review article picture archiving and communication system - rbrs

non- or pre-DICOM communication
standards between their modalities
and workstations with a special
gateway to the outside DICOM
world (5).
PACS-RIS-HIS integration
A fundamental tenet of current
PACS implementations is that
images should not be available
without information. Therefore, each
PACS has a mechanism for linking
the pertinent patient information
(e.g. demographics, clinical history,
allergies) with the image. Each
image data set must be “labelled”
or identified with a specific patient
and linked to a patient folder or
some other useful construct within
PACS. Therefore, there are two components
to a PACS archive. One
component is the database that
maintains patient metadata information
and the other component is
the file server that actually stores
the image data sets (37).
Current PACS with secure
Internet or Intranet web techniques,
enables rapid and simultaneous
access to images in different physical
locations. With prompt interpretation
and voice recognition technology,
reports should be available
rapidly and may automatically be
associated and delivered with the
images (36). However, such successful
PACS implementation requires
RIS and HIS integration.
Many institutions already have a
HIS or RIS in place in addition to the
PACS information system. Ideally,
these systems should be integrated
for image management. The most
important roles of HIS related to
PACS are to provide a “clean” master
patient index that identifies
every patient uniquely on a one-toone
basis, as well as to provide
admission, transfer, and discharge
information. The RIS provides notification
of events – particularly the
scheduling of an imaging procedure,
with relevant clinical information.
The RIS provides unique identification
of the imaging procedures
requested and performed, allowing
PACS to handle and archive them
unambiguously, and to associate a
diagnostic report with each
study (36).
Problems may occur even with
highly integrated PACS-RIS-HIS.
One of the most bothersome is that
the PACS database, even with the
best pre-fetching, usually is
unaware of prior studies existing
only on film. In addition, the present
RIS database usually does not dis-
PICTURE ARCHIVING AND COMMUNICATION SYSTEM — DE BACKER et al. 239
tinguish between studies on film
and those archived digitally, without
film (36).
For most cross-sectional examinations,
such as CT and MRI, the
technologist manually enters
patient demographic information
into the acquisition device. The
study and associated information
are then “pushed” into PACS via a
gateway (preferable using the
DICOM standard). PACS then needs
to handle or deal with both the
image data set and associated information.
If a HIS/RIS/PACS communication
link is in place, then PACS
attempts to match the incoming
study with what exists on its database.
If a discrepancy occurs, PACS
may reject the study (i.e., not allow
into the system), place it on the special
list (e.g., “unspecified folder”,
“exceptions list”, or “penalty box”),
or create a new patient folder (i.e.,
new study) with the erroneous data.
This scenario is not uncommon
because dual entry of patient information
is fraught with problems,
including a substantial potential for
misspelling and other alphanumeric
data errors (e.g., transpositions).
Another problem that is not specific
to digital image storage but in a full
PACS environment occurs when a
patient has been assigned a new
patient identification number in the
HIS or RIS on a repeat visit to the
hospital. This results in previous
images not being found in the PACS
archive. In both situations operator
intervention is required to rectify the
situation. An operator must then
have access to a PACS workstation
to identify the problem and accomplish
a solution “after the fact” (5,
38).
PACS should be considered part
of the hospital infrastructure with
distribution of radiological images
throughout the hospital. Through an
appropriate HIS/RIS/PACS interface,
the current location of a patient in
the hospital is made known to PACS
to enable the correct distribution of
images to the clinics and wards. In
the future, viewing of radiological
images should become an integrated
part of the HIS. Both to assure
data security of the PACS archive
and to provide fast access to the
users, image distribution throughout
the hospital should be accomplished
by using one or more separate
image servers (5).
PACS workflow
Early PACS installations focused
on just providing the most basic
PACS functions, image retrieval and
viewing. Workstations were rather
clumsy and tended to reflect a lack
of experience and understanding of
radiologists’ work habits. Continuous
technological improvement and
better understanding of workflow
within PACS resulted in a broader
level of acceptance by radiologists.
Workstation design and system
architecture have improved as many
institutions and manufacturers
actively involved radiologists in the
design process, resulting in the
development of user-friendly workstations
that are more suitable for
the radiologists’ task.
The smooth flow of images to the
location at which they are needed, at
the time they are needed, and displayed
in the preferred manner as
required by the radiologist to
achieve both with efficiency and
high diagnostic accuracy, requires
management of the studies. This
study management, often referred
to as folder management, provides
PACS with intelligent functionality
for image acquisition, routing, storage,
presentation, and retrieval
functions (36,39). For example,
when a patient is scheduled for a
given type of procedure, the workflow
manager will know where the
images are likely to be viewed, what
prior studies are relevant and prefetch
these studies from the longterm
archive and then to the workstation
before the arrival of the
images from the current study.
Reports from prior procedures will
be available at the workstation.
When the study is completed the
images are automatically sent to
PACS and routed to the appropriate
workstation. When the new study is
called up for review, images appear
in the correct sequence and at the
appropriate window width and
level. Prior images are available
immediately for display.
To ensure an ergonomic interface,
an operating system based on
the windows metaphor may be used
for the viewing station. Image preprocessing
with its potential to
improve visualization of certain radiographic
findings may often be very
time-consuming with current workstations
and, therefore, is rarely
used in clinical routine. However,
many preprocessing tasks could be
automated by appropriate software.
Automatic arrangement of images
in pre-set orders and managed by a
rule-based system may be provided.
In soft-copy viewing of radiological
images, it is often desirable to block
out white, unexposed image areas.