Body position can be monitored in 3D using miniature accelerometers and earth-magnetic field sensors.
OBJECTIVE
The study and diagnosis of movement disorders can be improved by monitoring body position simultaneously with the EMG.


METHODS
We developed a monitor of the 3-dimensional (3D) orientation of body parts that can be applied in long-term ambulatory recordings in the daily life of a patient. The 3D sensor combines miniature sensors for earth's gravity and magnetism. It measures 60 x 50 x 10 mm and draws less than 1 mA of current from +/-5 V battery power. The non-horizontal direction of earth magnetism, as well as torque (pronation) of the body part, is corrected mathematically.


RESULTS
This results in a measurement of the 3D orientation of a body part in terms of vertical inclination and horizontal azimuth.


CONCLUSIONS
Calibration measurements indicate that this method is fairly accurate and practically applicable.
Kemp
B
B
Department of Neurology and Clinical Neurophysiology, University Hospital Leiden, The Netherlands. kemp@rullf2.leidenuniv.nl
Janssen
A J
AJ
van der Kamp
B
B
D000054:Acceleration; D004576:Electromyography; D006112:Gravitation; D008280:Magnetics; D008433:Mathematics; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D009949:Orientation / Q000502:physiology; D011187:Posture / Q000502:physiology*