Auxiliary archive aims at long-term thin-slice storage

A new thin-slice archive scheme has been proposed to more efficiently deal with the huge number of images generated by multislice CT scanners and the demands of 3D image processing.

To meet storage, retrieval, and associated 3D processing demands, researchers at the University of Maryland School of Medicine installed a 4-TB thin-slice archive alongside their PACS. Now, while thick-section (3 to 5-mm) data sets captured at the modality are routed directly to the PACS, thin slices (<1 mm) are automatically sent to the central 3D archive.

The technique, documented in a recent paper (J Digit Imaging 2006;Sep 20), allows 3D models to be created on the fly with server-side rendering for real-time delivery to radiologists.

According to Christopher Meenan, director of clinical information systems at Maryland, this approach has several advantages:

• a single destination for routing, with fewer demands on technologists

• real-time access to 3D data across the enterprise

• online demand query and retrieval access for thick-client specialty workstations

• longer term access to thin-slice data

The technique addresses a lingering problem of how to manage the deluge of data streaming from new modalities. As the number of images per study has increased, facilities have been forced to devise strategies for handling thin-slice CT data, schemes that usually mean circumventing their PACS.

Most commercial PACS are unable to deliver thin-slice data to the desktop in real-time or provide acceptable performance to radiologists or clinicians when processing these data.

"Without a centralized architecture in place, technologists must manually route images directly to the point of care each time access is required," Meenan said.

With CT data sets now measured in gigabytes, it becomes impossible to provide CT data through manual routing.

In many clinical settings, thin-section CT data are discarded after a short time because of storage limitations on CT scanners, stand-alone advanced workstations, and PACS archives.

One facet of the Maryland research was to explore whether thin-slice data had enduring diagnostic value. The researchers did this by asking radiologists for their opinion on the value, diagnostic use, and retention requirements of thin-slice data.

"We found that surveyed radiologists thought thin-slice data had real diagnostic value and that they wanted access to this data for an extended period of time," Meenan said.

At present, their archive holds slightly less than 90 days of storage, even after doubling storage capacity to 8 TB.

One of the survey responses said saving thin-slice data forever would be better.

Meenan and colleagues believe that permanent storage of thin-slice data as part of the PACS, and as part of the permanent medical record, will eventually be recognized as best practice and will become a mission-critical pursuit for healthcare IT professionals.

"We see server-side rendering as a real solution to the problem of delivering large-volume CT data sets to the enterprise in real-time," he said.