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In medical imaging, picture archiving and communication systems (PACS) are computers or networks dedicated to the storage, retrieval, distribution and presentation of images.

Types of PACS

Full PACS handle images from various modalities, such as ultrasonography, magnetic resonance imaging, positron emission tomography, computed tomography, endoscopy, mammography and radiography (plain X-rays).

Small-scale systems that handle images from a single modality (usually connected to a single acquisition device) are sometimes called mini-PACS.

Uses

PACS replaces hard-copy based means of managing medical images, such as film archives. It expands on the possibilities of such conventional systems by providing capabilities of off-site viewing and reporting (distance education, tele-diagnosis). Additionally, it enables practitioners at various physical locations to peruse the same information simultaneously, (teleradiology). With the decreasing price of digital storage, PACS systems provide a growing cost and space advantage over film archives.

PACS is traditionally offered by major medical imaging equipment manufacturers at a relatively high price compared to the cost of the hardware alone. The individal workstations are traditionally locked into single use. Typical traditional vendors include INIFINITT, McKesson, GE, Fuji, Kodak, Agfa and the brazilian's Pixeon.

More recently PACS have been developed by specialist PACS vendors such as E-film and InteleRad Medical Systems which both offer software licenses without tying into a hardware purchase from them. Other companies offer open source software, the most successful of these being Osirix which runs on the Apple Macintosh platform and offers unique features such as navigation in 5 dimensions and integration into consumer products such as the iPod or iChat AV for (teleradiology-conferencing).

The most difficult area for PACS systems is interpreting the DICOM image format which is slightly variably implemented between different radiology equipment vendors. The ability to point the tags in the DICOM format coming from vendors equipment to useable titles in a PACS is a feature common to most vendors and software offerings.

Architecture

Typically a PACS network consists of a central server which stores a database containing the images. This server is connected to one or more clients via a LAN or a WAN which provide or utilize the images. Web-based PACS is becoming more and more common: these systems utilize the Internet as their means of communication, usually via VPN or SSL. The software (thin or smart_client) is loaded via ActiveX, Java, or .NET_Framework. Definitions vary, but most claim that for a system to be truly web based, each individual image should have its own URL. Client workstations can use local peripherals for scanning image films into the system, printing image films from the system and interactive display of digital images. PACS workstations offer means of manipulating the images (crop, rotate, zoom, brightness, contrast and others).

Modern radiology equipment, modalities, feed patient images directly to the PACS in digital form. For backwards compatibility, most hospital imaging departments and radiology practices employ a film digitizer.

The medical images are stored in an independent format. The most common format for image storage is DICOM (Digital Imaging and Communications in Medicine), a NEMA standard.

Integration

A full PACS system should provide a single point of access for images and their associated data (i.e. it should support multiple modalities). It should also interface with existing hospital information systems: hospital information system (HIS) and radiology information system (RIS).

Interfacing between multiple systems provides a more consistent and more reliable dataset:

  • Less risk of entering an incorrect patient ID for a study – the PACS will have received a list of scheduled studies from RIS, and can flag a warning if results are received for an unexpected patient.
  • Data saved in the PACS can be tagged with unique patient identifiers (e.g. social security number, NHS number) obtained from HIS. Providing a robust method of merging datasets from multiple hospitals, even where the different centers use different ID systems internally.

An interface can also improve workflow patterns:

  • When a study has been reported by a radiologist the PACS can mark it as read. This avoids needless double-reading. The report can be attached to the images and be viewable via a single interface.
  • Improved use of online storage and nearline storage in the image archive. The PACS can obtain lists of appointments and admissions in advance, allowing images to be pre-fetched from nearline storage (e.g. DVD jukebox) onto online storage (RAID array).

Recognition of the importance of integration has led a number of suppliers to develop fully integrated RIS/PACS systems. These may offer a number of advanced features:

  • Dictation of reports can be integrated into a single system. The recording is automatically sent to a transcriptionist's workstation for typing, but it can also be made available for access by physicians, avoiding typing delays for urgent results, or retained in case of typing error.
  • Provides a single tool for quality control and audit purposes. Rejected images can be tagged, allowing later analysis (as may be required under radiation protection legislation). Workloads and turn-around time can be reported automatically for management purposes.

History

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 1981Duerinckx 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.. Dr Samuel Dwyer, though, credits Dr Judith M. Prewitt for introducing the termSamuel 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.

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External links

Medical imaging

Picture Archiving and Communication System | Picture archiving and communication system | Picture archiving and communication system | 醫療影像儲傳系統

 

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