Quantification of the tip movement of lithotripsy flexible pneumatic probes

Purpose: We developed an optical system to quantify in vitro tip movement o f the Lithoclast double dagger flexible probe, and correlated various physi cal parameters of the vibrating probe tip with resultant stone fragmentatio n. Materials and Methods: A noncontact optical measurement system was develope d to quantify in vitro tip movement of the Lithoclast flexible probe. This system and an in vitro fragmentation model were used to determine the tip d isplacement, velocity, impact momentum, impact energy and stone fragmentati on of the flexible probe at 5 deflection angles between 0 and 48 degrees, a nd the 2 pneumatic pressure levels of 2.0 and 2.5 bar. Results: An increase in maximum probe tip displacement, velocity, impact mo mentum and energy, and stone fragmentation was seen as the pneumatic pressu re was increased from 2.0 to 2.5 bar. A progressive decrease in these param eters was demonstrated as the probe tip was deflected, especially at deflec tion angles greater than 24 degrees. Impact momentum appears to be the phys ical parameter most closely correlated with stone fragmentation efficiency. Conclusions: The optical measurement system and in vitro fragmentation mode l developed allow one to quickly and reliably assess the performance of fle xible pneumatic probes in vitro. This system can be used for general bench testing and basic research that can provide critical information for the de sign of more effective and efficient flexible pneumatic lithotripsy probes.