Patent ID: 6859555

Claim:
A method for determining a circle in a region of interest comprising the steps of: extracting a first pair of edge points along an x-axis of the region of interest; extracting a second pair of edge points along a y-axis of the region of interest; determining an intersection of a first and second line extending perpendicular from a pair of midpoints of the first and second pair of edge points respectively; determining a radius from the intersection to any edge point; verifying a connectivity of the first and second pair of edge points in the presence of a foreign structure in the region of interest, wherein verifying comprises: scanning the image along the x-axis of the region of interest, scanning the image along the v-axis of the region of interest, performing a horizontal gradient and a vertical gradient along the x and y-axis of the region of interest respectively, and determining whether a local maximum along the gradients match the coordinates for any edge point comprising: determining a position, relative to the circle of the foreign structure, wherein if the foreign structure is inside, searching from each edge of the region of interest, inward, to determine the local maximum, if the foreign structure is outside, searching from the center of the region of interest, outward, to determine the local maximum, and if the foreign structure is both inside and outside the circle, randomly scan at a plurality of points each axis of the region of interest within ½ of the total axis length, conduct a gradient operation at each point scanned, determine a plurality of potential edge points, determine a coordinate for center of the circle, save the coordinate in an array, determine, based on the plurality of edge points a median value for each coordinate of the center of the circle; and determining the circle upon verifying the connectivity of the first and second pair of edge points.