HEAT-RESISTANT CYLINDRICAL DIFFUSER FOR INTERSTITIAL LASER COAGULATION - COMPARISON WITH THE BARE-TIP FIBER IN A PORCINE LIVER MODEL

Background and Objective: Interstitial laser coagulation is an experim ental treatment to eliminate solid tumors such as hepatic metastases. The pattern of light emission from the fiber tip is probably an import ant factor in determining the size and shape of a lesion. A heat-resis tant cylindrical light diffusing tip of 2 cm length was developed for this application. We performed an in vitro study to compare this diffu sing-tip with a bare-tip fiber. Study Design/Materials and Methods: Fi ber ends were positioned between two porcine liver slabs (37 degrees C ) and Nd:YAG laser light (1064, nm) was guided through either fiber wi th an output of 3-9 W and exposure times of 6-18 minutes. Results: Les ions produced by the cylindrical diffuser tip were significantly large r and more predictable. With the diffuser tip, lesions up to 36/23 mm (length/width) could be produced at 7 W and 9 min without any central charring. The maximum size of lesions produced with the bare-tip fiber was 32/20 mm at 6 W for 9 min with massive charring. Conclusions: The results indicate that at optimal laser settings, the diffuser tip pro duces a larger coagulation volume than a bare-tip fiber. For clinical application, cylindrical diffusing fibers should be used with a diffus ing length adapted to the diameter of the tumor. (C) 1997 Wiley-Liss, Inc.