Hollow Waveguides for CO₂ Laser Radiation in Operative Laparoscopy: An In Vitro Study

Abstract

The purpose of this study was to compare the transmission and incision properties of two different CO2 laser radiation delivery systems: the Hopkins\s=r\CO2 laser laparoscope and the hollow waveguide, respectively, in view of a practical use of the latter in laparoscopic surgery. Using a CO2 gas flow rate of 4 L/min, the waveguide delivers CO2 laser power between 10 and 50 watts (W) to tissue with significantly less intensity loss than the laparoscope (9\p=n-\15% and 33\p=n-\40%, respectively). The laparoscope emits radiant energy with the most fundamental TEM00 mode. In contrast, because of loss of coherence and collimation, the output beam profiles of the waveguide is characterized by a quasi-top-hat function with sharp edges and hot spots randomly distributed over the beam. Histologie tissue analysis on fresh uterine tissue of the pig revealed significantly greater incision depths for lesions created with the waveguide, and no enlargement of tissue spot-size at higher power settings. The extent of thermal damage adjacent to the laser incision did not differ between the two delivery systems tested. In comparison to the Hopkins\s=r\laparoscope, the hollow waveguide delivers CO2 laser radiation with less absorption and without a "blooming" effect by the CO2 insufflation gas. These advantageous transmission properties render possible higher power and power density at tissue level, and thus a more precise and efficient cutting in the power range needed for most laparoscopic surgical applications. (

Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

“…Hence, large diameter metallic hollow core waveguides are used to delivering CO 2 laser radiation over considerable distances, e.g., for surgical applications [10][11][12]. In this paper, we use metallic hollow core waveguides with a dual purpose: (i) for guiding broadband mid-infrared radiation to a certain distance in a confined volume, and (ii) to confine gaseous analytes inside the core of the hollow waveguide serving as a miniature gas cell.…”

Miniaturized mid-infrared sensor technologies

“…Hollow waveguides (HWG) are an interesting alternative to conventional gas cells due to their smaller volume and efficient intimate contact between photons and analyte molecules within the hollow fiber core [10]. Initially, HWGs were conceived for CO 2 laser radiation delivery in surgical or industrial applications [11][12][13]. Conventional HWG fibers utilize a metallic reflection coating (e.g., Ag, Au, etc.)…”