Picture archiving and communication system

Last revised by Raymond Chieng on 9 Jun 2023

Picture archiving and communication system (PACS) is a modality of imaging technology which helps in image transmission from the site of image acquisition to multiple physically-disparate locations. This technology not only is economical (film-less department), but also convenient to access multiple modalities (radiographs, CT, MR, ultrasound etc.) simultaneously at multiple locations within hospitals or across the globe.

PACS is usually an integration of 1:

  1. input from digital or digitized analog devices, which may be any radiological modality e.g. x-ray, CT, MRI or ultrasound

  2. image acquisition device

  3. image storage device/server for short or long-term storage of data

  4. transmission network: local area network (within a building, office, department or campus) or wide area network (across a geographical area or around the world)

  5. display stations: imaging workstation and user interface

  6. camera: to convert into hard-copy images on need basis

  7. integration with radiology information system (RIS) and hospital information system (HIS)

Storage media for PACS can be divided into online, nearline, and offline storage. Online storage allows immediate access to data. It refers to hard discs (or hard disc drive) that uses the principle of magnetic discs to store data. Hard disc drives can be connected together to resemble the function of a hard disc with large storage capacity, known as redundant array of inexpensive discs, RAID. Data that does not require immediate access can be stored in nearline storage, namely magnetic tapes and optical jukeboxes. Offline storage refers to magnetic tapes and optical discs that are useful for long-term storage and data backup. However, it would be more time consuming to access the data located in the offline storage 2.

A patient may undergo a battery of radiological investigations at separate locations, which need to be accessed by multiple radiologists and multiple treating physicians in different locations (sometimes across the globe). A system for rapid transfer of images, while maintaining the original quality is a vital, albeit complex technological need. 

Also, hard-copy films are difficult to store and archive, and the quality deteriorates over time (although electronic media are not immune to the latter issue).

Capital cost was a major limitation in the early years but entry of multiple vendors into the market, as well as the geometric increase in processing power and digital storage has significantly brought expense down. The major limitation of PACS or teleradiology devices, is the quality of images, which may be compromised by suboptimal resolution display monitors at different locations. Also, any technical failure, and improper back-up storage may hamper the data retrieval and carries the - rare - risk of massive data loss.

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