Bi-component conformal electrode for radiofrequency sequential ablation and circumferential separation of large tumours in solid organs: development and in-vitro evaluation

Objective: Complete destruction of large tumours by radiofrequency ablation (RFA) with surrounding tumour-free margin is difficult because of incomplete or non-uniform heating due to both heat sink effect of circulating blood and limitations of existing RF electrode design. A new RF electrode is described to overcome this limitation. Methods: A bi-component conformal (BCC) RFA probe providing sectorial sequential ablation followed by circumferential cutting is designed and evaluated. Three-dimensional finite-element analysis model was developed with temperature feedback-controlled simulation of RFA for electrode design and optimization. The prototype bipolar BCC probe with 3 embedded thermocouples was constructed and evaluated in tissue-mimicking phantoms. Results: Maximum tissue temperature was kept < 100 ºC with power applied < 15 W. A 10 min ablation time was used for each sequence and after four sequential RFA, a large ablation zone of 55 cm3 was achieved. Our experiment confirmed that lesions exceeding 3.7cm could be ablated and separated from the surrounded tissue. Conclusion: The new BCC probe is thus capable of controlled ablation followed by circumferential separation of the lesions, when required. Significance: The results of these experiments provide proof of concept validation that the BCC probe has the potential to ablate by sequential heating tumours in solid organs > 3.5cm then separate them by electrosurgical cutting from the surrounding normal parenchyma. The combined RF ablation and physical separation could completely destroy the cancer cells at the ablation site thus avoid any local recurrence of cancer. It requires further in-vivo validation studies in large animals.