November, 2000 | Ask most people how DVD is used,
and they're likely to focus on the field of entertainment,
and perhaps mention corporate communications as well. But
the same attributes that make DVD attractive for video entertainment
and corporate informationsuch as a widely available
playback platform and the capacity to handle large, high-resolution
filesmake the format a contender in areas far removed
from Hollywood, Wall Street, or Madison Avenue. One such
area is medical imaging, where the way has already been
paved by the acceptance of CD-R technology.
The field of medical imaging involves several distinct
applications, including archiving, interchange, and informatics.
In the medical field, "archiving is the preservation of
patient images and information for many years in a secure
manner," says Robert Petrocelli, president and CEO of Heartlab,
Inc. in Westerly, Rhode Island, a company that sells DVD-based
medical archiving systems for cardiology. "Regulations typically
require that patient images be kept for seven years, and
there are some institutions that never discard this data.
In the ideal scenario, media is only removed from an archival
system to be discarded."
In contrast, Petrocelli describes interchange as "the
exchange of patient images and information, typically between
hospitals. This can happen electronically or using media.
In either case, the exchange should be secure and not subject
to modification after it has left the sender. Interchange
media is also sometimes discarded after its contents have
been transferred to the receiving image-management system.
Interchange media must be highly standardized and widely
The patient information (as distinct from images) that
Petrocelli refers to falls into the category of informatics,
according to Chuck Alcon, vice president of sales and marketing
at MicroBoards Technology of Chanhassen, Minnesota, a longtime
supplier of CD and DVD recording media and production systems
that has recently opened a medical imaging division. "Informatics,"
Alcon says, "refers to the processing by hospitals and the
medical industry of generic data such as patient records,
insurance information, and past history." While the volume
of this data for a given patient does not approach the size
of the images themselves, storing, updating, and retrieving
the information along with the images adds another consideration
to the overall picture.
The primary distinction in requirements for systems and
media, however, is between archiving and interchange. "For
the purposes of interchange, it's important that two different
vendors of systems can read and write the same media," says
David Clunie, development director of medical imaging products
at Comview Corporation in Pleasanton, California, a vendor
of capturing, viewing, distributing, and archiving systems
for cardiology. "But for archiving, in theory, it doesn't
matter what media you use inside. For example, some people
use 12-inch optical disc platters, some use 5.25-inch MO,
some use Exabytes or DLT or AIT tape-based technology. And
recently, an increasing number of people have been trying
to use DVD-R and DVD-RAM in that role as well."
LEADING WITH THE HEART
Archiving, interchange, and informatics are concerns across
all areas, or modalities of medical imaging, which includes
disciplines such as MRI/CT, ultrasound, and cardiology. Classifying
other areas under the general umbrella of radiology, Heartlab's
Petrocelli describes the difference between cardiology and
the rest. "Cardiology produces more data per patient than
radiology," he says. "But the number of radiological studies
is much greater. So radiology is a high-transaction rate,
low-transaction size application, while cardiology tends to
be moderate-transaction rate, high-transaction size." The
higher the transaction size, the greater the need for a large-capacity
medium like DVD.
Also of interest in relation to DVD is the fact that cardiology
is out in front of other modalities in terms of implementing
new technologies. "Although the installed base of cardiology
systems is very small in comparison to the rest of the modalities,"
MicroBoards' Alcon says, "cardiology typically leads the
technology curve, and then the rest of the modalities begin
to adopt the new technology." This description seems to
have held true with regard to the advent of CD-R initially
adopted as a replacement for cine film in cardiology. "Cine
film is simply 35mm movie film that records a full motion
record of an x-ray angiogram in the cardiac cath-lab," Petrocelli
explains. "This film is expensive to produce, can't be duplicated,
and is frequently misplaced."
Despite its drawbacks, cine film was used in cardiology
because alternatives based on video lacked the required
resolution. "The x-ray beam, once it's been through the
patient, can be used to expose film without actually having
to go through a video chain," Comview's Clunie says. "So
you get very high quality, much higher than one would get
off a video image."
As computerization took hold in all types of workplaces
in the late 1980s and early 1990s, vendors of imaging tools
developed systems called PACS, for Picture Archiving and
Communication System. "There are multiple workstations set
up as viewing stations," Alcon says, "so that doctors and
technicians can review the results of patient procedures
over the network."
In many areas of medical imaging, the main need for viewing
is within the same facility where the image is generated.
"Outside cardiology," Clunie says, "most of the focus has
been on exchanging images via the network. With CT scans,
MRIs and ultrasounds, it turns out that it's unusual to
want to transfer images between institutions; much more
often they're used within the same organization. So a high-speed
local area network is more appropriate for storing those
images and retrieving them." The pattern in cardiology,
however, is quite different. "There is a referral pattern,"
Clunie says, "where a cardiologist will do a study, and
then if the patient needs surgery, they will pass the angiogram
on to the cardiac surgeon who does the coronary artery bypass,
for example. So they have to interchange these very large
collections of images."
With cine film sticking out like a sore thumb in an otherwise
digital world"They used to literally ship a can of
film to the surgeon," Clunie saysthe consensus by
the mid-'90s was that a digital medium was needed that would
allow image interchange between different PACS. Vendors,
radiologists, and cardiologists formed a standards committee
dealing with digital imaging and communication for medicine,
dubbed DICOM. Clunie currently serves as industry co-chairman
of the group, as well as chairman of the working group on
"DICOM looked around for a medium," Clunie recalls, "and
recordable CDwhich was already being used informallyseemed
to be the best choice. So DICOM defined an 'interchange
format,' including a network protocol as well as a choice
of media, objects, and file system to put onto CD-R. It's
been a very popular application in cardiology. You can record
a patient's entire angiogram onto one CD, and then take
it to another station and plug it into a DICOM viewer and
look at the images, without having to worry about film and
Alcon adds that the protocol is Windows NT-based and runs
on off-the-shelf architecture. "But the actual DICOM software,"
he says, "has very specific requirements as far as how images
are transported over a network, how they're viewed, and
how they're stored." As a result of DICOM, Alcon says, CD-R
usage has been widely accepted in the health-care environment.
BIGGER IS BETTER
"CD-R has been wildly successful in cardiology, especially
in the cardiac cath-lab," Heartlab's Petrocelli says. "It
was selected because it is standardized, widely available,
secure once written, and stable. But its main limitation has
been capacity. As additional information is added to the basic
unit of interchange for a cardiac patient, denser media with
similar attributes will be needed."
"Capacity is a big problem," Comview's Clunie agrees.
"The images we capture at present are 512 x 512 x 8-bit.
We want to move to using 1024 x 1024 x 10-bit. One angio
session just will not fit on a CD-R, and handling multiple
volumes of CD-R is a pain."
"The other thing," Clunie continues, "is that we're trying
to integrate images from multiple acquisitions onto the
same disc. For example, a patient might come in for a single
session, and have various different kind of imaging studies:
echocardiography, angiography, intravascular ultrasound.
Reports and measurements may be generated, waveforms may
be recorded, and ideally we'd like to put all that on a
single disc that can be sent to the next physician down
One might think that in the age of the network, no physical
media at all would be required for interchange. But the
size of the image files is sufficiently large to discourage
a move toward network-based interchange between health facilities,
which would hog too much band-width. "We exchange stuff
over the Internet all the time now," Clunie says, "but media
has become well-established as a very low-cost way of shipping
stuff around. You can talk about all this electronic technology
as much as you want, but couriers are fast, reliable, and
Magneto-optical (MO) media are used in some storage and
archival applications, but are largely out of the running
when it comes to interchange because of a lack of standardization
on form factor and capacity. Tape-based media are also used
for archiving, but Clunie says that "optical media are so
much more robust in the face of being stuck in a mailer
and sent across the country, compared to tape, that no one
has really seriously considered using tape as an interchange
DVD-R, on the other hand, fits the description of being
"denser media with similar attributes" to CD-R, and has
the added attraction that the DVD-ROM drives used to read
DVD-Rs will read existing CD-Rs. "DVD-R is in a similar
position to where CD-R was just a few years ago," Petrocelli
says. "The great majority of PCs are shipping with DVD-ROM
readers. DVD-R writers are still relatively expensive for
desktop use. But DVD-R has much greater capacity, and will
see significant increases in capacity during its life-cycle.
It is by far the most interchangeable media next to CD-R."
READY OR NOT?
Clunie agrees that DVD-R has tremendous potential for medical
imaging. But while Petrocelli's company has moved aggressively
to incorporate the format into its archiving products, Clunie
says neither DVD-R or DVD-RAM is "quite ready to be standardized"
for interchange applications.
For DVD-R, one of Clunie's concerns is the high cost of
the writing drives. Another is the fact that the drives
are available only from Pioneer. "The rules under which
DICOM is formed do not allow us to standardize on a single-vendor
solution," Clunie says. "Even if we wanted to, it's not
good to OEM from a single source. So the fact that other
people haven't signed on to make DVD-R drives is a real
killer for that particular format."
While acknowledging the single-vendor problem as "the
most important barrier to DVD-R's acceptance as an interchange
format," Petrocelli says that the problem will fade when
lower cost, consumer-oriented, 650nm drives enter the market
early next year. MicroBoards' Alcon agrees, saying that
"as soon as another DVD-R drive vendor/ manufacturer enters
the marketplace, then DICOM's restrictions will be lifted,
and they'll be able to officially endorse DVD-R."
But Clunie sees a downside to the circumstances under
which other manufacturers will join the market, meaning
the advent of version 2, with its split of DVD-R into, at
a minimum, 650nm General and 635nm Authoring varieties.
"It means that your old drives are history," he says, "and
you have to wait until December to buy new drives and new
media. This churn, in terms of what there is to standardize
on, causes us tremendous problems. For instance, had we
picked DVD-R last year, then we wouldn't be able to leverage
the consumer format, which has low-cost media and drives,
in our products."
Petrocelli, however, sees no reason for version 2.0 to
delay DVD-R implementation, because "all media written by
either version 1.9 or 2.0 drives at either the 650 or 635nm
wavelengths will be readable in any DVD-ROM drive. Different
media will be needed for 650 and 635nm recorders, but that's
not relevant once the media is written." In other words,
media created on existing systems should continue to be
readable even as newer systems are introduced using the
newer, less expensive drives.
As for DVD-RAMfacing some changes of its own with
the advent of 4.7GB-per-side version 2Petrocelli says
he thinks the format has "a smaller role to play, since
it is erasable and not as universally readable as DVD-R.
We have also found that its sequential read and write rates
are rather disappointing for cardiac applications. There
is no such thing as 'fast enough' in cardiology."
"DVD-RAM has the advantages of multiple vendors, very
low-cost media, and very low-cost drives," Clunie says.
"But the disadvantage is that you can't just take out a
type-2 cartridge DVD-RAM, stick it in your PC, and play
it back on most of the installed base of DVD-ROM players.
That may change a bit in the future, as more DVD-ROM drives
have the firmware and the hardware to be able to read DVD-RAM,
but that's not the current state of the installed base.
And that's a big point against DVD-RAM for interchange purposes."
Whatever the relative merits of DVD-R and DVD-RAM for interchange,
their suitability for archiving is, as Clunie points out,
"a completely separate question. The issues are much more
about performance, access, speed, longevity of the media,
stability, and physical handling. There are proponents of
both DVD-R and DVD-RAM. Both are excellent technologies for
the purpose, and I've seen medical imaging archives that use
one or the other or both. I kind of think of them as MO replacements
that are cheaper and have a longer life in terms of support
from the vendors."
Clunie's expectation of longer life reflects the broad
support enjoyed by the DVD standard as a family of formats.
"Since archive media is not interchanged," Petrocelli says,
"it need not be based on a standard. But an open standard
is nonetheless superior to a proprietary system because
the life of the data often exceeds the life of the image
management system. We have been faced with many instances
where a customer cannot access their own data without the
proprietary system that created it, and that leads to complex
and expensive data conversion projects."
In the archiving arena, however, tape jukeboxes become
realistically competitive to DVD. Chuck Thomas, general
manager of MicroBoards' Medical Data company, points out
that while DVD's random access means that information is
faster to get to, tape systems support much higher data
Because of this speed, Clunie says, "you can't use anything
but tape in certain applications, where you really need
the transfer rate. And tape is cheaper by the byte. But
most people, when they get serious about a big archive,
have a huge RAID that contains all of the immediately current
information, and the other mediabe it MO, CD-R, DVD-R,
DVD-RAM, or some form of tapeis really only used as
long-term storage. So both access time and transfer rates
are slightly less of an issue. My personal opinion is that
I don't really trust tapeI've had too many dead, jammed
tapes and lost too many files."
Petrocelli agrees that DVD has the edge as far as reliability.
"We used tape when it was the only practical choice for
large storage systems," he says, "but anyone who has spent
any time at all trying to make a truly robust tape archive
system work in cardiology has probably learned that it is
extremely problematic. Our service organization spends about
10 times the effort maintaining the DLT-based systems we
have in the field compared with the DVD systems. That's
why we have been in this market with DVD-R."
While DVD may be a newcomer to medical imaging, Petrocelli
is excited about the reaction so far. "Since January 2000,"
he says, "Heartlab has shipped over 75 terabytes of storage
capacity on DVD-R for long-term archiving. The industry
can be slow to change, but the customers are not. They have
a very high level of interest in DVD technology for image
archiving, and I expect that we will see DVD added to the
interchange standard when additional vendors begin manufacturing
recorders early next year. We believe that this technology
will provide the convergence of archival and interchange
Companies Mentioned in this Article
5870 Stoneridge Drive, Suite One, Pleasanton, CA 94588;
800/444-3022; 925/416-8950; Fax 925/416-8961; http://www.comview.com
101 Airport Road, Westerly, RI 02891; 800/959-3205, 401/596-0592;
Fax 401/596-8562; firstname.lastname@example.org;
MicroBoards Technology, Inc.
1721 Lake Drive West, Chanhassen, MN 55317; 612/556-1614;
Fax 612/556-1620; http://www.microboards.com
Pioneer New Media Technologies, Inc.
2265 East 220th Street, Long Beach, CA 90810; 310/952-2111;
Fax 310/952-2990; http://www.pioneerusa.com