Caught up in the high-tech glamour of PACS and teleradiology, radiologists may ignore the nuts and bolts of their in-house workhorse computer network. But they run the risk of installing an extensive PACS setup on a network that will routinely crash and burn.
"When people think about PACS, they forget that one of the most important areas is good support from your in-house IS staff," said Dr. David Channin, chief of imaging informatics at Northwestern University.
During a packed infoRAD session, Channin stressed the importance of thorough PACS network modeling and simulation before installing a system.
"The transmission of information often is overlooked when radiologists think about PACS," he said. "They're looking at fancy displays and archives, but if you don't have a network that can transmit this information, your PACS isn't going to work."
Moreover, a computer network actually plays a more important role than any single modality. If a CT scanner goes down for two hours, patients can be imaged on another unit. But if the computer network goes down, the department will have nowhere to turn.
"When you lose your network, you're dead in the water," he said.
Departments often underestimate the transmission demands placed on a network. A single CR file takes about 8 MB per image, with two to three images per study. CT and MR each need about 30 MB per study.
"That doesn't sound like much, but we do 125,000 CR exams a year and about 32,000 CT studies," Channin said. "Add in MR and you're talking about 36TB per year. That's not a trivial amount."
If daily network demands were averaged over 24 hours, the load wouldn't be too heavy#150;about 5 Mb per second. But "rush hour" demands mean that a network may have to carry 22.5Mb per second.
"If you build it they will come, and however much bandwidth you provide, they will find a way to fill it," Channin said.
With off-the-shelf modeling and simulation software available from companies like CACI (www.caci.com), departments can experiment with network needs and figure out where bottlenecks could occur.
"You can reengineer with modeling software before you spend your PACS money," Channin said. "You want to make sure that a single modality like CR isn't hogging all your bandwidth."
Modeling also helps departments determine how much they'll have to spend on their network to meet PACS needs. Sticker shock is common, and modification to a PACS may be necessary to stay within the bounds of network capacity.
