Automatic Control of Electrodes in Lithotripsy Machine

Extracorporeal shock wave lithotripsy (ESWL) employs high-energy shock waves that propagate through the body and focus on the stone to break it into small grains, which travel out of the body along with the urine. The distance between lithotripsy long-life electrodes tends to vary after every session. This variation causes an associated pain for the patient, and hence the need for re-calibration and adjustment of the distance. Both manual calibration and adjusting procedure are time wasting, inaccurate, and must be performed by an expert operator.In this paper, a mathematical model has been developed to predict the number of shocks needed for every patient, depending on input information regarding his age, stone size, and location. An automatic adjustment procedure for the distance between electrodes, utilizing a proportional integral derivative controller, is also proposed in order to increase treatment effectiveness and to reduce patient pain. This also enables better planning of treatment and allows the possibility for any operator to use, and thus resulting in a better utilization of apparatus. Results from trials in a hospital were adequate, and the experimental data matched those predicted by the model.