This program initially developed laser microsurgical techniques centered on ophthalmological applications (pulsed carbon dioxide lasers and pulsed ND:YAG slit lamp-based laser systems). Its primary focus for the last seven years, however, has been in cardiological applications, in particular laser angioplasty and the development of pulsed, solid-state infrared lasers for microsurgery. We demonstrated the feasibility of transmission through flexible fiber optics of pulsed infrared, visible, and ultraviolet lasers, and the tissue responses to these lasers. In particular, we have measured the dependence of acoustic transients and ablation efficiency on increasing pulse fluence with catheter systems used clinically, and have concluded that acoustic transients play a dominant role in the clinical results of pulsed laser angioplasty. In conjunction with the Naval Research Laboratory and Quantronix Corporation, new infrared laser sources were developed which utilize strong water absorption and can be transmitted through lowloss, cladded optical fibers. Clinical trials of peripheral and coronary laser angioplasty were completed, using either pulsed-dye or pulsed infrared lasers with computer-controlled fluorescence guidance. Recent work has involved identification of the tissue and biological effects of pulsed lasers--in particular, the large role that acoustic transients and transient, moderate (approximately 60 degrees C) thermal elevations play in acute and chronic clinical responses. Principally, since pulsed laser angioplasty mechanically disrupts the atheroma at stenoses rather than ablating or removing it, optimization of clinical results must be balanced against increased rates of dissection.
