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Over the last 2 decades, echocardiography has created a tremendous
impact in healthcare. Much of the success of echocardiography
is due to its ability to provide “live” moving
images that can be reviewed and easily understood by all sorts
of health care providers and patients alike. Yet this ability
has been only minimally exploited in the past, given the limitations
of analog technology. Meanwhile, other areas of medical imaging
have adopted digital recording as the standard. The first
efforts in digital echocardiography occurred in the early
1980s. Given storage capacity and processing speed limitation,
digital echo was limited to stress testing and evaluation
of co ronary artery disease, using a quad screen format and
grayscale images. New
technological advances in echocardiography today permit to
register moving images in digital format, allowing logical
archival, rapid data retrieval, copy and transfer, off-line
quantitative analysis, and side-by-side comparison with superior
image resolution. The
American Society of Echocardiography first established in
1992 a task force to educate the echocardiographic community
on the promise and pitfalls of digital echocardiography and
advise the Digital Images and Communications in Medicine (DICOM)
committee on a standard image format for echocardiography.
New!
Approaches to Digital Study
Acquisition
in the
Echocardiography
Laboratory The
problems associated with videotaping echocardiography
studies are well known.“Digital echo” enables
productivity gains through improved workflow by eliminating videotape
and its associated problems, improving access to current
and prior exams, and streamlining
study review. Download
PDF of this article provided by Camtronics.
Analog
vs. Digital Imaging - The principal feature of
analog data is its continuous nature. Their elect ronic
transmission is accomplished by adding signals of varying
frequency or amplitude to carrier waves of a given frequency
of alternating electromagnetic current. Analog data is typically
represented as a series of sine waves
Data
Acquisition - Cardiac ultrasound imaging
equipment obtains initially analog data from the imaging
transducer, where ultrasonic reflections stimulate a piezo-electric
crystal to produce electrical impulses. In order to convert
these electrical impulses into images, they need to be
processed by a computer that analyzes time delay, signal
intensity and frequency shifts in order to determine the
location, density and velocity of each cardiac structure.
Data
Compression - A single frame echocardiographic
image has a resolution of 640 horizontal ´ 480 vertical pixels ´ 24-bits
per pixel, equalling 922 KB. Thus, at an average frame rate
of 30 Hz, a 15 min uncompressed echocardiography study requires
about 25 GB. Handling uncompressed data therefore becomes
impractical, given current storage and transfer speed limitations.
Data
Storage - Once a digital echocardiographic
study is acquired and transferred, it will require
some type of storage. In general terms, it is best
to think
of storage at different levels. Storage for immediate
review of current studies needs to be rapidly accessible,
while long term storage for older studies already
reviewed and interpreted requires higher capacity
and not necessarily
fast speed. There is an inverse relationship between
capacity and access speed and a direct relationship
between speed
and cost.
.
Data
Transfer Network transfer is the most
efficient method to deliver echocardiographic studies
from the acquisition
to the interpretation and to the final storage location.
A network is a series of nodes (input and output devices)
interconnected by communication paths. Networks can be
characterized in terms of spatial distance as local area
networks (LAN), metropolitan area networks (MAN), and
wide area networks (WAN).
Remote
access - One useful feature
of the digital echo lab is remote access capability. In theory,
a client can
be
located at any remote location as long as an Internet location
is in place. There are, however, 2 practical limitations: remote
access speed and data confidentiality. Data encryption should
be implemented for data transmission outside the hospital “firewall”in
order to protect patient confidentiality and to comply with
State and Federal regulations.