Pulsed versus continuous wave Nd-YAG laser-induced necrosis: Comparison in the rat liver in vivo
It is assumed that a pulsed Nd-YAG laser will avoid heat diffusion in tissue and thus produce more predictable and less deep lesions. The aim of this study was to compare lesions induced in an homogeneous tissue by the pulsed wave (PW) and the continuous wave (CW) modes of the Nd-YAG laser. Single laser shots were delivered to the liver surface of anaesthetized rats after laparotomy, in vivo. In experiment 1, the quartz fibre was handled close to the liver surface. Energies of 10, 20, 40 J were applied. In experiment 2, the quartz fibre was fixed at a distance from the liver and the laser beam was focused through a handpiece, to obtain a spot of 3 mm in diameter at the liver surface. Energies of 20, 40, 80 J were applied. In both studies, four or five shots were performed for each parameter with each laser mode. After excision of the liver, the maximal depth and width of the crater, the necrotic area and the total affected tissue were measured for each lesion. In experiment 1, there was no difference in any dimension of lesion between the two modes. In experiment 2, the only statistical difference was observed at the fluence of 566 J cm−2 where the necrotic area as well as the total lesion were deeper with the pulsed mode. This difference was not observed for the crater. In this experimental model depths and widths of the different layers of the lesion induced by the PW mode were comparable to those obtained with the CW mode. This PW mode of Nd-YAG laser does not prevent heat diffusion in tissue.
Key wordsLaser-tissue interaction Laser-induced lesion 1064 nm wavelength Continuous wave Nd-YAG laser Pulsed Nd-YAG laser
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- 4.Lambert R. Laser for colorectal polyps and cancer.Can J Gastroenterol 1990,4:546–8Google Scholar
- 5.Sibille A, Gobet B, Descos F, Lambert R. Long term results of Nd-YAG laser photodestruction with curative intent for early adenocarcinomas of the rectum.Gastrointest Endoscopy 1993,39:305 (Abstract)Google Scholar
- 6.Mordon SR, Cornil AH, Brunetaud JM et al. Nd-YAG laser thermal effect: comparative study of coagulation in rat liver in vivo by continuous wave and high power pulsed laser.Lasers Med Sci 1987,2:285–94Google Scholar
- 7.Mordon SR, Cornil AH, Jensen DM, Brunetaud JM. Comparative study of high power pulsed Nd-YAG and CW Nd-YAG lasercoagulation in dog stomach. Proceedings of the Third International Nd-YAG Laser Symposium, Tokyo 1987:217–22Google Scholar
- 12.Halldorsson T, Langerholc J. Thermodynamic analysis of laser irradiation of biological tissue.Appl Opt 1978,17:3948–58Google Scholar
- 16.Brackett KA. Tissue interactions of Nd-YAG lasers. In: Joffe SN, Oguro Y (eds)Advances in Nd-YAG Laser Surgery. New York: Springer-Verlag, 1988:Chap 43Google Scholar