INTERSTITIAL LASER THERMOTHERAPY IN PIG-LIVER - EFFECT OF INFLOW OCCLUSION ON EXTENT OF NECROSIS AND ULTRASOUND IMAGE

Background/Aims: The aim was to investigate the effect of blood inflow occlusion. on lesion. size and ultrasonographic findings during inter stitial laser thermotherapy of normal liver. Methodology: Pigs were tr eated with or without hepatic inflow occlusion at a Laser power of 3W or without inflow occlusion at 5 W (target temperature 43 degrees C). The thermotherapy system consisted of an Nd:YAG Laser and a temperatur e feedback circuit. Ultrasonography was performed immediately after tr eatment. Lesion size was determined using Light microscopy including i mmunohistochemistry with bromodeoxyuridine. Results: Hyperechoic ultra sonographic changes were observed after treatment with inflow occlusio n or when there was carbonization. If carbonization did not occur, uno ccluded blood flow was associated with hypoechoic lesions. Following i nflow occlusion, maximum lesion width 2 and 6 days after thermotherapy averaged 21.9 +/- 1.3 and 20.2 +/- 0.8 (means +/- SEM) mm, respective ly. This was larger than the corresponding values of 10.8 +/- 0.8 and 11.1 +/- 2.0 observed after treatment without inflow occlusion at 3W ( p<0.01). Increase in, laser power from 3 to 5W in experiments without inflow occlusion produced early carbonization. and a slight increase i n. lesion size that did not match that produced by inflow occlusion. U ltrasound gave a correct prediction of necrosis size after treatment w ith inflow occlusion but overestimated the necrosis when inflow occlus ion was not used. Ultrasound was furthermore unable to predict size of necrosis in individual experiments. Conclusion: Blood flow has a majo r influence on lesion size in interstitial laser thermotherapy of the liver and affects ultrasonographic images. Also, it appears that intra operative ultrasonography cannot monitor lesion size with an accuracy that is sufficient for clinical use.