PACS archive storage performance (there's never enough or it's not fast enough) and cost (always too much) continue to concern PACS administrators. Yet media performance continues to trend upward and prices reciprocally slide downward, according to presentations at the RSNA meeting Wednesday.The reason for the conflict is the pressing need to store exams that continue to grow in volume and size. A single digital mammogram can exceed 30 MB. A CT chest study can create 140 images in less that 20 seconds, creating 73 MB of data. Biplane rotational angiography machines using image intensifiers produce eight to 32 images per tube rotation, easily generating 500 MB per study. Some ultrasound units are able to capture cine loops, which generate 24 MB of data every second from 30-image loops.
Relief is just a paradigm shift away. Next-generation storage media will include holography, which may ease the burden on jukeboxes and redundant array of inexpensive disks (RAID) devices employed by hospitals to archive digital images. Theoretically, this technology can store trillions of bytes in a piece of crystalline material the size of a sugar cube or a standard CD platter, using transfer speeds not possible with current electromagnetic methods.
A research effort organized and cofunded by DARPA (Defense Advanced Research Projects Agency), attracted the usual cutting-edge players -- IBM, Rockwell, Lucent Technologies, and Bayer -- all of whom are striving to produce a practical commercial holographic storage system within the next decade.
Already, Aprilis, a startup in Cambridge, MA, has demonstrated a holographic system capable of storing 100 to 1000 Gb per disk at transfer rates from hundreds to thousands of Mb per second, according to Glen Horner, Ph.D., Aprilis' vice president of business development.
Horner said Aprilis hopes to have a system suitable for medical applications available within two years. It would be capable of storing 100 Gb per disk, or thousands of images. A typical CD can hold about 60 average CT exams. These holographic disks are as removable as today's CDs, which reassures PACS and IT administrators concerned with PACS archive backup and disaster recovery planning.
Another attractive aspect is cost.
"The system has been designed from the ground up to be priced in the moderate to low range," Horner said.
The Aprilis system's specifications call for an eventual capacity of one Tb on one disk, and a sustained data rate of 6 Gb per second using a single optical head. Right now channel speed is limiting the system to a transfer rate of 1 Gbps.
"At the time the pipes were designed no predicted the need to handle speeds greater than 1 Gbps," Horner said. "We'll go even faster once channel speeds improve."
