ZERO-CROSSING RECEIVER FOR ORTHOPEDIC PARAMETER SENSING

• US 20100331681A1
• Filed: 06/29/2010
• Published: 12/30/2010
• Est. Priority Date: 06/30/2009
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Stein, Marc, Kelly, Andrew
• Granted Patent: US 8,337,428 B2
• Time in Patent Office: Days
• US Class Current: 600/437
• CPC Class Codes: A61B 5/4509 Bone density determination
• CPC Class Codes: A61B 5/4528 Joints A61B5/4533, A61B5/4538 take precedence
• CPC Class Codes: A61B 5/6846 specially adapted to be brought in contact with an internal body part, i.e. invasive
• CPC Class Codes: A61B 5/6878 Bone
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 8/15 Transmission-tomography

Abstract

A sensor system uses positive closed-loop feedback to provide energy waves into a medium. It comprises a transducer (604), a propagating structure (602), and a transducer (606). A parameter is applied to the propagating structure that affects the medium. A sensor is coupled to a propagation tuned oscillator (416) that forms a positive closed-loop feedback path. The propagation tuned oscillator (416) includes a zero-crossing receiver (200) that generates a pulse upon sensing a transition of an energy wave from the propagating structure (602). The zero-crossing receiver (200) is in the feedback path that maintains the emission of energy waves into the propagating structure (602). The zero-crossing receiver (200) comprises a preamplifier (206), a filter (208), an offset adjustment circuit (210), a comparator (212) and a pulse circuit (218). The transit time, phase, or frequency is measured of the propagating energy waves and correlated to the parameter being measured.

Claims

1. A zero-crossing receiver to detect transition states of energy waves propagating through a medium including transition of each energy wave through a mid-point of a symmetrical or cyclical waveform to measure a parameter of a muscular-skeletal system.

2. The receiver of claim 1 where the zero-crossing receiver converts an incoming symmetrical, cyclical, or sine energy wave to a square or rectangular digital pulse sequence.

3. The receiver of claim 2 where the receiver discriminates between noise and the energy waves of interest by way of adjustable levels of noise reduction.

4. The receiver of claim 3 where an energy wave is ultrasonic and where the energy wave is converted to a corresponding electrical wave having an equal frequency or repetition rate.

5. The receiver of claim 4 further comprising:

a preamplifier coupled to receive the energy wave;

a filter operatively coupled to the preamplifier to reduce noise in the receiver;

an offset adjustment operatively coupled to the filter to offset the energy wave;

a comparator operatively coupled to the offset adjustment; and

a pulse circuit operatively coupled to the comparator where the comparator triggers the pulse circuit when a trigger level is detected and where the pulse circuit outputs a pulse in response to the comparator detecting the trigger level.

6. The receiver of claim 5 where the energy wave is a sine wave.

7. The receiver of claim 5 where the energy wave is a pulsed energy wave.

8. The receiver of claim 5 where the filter is a low-pass filter.

9. The receiver of claim 5 where the filter is a band-pass filter.

10. The receiver of claim 1 where the zero-crossing receiver maintains positive close-loop feedback to continue the emission, propagation, and detection of energy waves in the medium when operating in continuous wave mode or pulse mode.

11. A method of propagating energy waves into a medium comprising the steps of:

providing energy waves in the medium at a first location;

sensing each energy wave after propagating to a second location;

maintaining positive closed-loop feedback with a zero-crossing receiver where an energy wave is provided at the first location after a transition of an energy wave at the second location is detected.

12. The method of claim 11 further including the steps of:

amplifying an electrical wave corresponding to an energy wave at the second location;

filtering the electrical wave corresponding to the energy wave;

adjusting an offset of the electrical wave;

triggering a pulse circuit when the transition is detected; and

generating a pulse.

13. The method of claim 12 further including a step of triggering the pulse circuit when a preset trigger level is detected during the transition.

14. The method of claim 12 further including a step of applying a parameter of the muscular-skeletal system to the medium.

15. The method of claim 11 further including a step of breaking the positive closed loop feedback to stop the propagation of pulsed energy waves in the medium.

16. The method of claim 11 further including a step of measuring one of transit time, phase, or frequency of energy waves propagating through the medium.

17. A system for measuring a parameter comprising:

a zero-crossing receiver comprising;

a preamplifier coupled to receive the energy wave;

a filter operatively coupled to the preamplifier to reduce noise in the receiver;

an offset adjustment operatively coupled to the filter to offset the energy wave;

a comparator operatively coupled to the offset adjustment; and

a pulse circuit operatively coupled to the comparator where the comparator triggers the pulse circuit when a trigger level is detected and where the pulse circuit outputs a pulse in response to the comparator detecting the trigger level.

18. The system of claim 17 further including:

a sensor coupled to the zero-crossing receiver where the sensor comprises;

a first transducer for emitting an ultrasonic energy wave;

a medium where the first transducer is coupled to the medium at a first location;

a second transducer for receiving a propagated ultrasonic energy wave where the second transducer is coupled to the medium at a second location, where the second transducer converts the propagated energy wave to a corresponding electrical wave having an equal frequency or repetition rate.

19. The system of claim 18 where the zero-crossing receiver and the sensor are coupled in a positive closed-loop feedback path to maintain emission, propagation, and detection of energy waves in the medium.

20. The system of claim 19 where the energy wave is sinusoidal or pulsed.