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Background.
To date, in most echocardiography laboratories,
acquisition and archiving of diagnostic echocardiographic images is
performed analog technology (recording on videotape). This technology,
in use in the past 30 years, has advantages and drawbacks. Among the
advantages are the low operative and archiving costs, and ease of use.
Disadvantages are represented by an immediate loss of quality of
archived images when compared to originals acquired by the ultrasound
equipment, the progressive loss in time of videotaped image quality, the
long time required to retrieve archived images, the difficulty to
compare side by side studies obtained at different times with an ensuing
negative impact on the diagnostic accuracy of the echo lab. Finally, the
impossibility to manage fully digitally - in both administrative and
scientific settings - the echo lab.
Based on these considerations, the transformation of the
echo lab from analog to digital technology has been advocated by
many. Digital technology would obviate all problems related to the use
of analog technology (1). But, in most echo labs,
digital (online) technology is applied only to echo reporting, and
usually only in text
mode. However, the (technically simple) strategy of
digitalizing only the echo report does not take into account that
imaging and not reporting is central to the echocardiographic
examination. Further, the echo examination – in that it is not only
tomographic but also (mainly) dynamic – may be adequately
reproduced only by archived dynamic image sequences.
The main functions of the digital echocardiographic
laboratory (DEL) may be summarized as:
1. Digital
aquisition, archiving and retrieval of still images and image
sequences.
2. Production
and archiving of the echo report.
3. Diagnostic,
scientific, educational, and administrative digital management of the
echo lab (random access to images; image reproduction without loss of
original quality; simplified side by side comparison of online and
archived images; remote retrieval of studies)
4. The
possibility to effectively introduce quality control in the echo
laboratory.
The drawbacks related to the introduction of digital
technology in the echo lab may be summarized as follows:
1. High
(or very high) initial costs, as related to the relatively low budget of
an echo lab when compared to other imaging techniques (angiography,
radionuclides, computed tomography). The minimum initial cost required
to start digitalizing echo images with a single echocardiographic
machine is approximately $25.000 for commercially avaliable equipments.
2. Proprietary
hardware and software, from different vendors, and thus difficult to
interface.
3. A
highly "technicalized" environment, when compared to the
analog echo lab.
And it is because of these drawbacks that the analog to
digital transformation of the echo lab - though advocated by many - has
been completed only in a very limited number of echo labs around the
world.
Aims.
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The present project has the aim to realize the trasformation from analog
to digital technology of the echo lab through the creation of a hardware
/ software system that stems from the joint efforts of a software
engineer and a cardiologist echocardiographer. The original software
program will be supported by an "off-the-shelf" hardware
architecture. The software system will be dedicated to digital
acquisition, and ensuing manipulation, reporting and archiving of images
produced by any ultrasound machine equipped by a s-VHS video output. The
integrated software/hardware system will address and solve each of the
above mentioned problems related to digital echocardiography, so to
offer a practical soution characterized by:
1. Minimal
initial costs
2. Complete
compatibility
3. Simplicity
of use
Project.
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The main characteristics of the project – given the
phylosophy underlying the project - will be the possibility to
provide the end user a complete system at a very low cost, accessible by
a single professional:
1. low cost of required hardware components
(because not limited to the medical hardware environment)
2. elimination of initial elevated project costs
secondary minimized "engineering: costs (a single software engineer
and a single cardiologist)
The system will be based on the utilization of a PC with
a Windows 2000ä
operating system.
After the initial software engineering phase and its
integration with a multimedia PC equipped with a digital analog (s-VHS)
to digital acquisition board and a CD writer, the system will be tested
in a Level III echocardiography laboratory, to optimize
echocardiographic image acquisition, archival, retrieval and reporting
protocols. Specifically, different acquired image compression algorythms
will be analyzed, as related to the clinical quality of the images and
the storage space utilized on the CD-Rs.
The system provides long-term echo study archiving on non
rewritable CDs, to preserve original image information (foreseeing
probable legal implications of long-term clinical image information
storage).
A fundametal characteristic of the project is the
acquisition of the echo study images through the s-VHS video output of
the ultrasound equipment, thus providing total compatibility with any
commercially available (and older) ultrasound machine, independent from
any proprietary storage system provided with the machine. It is
important to note that recent clinical studies have evidenced that the
resolution provided by the s-VHS video signal is, in the diagnostic
setting, sufficient (2, 3). Another
advantage of the project is the creation, and thus online availability,
of libraries of file names
(for both acquired still frames and loops)
and of standardized diagnostic comments and conclusions for echo
reporting, following published recommendations of the American
Society of Echocardiography and the Italian Society of Cardiovascular
Echography (4).
The different phases of the project are the
following:
1. Determination
of the required hardware components necessary for the integration with
the software of the project. A) Determination of the hardware
necessary to digitalize in real time echocardiographic moving images,
with the best cost/performance ratio, taking into account compatibility
with the Windows 2000ä
operating system. B) Determination of the most appropriate
storage media, given the large quantity of data generated by digital
acquisition of moving images.
2. Construction
of the software necessary to manage digital acquisition, archiving, and
reporting of the echocardiographic examination, with a simple to use
user interface. Initially, the software will function as a
"stand-alone" system (not connected to the hospital
network).
3. Study
of the best (optimal) compression ratio obtainable online during
image digitalizzation, so to increase the image quality / storage volume
ratio.
4. Extension
of digital technology to the entire echo lab, connecting the single
hardware/software systems to the local net, thus providing the hospital
network with the possibility to retrieve single studies through
eventually a CD-R jukebox.
Published: August 1999
References:
- Thomas
JD, Main ML. Digital echocardiographic laboratory: where do we stand
? J Am Soc Echocardiogr 1998;11:978-83.
- Soble
JS, Yurow G, Brar R, Stamos T, Neumann A, Garcia M, Stoddard MF,
Cherian PK, Bhamb B, Thomas JD. Comparison of MPEG digital video
with super VHS tape for diagnostic echocardiographic readings. J Am
Soc Echocardiogr 1998;11:819-25.
- Karson
TH, Chandra S, Morehead AJ, Stewart WJ, Nissen SE, Thomas JD. JPEG
compression of digital echocardiographic images: impact on image
quality.
J Am Soc Echocardiogr
1995;8:306-18.
-
Scarpini S, Badano L, Gambelli G, Nicolosi GL. Standardizzazione del
referto ecocardiografico nell’adulto. Documenti Ufficiali della
Societa’ Italiana di Ecografia Cardiovascolare 9° cura del
Consiglio Direttico SIEC 1995-1997). Giornale Italiano di Ecografia
Cardiovascolare. Suppl. Vol. 7, n’2, Giugno 1997.
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