Tailly GG et al, 2014: Optical Coupling Control: An Important Step Toward Better Shockwave Lithotripsy.
Tailly GG, Tailly-Cusse MM.
Department of Urology, AZ Klina , Brasschaat, Belgium.
Abstract Background: In modern "dry" lithotripters, shockwaves are generated in a membrane-covered water cushion that is then coupled to the patient.To limit energy loss, a coupling agent, usually ultrasound gel, is used in this acoustic interface. During the coupling
process, air pockets are inevitably trapped in the coupling area, which subsequently remains invisible to the operator. These air pockets dramatically decrease stone fragmentation efficiency up to 40%. Materials and Methods: To check for air bubbles in the coupling
interface, a video camera was installed in the therapy head of our Dornier Gemini lithotripter: all air bubbles observed in the coupling zone could then be removed under visual control. We evaluated the effect of this optically controlled coupling (OCC) on treatment results (10/1/12-9/30/13) and compared these to the results obtained in a "blind" coupling mode (4/1/11-4/30/12).
Results: Optically controlled removal of air bubbles from the coupling area reduced the required number of shockwaves with 25.4% for renal stones and 25.5% for ureteral stones. Energy level was reduced by 23.1% for renal stones and by 22.5% for ureteral stones.
For renal stones, total applied energy was thus reduced by 42.9%. Effectiveness quotients were comparable. Conclusions:
Optical control with a video camera proved pivotal in the realization of bubble-free coupling. Bubble-free coupling significantly reduced the total energy needed to obtain comparable treatment results. Theoretically, this should also lead to a reduced incidence and severity of shockwave-induced adverse effects. We consider this an important step toward better and safer shockwave lithotripsy and would therefore advocate the standard incorporation of an OCC system in all new lithotripters.
J Endourol. 2014 Aug 12. [Epub ahead of print]
This comparison between two series of SWL, clearly shows the importance of optimal coupling conditions. It is important to note, however, that the authors already before installing the new device had had careful control of the coupling between the shock wave source and the body. Far from all operators have that.