Optimizing Videokymographic Image Quality

Recommendations for optimizing videokymographic image quality:

The videokymography camera marketed by Kay is used in conjunction with a rigid endoscope, lens adapter, light source, videocassette recorder, and monitor. With the very short time integration (approximately 125 msec) of the single line of data being scanned with the VKG technique, an abundant amount of light is required for adequate illumination of the vibrating vocal folds. Therefore, in order to obtain acceptable VKG image quality, it is critical to use a rigid endoscope with good light transmission properties. Some rigid endoscopes, particularly those with a detachable light cable, while acceptable for stroboscopic and general endoscopic usage, may not be adequate when used with the VKG system. Kay recommends usage of an endoscope with a continuous (non-detachable) light cable and with good transmission qualities (e.g., Kay Rigid Endoscope, Model 9106).

The lens adapter used with the VKG camera is another system component which affects image brightness. If the image you obtain is somewhat dark, you may benefit from using a lens with a shorter focal length than what you are using.

Another critical element in the VKG system is the light source. When using an endoscope with excellent transmission properties and a 35 mm lens adapter, it may be acceptable to use a 150 watt halogen light source (e.g., the constant light source provided on the Kay stroboscopy system), but it may not be adequate in all cases. To be on the "safe side", Kay recommends a constant xenon light source (300 watts).

Note: When using a xenon light source with the VKG system, the tip of the rigid endoscope may become very hot—only turn the light source on just before the procedure begins and keep the exam as short in duration as possible. Clinicians should monitor the heat of the endoscope to ensure patient comfort and safety.