Single sensor tensiometer
An apparatus for measuring forces in connective tissue employs a single sensor receiving a shear wave, band-limited, wavelet signal from an actuator and processing it to determine a delay for the determination of shear wave speed and related tension or force. Delay may be a combined analysis of a group delay of the wavelet and a phase delay of the wavelet.
1 . An apparatus for measuring forces in connective tissue comprising:
at least one support adapted to attach to an individual at a location of connective tissue;
a transducer probe held by the at least one support and receiving a transmission waveform signal to generate a predefined excitation in the connective tissue at a transmission time to generate a shear wavelet that travels longitudinally along the connective tissue from a first location;
a motion sensor to detect a reception waveform signal of the wavelet in the tissue at a reception time at a second location separated by a predetermined longitudinal distance from the first location; and
a processing circuit operating to determine a wavelet delay from the transmission waveform signal and the reception waveform signal and, based on the wavelet delay, output a measure of connective tissue force.
2 . The apparatus of claim 1 wherein the wavelet delay is a function of a group delay describing transmission time of an envelope of the wavelet.
3 . The apparatus of claim 2 wherein the measure of wavelet delay is further a function of phase delay between a transmission frequency component of the transmission waveform signal and a reception frequency component of the reception waveform signal.
4 . The apparatus of claim 3 wherein the transmission frequency component and the reception frequency component are a wavelet frequency.
5 . The apparatus of claim 1 wherein the processing circuit operates to repeatedly determine a series of wavelet delays from a corresponding series of transmission waveform signals and reception waveform signals and applies an adaptive filter to the wavelet delays to provide the measure of connective tissue force.
6 . The apparatus of claim 5 wherein the adaptive filter is a Kalman filter.
7 . The apparatus of claim 1 wherein the processing circuit further operates to adjust the transmission waveform signal to compensate for delays introduced by the transducer probe prior to determining wavelet delay.
8 . The apparatus of claim 1 wherein the wavelet transmission signal is a multi-lobed, time-limited sine wave.
9 . The apparatus of claim 1 wherein the measure of connective forces is selected from the group consisting of stress and tension.
10 . A method of measuring forces in connective tissue comprising the steps of:
attaching a support to an individual at a location of connective tissue;
receiving a transmission waveform signal at a transducer probe held by the support to generate a predefined excitation in the connective tissue at a transmission time to generate a shear wavelet that travels longitudinally along the connective tissue from a first location;
detecting with a motion sensor held by the support, a reception waveform signal of the wavelet in the tissue at a reception time at a second location separated by a predetermined longitudinal distance from the first location; and
determining a wavelet delay from the transmission waveform signal and the reception waveform signal; and
outputting a measure of connective tissue force based on the wavelet delay.
11 . The method of claim 10 wherein the wavelet delay is a function of a group delay describing transmission time of an envelope of the wavelet.
12 . The method of claim 11 wherein the determining of the wavelet delay is further a function of phase delay between a given frequency component of the transmission waveform signal and a corresponding given frequency component of the reception waveform signal.
13 . The method of claim 12 wherein the given frequency component and corresponding given frequency component are a wavelet frequency.
14 . The method of claim 10 further including measuring a series of wavelet delays from a corresponding series of transmission waveform signals and reception waveform signals and applying an adaptive filter to the wavelet delays to provide the measure of connective tissue force.
15 . The method of claim 14 wherein the adaptive filter is a Kalman filter.
16 . The method of claim 10 further including adjusting the transmission waveform signal to compensate for delays introduced by a transducer probe generating the predefined excitation prior to determining wavelet delay.
17 . The method of claim 10 wherein the wavelet transmission signal is a multi-lobed, time-limited sine wave.
18 . The method of claim 10 wherein the measure of connective forces is selected from the group consisting of stress and tension.