This interview was recorded in October 2010 as part of the Dental Files audio magazine. It is reproduced here by permission of the Australian Dental Association.

Listen to Part 1

Listen to Part 2

• B&B Computer Consultants (Ohio, Kentucky, Indiana)
• Cieos Digital Infrastructures
• Computek
• Dental Systems Integrators Inc. Portland, Oregon
• Ed Ensor
• Erickson Technologies, Inc. (Minnesota)
• kbs Computer Solutions, Inc. (Albuquerque, New Mexico)
• Simon Says Solutions (Scottsdale, AZ)
• T2 Consulting Inc. (Minnesota)

• American Association Of Dental Radiographic Technicians
• Dental Learning Centers
• Dental Town
• Emmott On Technology
• Barry Freydberg

Dale A. Miles DDS, MS, FRCD

Back to Part I

In this article, I’ll present information on the software or “image processing”, the part of the system which truly impacts patient care, the part of the imaging system which is so foreign to us all as dentists who were brought up on “film”. I will not attempt to compare and/or rank the various systems.

Frankly, I have not played with all of them yet. I am familiar with
most image processing tools and have used dental image processing
software from Trophy, Schick, Dent-X (CCD systems), and Digident (PSP
system). I have evaluated other packages as well. However, like many of
you I have also used standard “desk top publishing” software programs
like Adobe Photoshop, Aldus Persuasion, MacPaint, etc…to make pictures,
graphics, tables with shading and so on. The operations are, for the
most part, very similar.

What are the common tools?

Most image processing software program for performing electronic image processing or image enhancement (DON’T USE THE WORD MANIPULATION) allow you to change the following image parameters or characteristics:

Brightness

Contrast

Image size (zoom)

Image orientation

Sharpness

Inversion (white to black and visa versa)

Pseudocolor alteration

either together or separately. These are all useful tools, and these are all available in desk top publishing software. There is nothing proprietary about these “enhancements”. You could purchase the software, scan a radiograph from your practice and practice! You could do digital imaging in your own
home. This is actually “indirect digital imaging” using a desk top
scanner. You just need to make sure your document scanner comes with
(or can have added) a “transparency adapter” which allows light to be
transmitted through the image (radiograph or color slide) to be scanned
in the lid of the scanner, instead of by reflection off the lid to the
CCD below. Yes, that’s right! I said to the CCD below. Scanners and fax
machines use a linear CCD device to capture the image. And all this
time you didn’t realize you were using digital technology already!

These five images show the use of the various tools.

original	brightness	contrast	inverted	sharpened

Technical Issues in Digital Imaging: How Do They REALLY Impact Clinical Care?

Dale A. Miles DDS, MS, FRCD

Forward to Part II

It’s truly hard for the practising dentists to begin to sort out the “hype”
from the truth about digital x-ray imaging systems. How many line
pairs/millimeter is good enough? Why do I need 4096 gray levels? Why
are some systems “wireless”? And, how do they do that? What is the
difference between a CCD and a CMOS receptor? Do I really care? All of
these questions arise each time I address a dental group. Then there’s
the ultimate question: how will digital imaging improve my practice and
my patient’s care?

I will attempt to answer all these questions in this two-part article. In
this first part I’ll discuss hardware; that is, the sensors (receptors). In the second article, I’ll present information on the software or “image processing”, the part of the system which truly impacts patient care.

The “hardware”

You can choose from 3 direct digital receptors: the CCD (charge-coupled device), the CMOS (complimentary metal-oxide semiconductor) or the PSP (photostimulable phosphor plate). All are quite capable of giving you a diagnostically accurate, reproducible image for any of the routine dental tasks: caries assessment, periodontal bone level information or periapical
lesion detection. You can read more about the principles of all of
these receptors using the references at the end of the paper.”

Buyer’s Guide 2001 ” details a comparison of the current
commercial systems.

To begin, let’s talk about some technical specifications of the hardware, and the claims by which the manufacturers try to win you over.

Line pairs/mm is a measure of the system’s ability to capture detail; that is
resolution. Manufacturers claim anywhere from 6 to as much as 22 lp/mm.
Does it really matter? In truth the human visual system can only resolve about 8 lp/mm at the best of times without magnification. So does 12 lp/mm or 20 lp/mm resolution really matter? The answer is NO! It doesn’t matter…all of the current digital x-ray systems use sensors capable of capturing a diagnostically acceptable image.

4096 grays are the number of gray shades a CCD or CMOS receptor is capable of displaying on a computer monitor that captures a 12-bit image (this is
just the number 2 raised to the 12^th power – do the math!). Some CCD or CMOS receptors actually capture this amount of gray level information. BUT, none of the manufacturers actually display a 12-bit image because the
computer monitor for all of these systems is usually capable of displaying ONLY AN 8-BIT IMAGE – or 256 shades of gray! So, do you need 4096 grays or more (PSP systems have even more gray levels or shades). The answer is NO! It doesn’t matter. And, even if you bought a very expensive medical grade monitor to display all those grays, the human visual system can only separate the differences between 64 grays! Once again…it doesn’t matter!

“Wired” vs. “Wireless”

The PSP systems are “wireless”. That’s because they use plastic plates coated with a phosphor material sensitive to x rays. The phosphor material stores the x-ray energy, like a latent image with film, until it is scanned by a laser. The light excited and released by the laser is captured as an electrical
signal which is then converted to a digital image (analog to digital
conversion) for display on the computer. The image is displayed
continuously by the computer’s “frame grabber”). The image is thus
“digital” and can be electronically processed just like the CCD or CMOS
image. However, the PSP systems are slower because the plate must be
placed in a drum scanner (DenOptix or Digident) or in a slot in the
computer for laser scanning (Digora) in this 2-step fashion. Thus the
CCD or CMOS systems are faster. The image appears on the monitor within
seconds after exposure. Retakes then, if necessary, can be performed
more quickly. You must decide if the saving in “tech time” is worth the
perceived “hassle” of having a wire. Most clinicians and auxiliaries
I’ve talked to say the wire is not a problem…you just have to use the
positioning instruments provided with the system. Which should I
choose? Here it matters! But, it’s largely a matter of personal preference. Remember, all of the systems improve your imaging capability and all are “up to the task”.

CCD vs. CMOS
This is a controversial area since CMOS receptors have only just become
available for x-ray use. They are great for video and digital still
cameras, video game interfaces, etc…. They use much less power, are
cheaper to make because they are used in EVERY computer already
(without the imaging sensor portion), and work very well in bright
light conditions. However, they have not been tested for x-ray image
acquisition yet, and have more noise (electronic cross-talk that
degrades an image), are less efficient at gathering light and x rays,
and thus have a lower quantum efficiency than CCDs. This means they
gather less x or light photon information and thus may not have as much
diagnostic information to display. The CMOS chip has a microprocessor
on it, some RAM (random access memory) as well as the sensor/receptor.
This means that there is less imaging “real estate” for the device, and
thus maybe less capability of recording incoming x-ray information than
the CCD. CCDs for x-ray imaging are a very stable and mature industry.
They just cost more. In order to compensate for less x-ray gathering,
the CMOS sensors have microlenses and scintillators (like CCSs) bonded
to them to gather more light. This “optical packaging” adds to the cost
of the sensor. So where are the savings? I don’t know, and we probably won’t see any! By the way CCD is not really “older technology” as claimed by
some manufacturers. It was better technology for x-ray imaging, and may
still be.

Table 2. Details
the comparison between CCD and CMOS features. So, CCD or CMOS? Here
again it matters…for my money, I’d stick with CCD for
now, and wait until the evidence from the academic/research community
is in.

Table 2 – CCD – CMOS RECEPTOR COMPARISON

Note- Bold Words are an advantage of the system.

• Arizona School of Dentistry & Oral Health
• Case University School of Dental Medicine
• Loma Linda School of Dentistry
• University of California San Francisco
• University of Connecticut
• University of Detroit Mercy
• University of Louisville
• University of Michigan
• University of Minnesota
• University of Missouri Kansas City
• University of Nevada Las Vegas
• University of North Carolina
• University of Southern California
• University of Texas Dental School at San Antonio