AUA 2017: Feasibility of Automating the Measurement of Kidney Stone Diameter, Volume, and Density from CT

Boston, MA ( A number of techniques and publications have explored methods of measuring renal stone volume; however, no gold standard exists. Dr. Ludwig and his team in the Department of Urology at Johns Hopkins University developed an algorithm to establish automation of stone measurement clinically and mitigate discrepancies in contemporary measurement methods.

Using DICOM images of patients with nephrolithiasis, a region of interest (ROI) around a renal stone was selected by a radiologist. MATLAB 9.1 software was used to create a computer program that then selected and established a single calculus based on the ROI and a threshold of 250 Hounsefield units. A three-dimensional (3D) sphere no larger than the size of the stone was then created within the software and its volume calculated. For a comparison, the program also measured the actual volume of the stone by summating the voxels of the calculus within the ROI. A correlation value of 0.807 was found between the smallest sphere surrounding the stone and the actual volume in 18 patients.

During his presentation, Dr. Wesley commented that this technique may be used to determine which approach is optimal for the surgical treatment of nephrolithiasis; however, equally valuable utilization of this software may be found in renal stone research that explores hypotheses with respect to change in stone volume. Furthermore, by using a sphere, the maximal diameter of the stone with variable morphology can be determined with this software. Whether or not stone volume is used as a metric, the maximal stone diameter has been used in the past to assess stone size and has value with respect to clinical questions in renal stone disease.

Presented By: Wesley Ludwig, MD

Authors: Wesley Ludwig, Pan Li, Justine Ziemba, Rishab Gurnani, Sungwhan Lim, Changhan Jun, Satomi Kawamato, George Fung, Dan Stoianovici, Brian Matlaga

Affiliation: Brady Urological Institute, Department of Radiology, Johns Hopkins Hospital

Written By: Daniel Lama for

at the 2017 AUA Annual Meeting - May 12 - 16, 2017 – Boston, Massachusetts, USA