Single- and multi-modality alignment of medical images in the presence of non-rigid deformations using phase correlation
A phase correlation method (PCM) can be used for translational and/or rotational alignment of 3D medical images even in the presence of non-rigid deformations between first and second images of a registered volume of a patient.
1. A computer program product comprising a non-transitory machine-readable medium storing instructions which, when executed by at least one programmable processor, cause the at least one programmable processor to perform operations comprising:
receiving a first medical image of a patient taken at a first time and at a first position and a second medical image of the patient taken at a second time and at a second position, the first medical image and the second medical image different due to a deformation present in the second medical image;
comparing the first medical image and the second medical image using a phase correlation method, the comparing comprising:
calculating an inverse Fourier transform of a cross-power spectrum of the first medical image and the second medical image, the inverse Fourier transform having a peak spread around neighboring voxels due to the deformation; and
calculating a displacement of the peak based at least partially on the intensities of the neighboring voxels;
determining, based on the displacement, a change to at least one of a physical location and a physical orientation of the patient; and
correcting, based on the determined change, the second position of the patient to more closely conform to the first position of the patient.
2. A computer program product as in claim 1 , wherein the inverse Fourier transform of the cross-power spectrum is normalized.
3. A computer program product as in claim 1 , the comparing further comprising:
finding a maximum intensity of the inverse Fourier transform of the cross-power spectrum; and
selecting as the peak, from a plurality of voxels having intensities greater than a threshold determined based on the maximum intensity, a voxel for which a sum of voxel intensities of neighboring voxels around the voxel is highest, wherein the neighboring voxels are in a window sized as a fraction of a number of voxels along each dimension of a common registration grid.
4. A computer program product as in claim 3 , wherein the threshold is 0.9 times the maximum intensity.
5. A computer program product as in claim 3 , wherein the fraction is 0.05.
6. A computer program product as in claim 3 , the comparing further comprising determining the displacement of the peak by calculating a centroid of the voxel intensities of the neighboring voxels in the window.
7. A computer program product as in claim 1 , the correcting further comprising causing translating or rotating of a patient by causing movement of a patient couch or bed.
8. A computer program product as in claim 7 , wherein the first medical image and the second medical image are aligned by generating one or more commands to automatically translate or rotate the patient couch or bed.
9. A system comprising:
at least one programmable processor; and
a non-transitory machine-readable medium storing instructions which, when executed by the at least one programmable processor, cause the at least one programmable processor to perform operations comprising:
receiving a first medical image of a patient taken at a first time and at a first position and a second medical image of the patient taken at a second time and at a second position, the first medical image and the second medical image different due to a deformation present in the second medical image;
comparing the first medical image and the second medical image using a phase correlation method, the comparing comprising:
calculating an inverse Fourier transform of a cross-power spectrum of the first medical image and the second medical image, the inverse Fourier transform having a peak spread around neighboring voxels due to the deformation; and
calculating a displacement of the peak based at least partially on the intensities of the neighboring voxels;
determining, based on the displacement, a change to at least one of a physical location and a physical orientation of the patient; and
correcting, based on the determined change, the second position of the patient to more closely conform to the first position of the patient.
10. A system as in claim 9 , wherein the inverse Fourier transform of the cross-power spectrum is normalized.
11. A system as in claim 9 , the comparing further comprising:
finding a maximum intensity of the inverse Fourier transform of the cross-power spectrum; and
selecting as the peak, from a plurality of voxels having intensities greater than a threshold determined based on the maximum intensity, a voxel for which a sum of voxel intensities of neighboring voxels around the voxel is highest, wherein the neighboring voxels are in a window sized as a fraction of a number of voxels along each dimension of a common registration grid.
12. A system as in claim 11 , wherein the threshold is 0.9 times the maximum intensity.
13. A system as in claim 11 , wherein the fraction is 0.05.
14. A system as in claim 11 , the comparing further comprising determining the displacement of the peak by calculating a centroid of the voxel intensities of the neighboring voxels in the window.
15. A system as in claim 9 , the correcting further comprising causing translating or rotating of a patient by causing movement of a patient couch or bed.
16. A system as in claim 15 , wherein the first medical image and the second medical image are aligned by generating one or more commands to automatically translate or rotate the patient couch or bed.
17. A computer program product as in claim 1 , wherein the first medical image and the second medical image are received from at least one of an MRI imaging device or a CT imaging device.
18. A system as in claim 9 , wherein the first medical image and the second medical image are received from at least one of an MRI imaging device or a CT imaging device.