MiniPACS networks bring advantages, integration challenges

MiniPACS networks were once a popular stepping stone to PACS for many imaging facilities not ready to make the jump into a department- or enterprise-wide digital image management system. Increasing adoption of larger PACS networks has reduced the role of miniPACS, but such networks still exist, and integrating them with a departmental PACS is feasible, according to Dr. Steven Horii of the University of Pennsylvania Medical Center (UPMC) in Philadelphia.

"MiniPACS exist to fill a gap that main PACS vendors have in their systems," said Horii, associate director of UPMC’s medical informatics group. "It is practical to run two systems, but careful planning helps for how they are to be interfaced or integrated."

Horii discussed miniPACS issues during PACS 2004: Working in an Integrated Digital Healthcare Enterprise in San Antonio, sponsored by the University of Rochester School of Medicine and Dentistry in Rochester, NY.

For users who have or are planning to install a departmental PACS network, a miniPACS can still serve a purpose, Horii said. An institution may already have a pre-existing miniPACS in place, or a PACS vendor can't support certain necessary functions.

For example, some vendors of departmental PACS networks may not be able to fully accommodate nuclear medicine studies, with their quantitative operations and image mathematics, Horii said.

"A lot of vendors of the main PACS workstations don't support this sort of thing," he said.

Other areas typically beyond the scope of larger PACS vendors include ultrasound, with its usage of cine loops and measurements on Doppler waveforms, as well as radiation therapy planning systems, Horii said. They all require the use of color displays.

With a pre-existing miniPACS, it's important to note that there's likely to be a sizeable archive; interfacing the miniPACS to the main PACS may be a simpler and less costly approach than replacing it and converting the database, Horii said. Institutions may also elect to keep the miniPACS going as part of a phase-in strategy, with the goal of eventual replacement.

MiniPACS networks can also serve as an element of a reliability strategy, splitting out certain critical PACS components as part of a miniPACS integrated with the overall system, Horii said.

"A system like this may actually be operated in parallel with a full PACS," Horii said. "If the mini- or full PACS fails, the working system can sustain operations."

At UPMC, the departmental PACS vendor initially was not able to support all of the functions needed for reading ultrasound studies, necessitating an ultrasound miniPACS, Horii said. After five years of serving UPMC, however, the initial miniPACS vendor left the market, and UPMC has since switched to a new vendor.

Today, the miniPACS supports DICOM modality worklist, a feature that yields vastly improved technologist productivity, Horii said.

"Our ultrasound volume has gone up about 17% in the last three years or so, and we've actually lost one sonographer FTE during that time," he said.

The ultrasound miniPACS captures cine loops and allows for flexible image playback, and can measure or remeasure images, including frame-grabbed and Doppler waveforms, he said. It also provides color support.

The miniPACS is not presently integrated with the departmental PACS, an intentional decision as UPMC was also planning to switch its main PACS vendor and didn't want to invest resources to integrate with a PACS that was going to be replaced, Horii said. About a year's worth of images are available online, and images are being archived in the storage system of the new departmental PACS.

A few integration issues have come up. For example, the vendor is supposed to provide the ability to view other DICOM images on miniPACS workstations, a capability that has yet to be delivered, Horii said. In addition, DICOM modality worklist operates through the RIS-PACS broker back to the ultrasound machines.

While the ultrasound scanners support DICOM performed procedure step and structured reporting, the PACS vendor and the miniPACS vendor don't currently support any of those features, Horii said.

 "Our technologist still has to get into the RIS and conclude the exam after the study is done," he said.

Speech recognition is not integrated into the miniPACS, and there's also no access to reports on the RIS from the miniPACS, Horii said. In addition, the ultrasound scanners support DICOM storage commitment, but the miniPACS doesn't.

Integration models

If you have a miniPACS network, and want to integrate the system with a departmental PACS, there are a few ways to go, including duplicate storage, duplicate online storage, and separate online storage with a single archive.

The best model depends on the capabilities of the miniPACS network and the ability to store information on the main PACS network from miniPACS or directly from image sources, Horii said. Another issue relates to the database of the main PACS, and to whether it can store studies coming from another PACS.

Duplicate storage, in which the studies are stored on both the miniPACS and main PACS archives, is typically used when the two systems can't be readily interfaced, Horii said. Images are sent to both systems from the image acquisition equipment, and two viewing applications or workstation types are employed, he said. With this model, the miniPACS may have to have its own enterprise-wide distribution method.

"If you're using a Web-based distribution system, you either have to be able to send images to those servers, or your system has to be able to do Web distribution on its own," Horii said.

Duplicate online storage approaches can be used when the two systems can be interfaced, Horii said. In this model, the miniPACS would handle only short-term online storage requirements, with the main PACS archive storing the images long-term.

Images are sent to the main PACS storage system either from the image source directly or from the miniPACS online storage, and are then available for distribution and archiving, Horii said. With this model, each system has its own viewing applications and workstation types, with the main PACS handling image distribution, Horii said.

Instead, UPMC uses a separate online storage/single-archive approach, suitable for cases where the main PACS can't handle display of the miniPACS images, but can store them. The miniPACS stores studies online and distributes them to dedicated applications, and the miniPACS archives studies on the main PACS and can retrieve them, Horii said.

Other integration variations include tasking the main PACS network to handle online storage for miniPACS, sending images back only as far as the miniPACS network and not to the main PACS workstations, Horii said.

As a caveat for miniPACS, Horii said there's a reason miniPACS exist and are still being used.

"You may get vendors that tell you, 'Well, we can deal with ultrasound and nuclear medicine,' but if you look around, you'll find that there's a lot of places with a model similar to ours, that have a separate system for ultrasound and a separate system for nuclear medicine," Horii said. "Before you accept that a main PACS vendor can support all of the functions that the miniPACS does, you want to see that demonstrated in use and not just as a demo."

By Erik L. Ridley staff writer
April 29, 2004

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Copyright © 2004

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