In vivo effects of interstitial ultrasound plane applicator on Dunning tumours

Despite their invasive nature, interstitial techniques remain a useful treatment for unresectable or deep-seated tumours. In the digestive endoscopy field, tumours around the biliary ducts induce stenoses. This study was a preliminary step to evaluate the feasibility of using a rotating plane interstitial ultrasound transducer for ablation of malignant tissues in vivo. The applicator active part consisted of a water-cooled plane rotating transducer, 3×10 mm. Experiments were carried out on Dunning tumours (AT₂ subline) implanted subcutaneously on abdomen of rats. All the control rats died of tumour growth or were sacrificed 15 days after the treatment date. An immediate tumour decrease occurred in all treated animals. 44% of the exposed rats were still alive without a tumoral trace 60 days after treatment. A local tumour recurrence was observed on 25% of the animals after 5 days. The last rats seemed to be cured, but a tumour appeared finally away from the implantation site 10 days after treatment demonstrating the difficulties during the tumour implantation. These experiments showed the short term efficiency of a plane rotating transducer and its possibility to destroy tumours. An MRI-guided therapy should allow one to reduce the long term failure