Distance Measuring Device Over Body Surface

Nerve conduction studies help to diagnose muscle and nerve diseases and point to the underlying cause and potential treatments. Conduction studies involve stimulating nerve at different points along its course and recording the response with an electrode, conduction velocity is determined by dividing the distance traveled by the time it takes the impulse to travel that distance. While the measurement of time is done electronically and is very accurate, measurement of distance in every commercial laboratory is done by marking the skin and measuring the distance with a flexible tape measure. Such distance measurement is highly error prone and leads to erroneous results and misdiagnosis. We present a device to measure distances along the body surface. It eliminates examiner error in the measurement of distance. It delivers an operator-independent and reproducible measurement and thereby increases accuracy of test results and avoids misdiagnosis. Furthermore, the device saves a significant amount of time. Stopping to pull out a tape measure, reading it and entering the data into the computer, all adds time to the length of the procedure. The measurement device eliminates these steps thereby increasing efficiency. It also transmits the measured distances directly to the computer, thus eliminating error in data entry. The device uses the established optical mouse technology at its core. It can measure displacements with a 0.0635 mm resolution. It is based on a commercial chip set, ADNS-5030 from ‘Avago Technologies.’ The system consists of an optoelectronic sensor which measures changes in position by optically acquiring sequential skin surface images (frames) and mathematically determining the direction and magnitude of movement. The sensor only needs to be pointing at but not touching the skin. The main advantage of this approach is that it is contactless, eliminating the need for disinfection. Although, current limitation of the device is in measuring accurately over non-planar surface due to its considerably large size making it difficult to maneuver over bumpy surfaces. Initial results for measurement studies performed over a diverse subject pool (in terms of skin color, hair density) results are promising with an error less than 9% for distances over 75 mm. A reduction in size of the device would lead to more accurate results as smaller size would help in easy maneuverability. Future implementations will exploit the contactless feature and integrate the measurement in the stimulus probe, reducing testing time and the need to operate multiple devices.