Surgery – Instruments – Electrical application
Patent
1997-09-30
1999-09-14
Cohen, Lee
Surgery
Instruments
Electrical application
606 49, 607 99, A61B 1739
Patent
active
059515465
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a novel electrosurgical instrument for tissue ablation, an apparatus for tissue ablation comprising the electrosurgical instrument and a method for providing a lesion in damaged or diseased tissue from a mammal. The present invention is useful for providing a lesion in any biological tissue such as tissue from a mammal. Hereby damaged or diseased tissue such as tumors, birth marks, lipomas, or the like, may be removed.
Radiofrequency (RF) tissue ablation is a well known technique for making thermal lesions around the tip of an electrode due to tissue coagulation caused by resistive heating. The electrode can be applied directly on superficial structures, surgically, endoscopically, laparascopically, or via a transcatheter access--the latter has become a well established treatment for many symptomatic cardiac arrhythmias (see Nath S, Haines D E. Biophysics and pathology of catheter energy deliver systems. Progress in Cardiovascular Disease 1995; 37: 185-204). Furthermore, a needle electrode can be inserted interstitially, mainly guided by imaging. Several studies have evaluated needle electrodes and thermal lesions in different organs such as liver (see McGahan J P, Schneider P, Brock J M, Tesluk H. Treatment of liver tumors by percutaneous radiofrequency electrocautery. Seminars in Interventionel Radiology 1993; 10: 143-149; Rossi S, Fornari F, Buscarini L. Percutaneous ultrasound-guided radiofrequency electrocautery for the treatment of small hepatocellular carcinoma. J Intervent Radiol 1993; 8: 97-103; Solbiati L, Ierace T, Goldberg S N, Livraghi T, Gazelle G S, Rizzatto G. Percutaneous US-guided RF tissue ablation of liver metastases: Long-term follow-up. Radiology 1995; 197(P): 199 (abstr); Livraghi T, Goldberg S N, Lazzaroni S, Meloni F, Monti F, Solbiati L. Saline-enhanced RF tissue ablation in the treatment of liver metastases. Radiology 1995; 197(P): 140 (abstr), prostate (see McGahan J P, Griffey S M, Budenz R W, Brock J M. Percutaneous ultrasound-guided radiofrequency electrocautery ablation of prostate tissue in dogs. Acad Radiol 1995; 2: 61-65, Goldwasser B, Ramon J, Engelberg S. Transurethral needle ablation (TUNA) of the prostate using low level radiofrequency energy: An animal experimental study. Eur Urol 1993; 24: 400-405), and lungs (see Goldberg S N, Gazelle G S, Compton C C, McLoud T C. Radiofrequency tissue ablation in the rabbit lung: Efficacy and complications. Acad Radiol 1995; 2: 776:784). Finally, needle electrodes have been used in neurosurgery for the interruption of pain pathways (see Anzai Y, De Salles A F, Black K L et al: Stereotactic and interventional MRI, in De Salles A F and Goetsch S J (eds): Stereotactic Surgery and Radiosurgery. Madison, Medical Physics Publishing, 1993: 47-60).
The electrophysiologic and thermodynamic conditions in monopolar RF tissue ablation have been described by Organ (see Organ LW. Electrophysiologic principles of radiofrequency lesion making. Appl Neurophysiol 1976; 39:69-76) and Nath et al (see Nath S, Haines D E. Biophysics and pathology of catheter energy deliver systems. Progress in Cardiovascular Disease 1995; 37: 185-204; Nath S, Dimarco J P, Haines DE. Basic aspects of radiofrequency catheter ablation. J Cardiovasc Electrophysiol 1994; 5: 863-876): An RF lesion is the result of tissue destruction due to resistive heating in the tissue that surrounds the uninsulated part of the electrode. Resistive heating is proportional to the square of the current density, the latter being inversely proportional to the square of the distance from the ablation electrode. Therefore, resistive heating decreases from the ablation electrode with the distance to the fourth power. In other words, significant resistive heating only occurs within a narrow rim (few mm) of tissue in direct contact with the ablation electrode. Deeper tissue heating occurs as a result of passive heat conduction from that rim.
A general problem in RF tissue ablation is limitation in lesion size. An increased generator power
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