Device and method for calibrating tracking systems in imaging systems

• US 9,746,540 B2
• Filed: 11/06/2013
• Issued: 08/29/2017
• Est. Priority Date: 11/06/2012
• Status: Active Grant

• Current Assignee: Albert Ludwigs University of Freiburg
• Original Assignee: Albert Ludwigs University of Freiburg
• Inventors: Speck, Oliver, Kadachevitch, Ilia, Ernst, Thomas, Zaitsev, Maxim, Lovell-Smith, Crispin, Maclaren, Julian
• Primary Examiner(s): Yentrapati, Avinash
• Application Number:
  US14/440,599
• Publication Number:
  US 20150331078A1
• Time in Patent Office: 1,392 Days
• Field of Search: None
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 6/03 Computed tomography [CT] echo-tomography A61B8/14
• CPC Class Codes: A61B 6/582 Calibration
• CPC Class Codes: F04C 2270/041 Controlled or regulated
• CPC Class Codes: G01R 33/28 Details of apparatus provided for in groups G01R33/44 - G01R33/64
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
• CPC Class Codes: G01R 33/58 Calibration of imaging systems, e.g. using test probes , Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material
• CPC Class Codes: G01T 1/161 Applications in the field of nuclear medicine, e.g. in vivo counting apparatus for radiation diagnosis A61B6/00

Abstract

A device and a method for calibrating the coordinate system of imaging systems having a tracking system prior or during image data acquisition, e.g. by way of magnetic resonance tomography.

Claims

1. A method for calibrating tracking systems in imaging systems and for prospective motion correction of a moving object being imaged or of a moving object being imaged in MRT, in IMRT or in CT, the method comprising the steps of:

a) providing a tracking system having a tracking coordinate system;

b) providing at least one imaging system having an imaging coordinate system;

c) providing at least one first marker that is stationary relative to the imaging system as a reference marker having a position and orientation;

d) cross calibrating the tracking coordinate system and the imaging coordinate system;

e) measuring a position and orientation of the first marker in the tracking coordinate system;

f) calibrating the position and orientation of the first marker in the imaging coordinate system;

g) monitoring a position and orientation of the first marker in the tracking coordinate system;

h) correcting the cross calibration of step d) using the results of step g), wherein the correction in the cross calibration is carried out using quaternion algebra;

i) disposing at least one second marker on the moving object;

j) detecting a position and orientation of the second marker in the tracking system coordinate system during imaging;

k) converting, following step h), the position and orientation of the second marker detected in step j) into the coordinate system of the imaging system using quaternion algebra; and

l) performing, following steps g) through k), a prospective motion correction such that an imaging volume remains stationary with respect to the moving object during imaging.

2. The method of claim 1, wherein said tracking system is arranged within said imaging system.

3. The method of claim 1, wherein said tracking system is arranged outside of said imaging system.

4. The method of claim 1, wherein said first marker is arranged within said imaging system.

5. The method of claim 1, wherein said first marker is arranged outside of said Imaging system.

6. The method of claim 1, wherein each of a plurality of markers is arranged in imaging systems such that positions and orientations thereof in a coordinate system of a respective imaging system are calibrated, wherein a position and orientation of the second marker arranged on the movable object is converted from a coordinate system of one imaging system into coordinate systems of other imaging systems.

7. The method of claim 1, wherein calibration is performed once as a cross calibration of the coordinate system of the tracking system with coordinates c₀ and C, wherein c₀ is the translation quaternion of the tracking system and C is a rotation quaternion of the tracking system and a position and orientation (r₀, R) of the first marker in the coordinate system of the tracking system are stored and a current position and orientation (x₀, X) of the reference point in the coordinate system of the tracking system is used for calibration in order to calculate a current cross calibration (s₀, S) as follows:

S=X*RC,

wherein X* is a conjugated rotation quaternion of a quaternion X and

s₀=c₀+C*r₀C−

S*x₀S,

wherein C* and S* are conjugates of rotation quaternions C and S.

8. A method for calibrating tracking systems in an imaging apparatus and for prospective or for retrospective motion correction of a moving object being imaged by the imaging apparatus or of a moving object being imaged in MRT, in IMRT or in CT, the method comprising the steps of:

a) providing a tracking system having a tracking coordinate system;

b) providing at least one imaging system having an imaging coordinate system;

c) providing at least one first marker that Is stationary relative to the imaging system as a reference marker having a position and orientation;

d) cross calibrating the tracking coordinate system and the imaging coordinate system;

e) measuring a position and orientation of the first marker in the tracking coordinate system;

f) calibrating the position and orientation of the first marker in the imaging coordinate system;

g) removing the tracking system from the imaging apparatus;

h) reinstalling the tracking system in the imaging apparatus;

i) measuring a position and orientation of the first marker in the tracking coordinate system following step h);

j) correcting the cross calibration of step d) using the results of step i), wherein the correction in the cross calibration is carried out using quaternion algebra;

k) disposing at least one second marker on the moving object;

l) detecting a position and orientation of the second marker in the tracking system coordinate system during imaging;

m) converting, following step j), the position and orientation of the second marker detected in step l) into the coordinate system of the imaging system using quaternion algebra; and

n) performing, following steps i) through m), a prospective or a retrospective motion correction such that an imaging volume remains stationary with respect to the moving object.

9. The method of claim 8, wherein said tracking system is arranged within said imaging system.

10. The method of claim 8, wherein said tracking system is arranged outside of said imaging system.

11. The method of claim 8, wherein said first marker is arranged within said imaging system.

12. The method of claim 8, wherein said first marker is arranged outside of said imaging system.

13. The device of claim 8, wherein each of a plurality of markers is arranged in imaging systems such that positions and orientations thereof are calibrated in a coordinate system of a respective imaging system, wherein a position and orientation of a marker arranged on a movable object is transferred from a coordinate system of an imaging system to coordinate systems of other imaging systems through measurement of position and orientation using said tracking system.

14. The method of claim 8, wherein calibration Is performed once as a cross calibration of the coordinate system of the tracking system with coordinates c₀ and C, wherein c₀ is the translation quaternion of the tracking system and C is a rotation quaternion of the tracking system and a position and orientation (r₀, R) of the first marker in the coordinate system of the tracking system are stored and a current position and orientation (x₀, X) of the reference point in the coordinate system of the tracking system is used for calibration in order to calculate a current cross calibration (s₀, S) as follows:

S=X*RC,

wherein X* is a conjugated rotation quaternion of a quaternion X and

s₀=c₀+C*r₀C−

S*x₀S,

wherein C* and S* are conjugates of rotation quaternions C and S.