ABSTRACT
We have created a bioimpedance probe designed to detect subtle changes in human cervical tissue composition in vivo, and thereby detect the onset of cervical remodeling in a noninvasive manner sooner than existing clinical methods allow. Our cervical bioimpedance measurement device, which can be used during a routine pelvic examination, is composed of a contoured probe with disposable tip and, within the probe's handle, a bioimpedance sensor equipped with an integrated chip capable of generating sinusoidal voltage of varying frequencies. A constant force spring assures consistent measurements through a range of contact forces applied. An activation switch allows the operator to control the application of current. The sensor can be synchronized with a computer data storage and analysis system, which interfaces with the device. With the probe placed in contact with a collagen gels of varying concentration, the relationship between measured bioimpedance and collagen concentration is verified to be positive exponential (R/sup 2/=0.94) and repeatability in saline solution showed that measurements varied by less than +/-10% over 20 trials. Finally, a variety of user-applied forces showed that impedance values plateau when forces exceed 1N.
ABSTRACT
We report on a wireless, electromyography (EMG)-based, force-measuring system developed to quantify hand-applied loads without interfering with grasping function. A portable surface EMG device detects and converts to voltage output biopotentials generated by muscle contractions in the forearm and upper arm during hand-gripping and traction activities. After amplifying and bandpass filtering, our radio frequency (RF)-based design operating at approximately 916 MHz wirelessly transmits those voltages to a data acquisition (DAQ) system up to 20 meters away. A separate calibration system is used to relate an individual user's EMG signal to known pull and clenching forces during specific applications. Real-time EMG data is processed and displayed in software developed with LabView (National Instruments, Austin, TX). Data is then converted to force data using individual calibration curves. With EMG electrodes placed over any major forearm muscle, calibration curves for seven subjects demonstrated linearity (R(2) > 0.9) and repeatability (<10% of average slope) to 110 newtons (N). Preliminary results in clinical application on newborn delivery suggest that this approach may be effective in providing an unobtrusive and accurate method of measuring hand-applied forces in applications such as rehabilitation and training.
