Framework for segmentation of cylindrical structures using two dimensional hybrid models

Claim 1

A method of modeling a structure comprising the steps of: initializing a parametric component of a hybrid model from a vohumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset wherein the forces include data forces and smoothing forces; introducing a scale factor to weight data locations from the dataset to provide a scaled force vector for more rapidly fitting the hybrid model to the dataset; and combining the data forces and the smoothing forces by introducing a trade-off parameter for balancing data forces against smoothing forces and thereby providing increased stability to the fitting of the hybrid model.

Claim 2

A method of modeling a structure comprising the steps of: initializing a parametric component of a hybrid model from a vohumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset wherein the forces include data forces and smoothing forces; introducing a scale factor to weight data locations from the dataset to provide a scaled force vector for more rapidly fitting the hybrid model to the dataset; and combining the data forces and the smoothing forces by introducing a trade-off parameter for balancing data forces against smoothing forces and thereby providing increased stability to the fitting of the hybrid model.

Claim 7

A method of modeling branching cylindrical structures comprising the steps of: initializing a parametric component of a three dimensional hybrid model from a volumetric image of the branching structure; the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the branching structure and the image planes; segmenting the branching structure by applying two dimensional active contours to the image planes to more accurately depict features of the branching structure; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the branching structure by applying forces to draw the hybrid model onto the data of the dataset; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid to data of the dataset; introducing a scale factor to weight data locations from the dataset to provide a scaled force vector for more rapidly fitting the hybrid model to the dataset, wherein the scale factor is represented by the formula: K data = max i  ∑ j = i M  N i  ( s  ( j ) ) where i is a set of all nodes and M is a number of datapoints associated with a node i,j which has a closest point to an element s(j) in element coordinates and N i is a shape function for node i with respect to element s(j).

Claim 8

A method of modeling branching cylindrical structures comprising the steps of: initializing a parametric component of a three dimensional hybrid model from a volumetric image of the branching structure; the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the branching structure and the image planes; segmenting the branching structure by applying two dimensional active contours to the image planes to more accurately depict features of the branching structure; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the branching structure by applying forces to draw the hybrid model onto the data of the dataset; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid to data of the dataset; introducing a scale factor to weight data locations from the dataset to provide a scaled force vector for more rapidly fitting the hybrid model to the dataset, wherein the scale factor is represented by the formula: K data = max i  ∑ j = i M  N i  ( s  ( j ) ) where i is a set of all nodes and M is a number of datapoints associated with a node i,j which has a closest point to an element s(j) in element coordinates and N i is a shape function for node i with respect to element s(j).

Claim 14

A method of modeling a structure, comprising the steps of: initializing a parametric component of a hybrid model from a volumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset, wherein the shape function is represented by a formula: N 1 ( s )=1+(2 s −1)(1 −s ) N 2 ( s )=1−(2 s −1) s where N 1 (s) is the shape function evaluated at a first node at point s and N 2 (s) is the shape function evaluated at a second node at point s.

Claim 15

A method of modeling a structure, comprising the steps of: initializing a parametric component of a hybrid model from a volumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset, wherein the shape function is represented by a formula: N 1 ( s )=1+(2 s −1)(1 −s ) N 2 ( s )=1−(2 s −1) s where N 1 (s) is the shape function evaluated at a first node at point s and N 2 (s) is the shape function evaluated at a second node at point s.

Claim 22

A method of modeling a structure comprising the steps of: initializing a parametric component of a hybrid model from a volumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset, wherein the shape function is represented by a formula: N 1 ( s )=(1 −s /max( s , (1 −s )) N 2 ( s )= s /max( s , (1 −s )) where N 1 (s) is the shape function evaluated at a first node at point s and N 2 (s) is the shape function evaluated at a second node at point s.

Claim 23

A method of modeling a structure comprising the steps of: initializing a parametric component of a hybrid model from a volumetric image, the volumetric image comprising image planes; creating starting points for two dimensional segmentations at intersections between the parametric component and the image planes; segmenting a boundary of the structure by applying active contours; sampling the active contours to create a dataset; parametrically and locally fitting the hybrid model to the dataset to represent the structure; reducing a number of iterations to fit the hybrid model by introducing a finite element shape function for distributing forces to draw the hybrid model to data of the dataset, wherein the shape function is represented by a formula: N 1 ( s )=(1 −s /max( s , (1 −s )) N 2 ( s )= s /max( s , (1 −s )) where N 1 (s) is the shape function evaluated at a first node at point s and N 2 (s) is the shape function evaluated at a second node at point s.