Turney and team, collected CT images from 391 extracorporeal shock wave lithotripsy (ESWL) cases from 2011 to 2016. The CTTA software was used to analyze CT images of stone before ESWL treatment. The software works by semi-automatically populating the largest cross-sectional slice of the stone and produces metrics based on statistical analysis of the Hounsfield unit (HU) values of all the available pixels. These metrics included: mean, standard deviation, entropy, and skewness of the HU values, and the total number of pixels present.
They found that the total number of pixels correlated to stone volume. Interesting, entropy had a non-linear but close relationship to total number of pixels and stone volume. Dr. Turney suggested that although entropy increases with stone size, it may also be adding information on stone heterogeneity. Skewness was negatively correlated with stone volume. Standard deviation of HU values showed no relationship to stone volume. Dr. Turney concluded by stating that these results show that CTTA variables appear to represent stone size and structure and may be able to objectively quantify stone burden.
Presented by Ben Turney, Senior Clinical Researcher, University of Oxford Consultant Urological Surgeon, Oxford Clinical Lead, Oxford
Written by Renai Yoon, Department of Urology, University of California-Irvine, medical writer for UroToday at the 36th World Congress of Endourology (WCE) and SWL - September 20-23, 2018 Paris, France