The feasibility of blind fragmentation in laser lithotripsy

In laser lithotripsy, it has been found that calculi fragmentation is always accompanied with the formation of a plasma which has two characteristics, i.e. the acoustic signal or shock waves, and the optical signal or plasma emission. By monitoring the feedback signals of the shock waves, the temporal behaviour and the spectra of plasma emission, the feasibility of so-called blind fragmentation has been investigated. The shock wave feedback is found to be not as reliable as the plasma emission feedback and the use of an optical multichannel analyser system to detect, analyse and display the spectra of the feedback plasma emission has proved to be reliable and direct for blind fragmentation. The blind fragmentation technique has been found to be successful in ex vivo experiments in which stones were inserted into pigs' ureters and then fragmented without the use of a ureteroscope. It has also been investigated in vivo in studies from about one dozen patients, and for the first time a series of the plasma spectra have been obtained and analysed in vivo. These indicate promising prospects for the clinical application of the technique and, in addition, application to real-time stone composition analysis. The technique has also been tested for biliary stone fragmentation and for laser angioplasty, again the results have shown good prospects.