Picture Archiving and Communication System
Picture Archiving and Communication System Diagram

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Picture Archiving and Communication Systems (PACS) are computers or networks dedicated to the storage (e.g. servers), retrieval, distribution and presentation of images. The medical images are stored in an independent format. The most common format or transmission protocol for image storage is DICOM (Digital Imaging and Communications in Medicine). PACS future began when the radiology department wanted to go to a “filmless” environment and away from film processing.

Picture Archiving and Communication System, used to communicate and archive medical imaging data, mostly images and associated textural data generated in a radiology department, and disseminated throughout the hospital.

The key fundamental components in the PACS are: [1]

1. acquisition devices where the images are acquired, 2. short and longer term archives for storage of digital and textural data, 3. diagnostic and review workstations, 4. a communication network linking the system components, 5. software to run the system, 6. a database and database management, 7. interfaces with other networks (hospital and radiological information systems). [2]

Most image are stored in a DICOM format.[3]


The principles of PACS were first discussed at meetings of radiologists in 1982. Various people are credited with the coinage of the term PACS. Cardiovascular radiologist Dr Andre Duerinckx reported in 1983 that he had first used the term in 1981.[4] Dr Samuel Dwyer, though, credits Dr Judith M. Prewitt for introducing the term.[5]

Dr Harold Glass, a medical physicist working in London in the early 1990s secured UK Government funding and managed the project over many years which transformed Hammersmith Hospital in London as the first filmless hospital in the United Kingdom. Dr Glass died a few months after the project came live but is credited with being one of the pioneers of PACS.

The first large-scale PACS installation was in 1982 at the University of Kansas, Kansas City. This first installation became more of a teaching experience of what not to do rather than what to do in a installation.


PACS Reader

A Cassette Reader

PACS is made up of four basic modalities: A xray/CT/MRI/Ultrasound device, a cassette reader, a laser printer, and a workstation/servers. An archive server, a Redundant Array of Inexpensive Disks (RAID) for short term storage or cache and a long term archive. These devices are the heart of the PACS and normally reside in one or two 42U racks in the hospital’s computer room. Input devices consist of all digital imaging modalities that are used in the Radiology department. These would include such equipment as: Computerized Radiography (CR), Computed Tomography (CT), Digital Mammography, Fluoroscopy, Magnetic Resonance Imaging (MRI), and Ultrasound. For the input devices to pass images to the PACS in a recognized digital format they must conform to the Digital Imaging and Communications in Medicine (DICOM) standard. This insures that digital images are transferred to the PACS in an acceptable manner utilizing DICOM Storage Class User(SCU) and that the technologist utilizing the modality can access a patient worklist via DICOM Modality Worklist (DMWL).

Output devices normally consist of PACS workstations, desktop PC’s, CD burners and laser printers.

PACs Workstation

A Workstation includes computer tower, keyboard, and monitors


The PACS workstations are normally used by Radiologists and will have 3 Mega Pixel (MP) or 5MP 21” grayscale monitors. They are normally in a two monitor configuration which provides ease of use and efficiency in looking at a multitude of radiology exams. Outside of the radiology department, clinicians normally view radiology exams on desktop PCs. If exams need to be transferred outside of the facility they can be sent electronically via a wide area network (WAN) using standard ports and protocols if that type of connection has been established between the facilities. If network connections do not exist between facilities then the exam can be transferred via “sneaker net” by either printing the exam to film from the local laser printer or to CD from a CD burner.

The Broker database transfers and translates the data from one system to another. In the broker model, the PACS vendor supplies the broker and the software, with all maintenance, upgrades, and repairs performed by the vendor rather than the local facility. Whether a linear connection or a broker is used, the matching up of data between the two protocols must be accomplished. Concepts such as patient name, patient identification, other patient data, examination data, and report data relevant to HIS and RIS operations must be buffered against concepts such as patient data, examination data, and image data needed to maintain the PACS database.


PACs Broker - "translator"

The Queue is a temporary working area or place for images to process or wait until the images are done processing or communicating. Basically, it processes incoming and outgoing images using the first in first out concept then finally moves those completed images to the delivered area.

The Network list enables a clinical management system (e.g. DoDs CHCS clinical management system) to retrieve a list of available network connections of patient accession data which the radiologist technician is waiting to x-ray. This listing is pulled off the Network List Managers storage database.

The delivered tab is a final destination where the images are processed, finalized, and sent to be read by a trained- radiologist. Registration is the act of enrolling a new patient in the database. A combination of accession number, patient name, sex, today’s date, date of birth, etc. should be entered into the database. For testing, only the patient name and today’s date are required to continue this segment.


The regular addition and removal of users, password changes, computer component swap-outs, new software, and new equipment means that regular security checks are advisable. In addition, comprehensive intrusion-detection testing should also be conducted every six months, or sooner if there is a major change on a network, experts recommend. Penetration testing, whether actual or simulated, will not only reveal areas of vulnerability but also will prioritize them. Both, vulnerability and intrusion-detection testing should be a regular testing audit for the hospital to ensure modality hardware and software security for the patient.[6]


  1. PACS Fundamentals
  3. |Wikipedia's DICOM
  4. Duerinckx AJ, Pisa EJ. Filmless Picture Archiving and Communication System (PACS) in Diagnostic Radiology. Proc SPIE 1982;318;9-18. Reprinted in IEEE Computer Society Proceedings of PACS'82, order No 388.
  5. Samuel J. Dwyer III. A personalized view of the history of PACS in the USA. In: Proceedings of the SPIE, "Medical Imaging 2000: PACS Design and Evaluation: Engineering and Clinical Issues", edited by G. James Blaine and Eliot L. Siegel. 2000;3980:2-9.
  6. Cynthia Keen. Intrusion-detection testing finds network vulnerabilities. AuntMinnie. August 11, 2008. [1]


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