Fiducial-less tracking with non-rigid image registration

An image registration system for registering at least one 2D image of an anatomical region with previously generated 3D scan data of the anatomical region, the anatomical region including at least one treatment target and at least one reference structure, wherein the 2D image is generated in near real time by detecting one or more radiographic imaging beams after the imaging beams have traversed at least a portion of the anatomical region, the imaging beams having known intensities and known positions and angles relative to the anatomical region, the system comprising:

• a) means for providing the 3D scan data of the anatomical region;
• b) a DRR generator configured to generate at least one DRR (digitally reconstructed radiograph) of the anatomical region, using the 3D scan data and the known locations, angles, and intensities of the imaging beams;
• c) an ROI selector configured to select an ROI (region of interest) within the DRR, the ROI including the image of the treatment target and of the reference structure;
• d) an image enhancer configured to enhance the DRR and the 2D image by applying a filter operator to the DRR and to the 2D image;
• e) a motion field generator configured to generate a 3D full motion field within the ROI by estimating a plurality of local motion fields within the ROI;
• and
• f) a parameter determiner configured to determine from the 3D full motion field a set of non-rigid transformation parameters that represent the difference in the position and orientation of the treatment target as shown in the 2D image, as compared to the position and orientation of the treatment target as shown in the DRR.

A system for registering at least one image of an object with scan data of the object, the object including a target region and a reference structure, the system comprising:

• a) means for providing the scan data of the object;
• b) a radiation source configured to generate one or more radiographic imaging beams, the imaging beams having known intensities, and having known positions and angles relative to the object;
• c) an imaging system configured to generate a radiographic image of the object by detecting the radiographic imaging beam after the beam has traversed at least a portion of the object;
• and
• d) a controller, including:
• i) a DRR generator configured to generate at least one DRR (digitally reconstructed radiograph) of the object, using the scan data and the known location, angle, and intensity of the imaging beam;
• ii) an ROI selector configured to select an ROI (region of interest) within the DRR, the ROI including the image of the target region and of the reference structure;
• iii) an image enhancer configured to enhance the DRR and the ROI by applying a filter operator to the DRR and to the ROI;
• iv) a similarity measure determiner configured to determine a similarity measure between the DRR and the ROI;
• v) a motion field generator configured to estimate, for each of a plurality of resolution levels, one or more 20 local motion fields within the ROI, using the similarity measure, and to derive a 3D full motion field from the estimated 2D local motion fields;
• and
• vi) a parameter calculator configured to compute from the full motion field a set of non-rigid transformation parameters representing the difference in the position and orientation of the target region as shown in the ROI, as compared to the position and orientation of the target region as shown in the DRR.

An image registration system for registering at least one 2D image of an anatomical region with previously generated 3D scan data of the anatomical region, the anatomical region including at least one treatment target and at least one reference structure, wherein the 2D image is generated in near real time by detecting one or more radiographic imaging beams after the imaging beams have traversed at least a portion of the anatomical region, the imaging beams having known intensities and known positions and angles relative to the anatomical region, the system comprising:

• a) means for providing the 3D scan data of the anatomical region;
• b) a DRR generator configured to generate at least one DRR (digitally reconstructed radiograph) of the anatomical region, using the 3D scan data and the known locations, angles, and intensities of the imaging beams;
• c) an ROI selector configured to select an ROI (region of interest) within the 2D image, the ROI including the image of the treatment target and of the reference structure;
• d) an image enhancer configured to enhance the DRR and the ROI by applying a filter operator to the DRR and to the ROI;
• e) a similarity measure calculator configured to determine a measure of similarity between the DRR and the ROI;
• f) a motion field generator configured to estimate, for each of a plurality of resolution levels, one or more 2D local motion fields within the ROI, using the similarity measure determined by the similarity measure calculator, and to derive a 3D full motion field from the estimated 2D local motion fields;
• and
• g) a parameter determiner configured to compute from the full motion field a set of non-rigid transformation parameters representing the difference in the position and orientation of the treatment target as shown in the ROI, as compared to the position and orientation of the treatment target as shown in the DRR.