Tissue perforation of vessel substitutes using a femtosecond Ti:sapphire laser system
Previous investigations of transmural capillary ingrowth into the inner surface of biosynthetic vascular prostheses through perforations created by an excimer laser have shown that spontaneous endothelialization of the protheses can be achieved. Disadvantages of the excimer laser are a large and non-circular beam profile and an inconvenient handling of the UV-radiation for medical applications. Therefore, a new commercial laser system, consisting of a mirror-dispersion- controlled Ti:S oscillator and a femtosecond multipass amplifier, which avoids these disadvantages was sued to perforate grafts made of a new biomedical. The laser-tissue interaction is based ona different mechanism due to the short pulsewidth high peak intensity and near IR wavelength. The very short pulsewidth reduces thermal damage of the tissue. The basic mechanism of the laser tissue interaction is not yet fully understood and still subject of investigations. Several biografts with 1 mm wall thickness have been used. The hole diameter could be varied between 50 and 200 micrometers and the distance between the holes was 4 mm. At laser intensities of approximately 20-30 TW/cm2 and a repetition rate of 1 kHz it took less than a second to drill a single hole. Subsequently to the perforation procedure, one perforated and one untreated biograft were implanted into the carotid arteries of several test sheep. It can be concluded that very intense near IR laser radiation is an ideal means for structuring biological tissue.
This paper was published in SPIE Proceedings Vol. 4166
Laser Florence '99: A Window on the Laser Medicine World, Leonardo Longo; Alfons G. Hofstetter; Mihail-Lucian Pascu; Wilhelm R. Waidelich, Editors, pp.54-59