Veterinary digital radiographic systems will cost between $50 and 150K. A recent article in the American Journal of Roengenology1 proves that all of the money spent on a system may be wasted if veterinarians don’t consider the ambient light level in the clinic when viewing digital images.
In this study, radiologists viewed the same images (wrist and chest radiographs) on the same monitor in different ambient lighting conditions. This study showed that improper ambient lighting can lead to misdiagnosis. Radiologists reviewing the radiographs in a room with an ambient light level that approximating a dim hotel room at night (40 lux and 25 lux) made fewer errors than radiologists reading in full office light or in total darkness. Interestingly, the errors and misdiagnosis made at appropriate lighting levels were false positives rather than missed fractures which were more common in rooms with inappropriate lighting.
The reason that ambient light is important for digital radiography is because the light level coming from LCD screens is much less than a traditional view box. The ability of the eye to discriminate between gray levels is best when the ambient light level of the room is close to the amount of light coming from the screen.
Most veterinarians should take note of this study because most veterinarians (at least most of the veterinarians I come in contact with) view their digital radiographic images in the full light of the clinic. This could lead to misdiagnosis.
Veterinarians may also decrease the diagnostic accuracy of their digital radiography system in two other important ways. First, many veterinarians view their images on monitors that are not at eye level. For example, monitors on a desk may be viewed while standing and looking down at the monitors. This “off axis” viewing can cause significant image degradation which can decrease the diagnostic accuracy of a monitor2. Many veterinary practices also use consumer grade monitors which may not be appropriate for radiographic interpretation. Consumer grade monitors can be significantly dimmer than medical grade grayscale monitors (used in this study) which can reduce diagnostic accuracy.
The bottom line on all of this:
- Use a bright monitor and keep it calibrated. A medical grade grayscale monitor is optimal
- Keep the ambient lighting dim and approximately equal to the brightness of your monitor
- View images at "eye level" to reduce the effect of “off axis” viewing of LCD screens.
References:
1. Ambient Lighting: Effect of Illumination on Soft-Copy Viewing of Radiographs of...
Brennan et al. Am. J. Roentgenol..2007; 188: W177-W180
2. Acad Radiol. 2005 Aug;12(8):957-64.