A. Miles DDS, MS, FRCD
of the concerns I hear from dentist
considering digital imaging is their
perceived need for a "hard copy";
that is, an x-ray.
based images have been the gold standard
in our profession for almost 100 years.
Changing that standard will have a
great impact on the profession. So
what are the reasons to change? The
advantages, the disadvantages? Are
we giving up something good for something
bad? If we need hard copy doesn't
have to be film? If we adopt soft
copy interpretation, what are the
best display methods? How do we archive
that digital image to insure a lifetime
of diagnostic quality? Let's examine
each of these questions.
to Change to Digital Images
should I begin? I lecture all over
North America and the world on the
advantages of going digital. I'm already
a convert. I started this Website
to try to accelerate and facilitate
the conversion of dentists and dental
educators to digital information management.
So, please forgive some repetition
if you except that computers are hereto
staying, if you have them at the front
desk and at home, then the next step
is to integrate them chairside. You
will be on your way to entering the
digital dental age. Digital data requires
computers and software. Digital images,
whether their clinical or radiographic,
are just another motive digital data.
And, you already know that moving
information between colleagues, you
and the payor, you and your patient,
etc... is necessary, desirable and
inevitable to keep up with the digital
changes impacting on our dental practices.
are the Advantages of Digital Images?
- Faster to acquire
- More economical
- More reproducible
- Easily transmittable
- More archival
- "Processable" after
- Better for clinical
there Any Disadvantages of Digital
- Using computers
- More time to process
- Learning a new
- More space for
I don't see these images as disadvantages,
but perceived obstacles or challenges.
Almost every doctor I asked, who has
adopted digital x-ray technology,
tells me that they would have a revolt
on their hands if they went back to
film. All the auxiliaries in the audience
nod vigorously in agreement. Other
articles on this Website address these
perceived obstacles more completely.
We Giving Up Something Good for Something
short answer is no, and emphatic no!
There is no doubt that film is good,
especially with the advances made
in film emulsion and technology by
Insight TM, an F-speed
film, represents another quantum leap
in technology. Most D-speed film users,
who had been dissatisfied with the
E-speed group films, say that they
now prefer Insight
TM to their old D-speed
film. I have to agree with their assessment.
Our dental school uses insight exclusively
and it's great! But, if you want to
go digital you'll need to scan youíre
Insight TM using a
desktop scanner with a transparency
adapter. This is truly a time-consuming
process. Those of you who have tried
it, no it! You can make any image
digital, but the personnel and personal
costs are much greater than they are
for acquiring an image instantly with
a solid-state detector such as a CCD
or CMOS device.
how many of you have or will go digital
with all of your clinical images?
If you really want to integrate all
of your images into digital databases
you have to use the solid-state detector
systems or photostimulable phosphors.
For the discussion of phosphors and
solid state detectors see the article
titled "Digital x-rays are here, why
then aren't you using them?" found
elsewhere in the articles on this
Website republished from the Journal
of the California Dental Association
in December, 1999.
are not giving up something good like
insight or D-speed film for something
bad! For any task we do in dentistry,
all of the digital systems have the
spatial resolution or detail we need
to make accurate clinical decisions.
And most have higher contrast resolution
and gray scale latitude from films
when we subjected to electronic image
processing. There is no downside.
And, the digital images don't go yellow
or brown in our film cabinets (figure
1), take up less space, and can be
attached is digital data to referral
letters, insurance claims, patient
letters, and email if necessary. Try
that with film!
X-ray film improperly fixed that
has yellowed with time
I really Need a "Hard Copy"
of My Image ?
it comes to "hard copy"
of radiographic or clinical images,
there are really only 2 choices, paper
or x-ray film. Both clinical and radiographic
images can be printed onto paper,
and there are some advantages to having
these printed images. If you do not
plan on using your computers chairside,
then you will still need a viewbox
for film and a printer somewhere in
the office for printing clinical photographs.
If you really need a "hard copy"
of an x-ray, why not print it to paper
like you do your clinical images?
do this you still need a computer
and a desktop, flatbed scanner with
a transparency adapter. But you still
do not need to have the computer in
the operatory. You can transfer the
camera images to the computer if youíre
using a digital still camera, and
you will connect the scanner to the
computer to scan photos (in reflective
mode) or x-rays (or 35 mm slides)
in the transmissive mode (hence the
need for a transparency adapter).
seems to me that, if youíve adopted
a clinical camera (and/or video camera)
in the operatory, you should have
a computer there as well. It is more
practical and useful. If you have
a computer in the operatory for these
devices, then why not also use a digital
x-ray system there as well?
can see where Iím going with this
discussion. If youíre going digital
with other peripheral devices, why
are you clinging to x-ray film with
the darkroom and wasted time for processing?
If youíre printing clinical photos
or still images captured from a video
camera, why not print your x-rays
to paper as well?
archival is a paper image ?
answer to this is "I honestly
donít know". But, I do know that
archiving images of any kind to CD
ROMs or DVDs (digital videodiscs)
is VERY ARCHIVAL! Kodak, for instance,
guarantees the image quality of digital
images recorded on their "Gold"
CDR discs for 100 years! Thatís certainly
longer than you or I will practice
or longer than any state statute requires.
if your images, clinical and radiographic,
are stored in your computer, on CD
ROMs or DVDs, you can print your "hard
copy" any time with the same
image quality as the original (figure
2). Very often you canít do that with
by now I hope youíre thinking "Hey,
I donít need a hard copy except in
a few instances".
so, how do you interpret your x-ray
images if you donít have film and
I Read an X-ray as a Soft Copy, What
Do I Need in the Way Of a Monitor
concept of reading "soft copy"
images is not new. If you think of
it, you really do this already, just
not with x-rays! If you stare at a
computer monitor when you browse the
web, you are already looking at "soft
copy" images. And, if you have
actually viewed an x-ray image on
a dental website, you are really on
the way to "going digital".
You just havenít thought about it
and you havenít had to "process"
the image electronically to extract
the information. But, you could!
view these web and x-ray images, youíre
already using a monitor. Depending
on the money you invested in your
computer, home or office, you are
viewing images with varying degrees
of spatial and contrast resolution.
Since we are color "animals",
we see can see color images on our
monitors clearly at low resolution
quality and it doesnít disturb us
because the color images containing
several million colors and shades
of those colors. But with x-ray image
itís a totally different story. Humans
can only separate about 16 shades
of gray. Most images displayed in
the digital x-ray systems contain
256 shades of gray (this is called
an 8-bit image; 28 = 265
shades). Manufacturers will tell you
they acquire 10- and 12-bit images
containing thousands of gray shades,
but for our diagnostic purposes, IT
DOESNíT MATTER. We can only see 16,
and so 256 is good enough for any
dental diagnosis we have to make.
All the systems have sufficient contrast
resolution. And we can even improve
that contrast or optimize it using
tools in the software provided by
the vendors of these systems.
that doesnít mean we shouldnít have
a great monitor, because we also have
to worry about spatial resolution.
We are trying to find very small disease
changes in dentistry, so we need a
capture system that captures fine
detail. We need monitors that display
that fine detail. And, we need excellent
printers to print that fine detail
if we want a "hard copy".
come in varying image resolutions.
With a computer monitor the resolution
is called the "dot pitch",
measured in mm (millimeters). It is
the distance between each pixel in
the monitor display.
most monitors the dot pitch is around
.26mm or .27mm. The higher the dot
pitch number, the further apart the
pixels. As the pixels spread
apart from one another, the fuzzier
the image becomes. Conversely,
the closer together the pixels, the
sharper the display. So, youíd like
to use a monitor with a smaller number
dot pitch. A .24 or .25 monitor would
be better. For this resolution you
will pay slightly more.
addition, itís been shown that LCD
flat panel displays, although having
great contrast detail and resolution,
lack the latitude (the ability to
display a wide range of gray shades)
that conventional CRTs have1.
So, before you switch to those "sexy"
flat panels, think about the display
capabilities you will be giving up
Simulation of what
a dental x-ray might look like on
a "flat panel" monitor (left)
Vs. a typical CRT computer monitor
(right). Note that the high contrast
of the "flat panel" is not
able to display the correct bone height
seen on the CRT with wider latitude
with a good stereo system, if you
have lousy speakers, youíll have lousy
sound. If you want your hard copy
to look like the monitor image, donít
scrimp on the printer. There are many
printers to choose from. Here is a
list of high quality, but affordable
printers (all ink jet types for under
DMI 1200 (sold as a package
with a digital camera, image software
- Hewlett Packard
- Epson 740
- Canon BJC 6000
Kodak DMI 1200 dental
printer and radiographic image Of
course you will also need to use high
quality print paper. A glossy finish
is best for displaying your image.
Click the image to Enlarge
printed on a Kodak DMI 1200 printer
and Kodak paper
E: Choosing the Right Monitor
and Interface for Viewing Medical
Images, Invited Symposium: Applying
Information Technology in Medicine,
Presentation #164, 6th
Internet World Congress for Biomedical