title: Kidney stone volume estimation from computerized tomography images using a model based method of correcting for the point spread function.
abstract: OBJECTIVE
  We propose a method to improve the accuracy of volume estimation of kidney stones from computerized tomography images.
  
  
  METHODS
  The proposed method consisted of 2 steps. A threshold equal to the average of the computerized tomography number of the object and the background was first applied to determine full width at half maximum volume. Correction factors were then applied, which were precalculated based on a model of a sphere and a 3-dimensional gaussian point spread function. The point spread function was measured in a computerized tomography scanner to represent the response of the scanner to a point-like object. Method accuracy was validated using 6 small cylindrical phantoms with 2 volumes of 21.87 and 99.9 mm(3), and 3 attenuations, respectively, and 76 kidney stones with a volume range of 6.3 to 317.4 mm(3). Volumes estimated by the proposed method were compared with full width at half maximum volumes.
  
  
  RESULTS
  The proposed method was significantly more accurate than full width at half maximum volume (p <0.0001). The magnitude of improvement depended on stone volume with smaller stones benefiting more from the method. For kidney stones 10 to 20 mm(3) in volume the average improvement in accuracy was the greatest at 19.6%.
  
  
  CONCLUSIONS
  The proposed method achieved significantly improved accuracy compared with threshold methods. This may lead to more accurate stone management.
authors: Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors: Xinhui
authors: X
authors: Duan
authors: Jia
authors: J
authors: Wang
authors: Mingliang
authors: M
authors: Qu
authors: Shuai
authors: S
authors: Leng
authors: Yu
authors: Y
authors: Liu
authors: Amy
authors: A
authors: Krambeck
authors: Cynthia
authors: C
authors: McCollough
mesh_terms: D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation; D007669:Kidney Calculi / Q000473:pathology*; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*