Intrinsic co-registration for modular multimodality medical imaging systems
A method and device are provided for matching a patient coordinate system (PCS) of a nuclear medical imaging scanner with a coordinate system of a CT scanner in a multimodality modular imaging system, based on a predefined relationship between a vertical position of a patient bed during the NM scan; an axial position of the patient bed during the NM scan; an axial distance between a gantry of the NM scanner and a gantry of the CT scanner; and a vertical distance between a center of orbit of the NM scanner and a center of rotation of the CT gantry.
1. A method for co-registering a nuclear medical (NM) reconstructed image obtained from an NM scan by an NM scanner having an NM gantry, and a computed tomography (CT) reconstructed image obtained from a CT scan by a CT scanner having a CT gantry in a multimodality imaging system, comprising:
matching a first patient coordinate system of the NM scanner to a second patient coordinate system of the CT scanner, based on a predefined relationship between:
a vertical position of a patient bed during the NM scan;
an axial position of the patient bed during the NM scan;
an axial distance between a gantry of the NM scanner and a gantry of the CT scanner; and
a vertical distance between a center of orbit of the NM scanner and a center of rotation of the CT gantry;
assigning an X-coordinate (X img ) to the CT reconstructed image by:
specifying a row vector [rv x , rv y , rv z ] to reflect the orientation of the CT reconstructed image relative to the second patient coordinate system, and
determining a distance (X center ) from a center of the second patient coordinate system and a transverse extents of the CT reconstructed image centered at an image center point (FOV).
2. The method according to claim 1 , wherein X img is determined according to Equation 1:
X img =X center −( rv x )(½)( FOV CT ) (1)
where (½) (FOV CT ) is given by Equation 2:
(½)( FOV CT )=(MatrixSize CT −1)(PixelSize CT /2) (2)
where MatrixSize CT is the image area of the CT scanner in pixels, and
wherein PixelSize CT is the size of a pixel in a CT image.
3. The method according to claim 1 , further comprising assigning an X coordinate (X NMImg ) to the NM reconstructed image by:
specifying a distance (X NMCenter ) in an X direction between the center of the NM reconstructed image and a center of the first patient coordinate system as 0, and
specifying a row vector [rv x , rv y , rv x ] to reflect the orientation of the NM reconstructed image relative to the first patient coordinate system, such that the row vector is [1, 0, 0].
4. The method according to claim 3 , wherein X NMImg is determined according to Equation 3:
X NMImg =(MatrixSize NM −1)(PixelSize NM /2) (3)
where MatrixSize NM is the image area of the NM scanner in pixels, and
wherein PixelSize NM is the size of a pixel in a NM image.
5. The method according to claim 1 , further comprising assigning a Z-coordinate (Z img ) to the CT reconstructed image based on the orientation of a patient on a CT bed, associated with the CT scanner.
6. The method according to claim 1 , further comprising assigning a Z coordinate (Z NMImg ) to the NM reconstructed image by:
specifying a column vector [cv x , cv y , cv z ] as [0, 0, −1],
specifying Z NMImg as the top row of the column vector.
7. The method according to claim 6 , further comprising determining a Z-position for at least one addition row based on the column vector and a distance of the additional row from the top row (Z NMIMg ).
8. The method according to claim 7 , wherein the Z-position of at least one additional row is the Z-position of a center row of the NM reconstructed image (Z NMCenter ), and wherein Z NMCenter is specified according to Equation 6:
Z NMCenter =Z NMImg +( CV z )(½)( FOV NM )= Z NMImg −(½)( FOV NM ) (6)
where (½) (FOV NM ) is given by Equation 2:
(½)( FOV NM )=(MatrixSize NM −1)(PixelSize NM /2) (2)
wherein MatrixSize NM is the image area of the NM scanner in pixels, and
wherein PixelSize NM is the size of a pixel in a NM image.
9. The method according to claim 1 , further comprising assigning a Y-coordinate (Y img ) to the CT reconstructed image by:
specifying a column vector [cv x , cv y , cv z ] to reflect the orientation of the CT reconstructed image relative to the second patient coordinate system, and
determining a distance (Y center ) from a center of the second patient coordinate system and a transverse extents of the CT reconstructed image centered at an image center point (FOV).
10. The method according to claim 8 , wherein a patient is scanned in a prone position and the column vector is specified as [0, −1, 0].
11. The method according to claim 8 , wherein a patient is scanned in a supine position and the column vector is specified as [0, 1, 0].
12. The method according to claim 1 , wherein
assigning a Y coordinate (Y NMImg ) to the NM reconstructed image by:
specifying a distance (Y NMCenter ) in a Y direction between the center of the NM reconstructed image and a center of the first patient coordinate system as 0, and
specifying a column vector [cv x , cv y , cv z ] to reflect the orientation of the NM reconstructed image relative to the first patient coordinate system, such that the row vector is [0, 1, 0].
13. The method according to claim 12 , wherein, for supine scans, Y NMImg is determined according to Equation 14:
Y NMImg =Y NMCenter −Y NMBed −(½)( FOV NM ) (14).
14. The method according to claim 12 , wherein, for prone scans, Y NMImg is determined according to Equation 15:
Y NMImg =Y NMBed −Y NMCenter −(½)( FOV NM ) (15).
15. A device for co-registering a nuclear medical (NM) reconstructed image obtained from an NM scan by an NM scanner having an NM gantry, and a computed tomography (CT) reconstructed image obtained from a CT scan by a CT scanner having a CT gantry, wherein the device comprises a programmable element, programmed to
match a first patient coordinate system of the NM scanner to a second patient coordinate system of the CT scanner, based on a predefined relationship between:
a vertical position of a patient bed during the NM scan;
an axial position of the patient bed during the NM scan;
an axial distance between the NM gantry and the CT gantry; and
a vertical distance between a center of orbit of the NM scanner and a center of rotation of the CT gantry.
wherein the programmable element is further programmed to:
assign an X-coordinate (X img ) to the CT reconstructed image by:
specifying a row vector [rv x , rv y , rv z ] to reflect the orientation of the CT reconstructed image relative to the second patient coordinate system, and
determining a distance (X center ) from a center of the second patient coordinate system and a transverse extents of the CT reconstructed image centered at an image center point (FOV).
16. The device according to claim 15 , wherein X img is determined according to Equation 1,
X img =X center −( rv x )(½)( FOV CT ) 1,
where (½) (FOV CT ) is given by Equation 2,
(½)( FOV CT )=(MatrixSize CT −1)(PixelSize CT /2) 2,
where MatrixSize CT is the image area of the CT scanner in pixels, and
wherein PixelSize CT is the size of a pixel in a CT image.
17. The device according to claim 15 , wherein the programmable element is further programmed to assign an X coordinate (X NMImg ) to the NM reconstructed image by:
specifying a distance (X NMCenter ) in an X direction between the center of the NM reconstructed image and a center of the first patient coordinate system as 0, and
specifying a row vector [rv x , rv y , rv z ] to reflect the orientation of the NM reconstructed image relative to the first patient coordinate system, such that the row vector is [1, 0, 0].
18. The device according to claim 17 , wherein the programmable element is further programmed to determine X NMImg according to Equation 3:
X NMImg =(MatrixSize NM −1)(PixelSize NM /2) (3)
wherein MatrixSize NM is the image area of the NM scanner in pixels, and
wherein PixelSize NM is the size of a pixel in a NM image.
19. The device according to claim 15 , wherein the programmable element is further programmed to assign a Z-coordinate (Z img ) to the CT reconstructed image based on the orientation of a patient on a CT bed, associated with the CT scanner.
20. The device according to claim 15 , wherein the programmable element is further programmed to assign a Z coordinate (Z NMImg ) to the NM reconstructed image by:
specifying a column vector [cv x , cv y , cv z ] as [0, 0, −1], and by
specifying Z NMImg as the top row of the column vector.
21. The device according to claim 20 , wherein the programmable element is further programmed to determine a Z-position for at least one addition row based on the column vector and a distance of the additional row from the top row (Z NMIMg ).
22. The device according to claim 21 , wherein the Z-position of at least one additional row is the Z-position of a center row of the NM reconstructed image (Z NMCenter ), and wherein the programmable element is further programmed to specify Z NMCenter according to Equation 6:
Z NMCenter =Z NMImg +( CV z )(½)( FOV NM )= Z NMImg −(½)( FOV NM ) (6)
where (½) (FOV NM ) is given by Equation 2,
(½)( FOV NM )=(MatrixSize NM −1)(PixelSize NM /2) (2)
wherein MatrixSize NM is the image area of the NM scanner in pixels, and
wherein PixelSize NM is the size of a pixel in a NM image.
23. The device according to claim 15 , wherein the programmable element is further programmed to assign a Y-coordinate (Y img ) to the CT reconstructed image by:
specifying a column vector [cv x , cv y , cv z ] to reflect the orientation of the CT reconstructed image relative to the second patient coordinate system, and
to determine a distance (Y center ) from a center of the second patient coordinate system and a transverse extents of the CT reconstructed image centered at an image center point (FOV).
24. The device according to claim 23 , wherein the programmable element is further programmed to specify the column vector as [0, −1, 0] when a patient is scanned in a prone position.
25. The device according to claim 23 , wherein the programmable element is further programmed to specify the column vector as [0, 1, 0] when a patient is scanned in a supine position.
26. The device according to claim 15 , wherein the programmable element is further programmed to assign a Y coordinate (Y NMImg ) to the NM reconstructed image by:
specifying a distance (Y NMCenter ) in a Y direction between the center of the NM reconstructed image and a center of the first patient coordinate system as 0, and
specifying a column vector [cv x , cv y , cv z ] to reflect the orientation of the NM reconstructed image relative to the first patient coordinate system, such that the row vector is [0, 1, 0].
27. The device according to claim 26 , wherein, for supine scans, the programmable element is further programmed to determine Y NMImg according to Equation 14:
Y NMImg =Y NMCenter −Y NMBed −(½)( FOV NM ) 14.
28. The device according to claim 27 , wherein, for prone scans, the programmable element is further programmed to determine Y NMImg according to Equation 15:
Y NMImg =Y NMBed −Y NMCenter −(½)( FOV NM ) 15.