Introduction

1. No. 058 Can parameters on computed tomography be used to determine the number of shocks and total energy required for successful stone fragmentation by extracorporeal shock wave lithotripsy? Sum Sum Lo, Basirun Ahmad, Patricia Metcalfe, Leanne Shaw, Kim Broome Hawke’s Bay Hospital, New Zealand, Hawke’s Bay Hospital, New Zealand, University of Auckland, New Zealand, Hawke’s Bay Hospital, New Zealand, Hawke’s Bay Hospital, New Zealand. No. of Shocks Posters Proudly Supported by: Results Introduction It has been shown in a prospective study that the number of shocks required for stone fragmentation increases as the stone attenuation (Hounsfield unit) increases. In the same study, the mean intensity of shock impulses required to fragment and clear the stone is directly proportional to stone attenuation [1]. There were 84 patients who had CT scans prior to ESWL. Fifty-seven patients had successful treatment.  The mean follow up time was 4.9 years (95% CI 4.4-5.3 years).  Stone attenuation correlated to number of shocks (r=0.25; 95%CI 0.03-0.44; p=0.03) and total energy used (r=0.30; 0.09-0.48; p=0.012).  Stone size correlated to number of shocks (r=0.3; 0.16-0.48; p=0.0076) and total energy used (r=0.30; 0.13-0.45 p=0.0079). SSD did not show significant correlation in patients who had successful ESWL (r=-0.06; -0.23-0.12; p=0.62).  Independent of stone attenuation and size, patients who received less than 4250 shocks with total energy between 98.5 and 144.5 joules had the highest success rate (89.3%). Aim In this retrospective cohort study, we aimed to investigate the feasibility of using parameters on computed tomography (CT) to determine the number of shocks and total energy delivered to patients who had successfully undergone extracorporeal shock wave lithotripsy (ESWL). The hypothesis was larger stones, greater stone attenuation and increased stone-to-skin distance (SSD) require higher number of shocks and total energy for successful fragmentation. Total Energy (J) • Methods • Between 1st February 2004 and 28th November 2011, all patients who had ESWL treatment in Hawke’s Bay region, New Zealand were included. The eligibility criterion was the availability of CT scans prior to ESWL. Success was defined as stone fragments of equal or less than 4mm. • Data on the number of shocks and total energy used were obtained from the database of Mobile Medical Technology (mobile lithotriptor which services New Zealand on a 5-weekly schedule). The parameters of stone attenuation, stone size and SSD were correlated to the number of shocks and total energy used in successful ESWL treatment. • Means were compared using Students t-test.  Correlations and statistical analyses were carried out using SAS version 9.3. The classification and regression trees (CART) were carried out on successful and unsuccessful treatments using rpart library in R. The primary outcome was successful fragmentation. Stone Size (mm) Stone Attenuation (HU) Graphs showing relationship between CT parameters and no. of shocks and total energy delivered Classification and regression tree in kV and shocks • Conclusions • The number of shocks and total energy required for successful ESWL cannot be pre-determined using CT parameters. • Success is not more likely through delivery of more shocks or higher total energy. References [1] Kartik S, Abraham K, Shashikant M et al. Predicting Effectiveness of Extracorporeal Shockwave Lithotripsy by Stone Attenuation Value. J Endourol 2010;24,1169-1173 Acknowledgements Megan Su, James Hayes, MMT Staff

2. No. 058 Can Parameters On Computed Tomography Be Used To Determine The Number of Shocks and Total Energy Required For Successful Stone Fragmentation by Extracorporeal Shock Wave Lithotripsy? ) Sum Sum Lo, Basirun Ahmad, Patricia Metcalfe, Leanne Shaw, Kim Broome Hawke’s Bay Hospital, New Zealand, Hawke’s Bay Hospital, New Zealand, University of Auckland, New Zealand, Hawke’s Bay Hospital, New Zealand, Hawke’s Bay Hospital, New Zealand. Posters Proudly Supported by: Results Importing / inserting files… Images such as photographs, graphs, diagrams, logos, etc, can be added to the poster. Avoid long numerical tables. To insert images, go through the menus as follows: Insert / Picture / From File. Locate the file on your computer, select and press OK. The best type of image files to insert are JPEG or TIFF, JPEG is the preferred format. Be aware of the image size you are importing. The average colour photo (13 x 18cm at 180dpi) should be about 3Mb (1Mb for B/W greyscale). Do not use images from the web. Notes about graphs… For simple graphs use MS Excel, or create the graph directly in PowerPoint. Graphs created in a scientific graphing program (eg. Sigma Plot, Prism, SPSS, Statistica) should be saved as JPEG or TIFF. Introduction It has been shown in a prospective study that the number of shocks required for stone fragmentation increases as the stone attenuation (Hounsfield unit) increases. In the same study, the mean intensity of shock impulses required to fragment and clear the stone is directly proportional to stone attenuation [1]. Aim In this retrospective cohort study, we aimed to investigate the feasibility of using parameters on computed tomography (CT) to determine the number of shocks and total energy delivered to patients who had successfully undergone extracorporeal shock wave lithotripsy (ESWL). The hypothesis was larger stones, greater stone attenuation and increased stone-to-skin distance (SSD) require higher number of shocks and total energy for successful fragmentation. Captions to be set in Arial font italic and no smaller than 6 points. Right aligned if it refers to a figure on its right. Caption starts right at the top edge of the picture (graph or photo). • Methods • All patients who had ESWL treatment in Hawke’s Bay region, New Zealand between 1st February 2004 and 28th November 2011, were included. • The eligibility criterion was the availability of CT scans prior to ESWL. • Success was defined as stone fragments of equal or less than 4mm. • Data on the number of shocks and total energy used were obtained from the database of Mobile Medical Technology (mobile lithotriptor which services New Zealand on a 5-weekly schedule). The parameters of stone attenuation, stone size and SSD were correlated to the number of shocks and total energy used in successful ESWL treatment. Means were compared using Students t-test.  Correlations and statistical analyses were carried out using SAS version 9.3. The classification and regression trees (CART) were carried out on successful and unsuccessful treatments using rpart library in R. The primary outcome was successful fragmentation. Captions to be set in Arial font italic and no smaller than 6 points. Left aligned if it refers to a figure on its left. Caption starts right at the top edge of the picture (graph or photo). Captions to be set in Arial font italic and no smaller than 6 points, to the length of the column in case when a figure takes more than 2/3 of column width. • Conclusions • The number of shocks and total energy required for successful ESWL cannot be pre-determined using CT parameters. • Success is not more likely through delivery of more shocks or higher total energy. References [1] Kartik S, Abraham K, Shashikant M et al. Predicting Effectiveness of Extracorporeal Shockwave Lithotripsy by Stone Attenuation Value. J Endourol 2010;24,1169-1173 Acknowledgements Megan Su, James Hayes, MMT Staff