Determination of acoustic velocity in bone

• US 7,112,173 B1
• Filed: 06/24/1998
• Issued: 09/26/2006
• Est. Priority Date: 03/03/1998
• Status: Expired due to Term

• Current Assignee: Beammed Ltd.
• Original Assignee: Sunlight Medical Ltd. (Beammed Ltd.)
• Inventors: Mordvinov, Andrey, Ledenev, Elena, Pasternak, Vladimir, Niv, Yehuda, Kantorovich, Edward, Ashkenazi, Shai
• Primary Examiner(s): Jaworski, Francis J.
• Application Number:
  US09/623,288
• Time in Patent Office: 3,016 Days
• Field of Search: 600/437, 600/439, 600/449, 735/97, 735/99, 736/02
• US Class Current: 600/449
• CPC Class Codes: A61B 8/0875 for diagnosis of bone A61B5/4504 takes precedence
• CPC Class Codes: A61B 8/4227 characterised by straps, belts, cuffs or braces
• CPC Class Codes: G01H 5/00 Measuring propagation velocity of ultrasonic, sonic or infrasonic waves , e.g. of pressure waves
• CPC Class Codes: G01S 15/8925 the array being a two-dimensional transducer configuration, i.e. matrix or orthogonal linear arrays

Abstract

A method for determining an acoustic velocity in a segment of a bone covered with a layer of soft tissue having an outer surface, which includes determining a first travel time of a first ultrasonic wave along a first path from the outer surface back to the outer surface which path includes at least a first part of the bone segment together with determining a second travel time of a second ultrasonic wave along a second path from the outer surface back to the outer surface, which path includes at least a second part of the bone segment and also determining a third travel time of a third ultrasonic wave along a third path from the outer surface back to the outer surface which path includes at least a third part of the bone segment, and deriving the acoustic velocity in the segment of bone from the three determined travel times.

Claims

1. A method of determining an acoustic velocity in a segment of a bone covered with a layer of soft tissue having an outer surface, comprising:

determining a first travel time of a first ultrasonic wave along a first path from said outer surface back to said outer surface which path includes a first bone path in at least a first part of said bone segment and a first soft tissue path in at least part of said soft tissue;

determining a second travel time of a second ultrasonic wave along a second path from said outer surface back to said outer surface which path includes a second bone path in at least a second part of bone segment and a second soft tissue path in at least part of said soft tissue;

determining a third travel time of a third ultrasonic wave along a third path from said outer surface back to said outer surface which path includes a third bone path in at least a third part of said bone segment and a third soft tissue path in at least part of said soft tissue; and

defining relationships between the acoustic velocity in bone and the travel times by a set of simultaneous equations, and deriving a value for the acoustic velocity in bone based on a solution of the set of simultaneous equations.

2. A method according to claim 1, wherein at least two of said first, second and third waves are generated simultaneously by a single transmitter.

3. A method according to claim 1, wherein at least two of said first, second and third waves are detected simultaneously by a single transmitter.

4. A method according to claim 1, wherein at least two of said first, second and third waves each have an average frequency that is substantially the same, when generated.

5. A method according to claim 1, wherein at least two of said first, second and third waves each have an average frequency that is substantially different, when generated.

6. A method according to claim 1, wherein at least two of said first, second and third waves each have an average frequency that is substantially different, when detected.

7. A method according to claim 1, wherein at least two of said first, second and third waves each have an average frequency that is substantially the same, when detected.

8. A method according to claim 1, wherein at least two of said first, second and third soft tissue paths have an overlap of at least 20%.

9. A method according to claim 1, wherein at least two of said first, second and third soft tissue paths have an overlap of at least 30%.

10. A method according to claim 1, wherein no two of said first, second and third soft tissue paths overlap by more than 20%.

11. A method according to claim 1, wherein no two of said first, second and third soft tissue paths overlap by more than 30%.

12. A method according to claim 1, wherein at least two of said first, second and third bone paths overlap at least 20% over their length.

13. A method according to claim 1, wherein at least two of said first, second and third bone paths overlap at least 40% over their length.

14. A method according to claim 1, wherein at least two of said first, second and third bone paths overlap at least 70% over their length.

15. A method according to claim 1, wherein no two of said first, second and third bone paths overlap by 20% or more of their length.

16. A method according to claim 1, wherein no two of said first, second and third bone paths overlap by 40% or more of their length.

17. A method according to claim 1, wherein no two of said first, second and third bone paths overlap by 70% or more of their length.

18. A method according to claim 1, comprising estimating a soft tissue velocity and wherein deriving said acoustic velocity comprises deriving said bone velocity using said estimated soft tissue velocity.

19. A method according to claim 1, comprising determining a fourth travel time of a fourth ultrasonic wave along a fourth path from said outer surface back to said outer surface which path includes at least a fourth part of said bone segment and wherein the set of equations comprises at least one equation defining a relationship between the acoustic velocity in bone and the fourth travel time.

20. A method according to claim 1, wherein geometric projections of at least tow of said acoustic wave paths onto the outer surface are parallel.

21. A method according to claim 1, wherein no geometric projections of said acoustic wave paths onto the outer surface are parallel to each other.

22. A method according to claim 1, wherein said acoustic waves are generated and detected by ultrasonic elements at end faces thereof and wherein said end faces are not coplanar.

23. A method according to claim 1, wherein said outer surface is not parallel to an outer surface of said bone, while said waves travel through said bone.

24. A method according to claim 1, wherein deriving comprises solving a set of simultaneous equations.

25. A method according to claim 1, comprising, repeating said determining of travel times and said deriving of acoustic velocity for a plurality of bone segments, to generate a map of acoustic bone velocity of at least a portion of a bone.

26. A method according to claim 1, comprising, repeating said determining of travel times and said deriving of acoustic velocity for a plurality of orientations of travel of said waves through said bone, to generate a map of directional acoustic bone velocity of at least a portion of a bone.

27. A method of determining at least one of a set of unknowns, including an acoustic bone velocity, acoustic soft tissue velocity, a thickness of said soft tissue and an inclination angle of an outer surface of said soft tissue relative to the bone, comprising:

determining the travel time of at least three ultrasonic waves which travel from said surface, to said bone, along a region in said bone and back to said surface;

assuming a value for at least one of said unknowns;

defining relationships between the remaining unknowns by a set of simultaneous equations that are dependent on the travel times and the assumed value; and

deriving, by solving the set of simultaneous equations, at least one of said unknowns from said three determined travel times and from said assumed value.

28. A method according to claim 27, wherein said assumed unknown comprises an acoustic soft tissue velocity.

29. A probe for acoustic bone velocity measurement, comprising:

at least four ultrasonic elements, at least one of which comprises a transmitter and at least one of which comprises a receive; and

a controller which controls said at least one transmitter to transmit at least three ultrasonic waves through a layer of soft tissue to a bone, which controller detects via said at least one receiver, at least relative travel times of said at least three waves, after they travel along a surface of in said bone and which controller derives an acoustic bone velocity based on a solution of a set of simultaneous equations that define relationships between the acoustic velocity in the bone and the relative travel times.

30. A probe according to claim 29, wherein said at least four ultrasonic elements comprise three transmitters and one receiver.

31. A probe according to claim 29, wherein said at least four ultrasonic elements comprise three receivers and one transmitter.

32. A probe according to claim 29, wherein said at least four ultrasonic elements comprise two receivers and two transmitters.

33. A probe according to claim 29, wherein all of said ultrasonic elements are coplanar.

34. A probe according to claim 29, wherein not all of said ultrasonic elements are coplanar.

35. A probe according to claim 29, wherein said probe comprises a surface a surface adapted to be urged against a skin layer of a soft tissue and wherein said ultrasonic elements are inclined relative to said surface of said probe at an inclination angle.

36. A probe according to claim 35, wherein said inclination angle is determined responsive to an expected acoustic bone velocity.

37. A probe according to claim 29, wherein said at least three ultrasonic waves are generated by a single transmitter as a single wave, which wave scatters to form said at least three waves.