Teleradiology -- What it is and what it isn't.
Teleradiology is the process by which diagnostic medical
radiographic images produced at one location are sent to a second
location usually for interpretation.
If the second location is elsewhere within the same medical
center, closed circuit television (CCTV) can be used. This
approach, which is teleradiology only in its broadest sense, is
best either for monitoring a study in progress or for consulting on
an individual case. A local area network (LAN) which allows
sharing of disk data is another local on-site solution.
If the second location is outside the medical center, a
different approach is typically used. Here, data in digital format
is transmitted via a computer modem to a second computer system for
interpretation. This is the usual understanding of the term
"teleradiology."
Teleradiology is often confused with a process called Picture
Archiving, Storage and Retrieval (PACS). Here, the purpose is long
range storage of diagnostic medical images in digital format on
large storage devices such Write Once Read Many (WORM) optical
disks. A common configuration is for a main viewing area to be
located in the Radiology department with multiple substations
strategically placed throughout the hospital. Ultimately, PACS may
replace standard xray transparencies which are often stored in
countless numbers in huge warehouses. Digital images stored on
disks are much more accessible and less easily misplaced.
The connection between PACS and teleradiology is that both
require digital images and that images archived on a PACS system
can be tele-modemed anywhere in the world. Teleradiology does
not, however, require a PACS system. Although there are many
actual and potential applications of teleradiology, this article
will concentrate mainly on the sending of medical images in an
emergency setting to an off-site radiologist for immediate
interpretation.
The Clinical Setting for Teleradiology
Because emergencies do not respect the "normal" workday,
radiologic imaging is available around the clock. Emergency room
physicians and senior medical staff are trained in the
interpretation of routine radiographs and CT scans and seldom
require the expertise of the radiologist who remains "on call" for
special procedures and difficult cases.
A radiologist may "cover" several hospitals on any given
night or weekend. If a scan does require an emergency
interpretation, the radiologist traditionally goes to the hospital
reads the films and then returns home. This can happen several
times a night at each hospital. A more civilized and efficient
approach would be to have the images sent to our Amiga computers at
home for off-site preliminary interpretations.
So how does one send an image from hospital to home?
Getting from "A" to "B"
If an image is to be modemed to a computer at home, it must
either already be in digital form inside a computer or else
digitized and then stored within a computer. CT (computerized
tomography) scans are inherently digital because the images are the
result of complex mathematical reconstructions of data collected as
the tube/detector system scans the patient. The data and images
are stored on disk and were a modem (and software!) attached to the
CT machine, you could download any image file you needed. The
problem would then be one of understanding the proprietary image
file format used by each manufacturer.
One solution that might be used would be to capture the video
data (as opposed to the "true" image data) by connecting the "video
out" from the CT machine to an Amiga with a frame grabber. The
quality of the data would then depend on the video display board
inside the scanner as well as the capability of the Amiga frame
grabber. A real advantage of capturing video data is that we can
store the resulting image in a standard Amiga IFF file format
without needing to interpret the manufacturer's proprietary file
format.
This "video out" approach should work for any imaging
modality that routinely produces video images including Magnetic
resonance (MR) and nuclear medicine (NM). Ultrasound images stored
on tape are also amenable to frame capture but image quality may
benefit from a time-base corrector (TBC).
But what about radiographs (xrays) which are, in most,
institutions imaged onto transparencies? A third and far simpler
approach (albeit one easier to criticize on theoretical grounds) is
to digitize the transparency. Indeed, because all imaging
modalities routinely output images onto transparencies, this method
is universally applicable. As Amigans, we are now truly on
familiar ground. We can use a Panasonic WV1410 black and white
video camera for image capture. The light source must be behind
the transparency just as if we were viewing a slide. Several frame
grabbers are available for the Amiga. The GVP IV24 that I use can
digitize an image at a resolution of 768 x 480 with 256 shades of
grey. But is it good enough?
Let us look at several medical imaging modalities and
determine the hardware and software requirements of each.
Teleradiology and Computed Tomography (CT)
The typical scenario is patient who sustains head trauma in a
automobile accident and is brought, unconscious, by ambulance to
the hospital at 2 A.M.. The emergency room physicians request a
head CT scan in order to determine if there has been bleeding into
the brain.
Hardware Requirements
A head CT scan may consist of 10 to 12 individual cross-
sectional images laser printed onto high quality transparency film
and read on a viewbox which provides rear lighting. As already
described, images may look like an anatomical "slices" of the
brain, but are, in fact, mathematical reconstructions of xray data.
Each image is a 512 x 512 data matrix containing 256 shades of grey
which would be sent via modem to the radiologist's computer at home
for an immediate or "stat" interpretation.
I think that most radiologists would insist on a 512 x 512
display matrix and at least 256 levels of grey so as not to miss
findings. The Amiga graphics display would then need to meet this
standard in order to be competitive.
Software Requirements
In emergent situations, most Radiologists would probably be
content with limited manipulation of the transmitted images.
Certainly a "zoom" function to hone in on a suspicious area would
be helpful as would a contrast control and a way to choose the
center for the grey level display. These functions are routinely
available while viewing images on a CT scanner console. The
ability to save, delete, send and receive from within the program
are obvious needs.
Teleradiology and Nuclear Medicine
Nuclear medicine is a branch of diagnostic radiology in which
a small amount of radioactive material is administered to a patient
who is then imaged with a special camera. A typical scenario for a
"stat" nuclear medicine scan would be one to exclude blood clots in
the lungs in a bed-ridden patient who suddenly became short of
breath. This is called "pulmonary embolism" and if, undetected has
a reasonably high mortality rate.
Hardware Requirements
Video graphics requirements for nuclear medicine are very
modest. Most images occupy 128 x 128 matrices although for some
purposes 256 x 256 matrices are used. For dynamic studies in which
images are acquired every 2 seconds, a 64 x 64 matrix is more
appropriate. A grey scale with 256 levels is adequate.
Software Requirements
Many nuclear medicine physicians, being the computer people
that they are, would like every bell and whistle on their home
computers. Even in the middle of the night, they would want to
enhance their images, overlay one image on another, compare the
count density in one area of an image with that in another area of
the same image, add images, subtract images, play them in a dynamic
sequence, and on and on and on. But as the wee morning hours
arrive, even the most ardent nuclear physician becomes more
realistic and settles for image display with zoom, brightness, and
contrast controls but I doubt if they would ever truly be content
with such limited software functionality given the image processing
power they have on-site at the hospital.
Teleradiology and Plain Film Radiography (X-Rays)
Plain film radiography is still the most common of all
imaging modalities. Suspected fractures, pneumonias, kidney
stones, intestinal obstruction, catheter placement are just a few
of the many indications for xrays.
Hardware Requirements
As already mentioned, most hospital medical staff are
sufficiently comfortable with radiographs as to be able to render a
preliminary diagnosis. From an image transmission point of view,
this indeed is fortunate because the resolution of xrays is so
great that some estimate that a computer matrix of 2k x 2k, and
perhaps even 4k x 4k, would be required to capture the detail.
Having emphasized the detail possible with plain film
radiography, I would add that most abnormalities are not so subtle
and the role of the radiologist is much more an interpretative one
rather than a strictly visual one. I would also point out that by
using a macro lens on the black and white video camera and focusing
on a critical area of the xray film, one can achieve a high overall
resolution because the 768 x 484 computer matrix is being applied
to a relatively small area.
Software Requirements
The limitations encountered with xrays usually relate to the
film being too light ("underpenetrated") or too dark
("overpenetrated") or the patient not able to be optimally
positioned for the study. If the quality of the study is high,
then the zoom, brightness, and contrast, and grey scale level
controls recommended for CT scan should be adequate.
Other Imaging Modalities
Ultrasound images, which are produced by the reflection of
sound waves by a transducer, have similar imaging requirements as
for CT scans. Because the transducer is hand-held and has gain
control and other user adjustable parameters, ultrasound is much
more operator dependent than is computed tomography (CT). The
quality of the study itself becomes the limiting factor.
Magnetic Resonance Imaging (MRI) has revolutionized radiology
because of its exquisite demonstration of anatomy in multiple
planes. Image resolution, at this point in time, conforms to a
surprising 128 x 128 or 256 x 128 matrix size, which is easily
handled on any computer system. On the other hand, MR scans are
characterized by large numbers of images with each set relating to
different magnetic pulse sequences and different imaging planes.
Except for certain back injuries that might result in spinal cord
compression, few true emergency situations seem to have developed
at present but this may easily change in the future.
Is the Amiga ready?
In terms of hardware, the answer, I believe, is a qualified
"yes." In terms of software, I'm not as sure.
Now that we have the Supra modem with its 14.4 bits per
second transmission rate, our limitation is the telephone line.
Until we have high speed digital (ISDN) lines, we will have to look
for lossless image compression techniques to speed data
transmission.
In terms of frame grabbing, the Panasonic WV1410 black and
white still video camera can generate 525 lines of resolution at
the center of its field and therefore is adequate for most of the
modalities described above. Frame grabbers such as the multi-
talented GVP IV24 board can capture an image in a 768 x 484 matrix
which also is adequate if one focuses the camera onto the image
itself which almost never fills its 512 x 512 matrix completely.
An interesting alternative to a combination video camera and frame
grabber may be the new Sharp JX-320 scanner with a transparency
option. I have not had experience with this unit although ASDG has
a driver for the scanner but, as yet, no software controls for the
transparency device (which is almost as expensive as the scanner
itself.)
The grey scale issue is more complicated. While the medical
images in my computerized teaching file adequately display
pathology using 256 levels of grey, this is a retrospective
evaluation. Only a prospective study, comparing detection rates
using 256 grey scale levels vs. 512 levels would have scientific
validity. My observation at this point is that 256 grey levels has
been adequate.
As this article goes to press, official announcement has been
made that the Amiga chip set has been upgraded. Therefore, we will
soon know if an unexpanded Amiga will be able to display high
resolution, 256 grey scale images. For standard Amiga 2000 and
3000 series computers, a 24 bit graphics board (or the equivalent
thereof) is necessary to view such images. I have used both
GVP's IV24 and Impulse's FireCracker24 graphics boards and can
state that both perform their display functions very well, although
the latter does not have frame capture options. I have not as yet
had experience with the new 24 (and 32 bit) graphics boards which
are based on the Texas Instruments Graphics Array (TIGA) processor
chip and which can have image displays of 1k x 1k or higher and
grey scales of 512 levels and potentially even more. These higher
resolutions would allow more than one 512 x 512 medical image to be
displayed on the same monitor screen without loss of individual
image detail. To be most useful in the medical environment, I
feel, these boards and the high quality monitors they require, need
to handle all Amiga graphics modes seamlessly and require only one
monitor for the whole system.
What about software? Image processing software up to this
point has largely related either to image format conversion or to
artistic modifications of images although Art Department
Professional (ASDG) does have image sharpening and smoothing
functions. Some of the image processing functions conceivable in a
medical environment are described in the nuclear medicine section
above. While most of these functions are useful to nuclear
medicine personnel, control (by mouse?) of zoom, contrast, and grey
scale level would be relevant to all and may be regarded as a
minimum. Zoom makes most sense if the data stored by the computer
is more than is being displayed on the monitor (otherwise one
merely gets a larger, more blurry image).
The Bottom Line?
There will probably always be cases in which the radiologist
will need to see the scan face to face. The Amiga with 24 bit
frame capture and display board(s), a high speed modem, a decent
size hard disk, and maybe Art Department Professional deserves long
term testing. Because the hospital at which I currently work has
24 hour emergency coverage provided by Resident physicians, I have
not yet set up an Amiga based image transmission system at this
facility. Nonetheless, I have received telephone calls from
individuals interested in using Amigas for this purpose. I hope
that this article will be of interest to them as well as others
interested in professional applications of the Amiga.
January, 1993