Effect of percutaneous interstitial thermal laser on normal liver of pigs: sonographic and histopathological correlations.

Tumour necrosis can be induced by interstitial application of low power laser light, which causes thermal damage to the tissue. In normal pig liver the effects were studied of low power Nd:YAG laser light (continuous wave; 1.5 W, 10 min, wavelength 1064 nm), administered percutaneously via a 600 micron fibre. Ultrasound images were compared with histopathological findings. Histopathology showed induction of sharply demarcated lesions with a mean diameter of 10-15 mm (days 0 and 7), consisting of coagulative necrosis. Healing of the lesion occurred by granulation, fibrosis and removal of cell debris. Lesions could not be seen by week 4, which suggests complete regeneration. Ultrasonography showed a good correlation with histopathology, especially at 1 week when different histopathological tissue layers could be discriminated by ultrasonography. It is concluded that thermal lesions in liver can be induced via a percutaneous route and that ultrasound imaging is useful in monitoring the lesions during and after the procedure.