SWL literature
SWL Literature

Cui HW. et al., 2020: The utility of automated volume analysis of renal stones before and after shockwave lithotripsy treatment

Cui HW, Tan TK, Christiansen FE, Osther PJS, Turney BW.
Oxford Stone Group, University of Oxford, Oxford, UK.
Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK.
Department of Urology, Urological Research Center, Lillebaelt Hospital, University of Southern Denmark, Vejle, Denmark.
Oxford Stone Group, University of Oxford, Oxford, UK.

Abstract

This study aimed to evaluate the additional utility of an automated method of estimating volume for stones being treated with shockwave lithotripsy (SWL) using computed tomography (CT) images compared to manual measurement. Utility was assessed as the ability to accurately measure stone burden before and after SWL treatment, and whether stone volume is a better predictor of SWL outcome than stone diameter. 72 patients treated with SWL for a renal stone with available CT scans before and after treatment were included. Stone axes measurement and volume estimation using ellipsoid equations were compared to volume estimation using software using CT textural analysis (CTTA) of stone images. There was strong correlation (r > 0.8) between manual and CTTA estimated stone volume. CTTA measured stone volume showed the highest predictive value (r2 = 0.217) for successful SWL outcome on binary logistic regression analysis. Three cases that were originally classified as 'stone-free with clinically insignificant residual fragments' based on manual axis measurements actually had a larger stone volume based on CTTA estimation than the smallest fragments remaining for cases with an outcome of 'not stone-free'. This study suggests objective measurement of total stone volume could improve estimation of stone burden before and after treatment. Current definitions of stone-free status based on manual measurements of residual fragment sizes are not accurate and may underestimate remaining stone burden after treatment. Future studies reporting on the efficacy of different stone treatments should consider using objective stone volume measurements based on CT image analysis as an outcome measure of stone-free state.

Urolithiasis. 2020 Sep 14. doi: 10.1007/s00240-020-01212-8. Online ahead of print. PMID: 32926195

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Comments 1

Hans-Göran Tiselius on Wednesday, November 11 2020 08:30

It is well recognized that correct interpretation of the outcome of stone removing procedures must relate to the initial stone burden. Several methods are described in the literature: the maximal length, the stone surface area measured in the frontal view either expressed as the surface of a rectangle, square, circle or ellipse. In other cases, the sum of the individual diameters has been used for multiple stones or of course better as the sum of individual surface areas. With introduction of CT examinations, the additional estimate of the depth enabled calculation of approximate stone volume(s). The latter process, although rather straightforward, requires careful measurements but adds to the description of the initial stone burden.

More complicated is it to get an estimate of the residual stone volume.
The semi-automated method described in this publication is of great value and its use should definitely improve interpretation of treatment results. It is important in modern health care to use the computerized facilities that are available and thus get sufficient and more accurate information on the pre-treatment stone volume as well as the post-treatment number of fragments and total volume of remaining fragments.

Hans-Göran Tiselius

It is well recognized that correct interpretation of the outcome of stone removing procedures must relate to the initial stone burden. Several methods are described in the literature: the maximal length, the stone surface area measured in the frontal view either expressed as the surface of a rectangle, square, circle or ellipse. In other cases, the sum of the individual diameters has been used for multiple stones or of course better as the sum of individual surface areas. With introduction of CT examinations, the additional estimate of the depth enabled calculation of approximate stone volume(s). The latter process, although rather straightforward, requires careful measurements but adds to the description of the initial stone burden. More complicated is it to get an estimate of the residual stone volume. The semi-automated method described in this publication is of great value and its use should definitely improve interpretation of treatment results. It is important in modern health care to use the computerized facilities that are available and thus get sufficient and more accurate information on the pre-treatment stone volume as well as the post-treatment number of fragments and total volume of remaining fragments. Hans-Göran Tiselius
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Tuesday, September 21 2021

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