[Extracorporeal lithofragmentation and of direct contact. Development of mathematical models for calculating the energy and predicting the fragmentation].

The present experimental 'in vitro' study pursues the development of mathematical equations which, prior to lithofragmentation, would allow to estimate the amount of energy required and to predict the degree of fragmentation for each of the different sources of energy. A total of 114 calculi with 6 different compositions were analyzed by conventional X-rays (Rx), computerized axial tomography (CT) and dual X-ray densitometry (DO). Calculi were then fragmented using 4 different types of energy: electrohydraulic (LEH), piezoelectric (LEP), ultrasounds (US) and pulse laser (LAS). The correlation between imaging techniques parameters on the one side, and the amount of energy used and degree of fragmentation obtained on the other one, allow with a multiple linear regression analysis, both to develop mathematical equations to estimate the amount of energy required, and to predict the fragmentation rate.