Peculiarities of soft biological tissue perforation induced by near infrared laser radiation with optic fiber delivery

The authors studied the process of perforation of soft biological tissue by continuous near infrared lasers (0.98 µm, 1.56 µm and 1.94 µm) with optic fiber delivery. Fiber drag force (FDF) during perforation of soft biological tissue was studied. Specific characteristics of laser radiation heat impact on the tissues surrounding the laser channel were examined. Three perforation modes were observed: mechanical perforation mode, intense evaporation and tissue destruction mode, “free” perforation mode. In the first mode, FDF is almost identical to FDF in the absence of radiation. In the second mode, FDF is significantly lower than FDF during laser radiation power of P = 0. In the third perforation mode, the formed channel becomes wider than the fiber diameter due to intense tissue evaporation and burning, and FDF is close to or below the sensitivity limit of the force sensor. The effect of burnt tissue deposit at the fiber tip on the laser perforation process was studied.