Emmott on Technology: Every Link on the Dental Digital Imaging Chain is Important

Emmott on Technology: The Digital Imaging Chain
Thursday, December 20, 2012

Is your digital x-ray image hard to read? You must have a lousy sensor.

Or, maybe not. Give the poor sensor a break.

If the diagnostic quality of the image is poor, most dentists immediately blame the sensor. However, the fact is the diagnostic quality of your digital x-rays will be determined by the entire imaging chain.

If any one of the links in the chain is weak, especially the final one the monitor, the diagnostic efficiency of the image will be compromised.

Here is the entire x-ray chain. An imaging issue could originate with any part of these connected technologies.

X-Ray Generator: In theory any x-ray generator will work with a digital sensor. However if your x-ray unit is old and poorly calibrated, you may have inconsistent results.

Sensor: All sensors are adequate, however all sensors are not equal. The best way to compare images is with side by side comparisons in your own office using your own x-ray generator. This is ideal but difficult to arrange.

When just looking at specifications, some significant areas of comparison are:

  • Resolution measured in lp/mm (line pairs per millimeter). Make sure you compare actual resolution, not theoretical.
  • Warranty time and cost. More reliable sensors will have less expensive, longer warranties.
  • Reliability of the vendor. What seemed like a great deal will become a nightmare if the vendor can’t provide service or goes out of business.

Software: Like the sensors, all the software is adequate, but all the software is not equal. The best measure of software is diagnostics and ease of use. For example, does the software have pre-set optimal settings to detect various conditions such as caries, bone loss, soft tissue or periapical conditions? And, how many mouse clicks does it require to go from one function to the next, or one image to the next?

Monitor: Even the best images will look bad if the monitor is inadequate.

One of the smartest guys I know is Dr. Doug Yoon. Doug is a dentist but more importantly he is a digital image scientist and the founder of XDR digital radiology. I asked Doug to give me some advice on the best clinical monitors for digital radiography. Here is what he had to say.

“Even the lowest end monitor has sufficient pixel resolution for most digital radiographs.  The two most important parameters that manufacturers publish are brightness and contrast ratio. 

We recommend a brightness of at least 350-400 candela per sq meter (cd/m2) and a static contrast ratio of at least 1000:1.”

Note: Dynamic contrast ratio is a misleading parameter because it compares contrast between frames which can generate amazing million to one ratios. This is not relevant for viewing radiographs because these are 'static' non-changing images.

However the best test is to view a few radiographs on some candidate monitors. Intangible, un-reported parameters like SNR and precision of voltage control over each pixel can greatly influence image quality—especially when it comes to discrimination of subtle differences in grayscale. Compromising in these parameters can allow manufacturers to cut corners in design and manufacturing costs, yet they can still tout 'good' specs for brightness and contrast ratio.

The future is coming and it will be amazing!

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