Picture Archiving and Communication System - Image Archival and Backup

Image Archival and Backup

Digital medical images are typically stored locally on a PACS for retrieval. It is important (and required in the USA by the Security Rule's Administrative Safeguards section of HIPAA) that facilities have a means of recovering images in the event of an error or disaster. While each facility is different, the goal in image back-up is to make it automatic and as easy to administer as possible. The hope is that the copies won't ever be needed, but, as with other disaster recovery and business continuity planning, they need to be available if needed.

Ideally, copies of images should be streamed off-site as they are created. (If using the Internet, the Security Rule's Technical Safeguards section of HIPAA requires that the images be encrypted during transmission.) Depending on upload bandwidth and image volume, this may not be practical if the back-up system cannot be configured to tune bandwidth usage and frequency of back-ups. Other options include removable media (hard drives, DVDs or other media that can hold many patients' images) that is physically transferred off-site. The content of these copies must be protected via encryption from exposure to unauthorized personnel or stiff penalties can be assessed.

Images may be stored both locally and remotely on off-line media such as tape or optical media, or partially or exclusively on hard disks ("spinning") media. The latter is becoming more common. The hard drives may be configured and attached to the PACS server in various ways, either as Direct-Attached Storage (DAS), Network-attached storage (NAS), or via a Storage Area Network (SAN).

However the storage is attached, the drives themselves are usually configured as a Redundant Array of Inexpensive (or Independent) Discs RAID, which may be configured to provide appropriate combination of faster disk access or protection against the failure of one (or even two) discs in the physical RAID array. Typically, failed drives may be physically replaced (hot swapping) without interruption of service. Since costs of computers has fallen, some sites opt for fully redundant Archives, rather than just protecting the drives through RAID. Further, RAIDs are fragile and can be rendered useless by one erroneous hit on the controller.

Data stored on disk may also be backed up to tape or optical media or copied, in real time, to a slower, inexpensive disc in another machine at another location. Some sites make two such backups and remove them from the site on a rotating basis.

In the event that it is necessary to reconstruct a PACS partially or completely from the back-up images, some means of rapidly transferring all of its images back to the PACS is required, preferably whilst the PACS continues to receive and provide current images.

The back-up infrastructure may also be capable of supporting the migration of images to a new PACS. Due to the high volume of images that need to be archived many rad centers are migrating their systems to a Cloud-based PACS.