System upgrade cuts network costs
Earlier this year, Gary Wendt, vice chair of informatics at the University of Wisconsin (Madison, WI), approached ALI Technologies Inc. (Richmond, BC, Canada) to expand its installed Picture Archive and Communication System (PACS) to include enterprisewide image distribution throughout the university's hospital and three outpatient clinics.
By closely evaluating requirements, the University of Wisconsin Hospital expanded its medical imaging network for maximum data access at minimal cost.
By R. Winn Hardin,Contributing Editor
Earlier this year, Gary Wendt, vice chair of informatics at the University of Wisconsin (Madison, WI), approached ALI Technologies Inc. (Richmond, BC, Canada) to expand its installed Picture Archive and Communication System (PACS) to include enterprisewide image distribution throughout the university's hospital and three outpatient clinics. Wendt recognized that, despite an existing Compaq Corp. (Houston, TX) ProLiant 8000 enterprise server and Gigabit Ethernet backbone, the hardware needed a radical upgrade to connect the hundreds of clinicians that wanted access to a campuswide radiology PACS (see Fig. 1).
The University of Wisconsin Hospital staff acquired and installed the computer and network hardware, and ALI Technologies provided UltraPACS software. By taking the hardware purchase, installation, and maintenance in-house, Wendt was able to expand the network's enterprise-server cluster and archival locations into several buildings. This network approach limited the risk of system failure and medical-record damage due to possible local fire or flooding disasters.
ALI Technologies provided a strong hardware blueprint for Wendt. He says, "We went with the hardware that ALI suggested, but we didn't want them to be the hardware vendor. We wanted better control over the hardware costs. The bottom line was that both Dell Computer (Round Rock, TX) and Compaq Computer sell business hardware at reasonable cost."
FIGURE 1. University of Wisconsin recently expanded its mini-PACS system from the radiology department to include a 463-bed hospital that employs 800 physicians and 30 radiologists. The medical staff conducts 250,000 imaging exams a year and generates 14 Tbytes of data per year. Medical facilities include 28 modalities (medical imaging systems) running over 10-Mbit/s connections to the main PACS network. Bandwidth to modalities, 100-Mbit/s connections to the workstations, and Gigabit Ethernet connections along the PACS backbone are set by Hewlett-Packard Procurve 4000M modular switches.
In addition, there were similarities between the existing radiology computer network and ALI's hardware blueprint that eased systems integration. The existing ALI image solution resided on a Compaq ProLiant 8000 enterprise server. A single server solution potentially means less downtime than the ALI-guaranteed 98%+. Triple servers would mean a higher quality of service to the participating clinicians, and dual on-line archives would provide double redundancy, which is not available in most image-archival systems.
At the core of the network resides a cluster of three ProLiant 8000 servers, each providing 2048 Mbytes of RAM and four Pentium III 700-MHz Xeon processors. This server cluster runs the Microsoft Corp. (Redmond, WA) Windows NT and Microsoft Cluster Server software for load sharing, server redundancy, and rebooting in the event of a single-server failure, says ALI's chief technology officer Len Grenier. Two servers are located at the hospital, and the third server is located 0.5 mile away at the Waisman Center.
Wendt implemented a three-level approach for image storage. The fastest and first level of storage is a 3.6-Tbyte, Fibre Channel-based Compaq RA4100 redundant array of independent disks (RAID) that is attached to the two hospital servers by a Compaq Fibre Channel switch. This switch allows either of the two enterprise servers at the hospital to access the image data and the UltraPACS Oracle 8I-based patient information and modality worklist database in the event of a server failure. The RAID stores the medical images in a lossless JPEG format with compression ratios of 2:1 to 3:1. Without this additional storage, Wendt claims, the hospital would fill the RAID array within eight months.
The second storage level includes a Dell 5.8-Tbyte PowerVault 735N network-attached-storage (NAS) rack. This rack comes with a pair of Pentium III 1-GHz processors and 219 Gbytes of standard hard-disk space. Wendt obtains more than 5 Tbytes of storage by adding five external Dell 210S SCSI storage systems to the NAS, each of which brings 876 Gbytes of hard-drive space to the hospital's storage-area network (SAN). Image data on the NAS is stored at 10:1 compression ratio, and data are received from the first-level RAID storage when it is full. Wendt says he chose the NAS method because it has a lower price compared to the Fibre Channel RAID while still maintaining a high access speed for a non-mission-critical storage device.
Backing up all the data is the responsibility of the third-level network-storage equipment—a pair of ADIC (Redmond, WA) Scalar 1000AIT tape drives. Each drive supports 1184 slots and provides 118 Tbytes of data. Images from every modality (medical imaging system) on the university's PACS network are stored on each tape archive using lossless compression. Typical access times range from two to five minutes for an archived exam, which is why the university makes use of the faster RAID and NAS equipment for primary image storage. Each Scalar 1000 is controlled by a Compaq ProLiant ML370 server with dual 733-MHz processors.
The hospital's two Compaq 8000 enterprise servers and local SAN, which comprises the 370 tape server, Scalar 1000 drives, Compaq 4100 RAID, and Dell PowerVault NAS, have been upgraded from standard 10/100-Mbit/s Ethernet to Gigabit Ethernet I/O. The same network approach also has been implemented for the Waisman Center redundant Compaq 8000 enterprise server, 370 tape server, and Scalar 1000 tape drive. Although Compaq manufactures its own chipset, Dell uses the Broadcom (Irvine, CA) NetXtreme BCM5701 single-chip Gigabit Ethernet PCI-X controller with an integrated gigabit copper transceiver.
ALI's Grenier says he pushed for gigabit connectivity along the university's PACS linear topology backbone to limit bottlenecks at the network's core. For the 28 imaging modalities and 14 workstations attached to the PACS network, 10- and 100-Mbit/s connections, respectively, proved adequate. Specific bandwidth allocations are controlled by several Hewlett-Packard (Santa Clara, CA) Procurve 4000M modular switches placed along the linear topology of the PACS network. Each switch offers 40 ports of 10/100-Mbit/s Ethernet connectivity and five expandable slots for Gigabit Ethernet connectivity. Typically, medical-imaging modalities from General Electric (Waukesha, WI), Fuji Film Medical Systems (Stamford, CT), Eastman Kodak Co. (Rochester, NY), and others transmit data at 10 Mbits/s. Via the Hewlett-Packard Procurve switch, the workstations are set at a 100-Mbit/s data rate to speed file access for clinicians. "They still say it would be better if it were faster," Grenier adds.
SEPARATION OF DUTIES
The UltraPACS software, which is based on a client/server architecture, consists of a number of server processes that interact with network clients, including the hospital information system/radiology information system (HIS/RIS), imaging modalities, and review workstations, among others. Four active-server processes in UltraPACS include the HL-7 Data Exchange Server, Digital and Imaging Communications in Medicine (DICOM) Worklist Server, DICOM Importer Server, and ALI Study Server; they all reside on Compaq 8000 servers (see Fig. 2).
The HL-7 Data Exchange Server receives patient order input from the hospital's Siemens Medical Solutions (SMS; Iselin, NJ) RIS database system and stores that information on an Oracle (Redwood Shores, CA) 8i database that comes with UltraPACS.
The HL7 data-transfer language is provided by a standards organization (www.HL7.org) that supports high-level command compatibility between multiple information systems in the medical industry. Some duplication of patient data is required, since the SMS-RIS database is stored separately from the UltraPACS Oracle 8i database. The Oracle 8i database resides on its own RAID drive separate from the directory-organized image data on the other RAID drives.
A DICOM Work List Server separates the orders by modality and creates work lists, which are then sent in DICOM format to control stations for the individual modalities. After an exam is completed, a DICOM Importer Server receives the digital image file from the modality and saves it to the primary image cache on the Fibre Channel RAID drives.
The university has installed 28 medical imaging systems (modalities), including the Kodak computed radiography digital x-ray systems, General Electric LOGIQ 700 PRO ultrasound and 1.5T Signa MR/i High-Speed Plus Magnetic Resonance Imager, and the Fuji Film FCR 500 computed radiography reader, among others.
After a modality has completed its exam, the clinician reviews the exam on one of 14 Dell 420 or 530 workstations. The ALI Study Server checks the Oracle database to determine in which directory the exam is saved. The workstation then directly accesses the storage device without requiring additional communication with the ALI UltraPACS backend server. Workstation imaging software supplied by ALI Technologies allows the clinician to view all standard DICOM image formats, including the DICOM multiframe format (a movie-like format such as AVI or Quick Time). Patient data can be edited and loaded back upstream through the enterprise servers to the SMS RIS database. Clinical reports can also be generated and viewed from the workstations (see Fig. 3).
FIGURE 3. Workstation software module allows clinicians to view DICOM-formatted pictures and access or search for exams using a multiscreen question-and-answer formatted dialog.
These workstations, typically outfitted with a 1.4-GHz Xeon processor and a Matrox Imaging (Dorval, QC, Canada) 32-Mbyte G450 dual monitor video card, are a recent upgrade from the Dell 420 with a Pentium processor. The university PACS includes four workstations with 21-in., 2048 x 1536-pixel, 128-dpi, C3 dual-flat-panel displays from Dome Imaging Systems (Waltham, MA) for showing gray-scale images from the computed radiography modalities. The remaining 10 workstations use Sony 21-in., 1600 x 1200-pixel, CPG-G500 color monitors; these are typically used for the remaining modalities, such as for magnetic-resonance scanners, computed-tomography scanners, ultrasound scanners, and others. Intranet connectivity is provided through resident Intel chipsets in the Dell workstations. Both monitor types were chosen for performance and price considerations, Wendt says.
The University of Wisconsin PACS offers several implementation lessons to companies and institutions looking at PACS emplacements. The initial request for proposal (RFP) issued in 1998 to expand the PACS from radiology to the remaining hospital departments and three external clinics elicited bids from $1 million to $12 million. A second RFP and further negotiations reduced that range to $1 million to $6 million; hardware was the major cost factor. In response to the university's RFP, one integrator said tape archives quoted a cost of approximately $36/Gbyte of storage. After a hardware survey, the university eventually implemented similar tape technology at a cost of $0.6/Gbyte.
Other equipment solutions, such as using an outside application service provider (ASP) also brought high costs. At the university's data-production rate of 14 Tbytes per year and a desire to hold medical records for a minimum of seven years at a base storage cost of $0.01/Mbyte per year for an ASP, Wendt's department would have to spend $325,000 per year for ASP-based storage.
As a result of closely evaluating the hardware selections and choosing a software provider that was flexible enough to support a server cluster with hierarchical data storage, Wendt was able to provide a redundant network that maximized data access for users while minimizing risk and network cost. Despite the savings, Wendt cautions, taking on hardware integration yourself creates its own problems. For example, workstation deployment took several months longer than anticipated, and the university has yet to find a full-time PACS technician and manager.
ALI Technologies Inc.
Richmond, BC V6X 3G5, Canada
Redmond, WA 98052
Irvine, CA 92619
Compaq Computer Corp.
Houston, TX 77269
Dell Computer Corp.
Round Rock, TX 78682
Dome Imaging Systems
Waltham, MA 02451
FujiFilm Medical Systems
Stamford, CT 060902
GE Medical Systems
Waukesha, WI 53188
Santa Clara, CA 95403
Kodak Medical Imaging
Dorval, QC H9P 2T4 Canada
Redmond, WA 98052
Redwood Shores, CA 94065
Siemens Medical Systems
Iselin, NJ 08830
Park Ridge, NJ 07656