The Bristol Oncology Centre found that compared with the new 5.2Gb magneto optic disks, CDR media’s capacity and robustness left a lot to be desired
Large capacity storage using Magneto Optical (MO) technology has been somewhat overlooked by the majority of organisations. However, within the medical, financial and academic sectors, optical storage solutions have been embraced for their low cost per Mb and legendary durability.
MO, although similar in form factor to writeable CD-ROM, differs primarily in storage capacity. A 51/2in disk can store over 5Gb of data on a highly robust platter surrounded by a protective cartridge. MO is not new, the first models and standards appeared in the early 1990s, and the technology has evolved to faster and higher capacity solutions.
Where MO has seen an increased popularity is in mission critical archiving and the migration of older tape archives into almost real time retrieval systems. Archive managers tend to stick with the MO solution once implemented, as many of the newer drives will also read older disk formats like 250Mb and 600Mb MO disks.
The Bristol Oncology Centre (BOC) is one such organisation that required a highly reliable data solution for their centralised image server. BOC is part of the United Bristol Healthcare NHS Trust (UBHT). Funding for the Centre comes mostly from two large purchasing health authorities: Avon Health Authority and Somerset Health Authority. The Centre treats about 4,000 new patients each year and is well known as a centre for clinical excellence.
The Centre has radiotherapy and chemotherapy departments treating cancers as well as dedicated CT scanners to help plan and analyse patient treatment. The CT scanners and digital radiographs generate complex images stored in huge data files. These images need to be both highly accessible, yet held reliably with total confidentiality.
The data generated by BOC is essentially write-once. Initially, inexpensive CD-R media were considered. However, there were concerns over the small capacity (650MB) and robustness of CD-R media compared with the new 5.2Gb magneto optic disks, which are widely used as the archive component of medical image servers. This, coupled with very little saving in the overall costs, kept MO as the preferred medium.
Paul Stevens, technical manager at the Centre, was charged with finding a cost-effective solution and says: "We might have come to a different conclusion if 5.2Gb disks had not been introduced or if a mature write-once DVD technology was available." Having evaluated a number of data archiving technologies, the chosen solution was from K-PAR using Plasmon Multifunction Magneto Optic Jukeboxes. The solution was based on Sun Microsystems server, centred around K-PAR's Archimedia Archive Management Software, a sophisticated jukebox management system designed to drive both MO and CD jukeboxes. Archimedia overcomes many of the problems normally associated with jukebox systems, such as slow response times, by caching key information on the hard disk.
The hardware installed was a Plasmon M-Series MO with advanced direct-drive robotics with dual picker assemblies. The 5.2Gb disk can be scaled to provide up to 2.6 Terabytes of storage. Regardless of where media is stored in the jukebox, the robotic picker system delivers the requested disk to the optical drive in approximately one and a half seconds, then performs an exchange operation without additional movements to cartridge storage slots. The jukebox design across the range also incorporates a convenient mechanised import/export element for fast and efficient online loading.
Stevens was happy with the final solution saying: "Our image server uses a Sybase database which stores medical images as individual files in what will be the industry standard DICOM format. Archimedia software makes it easy to add archiving to this image server software and provides the ability to automate the archiving of data from the planning systems and clinical documents using the same jukebox."
The system was implemented within eight months with the help of Productivity Computer Solutions, a specialist in Solaris systems and medical imaging.
Stevens explains how they intend to meet future requirements. "Future plans include obtaining the radiographs used for planning in digital format and to digitise conventional X-rays. All this equipment is networked, including the linear accelerators used to deliver the treatment. An essential component is a central image server using DICOM 3.0 (Digital Imaging Communications in Medicine) protocols to transfer plans and images. As a further example of the active development in networking in the Centre, we expect to provide access to all images from the PCs in doctors' offices in the near future."
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