Apparatus for dynamic stress measurement

Patent metadata

Field	Value
Publication number	US-10631775-B2
Application number	US-201514839448-A
Country	US
Kind code	B2
Filing date	Aug 28, 2015
Priority date	Aug 28, 2015
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

Axial stress or similar properties in a stressed tendon or ligament are measured by mechanical excitation of a shear wave in the tendon or ligament measured using ultrasonic displacement techniques at least two different longitudinal positions to derive a shear wave propagation speed. This shear wave propagation speed may be equated to an axial stress on the tissue using a model. Rapidly repeated measurements allow dynamic axial stress measurements to be obtained for clinical study.

First claim

What we claim is:

1. A device for in vivo dynamic measurement of properties of connective tissue extending along a longitudinal axis, the device comprising:
a stimulator probe including an electromechanical actuator adapted to apply a superficial, mechanical transverse stimulation through a patient's skin to the tissue to generate a shear wave that travels longitudinally along the tissue when the stimulator probe is placed against the skin proximate to the connective tissue;
a first motion sensor detecting the shear wave in the tissue caused by the stimulator probe along a first transverse axis at a first longitudinal position along the longitudinal axis when the first motion sensor is placed against the skin proximate to the tissue;
a second motion sensor detecting the shear wave in the tissue caused by the stimulator probe along a second transverse axis at a second longitudinal position along the longitudinal axis further from the stimulator probe than the first motion sensor when the second motion sensor is placed against the skin proximate to the tissue; and
a processing circuit operating to:
(a) receive a signal from the first motion sensor to provide a first transverse motion signal indicating a first transverse movement of the tissue at the first transverse axis over time;
(b) receive a signal from the second motion sensor to provide a second transverse motion signal indicating a second transverse movement of the tissue at the second transverse axis over time;
(c) compare the first transverse motion signal to the second transverse motion signal to determine a travel time of passage of the shear wave between the first and second transverse axes;
(d) output a display of axial stress on the connective tissue along the longitudinal axis between the first motion sensor and the second motion sensor at a time of the comparison determined from the travel time of passage of the shear wave along the longitudinal axis.

2. The device of claim 1 wherein at least one of a repetition speed of the mechanical transverse stimulation and a separation between the first and second transverse axes is selected to provide measurement of a range of shear wave speeds.

3. The device of claim 1 wherein the processing circuitry operates to repeat (a)-(c) for multiple time periods and the stimulator probe provides intermittent impulsive mechanical stimulation only between the time periods.

4. The device of claim 1 further including a longitudinally spaced array of motion sensors and wherein the processing circuit selects the first and second motion sensors from among the longitudinally spaced array of motion sensors to vary longitudinal positions of the first and second transverse axes with respect to the tissue between measurements to provide the measure of stress on the connective tissue along the longitudinal axis between the first motion sensor and the second motion sensor at a time of the comparison through different longitudinal segments of the tissue.

5. The device of claim 4 wherein the processing circuit further outputs multiple measures of stress on the connective tissue along the longitudinal axis between the first motion sensor and the second motion sensor at a time of the comparison as a function of the longitudinal position of the tissue.

6. The device of claim 1 further including a mechanical actuator for moving the first and second motion sensor longitudinally to vary a position of the first and second transverse axes between measurements to provide a measure of stress on the connective tissue along the longitudinal axis between the first motion sensor and the second motion sensor at a time of the comparison through different longitudinal segments of the tissue.

7. The device of claim 1 further including the step of comparing signals received from the first and second motion sensors to analyze at least one of amplitude change and frequency change and to output a second value functionally related to at least one of amplitude change and frequency change.

8. The device of claim 1 wherein the output display of axial stress is a function of shear wave speed squared times a predetermined density of the connective tissue.

9. The device of claim 1 wherein the output provides a graph depicting a measure of stress as a function of time.

10. The device of claim 1 wherein the first motion sensor is a first ultrasonic transducer element detecting first ultrasonic data measuring the first received ultrasound at a set of different times along the first transverse axis at the first longitudinal position when the first ultrasonic receiver is placed against the skin proximate to the connective tissue;
wherein the second motion sensor is a second ultrasonic transducer element detecting second ultrasonic radiofrequency data measuring a second received ultrasound at a set of different times along the second transverse axis at the second longitudinal position when the second ultrasonic receiver is placed against the skin proximate to the connective tissue; and
wherein the processing circuit receives the first and second ultrasound data to:
(i) compare the first received ultrasound data at different times over a time period to determine a change in position of the tissue between the different times to provide the first transverse motion signal indicating first transverse movement of the tissue at the first transverse axis over time; and
(ii) compare the second received ultrasound data at different times over the time period to determine a change in position of the tissue between the different times to provide the second transverse motion signal indicating second transverse movement of the tissue at the second transverse axis over time.

11. The device of claim 10 wherein the processing circuit further receives the first and second ultrasound to provide a B-mode image of the tissue.

12. The device of claim 10 wherein the comparison of the first received ultrasound and the second received ultrasound determines a change in position of tissue at two different longitudinal depths to provide separate first and second transverse motion signals for each depth and wherein the processing circuit uses the separate first and second transverse motion signals for each depth to provide an output of a measure of stress on the connective tissue along the longitudinal axis between the first motion sensor and the second motion sensor at a time of the comparison for each depth.

13. The device of claim 10 wherein the comparison of (i) matches the first received ultrasound data of the different times at different relative times to determine a relative time difference in the matching of data of the different times and the relative time difference is used to provide the first transverse movement, and the comparison of (ii) matches the second received ultrasound data of the different times at different relative times to determine a relative time difference in the matching of data of the different times and the relative time difference is used to provide the second transverse movement.

14. The device of claim 10 further including a housing supporting each of the stimulator probe and first and second ultrasonic transducer elements in a line for contact to a patient's skin adjacent to a tendon or ligament.

15. The device of claim 1 wherein the first and second motion sensors are first and second skin-contacting accelerometers measuring acceleration along the first and second transverse axes, respectively.

16. The device of claim 1 further including cuff for retaining the stimulator probe, the first motion sensor, and the second motion sensor a

Assignees

• Wisconsin Alumni Res Found

Inventors

• Thelen Darryl Gerard
• Martin Jack Anthony
• Allen Matt S
• Segalman Daniel Joseph
• Slane Laura Ann

Classifications

• A61B8/4494

  characterised by the arrangement of the transducer elements · CPC title

• A61B8/5207

  involving processing of raw data to produce diagnostic data, e.g. for generating an image · CPC title

• A61B5/4533

  Ligaments · CPC title

• A61B2562/0219

  Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches · CPC title

• A61B5/0053

  by applying pressure, e.g. compression, indentation, palpation, grasping, gauging · CPC title