TAIPEI, TAIWAN (UroToday.com) - Introduction and Objectives: Numerous CT-based parameters describing stone size have been reported to predict shockwave lithotripsy (SWL) success. Amongst these, stone volume has greatest predictive value. Widespread use of this metric is limited by the specialized software and expertise required for its determination. The majority of stones considered for SWL are ellipsoid in shape. Therefore, we hypothesize that the manually measured ellipsoid stone volume (ESV) can closely approximate the computer-generated stone volume (CSV).
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Methods: CT scans for 24 patients with urinary stones greater than 4mm were reviewed by a radiologist. CSV was generated utilizing the TeraRecon® 3D volume rendering software. To determine ESV, the anteroposterior (AP), horizontal (H) and craniocaudal (CC) stone dimensions were measured. ESV was calculated based upon the ellipsoid volume formula, volume = (π /6) x (AP x H x CC). Correlation was assessed utilizing the Pearson product-moment correlation coefficient.
Results: Twenty-eight stones were analyzed. 25/28 (89.2%) stones were ellipsoid in shape. For all stones analyzed, the correlation coefficient between CSV and ESV was 0.9778. When non-ellipsoid stones were excluded from the analysis, the correlation coefficient between CSV and ESV was 0.9893.
Conclusions: We describe a novel method for estimating stone volume that is accurate and easy to rapidly determine. Incorporation of the ellipsoid stone volume into preoperative planning can facilitate better preoperative patient selection for SWL.
Source of Funding: None
|Listen to an interview with Timothy Tran, one of the authors of this study.|
Presented by Timothy Tran, Darren Bialo, and Gyan Pareek at the 32nd World Congress of Endourology & SWL - September 3 - 7, 2014 - Taipei, Taiwan
Alpert Medical School of Brown University, Providence, RI USA