Reciprocating Side-Firing Fiber for Laser Sealing of Blood Vessels

Abstract

Infrared lasers may provide faster and more precise sealing of blood vessels and with lower jaw temperatures than ultrasonic and electrosurgical devices. This study explores an oscillating or reciprocating side-firing optical fiber method for transformation of a circular laser beam into a linear beam, necessary for integration into a standard 5-mm-diameter laparoscopic device, and for uniform irradiation perpendicular to the vessel length. A servo motor connected to a side-firing, 550-μm-core fiber, provided linear translation of a 2.0-mm-diameter circular beam over either 5 mm or 11 mm scan lengths for sealing small or large vessels, respectively. Laser seals were performed, ex vivo, on a total of 20 porcine renal arteries of 1-6 mm diameter (n = 10 samples for each scan length). Each vessel was compressed to a fixed 0.4-mm-thickness, matching the 1470-nm laser optical penetration depth. Vessels were irradiated with fluences ranging from 636 J/cm² to 716 J/cm². A standard burst pressure (BP) setup was used to evaluate vessel seal strength. The reciprocating fiber produced mean BP of 554 ± 142 and 524 ± 132 mmHg, respectively, and consistently sealing blood vessels, with all BP above hypertensive (180 mmHg) blood pressures. The reciprocating fiber provides a relatively uniform linear beam profile and aspect ratio, but will require integration of servo motor into a handpiece.

Keywords: blood vessel; burst pressures; coagulation; compression; laser; optical fiber; sealing.

Figure 1.

(A) Normalized reflected power from side-firing fiber for S and P polarization states as a function of tip angle. Width of red lines is percent error given by S.D. in NA of fibers used in this study. Black line represents angle at which chief ray will propagate out of the fiber as a function of tip angle. (B) Conceptual representation of the geometrical ray tracing for a side-firing fiber with incident (ρ_i), polished tip (θ), and deflection angles (Φ), labeled.

Figure 2.

Linear spatial beam profile simulations (blue lines) and experimental results (green lines) for the four data groups.

Figure 3.

(A, B) Magnified image of 40° angle, side-firing, fiber tip; (C) Photograph of visible red aiming beam, showing 90% reflection of light from side-firing fiber with 1 s prolonged shutter time in a water misted environment.

Figure 4.

Benchtop setup for testing a reciprocating side-firing fiber and its laser beam profile captured with a prolonged shutter exposure of 3 s. (Image not drawn to scale.)

Figure 5.

(Left) Diameter of blood vessels before and after compression to 0.4 mm thickness in benchtop setup. (Right) Percent change in compressed vessel width after compression. Mean percent increase in vessel width measured 47 ± 28% (n=30).

Figure 6.

Representative photographs of IR sealed porcine blood vessels. (A) 5 mm vessel sealed using 11 mm stroke length; (B) 2 mm vessel sealed using 5 mm stroke length.