Welcome to Dental Display QA. Your image is what we are all about.

In order to provide quality assurance (QA) for digital dental radiography every component in the imaging chain should be evaluated. This includes the x-ray source, the image receptor/sensor and most importantly the diagnostic image display system. If your display is not performing optimally you could be missing subtle changes in the radiographic image which represent dental disease. The American Dental Association (ADA), American Association of Physicists in Medicine (AAPM) and the National Council on Radiation Protection (NCRP) all recommend that regular quality assurance assessments be made for any diagnostic display.

Dental Display QA provides a one-stop source for all your display QA needs. By creating a user account you will have access to a FREE quality assurance assessment using either the Society of Motion Picture and Television Engineers (SMPTE) Diagnostic Imaging test pattern or the American Association of Physicists in Medicine (AAPM) TG18-QC test pattern.

All display QA test results are recorded and stored in your secure password protected account. You can review the performance of every display in your dental practice and generate reports to verify your compliance with state, federal, and professional guidelines. The best part is that the entire procedure can be performed by any dental staff member in only a few minutes and of course the cost is FREE.

We provide this service FREE of charge to all U.S. dental practices to encourage better quality digital imaging with the least amount of radiation to the patient. We also have products which are available for sale which allow for the monitoring of ambient (room) lighting and a comprehensive display calibration system based on the DICOM Grayscale Standard Display Function. For more information go to the Products page of this website.

Best Practices for Display QA

Dental Display QA logo

The dental display quality assurance program is designed to optimize the display of digital images throughout the dental practice; to assure compliance with all state, federal, and professional guidelines; to improve the presentation and diagnostic interpretation of those images; and a total quality assurance solution from calibration to reporting that allows the dentist to concentrate on patient care.

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Diagnostic Display Basics

Schematic of LCD display device showing basic components.

In order to understand the methods used to assess digital image display quality, we will need to understand some basics on how a display works and how to evaluate a display’s performance.

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Visual Test Patterns

SMPTE Diagnostic Image Test Pattern

In 1985, the Society of Motion Pictures and Television Engineers (SMPTE) published a Recommended Practice (RP-133) document entitled Specifications for Medical Diagnostic Imaging Test Pattern for Television Monitors and Hard-copy Cameras. The idea was to create a pattern that could be used for both quantitative and qualitative assessments of an image display system. The document describes the attributes and specifications of the test pattern, it does not provide the test pattern in digital, analog, or film form. The test pattern was intended to provide for initial acceptance testing as well as quality assurance purposes in a clinical setting.

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Human Visual System

Relationship between luminance and just noticable differences (JND).

In order to optimize a display system to allow for the detection of small changes in radiographic density and small spatial features in a digital image, it is necessary that we understand how the human visual system works.

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Effects of Ambient Light

Ambient light levels in dental operatory.

Excessive ambient lighting can have a negative effect on visualization of normal and abnormal structures on digital dental radiographic images. Ambient light reflects off the front surface of the display increasing luminance in dark areas of the image reducing the contrast ratio. Bright light also interferes with the eye's ability to adapt fully to luminance emitted from the image, thereby reducing the discriminating property of the eye and limiting visualization of subtle changes in radiographic density. The medical literature is repleat with studies that support this conclusion.

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What is Bias Lighting?

Bias lighting system for dental diagnostic display device.

Bias lighting is the lighting that is placed behind the screen you are viewing such that it raises the ambient light levels in the viewing area without directly shining light toward the viewer nor shining light past the viewer toward the screen (where it could create reflections and other viewing problems). Because the light originates outside of the sightline of the viewer and is not in a direct path to reflect onto the screen, you get all the benefits of increased luminance in the room without the problems of glare or light shining directly from the source into your eyes.

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Calibration of Diagnostic Displays

Calibrated image of a maxillary molar periapical radiograph.

As described previously in Diagnostic Display Basics and Human Visual System, different display devices have different characteristic response curves and the human visual system does not respond linearly to incident light intensity. These two properties of the display system and the human visual system can be corrected by creating a perceptual linearity across the grayscale values. Perceptual linearity can be achieved by setting display luminance values such that each change in pixel gray value corresponds to the same quantity of just noticeable difference (JND).

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Want to reduce the amount of radiation you give to your patients and improve the quality of your images?

The Digital Dental Quality Assurance Phantom provides for exposure optimization and image quality assurance for every type of digital intra-oral radiographic system. With this phantom you can ensure that you are using the lowest amount of radiation to produce images of the highest diagnostic quality. The phantom is ADA TR-1094 Report and AAPM TG-175 compliant.

For more information go to the Dental Radiology QA website.

News Update
American Association of Physicist in Medicine (AAPM) Task Group 175 releases report entitled “Acceptance Testing and Quality Control of Dental Imaging Equipment”. The intent of this report is to provide useful information and guidance for performing acceptance testing and quality control of dental imaging equipment. It is important to properly perform tests for image quality and safety purposes right after the installation and during routine operation of a dental x-ray unit. Having a quality control (QC) program for dental x-ray facilities is instrumental in ensuring that patients are not receiving excessive radiation during their examination. Recommendations for specific parameter evaluations and practical procedures for quality control evaluations of dental imaging equipment are described. You can download the complete report at http://www.aapm.org/.../RPT_175.pdf