Method and apparatus for aligning a multi-modality imaging system

1. A method of determining component misalignment in a multi-modality imaging system including a first modality unit and a second modality unit, said method comprising:

imaging a plurality of target objects with the second modality unit to generate an emission image data set;

determining a location of the target objects in the emission image data set to produce emission target object location coordinates;

calculating a positional alignment vector for each target object based on the emission target object location coordinates; and

aligning the multi-modality imaging system based on the positional alignment vectors.

2. A method in accordance with claim 1 further comprising:

imaging the plurality of target objects with the first modality unit to generate a transmission image data set;

determining a location of the target objects in the transmission image data set to produce transmission target object location coordinates; and

calculating a positional alignment vector for each target object based on the emission target object location coordinates and the transmission target object location coordinates.

3. A method in accordance with claim 1 further comprising masking a portion of the multi-modality imaging system mask that lies outside of a field of view of the plurality of target objects to reduce attenuation noise.

4. A method in accordance with claim 1 further comprising registering the emission image data set with a transmission image data set to calculate a positional alignment vector for each target object.

5. A method in accordance with claim 1 further comprising imaging an alignment object that includes the plurality of target objects embedded within the alignment object.

6. A method in accordance with claim 1 further comprising imaging an alignment object that includes the plurality of radioactive target objects embedded within an alignment object, wherein each of the target objects has a diameter that is greater than a slice thickness produced by either the first modality unit or the second modality unit.

7. A method in accordance with claim 1 further comprising imaging an alignment object that includes the plurality of radioactive target objects embedded within the alignment object, wherein each of the target objects has a diameter that is between three and six time larger than a thickness of an image slice produced by either the first modality unit or the second modality unit.

8. A method in accordance with claim 1 further comprising imaging an alignment object that includes the plurality of radioactive target objects embedded within the alignment object to achieve a maximum error measurement between the emission image data set and a transmission image data set.

9. A method in accordance with claim 1 wherein the second modality comprises a PET imaging system said method further comprising calculating a misalignment of an imaging table relative to the PET imaging system based on the positional displacement vectors.

10. A method in accordance with claim 1 wherein the first modality comprises a CT imaging system and the second modality comprises a PET imaging system said method further comprising calculating a misalignment of the CT imaging system relative to the PET imaging system based on the positional displacement vectors.

11. A method in accordance with claim 1 further comprising performing a mechanical alignment of the multi-modality imaging system when at least one of the positional displacement vectors is greater than a predetermined tolerance value.

12. A method in accordance with claim 1 further comprising performing a mechanical alignment of the multi-modality imaging system when at least one of the positional displacement vectors is greater than approximately five millimeters.

13. A method in accordance with claim 1 further comprising performing a software alignment of the multi-modality imaging system when at least one of the positional displacement vectors is less than or equal to a predetermined tolerance value.

14. A method in accordance with claim 1 further comprising performing a software alignment of the multi-modality imaging system when at least one of the positional displacement vectors is less than approximately five millimeters.

15. A method in accordance with claim 1 wherein the first modality comprises a CT imaging system and the second modality comprises a PET imaging system said method further comprising calculating at least one of a PET unit to table gantry linear misalignment in x parameter, a PET unit to table gantry linear misalignment in y parameter, a PET unit to table gantry linear misalignment in z parameter, a PET unit to table gantry tilt parameter, a PET unit to table gantry vase parameter, a gantry roll parameter, a CT unit to table gantry tilt parameter, and a PET unit to gantry yaw parameter.

16. A multi-modality imaging system comprising a first modality unit, a second modality unit, and a computer operationally coupled to the first and second modality units, wherein the computer is programmed to:

image a plurality of target objects with the second modality unit to generate an emission image data set;

determine a location of the target objects in the emission image data set to produce emission target object location coordinates; and

calculate a positional alignment vector for each target object based on the emission target object location coordinates, the positional alignment vectors used to align the multi-modality imaging system.

17. A multi-modality imaging system in accordance with claim 16 , wherein the computer is further programmed to:

image a plurality of target objects with the first modality unit to generate a transmission image data set;

determine a location of the target objects in the transmission image data set to produce transmission target object location coordinates; and

calculate the positional alignment vector for each target object based on the target transmission target object location coordinates.

18. A multi-modality imaging system in accordance with claim 16 , wherein the computer is further programmed to generate an indication to perform a mechanical alignment if at least one of the positional displacement vectors is greater than a predetermined tolerance value.

19. A multi-modality imaging system in accordance with claim 16 , wherein the computer is further programmed to generate an indication to perform a software alignment if at least one of the positional displacement vectors is less than or equal to a predetermined tolerance value.

20. A multi-modality imaging system in accordance with claim 16 , wherein the computer is further programmed to calculate a matrix T that includes a number of points in a first modality image space that match points in a second modality imaging space.

21. A multi-modality imaging system in accordance with claim 16 , wherein the computer is further programmed to calculate the inverse (I) to the matrix.

22. A computer readable medium encoded with a program programmed to instruct a computer to:

image a plurality of target objects with the second modality unit to generate an emission image data set;

determine a location of the target objects in the emission image data set to produce emission target object location coordinates; and

calculate a positional alignment vector for each target object based on the emission target object location coordinates, the positional alignment vectors used to align the multi-modality imaging system.

23. A computer readable medium in accordance with claim 22 wherein the computer readable medium is further programmed to:

image a plurality of target objects with the first modality unit to generate a transmission image data set;

determine a location of the target objects in the transmission image data set to produce transmission target object location coordinates; and

calculate the positional alignment vector for each target object based on the target transmission target object location coordinates.

24. A computer readable medium in accordance with claim 22 wherein the computer readable medium is further programmed to use the positional displacement vectors to calculate a misalignment of the table relative to the second modality unit and to calculate a misalignment between the first modality unit and the second modality unit.

25. A computer readable medium in accordance with claim 22 wherein the computer readable medium is further programmed to calculate a matrix T that includes a number of points in a first modality image space that match points in a second modality imaging space.

26. A computer readable medium in accordance with claim 24 wherein the computer readable medium is further programmed to calculate the inverse (I) to the matrix T.