Lasers in gastroenterology

Table 3 Comparison of interstitial laser photocaogulation (ILP) and photodynamic therapy (PDT)

	ILP	PDT
Nature of biological effect	Thermal	Photochemical
Wavelength of light used	Infrared (805-1064 nm)	Green (510-530 nm) Red (630-675 nm)
Typical laser power per fibre	3-5 W	0.1-0.3 W (higher for illuminating hollow organs)
Effect on connective tissue	Destroyed	Largely unaffected
Healing	Resorption and scarring, some regeneration	Regeneration, sometimes with scarring
Selectivity of necrosis between tissue of origin of tumour and other adjacent tissues	None	Possible between mucosa and underlying muscle in hollow organs
Selectivity of necrosis between tumour and tissue of origin of tumour	None	Minimal
Cumulative toxicity	None	None