Patent ID: 8019140

Claim:
A method for determining a size of an airway lumen and a thickness of an airway wall, comprising: computing a centerline of an airway; computing a three-dimensional (3D) gradient of a volume of the airway within a first threshold; positioning a tube along the centerline; iteratively expanding the tube by increasing its radius until the radius of the tube reaches the first threshold; determining inner and outer radii of the tube by checking the 3D gradient computed along an x-axis and a y-axis of the tube at a boundary of the tube at each iteration; and fitting the tube to the airway by using the determined inner and outer radii, wherein the inner radius of the fit tube is half an inner diameter of the airway lumen and the outer radius of the fit tube minus the inner radius of the fit tube is a thickness of the airway wall, and an outer diameter of the airway is equal to two times the outer radius; wherein fitting the tube to the airway by using the determined inner and outer radii comprises: validating, as part of the airway, points from the inner and outer diameters that are common to the 3D gradients computed along the x and y-axes of the tube; computing a second threshold corresponding to a third of a maximum value of the 3D gradients computed along the x and y-axes of the tube for inner and outer diameter points from only one of the 3D gradients computed along the x and y-axes of the tube; discarding points from only one of the 3D gradients computed along the x and y-axes of the tube when they are below the second threshold; and validating points from only one of the 3D gradients computed along the x and y-axes of the tube when they are above the second threshold.