Patent ID: 7499578

Claim:
A method for correlating a segmentation of 3-d images of a pulmonary nodule from a high-resolution computed tomography (CT) scans, the images being in a floating point pixel-format associated with a 6-dimensional parameter space and including a first image (im 1 ) obtained at time- 1 and a second image (im 2 ) obtained at time- 2 , the method comprising the steps of: (a) selecting a first region-of-interest (ROI 1 ) for the nodule in the first image (im 1 ); (b) selecting a second region-of-interest (ROI 2 ) for the nodule in the second image (im 2 ); (c) registering the second region-of-interest (ROI 2 ) to the first region-of-interest (ROI 1 ) to obtain a transformed second region-of-interest (ROI 2t ); (d) separately segmenting both the nodule in the first region-of-interest (ROI 1 ) and the transformed second region-of-interest (ROI 2t ); and (e) adjusting the first segmented nodule (S 1 ) and the second segmented nodule (S 2 ), registering the second region-of-interest (ROI 2 ) to the first region-of-interest (ROI 1 ) to obtain a transformed second region-of-interest (ROI 2t ) comprising the substeps of: calculating initial rigid-body transformation parameters for a rigid-body transformation on the second region-of-interest (ROI 2 ); determining the optimum rigid-body transformation parameters by calculating a registration metric between the first region-of-interest (ROI 1 ) and the rigid-body transformation on the second region-of-interest (ROI 2 ); and generating a registered image from the optimum rigid-body transformation parameters, the registration metric being calculated by: transforming the second region-of-interest (ROI 2 ) with the initial rigid-body transformation parameters to obtain a transformed second region-of-interest (ROI 2t ); calculating the registration metric as a mean-squared-difference (MSD) between the transformed second region-of-interest (ROI 2t ) and the first region-of-interest (ROI 1 ); and searching for the minimum mean-squared-difference (MSD) in the 6-dimensional parameter space, the transforming of the second region-of-interest (ROI 2 ) to obtain the transformed second region-of-interest (ROI 2t ) is a mapping of a point v in 3-d space to a point v′ in transformed space defined by: v ′ = R x ⁢ R y ⁢ R z ⁢ v + [ t x t y t z ] wherein R x , R y , and R z are rotation matrices defined as: R x = [ 1 0 0 0 cos ⁡ ( r x ) - sin ⁡ ( r x ) 0 sin ⁡ ( r x ) cos ⁡ ( r x ) ] R y = [ cos ⁡ ( r y ) 0 sin ⁡ ( r y ) 0 1 0 - sin ⁡ ( r y ) 0 cos ⁡ ( r y ) ] R z = [ cos ⁡ ( r z ) - sin ⁡ ( r z ) 0 sin ⁡ ( r z ) cos ⁡ ( r z ) 0 0 0 1 ] .