Novel Optical Linear Beam Shaping Designs for use in Laparoscopic Laser Sealing of Vascular Tissues

Abstract

Suture ligation of vascular tissues is slow and skill intensive. Ultrasonic (US) and radiofrequency (RF) devices enable more rapid vascular tissue ligation to maintain hemostasis, than sutures and mechanical clips, which leave foreign objects in the body and require exchange of instruments. However, US and RF devices are limited by excessive collateral thermal damage to adjacent tissues, and high jaw temperatures that require a long time to cool. A novel alternative method using infrared (IR) laser energy is being developed for more rapid and precise sealing of vessels. This study describes design, modeling, and initial testing of several optical beam shaping geometries for integration into the standard jaws of a laparoscopic device. The objective was to transform the circular laser beam into a linear beam, for uniform, cross-irradiation and sealing of blood vessels. Cylindrical mirrors organized in a staircase geometry provided the best spatial beam profile.Clinical Relevance-This study explored several optical designs for potential integration into the standard jaws of a laparoscopic vessel sealing device, transforming a circular laser beam into a linear beam for sealing of vascular structures.

Fig. 1.

(a) Ligasure^™ Maryland style laparoscopic RF device, 5-mm-OD arm/shaft, and jaws for grasping vascular tissues. (b) Open surgical IR laser vessel sealing device, featuring a plunger style tissue clasping mechanism in a cylindrical head with ½ inch (12.7-mm-OD) components [17].

Fig 2.

Jaw-style laparoscopic clamp design model. Multimode fiber output enters beam shaping chamber and is transformed into a longitudinal linear beam (red), which exits through the window.

Fig. 3.

Conceptual designs considered for beam shaping in a laparoscopic device. An optical fiber output is transformed into a side firing linear beam, exiting the top surface. The concepts shown are not intended to be to scale, merely representative of beam shaping techniques. For instance, the number of fibers or beamsplitters used may vary in designs #2 or #3, respectively.

Fig. 4.

FRED simulation of single cylindrical mirror. Arbitrary scale.

Fig. 5.

FRED parameter space for cylindrical staircase design is shown. The size of jaw was fixed: window (20L×3W×0.5H mm), reflecting chamber (1W×2H mm entry), and fiber (600 μm diameter). Variable parameters included: fiber spacing (0–5 mm from start of ramp), fiber tilt (±5° up/down), fiber height (0.5–1.5 mm), and cylindrical mirror diameter (0.5–1 mm).

Fig. 6.

FRED simulations of linear beam output. Single mirror parameters: 0.5 mm fiber height, 0 mm fiber spacing, 0° fiber tilt. Cylindrical staircase parameters: 0.5 mm diameter cylinders, 1.5 mm fiber height, 2.5 mm fiber spacing, 0° fiber angle. Width and length are scaled independently in figure.

Fig. 7.

Prototype of gold coated cylindrical mirror staircase insert.

Fig. 8.

(a) Beamsplitters and angle mirror in jaw. (b) Cylindrical lenses used to condense 5 mm beams into ~ 1 mm width linear beam. (c) Beam outputs w/o cylindrical lenses, and (d) with cylindrical lenses. Ruler increments in mm.