Cavitation bubbles produced when delivering laser energy into liquid media can cause undesired tissue damage. Bubbles were generated in various media using a 308nm XeCl Excimer laser. The maximum bubble radius and pressure upon collapse were measured using a PVDF transducer and oscilloscope. The Raleigh relation and the 1/R law were used to calculate numerical values. In contrast media, these values were highest, where bubbles of radius 1.9mm gave a maximum pressure of 17kbar upon collapse, whereas in whole blood they were lower (15kbar, 1.2mm). Dilution of these two media with distilled water lowered these values with the effect being dramatic in diluted blood (250Bar, .24mm for four fold dilution). Blood/contrast mixtures produced almost the same Rmax and Pressures as contrast alone (15kbar, 1.6mm for 1:1 mixture). In saline no acoustic signal was detected, indicating that no bubble is formed in saline.
The elimination of large cavitation bubbles in vivo during excimer laser atherectomy would require delivery of laser light in a non-absorbing liquid medium such as saline.
Grunkemeier JM, Gregory KW: Acoustic Measurements of cavitation bubbles in blood, contrast and saline using an excimer laser: implications for laser atherectomy, Lasers in Surgery and Medicine, (Suppl) 4:16, 1992.