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Stentor: Just what the doctor ordered

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The diagnosis at Ann Arbor Veterans Administration Healthcare System in Michigan was that X-ray film system costs were skyrocketing and the healthcare facility needed a faster way to get images to doctors. The prescription: Bring in Stentor imaging technology to deliver X-rays over the hospital intranet without requiring a network upgrade.

Today, physicians and clinicians at the hospital do their X-ray, CAT scan and magnetic resonance imaging (MRI) result viewing on a standard PC, rather than putting film up on a traditional device known as a lightbox. Now doctors and staff can log on to a PC, select a patient and pick which images they want to see. Multiple images can be selected from different series (sets of images) taken over a period of time to make comparisons.

Three years ago, the hospital moved to a filmless radiology department, a move that cut developing and film costs about $110,000 annually, to $20,000 per year. The move also helped eliminate lost X-rays and films, which had to be reprinted, taking time away from patient care. Despite the move, viewing images was still cumbersome and expensive. A $60,000 super-high resolution view station was needed, retrieval was slow, and the view station needed to be recalibrated monthly.

Recently, the hospital brought in iSite Enterprise from San Francisco company Stentor to serve the images over the intranet.

"We give [the staff] the tools they need on a PC instead of making them come to the radiology reading room and using the $100,000 workstations the radiologist use," says Leann Beird, the Picture Archival and Communication Systems (PACS) administrator at the VA hospital.

Big files

Delivering high-quality X-rays over an intranet is a challenge considering a single CAT scan "slice" is 1M byte in size, and there can be up to 800 slices in a series. Images must be delivered in full fidelity and cannot use compression techniques that result in any type of image quality degradation, which would be bad news when examining a chest scan for possible tumors.

To solve the problem, Stentor uses wavelet algorithms, which reduce an image into layers that are delivered as needed over the network without the need for compression. Only the part of the image being viewed on screen is delivered.

"When a clinician is looking at a study, it's like reading the newspaper: You can the headlines then drill down from there to zero in on an article to read," Beird says of the wavelet technology. "The same is true for medical images."

In July 2000, Beird replaced the expensive stations with Dell PCs equipped with 1600 Superwide SGI flat panel monitors and 3D Labs Oxygen graphics cards.

"We get the same resolution as the $60,000 station for $1,500," Beird says.

At the core of the architecture is PACS, a 17-terabyte StorageTek system that replaces need for hard copies of X-rays. The hierarchical storage system runs on a Sun 4500 Unix box.

When a patient has an X-ray, CAT scan or MRI, the images are delivered first to the PACS system for storage. From there, images are sent to the Stentor iSite, a Web server running custom image delivery software.

The Stentor server runs on a Compaq Proliant dual-Xeon processor box with a RAID storage array that warehouses about six months' worth of images. Soon, a 1-terabyte RAID array, capable of handling a year's worth of images, will be installed, Beird said.

Images for inpatients are kept on the Stentor box the longest, with single images that will only be used once dropped first. Everything is stored for at least five years on the PACS and can be pushed to the Stentor server if needed.

Stentor monitors its product externally, making sure the operating system and applications are running properly. In late October it helped the hospital as a construction crew accidentally cut the hospital's OC-12 connection to the outside world, and Stentor was the first to notify Beird that something was wrong because they could no longer "see" the server.

Solid foundation

The VA hospital's network infrastructure includes a Gigabit Ethernet backbone connected to a Cisco 6500 router with single strands of fiber running to network closet containing a Cisco 3500 switch. All clients have Fast Ethernet cards in them.

"We've had no bandwidth issues," Beird says, adding there could be 200 to 300 people viewing images simultaneously.

If that many people simultaneously tried to download the full image, the network would slow to a crawl.

Users can access the Stentor server directly through a Web browser (a plug-in is downloaded) using the same logons and passwords they use for the network, or via the patient record system. A VA programmer built the interface to the medical records system. Included with the image is the radiology report, a text document explaining the findings of the study.

Images also are accessible from 15 PCs at nearby University of Michigan, which lets physicians teaching at the school access important patient data. Access can also be granted via the national Veteran Administration Intranet. A logon needs to be issued to those on the national Intranet.

Groups such as the Tumor Board - which includes physicians from different departments who review cancer patients' progress and prognosis - use the imagine technology in their reviews. A laptop attached to a high-resolution projector is used to view the information.

Another benefit of the Web technology is that it's easy to learn. Ann Arbor is a teaching facility, with staff rotating between the hospital and university classrooms on a monthly basis.

Beird says it's easier to teach users the Web system in a short period of time, something necessary with a lot of staff turnover.


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