Systems and methods for determining circumference and a percent change in circumference of a structure are provided. Certain methods include receiving first and second sets of at least three vertical plane images of a structure about a long axis of the structure that were acquired at first and second points in time, respectively. Data points from each of the images of each of the sets that define a contour of the structure are identified. The circumference of the structure at a horizontal plane of the structure at the first and second points in time using identified data points positioned on the horizontal plane is estimated. A percent change between the estimated circumference of the structure at the first point in time and the estimated circumference of the structure at the second point in time is determined.
