Picture archiving and communication system

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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. The term 'PACS' was first used by Dr Andre Duerinckx.

1 Types of PACS
2 Uses
3 Architecture
4 Integration
5 See also
6 External links

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Types of PACS

Full PACS handle images from various modalities, such as ultrasonography, magnetic resonance imaging, positron emission tomography, computed tomography, 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.

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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 archival.

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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 and/or utilize the images. 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 feeds images directly into 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).

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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.

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