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Cancer's New Enemy

Building a national mammogram archive

by William Murray

New Architect
October 2002

The creators of the National Digital Mammography Archive (NDMA) have lofty goals: to save money and to save lives. Funded by a three-year, $6.5 million grant from the National Library of Medicine's Next Generation Internet (NGI) initiative, the NDMA project (nscp.physics.upenn.edu/ndma/) lets radiologists at four university hospitals retrieve and view mammography images online. The result is the fusion of leading healthcare and technology—exactly the sort of vision that the U.S. government is looking to inspire with the NGI initiative.

The NDMA project is led by the University of Pennsylvania, where Professor Robert Hollebeek teaches physics and serves as co-principal investigator for NDMA. "[X-rays of] broken bones are not useful year after year, but mammography images are," says Hollebeek. Past mammograms are useful because physicians can compare them to a patient's current scan to detect changes over time. A lump that has been around for years may be harmless, and proper classification as such would prevent women from having to undergo unnecessary surgeries.

Beyond storing patient history, NDMA gives doctors remote access to patient data—another feature that will save time and money for both hospitals and patients. For example, a woman who moves from Pittsburgh, to Phoenix, and then to San Diego can have her new doctor in San Diego view her previous mammograms digitally with the help of custom client software. Researchers and medical residents also will be able to use the archive to learn more about radiology. In addition, archives could help improve the promise of computer-assisted diagnostic tools as an aid to radiologists, according to Hollebeek. The hospitals involved—at the University of Pennsylvania, University of North Carolina at Chapel Hill, University of Chicago, and University of Toronto—each hope to save as much as $1 million per year by bypassing traditional film and development costs.

A system built on the high-speed Internet2 network lets U. Penn radiologists study patient data remotely.

Next Generation

NDMA's architects include five people on Hollebeek's U. Penn team who design and maintain the hardware and network, plus three contractors at Oak Ridge National Laboratory in Oak Ridge, Tennessee, who handle portal security and Java development.

The group works primarily with newer mammogram imaging systems that produce digital images. Older film-based images can be scanned and converted to digital format that is of "reasonable" quality, but not great, according to Hollebeek. Because every last detail in a mammogram is important, images are saved "bit for bit, exactly as presented to us by the hospital," he says. The images are saved in a binary standard known as Digital Imaging and Communications in Medicine.

The project's affiliation with the Next Generation Internet, a government-sponsored initiative that's also known as Internet2, gives NDMA access to an advanced backbone network that can transfer images around the country without data loss or delays. In addition to simply providing users with more bandwidth, Internet2 places guarantees on quality of service—something the standard Internet infrastructure doesn't always deliver.

NDMA accesses Internet2 through Qwest's Abilene backbone. Each participating hospital has an OC-3 connection to Abilene, which gives users 100Mbps connectivity, with sustained throughput of 30 to 50Mbps. "Not everyone has that," says Fred Behlen, principal of LAI Technology of Homewood, Illinois, which is an NDMA consultant to U. Penn. Currently, hospitals that don't have or can't afford such connections can't participate. "We're working on providing some services to clients with low bandwidth connections" he says.

On a 10Mbps connection it takes users eighty seconds to download a 100MB mammogram. Hollebeek calls eighty seconds "beyond the patience level of most radiologists," so some lower-bandwidth hospitals may download mammograms the night before the patient's scheduled appointment. One way to speed the process is to pre-cache images, bringing them closer to the edge of the network. "At the moment, we have not yet implemented any extensive caching because we do not yet need it," says Hollebeek. "But we expect to roll it out beginning next year."

While each of the participating hospitals has an IBM SP2 parallel computer with parallel disks, the heart of the archive is in Philadelphia and has a 32-node rack-mounted IBM e1300 server with high-speed SCSI disks. From January through May, the archive accumulated roughly 142,000 files in test traffic sent from the four hospitals, for a total volume of 1.14 terabytes. Hollebeek and his team members started storing the first clinical data from U. Penn in May. "When [U. Penn] reaches full volume, it will be about sixty a day," he says of NDMA files. That volume should increase two or threefold when the other hospitals are fully online at the end of the summer.

NDMA stores the mammography images in an IBM DB2 database run on multiprocessor, clustered servers. Each image is stored with a corresponding index that provides basic metadata. The group plans to geographically mirror the database in the future.

Privacy and Security

The Health Insurance Portability and Accountability Act (HIPAA) of 1996 calls for health care organizations to audit network user actions, identify and authenticate users, and institute policies and procedures for patient data confidentiality. To ensure HIPAA compliance, the four participating hospitals spent months hashing out interinstitutional agreements concerning each hospital's patient record management and accountability policy.

Whereas a financial institution or military organization would want to gear its security methods to lock out criminals and cyber terrorists, hospital networks are designed to stress user accountability over information security (although both are necessary). A hospital wouldn't want to deny a doctor access to a patient's medical records through the network because it might risk the patient's life. However, network administrators would monitor whether the doctor has rightful access to that patient's data.

The hospitals decided to assign smart cards to each NDMA user. Officials at a systems integrator in Oak Ridge serve as the certificate authority, which means that they maintain a central database with user names, passwords, and privileges. Also, each mammography patient must, in writing, authorize use for the images to become a part of NDMA. Once a radiologist has sent a mammogram for inclusion in NDMA, a local hospital administrator must also approve the image's addition to the archive. Both the data senders and viewers are radiologists.

In planning the system architecture, the group wanted to keep each hospital's network physically separate from NDMA. Archive users access their hospital network with a Windows-based IBM X300 PC, with a companion X300 running Linux that's used for NDMA access. "It just means that if you breach the security of one [network], you don't breach the security of the other," notes Behlen. A software developer at Oak Ridge created Linux drivers for the 3Com network cards that NDMA uses.

Scalability

If the NDMA program succeeds beyond the initial group, it could spread to the estimated 2,000 U.S. hospitals that offer mammography procedures. Because there are fifty-eight million women over forty years of age in the U.S., the annual volume on such a system could exceed 5.6 petabytes if just 60 percent of those women undergo an annual screening exam. (The average exam results in 160MB of data.) The minimal daily traffic in the system would amount to 28 terabytes.

But to grow rapidly to hundreds of hospitals, NDMA must have a "light footprint" and not increase the administrative burden on hospital IT staffs, Hollebeek says. And it has to have some system redundancy and self-healing capabilities. "It's the jump between making something that works in the lab most of the time to something that can work in the field hands-off," adds Behlen. One of the group's plans for reducing the system's impact is to develop easy-to-install portal boxes that provide many of the main features that NDMA users need to interact with the system.

Some of the more ambitious plans for growth include Computer Aided Diagnosis (CAD) tools to help radiologists spot cancerous growths. Robert Nishikawa, director of the University of Chicago's NDMA deployment, is testing a CAD server that scans images, flags potentially cancerous areas, and sends the images to the radiologist. It takes about twenty seconds for the server to process each image.

Nishikawa notes that it makes more sense to deploy a centralized CAD server for all of NDMA—rather than one at each hospital—because it lets the system architects concentrate their resources. "I think it will eventually come down to throughput," he says of the key to NDMA's chances of success. "Deploying multiple CAD servers could enable users to process images faster, but it will take time to determine the best approach, given the available resources."

It remains to be seen whether Hollebeek's vision of hundreds of hospitals using NDMA plays out. U. Penn submitted its follow-on request for 2003 to 2005 NDMA funding this May. Several hospitals have already contacted the university hoping to become part of NDMA, Hollebeek says. Next year's grant will explicitly add some new participants, he notes, but he is cautious about increasing the administrative load too quickly.

"To make the large-scale deployment work, we need buy-in from some major vendors, and there is some work going on in that direction," says Hollebeek. This, too, poses challenges. NDMA architects must ensure that the archive will remain vendor neutral, so local hospital archives can accept each other's records without forcing hospitals to deploy specific products. "The region-to-region interface doesn't have to be a monopoly," Behlen says. "It's intended to be a multi-vendor archive."

In the meantime, the group continues rolling out features that outline the benefits of the NDMA system. At the University of Toronto, hospital officials are using a mobile van to enable radiologists to download mammograms in remote locations like Thunder Bay, Ontario. Such projects show NDMA's promise of delivering remote healthcare, Hollebeek says. "I am firmly convinced that systems of this type will be revolutionary. Sadly, the revolution has not yet occurred, but we are working just as fast as we can to help it along."

William is a freelance writer based in Rockville, Maryland, and has been covering information technologies for the past seven years. Email him at wamurray@familink.com.

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