Digital imaging is a broad term.
Term was first used medically in 1970s in Computed
Tomography (CT).
Digital imaging is defined as any image acquisition process that
produces an electronic image that can be viewed and manipulated on a computer.
In radiology, images can be sent via computer networks to a
variety of locations.
Uses storage phosphor plates Uses existing equipment Requires special cassettes Requires a special cassette reader Uses a computer workstation and
viewing station and a printer
Method was slow to be accepted by radiologists. Installation increased in the early 1990s. More and more hospitals are replacing film/screen
technology with digital systems.
Picture-referring to images and reports.
Archiving-referring to the film file or film jacket
component of storing images.
Communications-referencing m1ultiple viewers of images
and reports at virtually unlimited viewing sites called workstations.
System-fostering the concept that a complex coordinated
network makes it all possible.
PACS is a medical imaging technology which provides
economical storage of, and convenient access to, images
from
multiple
modalities(source
machine
types).
Electronic images and reports are transmitted digitally via PACS. The universal format for PACS image storage and transfer is DICOM(Digital Imaging and Communications in Medicine).
Early systems did not have standardized image formats. Matching up systems was difficult. Vendors kept systems proprietary and did not share information. DICOM standards helped change this by allowing communication
between vendors products.
A PACS consists of four major components: The imaging modalities such as X-ray computed tomography(CT)
and magnetic resonance imaging (MRI)
A secured network for the transmission of patient information,
workstations for interpreting and reviewing images, and archives for
the storage and retrieval of images and reports.
Combined with available and emerging web technology, PACS has
the ability to deliver timely and efficient access to images, interpretations, and related data. PACS breaks down the physical and
time barriers associated with traditional film-based image retrieval,
distribution, and display.
There are seven basic functions carried out by a PACS system and network:
Image Capture Image Transfer Short Term Storage Long Term Storage Retrieval Image viewing Networking
NonDICOM Modality
Diagnostic Workstations (DICOM)
Clinical Workstations (DICOM)
Web Server
CR QA Workstation Computed Radiography
Film Digitizer
Data Base Server Archive
RIS
The first step in typical PACS system is the modality. Modalities are typically computed tomography (CT) ultrasound, nuclear medicine, positron emission tomography (PET), and magnetic resonance
imaging(MRI). Depending on the facility's workflow most modalities send to a quality assurance(QA) workstation or sometimes called a PACS gateway. The QA workstation is a checkpoint to make sure patient
demographics are correct as well as other important attributes of a study.
If the study information is correct the images are passed to the archive for storage. The central storage device (archive) stores images and in some
cases reports, measurements and other information that resides with the
images.
As the need for distribution of images and reports become
more widespread there is a push for PACS systems to
support DICOM part 18 of the DICOM standard. Web
Access to DICOM Objects (WADO) creates the necessary standard to expose images and reports over the web through truly portable medium.
Digital medical images are typically stored locally on a PACS for retrieval. It is
important that facilities have a means of recovering images in the event of an
error or disaster. While each facility is different, the goal in image back-up is to make it automatic and as easy to administer as possible. The hope is that
the copies won't ever be needed, but, as with other disaster recovery and
business continuity planning, they need to be available if needed. Images may be stored both locally and remotely on off-line media such as tape or
optical media, or partially or exclusively on hard disks ("spinning") media.
The latter is becoming more common. The hard drives may be configured and attached to the PACS server in various ways, either as Direct-Attached
Storage (DAS), Network-attached storage (NAS), or via a Storage Area
Network (SAN).
Made up of different components
Reading stations Physician review stations Web access Technologist quality control stations
Administrative stations
Archive systems Multiple interfaces to other hospital and radiology systems
Early PACS seen only in radiology and some cardiology
departments.
PACS now can be used in multiple departments. Archive space can be shared among departments. PACS reading stations may also have image processing
capabilities.
PACS allows radiologists to reconstruct and stitch images in
their offices.
Orthopedic workstations are available for the following:Surgeons can plan joint replacement surgery. Specialized
software
allows
matching
of
best
replacement for patient with patient anatomy.
System saves time and provides better fit.
