Virtual mapping of an anatomical pivot point and alignment therewith

• US 8,864,686 B2
• Filed: 08/10/2010
• Issued: 10/21/2014
• Est. Priority Date: 12/01/2005
• Status: Active Grant

• Current Assignee: Howmedica Osteonics Corp. (Stryker Corporation)
• Original Assignee: OrthoSensor, Inc (Stryker Corporation)
• Inventors: Roche, Martin, Boillot, Marc, McIntosh, Jason
• Primary Examiner(s): ROZANSKI, MICHAEL T
• Application Number:
  US12/853,987
• Publication Number:
  US 20110060220A1
• Time in Patent Office: 1,533 Days
• Field of Search: 600/447, 345/156, 345/158, 367/117, 367/118, 367/124, 367/125
• US Class Current: 600/587
• CPC Class Codes: G06F 3/017 Gesture based interaction, e.g. based on a set of recognized hand gestures interaction based on gestures traced on a digitiser G06F3/04883
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/04847 Interaction techniques to control parameter settings, e.g. interaction with sliders or dials

Abstract

A system and method is provided for resolving a pivot point via touchless interaction. It applies to situations where one end of a rigid object is inaccessible but remains stationary at a pivot point, while the other end is free to move and is accessible to an input pointing device. As an example, the rigid object can be a leg bone where the proximal end is at the hip joint and the distal end is at the knee. The system comprises a wand and a receiver that are spatially configurable to touchlessly locate the pivot point without contact. The receiver tracks a relative displacement of the wand and geometrically resolves the location of the pivot point by a spherical mapping. The system can use a combination of ultrasonic sensing and/or accelerometer measurements. Other embodiments are disclosed.

Claims

1. A method for determining an anatomical pivot point and alignment therewith, the method comprising the steps of:

transmitting ultrasonic signals from an ultrasonic wand to an ultrasonic receiver, where the ultrasonic receiver is attached to a first end of a bone, the bone comprises two ends, and a second end of the bone is sufficiently stationary;

determining paired transmit-receive ranges between the ultrasonic wand and the ultrasonic receiver by weighted time of flight and phase differential measurements of the ultrasonic signals captured and processed at the ultrasonic receiver;

tracking the ultrasonic wand by way of, and relative to, the ultrasonic receiver during constrained rotational and translational movement at the first end from the paired transmit-receive ranges while the ultrasonic wand is positioned stationary, in proximity and in-sight of the ultrasonic receiver;

calculating a three-dimensional displacement and orientation time trajectory of the ultrasonic wand relative to the ultrasonic receiver from the tracking of the ultrasonic, wand and the time of flight and phase differential measurements;

generating a hemispherical surface representation of the constrained movement at the first end of the bone from the three-dimensional displacement and orientation time trajectory; and

calculating a pivot point of the second end of the bone from the hemispherical surface representation of the constrained movement relative to a predetermined origin of the ultrasonic receiver at the first end of the bone.

2. The method of claim 1, where the ultrasonic receiver further performs the steps of;

tracking a wand tip location of the ultrasonic wand upon movement away from the stationary position;

registering a reference point on the bone pointed to by way of the wand tip;

creating a first vector from the pivot point to the reference point;

registering a tracking point on a second bone pointed to by way of the wand tip;

creating a second vector from the reference point to the tracking point; and

reporting alignment of the first vector and the second vector,

where the wand tip has no sensory electronics, transmitters or labeled markers affixed or attached thereon.

3. The method of claim 1, wherein the step of generating a hemispherical surface representation comprises calculating a least squares spherical fit of a locus of three-dimensional surface points produced from the tracking of the ultrasonic receiver during the constrained movement.

4. The method of claim 3, wherein the the east squares sphere fit resolves a radial length of the bone and an origin of the pivot point relative to the ultrasonic receiver from the constrained movement, where the bone is:

an arm bone that moves with respect to a relatively stationary elbow or shoulder pivot joint, or

a leg bone that moves with respect to a relatively stationary knee or hip pivot point.

5. The method of claim 1, further comprising weighting a direct time of flight and phase differential measurements according to a relative location of the ultrasonic wand with respect to a location of the ultrasonic receiver.

6. The method of claim 1, further comprising:

synchronizing a transmit pulsing of the ultrasonic signals transmitted at the ultrasonic wand and

incorporating timing of the synchronized transmit pulsing for determining the time of flight and phase differentials.

7. The method of claim 6, comprising periodically transmitting an optical pulse from a transmitter to the receiver to establish a synchronized and periodic time reference for the time of flight and the phase differential measurements.

8. The method of claim 1, comprising:

creating a sound map of the acoustic propagation characteristics of the-ultrasonic wand transmitters at a plurality of locations in physical space in proximity to the ultrasonic receiver; and

weighting the time of flight and the phase differential measurements of the ultrasonic signals according to the sound map,

where the sound map identifies transmission parameters of temperature, attenuation, frequency and phase.

9. A method for determining an anatomical pivot point and alignment therewith, the method comprising the steps of:

producing a three-dimensional acceleration surface according to changes in a local orientation of an ultrasonic receiver due to acceleration,

where the ultrasonic receiver is attached to a first end of a bone, the bone comprises two ends, and a second end of the bone is sufficiently stationary;

generating a hemispherical surface representation of constrained rotational and translational movement at the first end from the three-dimensional acceleration surface; and

calculating, relative to the ultrasonic receiver, a pivot point of the bone at the second end from the hemisphencai surface representation of the three-dimensional acceleration surface.

10. The method of claim 9, where the ultrasonic receiver further performs the steps of:

directing an ultrasonic wand to transmit ultrasonic signals by way of three or more ultrasonic transducers located thereon;

determining time of flight and phase differential measurements of the transmitted ultrasonic signals at the ultrasonic receiver; and

tracking a wand tip location of the ultrasonic wand that is in proximity and in-sight of the ultrasonic receiver.

11. The method of claim 10, where the ultrasonic receiver performs the steps of:

registering a reference point on the bone pointed to by way of the wand tip;

creating a first vector from the pivot point to the reference point;

identifying a tracking point on a second bone by way of the ultrasonic wand;

creating a second vector from a distal point to the tracking point; and

reporting alignment of the first vector and the second vector,

where the wand tip has no sensory electronics, transducers, or labeled markers affixed or attached thereon.

12. The method of claim 9, comprising

calculating a least squares spherical fit of the acceleration surface for each of a plurality of three or more transducers;

determining an intersection of the least squares spherical fit representing each of the three or more transducers; and

resolving a radial length of the bone and an origin of the pivot point from the intersection.

13. A system for determining an anatomical pivot point and alignment therewith, the system comprising:

an ultrasonic wand including;

three or more ultrasonic transmitters to transmit ultrasonic signals through air;

an electronic circuit to generate and shape driver signals to the three or more ultrasonic transmitters for producing the ultrasonic signals;

an interface to receive user input for registering a wand tip location of the ultrasonic wand,

a communications port to relay the user input and or receiving timing information to control the electronic circuit; and

a battery to power the electronic circuit and associated electronics,

where the wand tip has no sensory electronics, transmitters or labeled markers affixed or attached thereon,

and

an ultrasonic receiver including;

a processor to generate timing information, track hemispherical movement of the ultrasonic receiver from the timing information, and resolve a pivot point of the hemispherical movement when the ultrasonic wand is in proximity;

a communications interface to transmit the timing information to the ultrasonic wand that in response transmits the ultrasonic signals;

three or more microphones to receive the ultrasonic signals transmitted through the air.

a memory to store received ultrasonic signals to produce a history of received ultrasonics signals,

a wireless communication interface to wirelessly convey positional information and alignment of pointing locations to a remote system; and

a battery to power the processor and associated electronics,

where the processor selectively references the history of stored ultrasonic signals to track the hemispherical movement of the ultrasonic receiver over time.

14. The system of claim 13, where the processor:

directs the ultrasonic wand to transmit the ultrasonic signals, where the ultrasonic receiver is configured to be attached to a first end of a bone, the bone comprises two ends, and a second end of the bone is sufficiently stationary;

determines paired transmit-receive ranges between the ultrasonic wand and the ultrasonic receiver by weighted time of flight and phase differential measurements of the ultrasonic signals captured and processed at the ultrasonic receiver;

tracks the ultrasonic wand by way of, and relative to, the ultrasonic receiver during constrained rotational and translational movement of the first end of the bone from the paired transmit-receive ranges while the ultrasonic wand is positioned stationary, in proximity and in-sight of the ultrasonic receiver; and

registers a pointing location of the wand tip responsive to the user input, and determines an alignment of the pivot point and two or more registered wand tip locations.

15. The system of claim 14, where the processor:

calculates a three-dimensional displacement and orientation time trajectory of the ultrasonic wand relative to the ultrasonic receiver from the tracking of the ultrasonic wand and the time of flight and phase differential measurements;

generates a hemispherical surface representation of the movement at the first end of the bone from the three-dimensional displacement and orientation time trajectory; and

calculates the pivot point of the second end of the bone from the hemispherical surface representation of the movement relative to a predetermined origin of the ultrasonic receiver at the first end of the bone,

where the bone is;

a leg bone that is relatively straight with respect to a hip pivot point, or

an arm bone that is relatively straight with respect to a shoulder pivot joint.

16. The system of claim 13, where the processor:

synchronizes a transmit pulsing of the ultrasonic signals at the ultrasonic wand; and

determines the time of flight and phase differentials from the synchronized transmit pulsing.

17. The system of claim 13, where the ultrasonic wand includes:

an infrared transmitter that pulses an infrared timing signal that is synchronized with the transmitting of the ultrasonic signals to the ultrasonic receiver,

where the ultrasonic receiver includes a photo diode for detecting the infrared signal and establishing a transmit time of the ultrasonic signals to permit wireless infrared communication there between.

18. The system of claim 13, where the communications interface of the ultrasonic receiver includes a wireless communication channel operating via BlueTooth, Zig-Bee or Radio Frequency.

19. The system of claim 13, where the ultrasonic receiver includes:

an accelerometer to determine a local orientation relative to the ultrasonic wand, where the ultrasonic receiver is configured to be attached to a first end of a bone, the bone comprises two ends, and a second end of the bone is sufficiently stationary, and the processor;

produces a three-dimensional acceleration surface according to changes in the local orientation of the ultrasonic receiver due to acceleration;

generates a hemispherical surface representation of the movement at the first end of the bone in three-dimensions from the three-dimensional acceleration surface; and

calculates, relative to the ultrasonic receiver, a pivot point of the bone at the second end from the hemispherical surface representation of the three-dimensional acceleration surface.

20. The system of claim 19, where the ultrasonic receiver

directs the ultrasonic wand to transmit ultrasonic signals by way of the three or more ultrasonic transducers located thereon;

determine time of flight and phase differential measurements of the transmitted ultrasonic signals at the ultrasonic receiver;

tracks a wand tip location of the ultrasonic wand that is in proximity and in-sight of the ultrasonic receiver to register two or more points of interest; and

reports alignment of the pivot point and the two or more points of interest.