Picture archiving and communication system
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An image as stored on a picture archiving and communication system (PACS) |
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The same image following contrast adjustment, sharpening and measurement tags added by the system |
In
medical imaging,
picture archiving and communication systems (PACS) are computers or networks dedicated to the storage, retrieval, distribution and presentation of images.
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.
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 offered by virtually all the major medical imaging equipment manufacturers.
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.
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.
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 â€" 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. tape libraries or
DVD jukeboxes) onto online disk 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.
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
[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.]. Dr Samuel Dwyer, though, credits Dr Judith M. Prewitt for introducing the term
[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.]*
X-ray*
DICOM*
Computed axial tomography*
Teleradiology, PACS and DICOM Software List of free PACS and DICOM software available on the web
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DICOM info and a list of free tools*
History of PACS
