards developments are mentioned briefly. Performance of medium-access protocols is studied in depth. Emphasis is placed on the three most popular methods, token ring, token bus, and CSMA/CD. Channel utilization and packet delay characteristics of each method are discussed. Factors such as the number of nodes, the length of the medium, and the physical distribution of the active nodes on a network are shown to drastically affect network performance, particularly for protocols with non-deterministic access. The relative importance of performance to marketing is questioned. The contention is made that networks are currently underutilized t...

Performance of the ACR/NEMA Protocol

In the last decade medical imaging has seen many changes. Various new and improved devices have been widely accepted allowing new noninvasive approaches and reduced radiation dosage for diagnostic imaging. The need then arises to interconnect different devices from a variety of manufacturers. These devices must also be able to communicate with disks, processing units and displays. For such Medical Picture Archiving and Communication Systems (PACS) to become feasible, a communication standard is required. Interfaces conforming to this standard should be provided by all manufacturers.

Xpress transfer protocol in a medical communication system

For a local area medical network, the performance of transfer protocols on top of the standard LAN protocols is explored. In this simulation the medical LAN is FDDI at 100 Mbps and the transfer protocols to be investigated are the commonly available TCP/IP and the relatively new, lightweight XTP. The performance measures used for their comparison are response time for an image and total transfer time for a series of images in one examination The image workloads ranged from current, potential digital image loads to larger image transmission loads in the future. Two different values for FDDIs target-token-rotation-time were also explored. Contrary to expectations XTP using less overhead bits than TCP/IP did not greatly outperform TCP/IP.

Algorithms for admission control in broadband communication networks

The throughput of virtual connections is negotiable in future broadband integrated services digital networks (B-ISDN). A new problem for admission control in broadband networks, thus, is to decide which calls to accept as well as at which throughput levels. This paper presents an optimization model and its solutions for the admission control and throughput negotiations in B-ISDN. The model is an extension of the knapsack problem, namely the flexible knapsack problem. It differs from the conventional knapsack problems in allowing different packing forms for the objects from the same class. Each packing form is associated with a different set of volume requirements and reward rates. The objective is to maximize the total reward. The decision space in the flexible knapsack problem is not only acceptance and denial, but also includes the choice of the optimal packing form for each accepted object. Three algorithms are provided in this paper to obtain the optimal access control decision for the connection throughput negotiations in B-ISDN.

On enhancing the performance of the ACR-NEMA protocol

The ACR-NEMA standard allows different medical devices to communicate compatibly in a picture archiving and communication system (PACS) environment. The performance of a PACS, incorporating the ACR-NEMA standard, has been previously analyzed. It was shown that the ACR-NEMA protocol results in excessive response time values for image viewing requests. In this paper, the authors propose and study the performance effects of a number of enhancements to the ACR-NEMA standard. The objective of such enhancements is to make the ACR-NEMA protocol better suited for transmission of large images. It is shown that such enhancements, indeed, result in a much improved system performance.

On placement of the ACR-NEMA bus in picture archiving and communications systems

The ACR-NEMA standard (1985) allows different medical devices to communicate compatibly in a picture archiving and communication system (PACS) environment. The authors evaluate the performance of PACSs incorporating the ACR-NEMA standard. The ACR-NEMA standard requires that the ACR-NEMA bus be placed between any medical device and a network interface unit. The authors propose the removal of the ACR-NEMA bus from the archive-workstation path. Therefore, the ACR-NEMA protocol delays would be eliminated from all viewing requests. The ACR-NEMA bus is to be kept at the image generating equipment (IGE) workstations. The authors introduce the enhanced PACS architecture. Some numerical results of the architecture are shown and compared to results obtained by following the ACR-NEMA bus placement specification as stated in the standard.

Grade of service for telemedical communication

This paper investigates the service demands of telemedical communications on a metropolitan area network (MAN) connecting several local area networks located at different hospitals. The flexible grade of service (GOS) is proposed for better network utilization and lower blocking rate as opposed to conventional fixed GOS. The GOS is supported by network resource allocation schemes. A new scheme to support the flexible GOS is also outlined in this paper. The new scheme can be used for both planning and management of a telemedical communication network. 1

Simulation Of An Interactive Workstation For Image Display

This paper presents a simulation of an image display system or workstation connected to a minicomputer system which is in turn connected to a larger computer system. The use of image display systems in a medical environment is summarized and parameters discussed include image and display resolution, communication bandwidth, and workstation configuration. User activities are broken down into five categories: display, edit, manipulation, generation and browse. Typical user sessions or workloads are then composed of these categories in various proportions and the response time and effectiveness of the simulated activity is measured. Some of the results are summarized in a number of charts and graphs, with conclusions and suggestions.