Device and method for a trackable ultrasound

• US 20070167787A1
• Filed: 06/21/2006
• Published: 07/19/2007
• Est. Priority Date: 06/21/2005
• Status: Active Grant

• Current Assignee: Philips Electronics Limited (Koninklijke Philips N.V.), United States Department Of Health And Human Services
• Original Assignee: Philips Electronics Limited (Koninklijke Philips N.V.)
• Inventors: Glossop, Neil, Wood, Bradford
• Granted Patent: US 9,398,892 B2
• Time in Patent Office: Days
• US Class Current: 600/447
• CPC Class Codes: A61B 8/00 Diagnosis using ultrasonic, sonic or infrasonic waves imaging of objects using sonar G01S15/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/4245 involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
• CPC Class Codes: A61B 8/445 Details of catheter construction
• CPC Class Codes: A61B 8/58 Testing, adjusting or calibrating the diagnostic device

Abstract

The invention provides a method for adjusting the calibration of a tracked ultrasound device using the measured difference between two sets of fiducial markings in two relative positions of a tracker and an scan head of the device. The invention also provides a trackable ultrasound device that enables repeatable attachment of a tracker to a scan head, thus preserving an initial calibration between the tracker and the scan head. Furthermore, the invention provides a calibration jig that can be used to repeatably attach a tracker to an ultrasound scan head or to measure the difference between two relative positions of a tracker and a scan head.

Claims

1. A method of adjusting a calibration of a tracked ultrasound device, wherein the tracked ultrasound device includes a tracker and a scan head, wherein the tracker includes one or more tracker fiducial markings and one or more sensor elements, wherein the scan head has at least one scan plane originating therefrom and includes one or more scan head fiducial markings, the method comprising:

attaching the tracker to the scan head in a first position;

calculating an initial calibration transformation matrix that relates the one or more sensor elements to the at least one scan plane, such that the position and orientation of the one or more sensor elements enables determination of the position and orientation of the at least one scan plane;

determining a first relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings when the tracker is attached to the scan head in the first position;

moving the tracker relative to the scan head into a second position;

determining a second relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings when the tracker is attached to the scan head in the second position;

calculating a difference between the first and second relative positions of the tracker fiducial markings and the scan head fiducial markings; and

adjusting the initial calibration transformation matrix using the calculated difference between the first and second relative positions of the tracker fiducial markings and the scan head fiducial markings.

2. The method of claim 1, wherein the one or more sensor elements include one or more electromagnetic sensor elements whose position and orientation is determined using an electromagnetic tracking device.

3. The method of claim 1, wherein the one or more sensor elements include one or more inertial guidance sensors, ultrasonic sensors, optical sensors, and fiber optic sensors.

4. The method of claim 1, wherein determining a first relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises sampling first positions of the one or more tracker fiducial markings and the one or more scan head fiducial markings in the same frame of reference,

and wherein determining a second relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises sampling second positions of the one or more tracker fiducial markings and the one or more scan head fiducial markings in the same frame of reference.

5. The method of claim 4, wherein sampling positions of the one or more tracker fiducial markings and the one or more scan head fiducial markings in the same frame of reference further comprises touching a tracked probe to each of the one or more tracker fiducial markings and each of the one or more scan head fiducial markings.

6. The method of claim 4, wherein sampling positions of the one or more tracker fiducial markings and the one or more scan head fiducial markings in the same frame of reference further comprises imaging the one or more tracker fiducial markings and the one or more scan head fiducial markings with an imaging modality.

7. The method of claim 4, wherein sampling positions of the one or more tracer fiducial markings comprises measuring a location of the one or more sensor elements whose positions are know relative to the tracker fiducial markings.

8. The method of claim 1, wherein determining a first relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises:

i) placing the tracker and the scan head into a calibration jig when the tracker is attached to the scan head in the first position, and

ii) determining the relative position of the one or more tracker fiducial markings to one or more calibration jig fiducial markings,

wherein determining a second relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises;

i) placing the tracker and the scan head into the calibration jig when the tracker is attached to the scan head in the second position, and

ii) determining the relative position of the one or more tracker fiducial markings to the one or more calibration jig fiducial markings,

and wherein a relative position of the one or more scan head fiducial markings and the one or more calibration jig fiducial markings remains the same in the first and second positions.

9. The method of claim 1, wherein determining a first relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises calculating a primary transformation matrix that relates the one or more tracker fiducial markings to the one or more scan head fiducial markings in the first position,

and wherein determining a second relative position of the one or more tracker fiducial markings in relation to the one or more scan head fiducial markings further comprises calculating a secondary transformation matrix that relates the one or more tracker fiducial markings to the one or more scan head fiducial markings in the second position.

10. The method of claim 9, wherein calculating a difference between the first and second relative positions of the tracker fiducial markings and the scan head fiducial markings further includes calculating a differential transformation matrix.

11. The method of claim 10, wherein adjusting the initial calibration transformation matrix further comprises applying the differential transformation matrix to the initial calibration transformation matrix.

12. A method for repeatable replacement of a tracker onto an ultrasound device, wherein the tracker includes at least one sensor element and one or more tracker alignment elements, wherein the ultrasound device includes a scan head and one or more scan head alignment elements, wherein at least one scan plane originates from the scan head, and wherein each of the one or more tracker alignment elements corresponds to one of the one or more scan head alignment elements, the method comprising:

calibrating the at least one scan plane to the at least one sensor element when the tracker is attached to the scan head in a first position, such that the position and orientation of the at least one scan plane is determinable from the position and orientation of the at least one sensor element;

removing the tracker from the scan head; and

replacing the tracker onto the scan head into the first position by aligning each of the one or more tracker alignment elements with its corresponding one of the one or more scan head alignment elements.

13. The method of claim 12, wherein the one or more scan head alignment elements and the one or more tracker alignment elements include one or more of:

spring loaded balls and corresponding divots,

pegs and corresponding holes,

clips and corresponding clip receiving divots,

mechanical alignment guides,

corresponding markings, and

matable grooves.

14. The method of claim 12, wherein the at least one sensor element is an electromagnetic sensor element whose position and orientation is determined using an electromagnetic tracking device.

15. The method of claim 12, wherein aligning each of the one or more tracker alignment elements with its corresponding one of the one or more scan head alignment elements further comprises:

attaching the tracker to the scan head,

placing the tracker and the scan head into a calibration jig that includes one or more calibration jig alignment elements that each correspond to at least one tracker alignment element or scan head alignment element, and

aligning each of the one or more calibration jig alignment elements to its corresponding tracker alignment element or scan head alignment element causing the tracker to be aligned onto the scan head in the first position.

16. A trackable ultrasound device, comprising:

a scan head that includes an ultrasonic transducer, wherein at least one scan plane originates from the ultrasonic transducer, and wherein the ultrasound device produces images of material present in the at least one scan plane, the scan head also including one or more scan head alignment elements; and

a tracker that includes at least one sensor element, wherein the tracker includes one or more tracker alignment elements, each one of the one or more tracker alignment elements corresponding to one of the one or more scan head alignment element,

wherein the tracker is attached to the scan head in a first position and the at least one sensor element is initially calibrated to the at least one scan plane such that the position and orientation of the at least one scan plane is determinable from the position and orientation of the at least one sensor element,

and wherein the tracker is removable from the scan head and repeatably replacable onto the scan head in the first position when each of the one or more tracker elements is aligned with its corresponding one of the one or more scan head alignment elements.

17. The trackable ultrasound device of claim 16, wherein the one or more scan head alignment elements and the one or more tracker alignment elements include one or more of:

spring loaded balls and corresponding divots,

pegs and corresponding holes,

clips and corresponding clip receiving divots,

mechanical alignment guides,

corresponding markings, and

matable grooves.

18. The trackable ultrasound device of claim 16, wherein the at least one sensor element is an electromagnetic sensor element whose position and orientation is determined using an electromagnetic tracking device.