Surgery – Instruments – Electrical application
Reexamination Certificate
2000-03-09
2002-09-17
Kearney, Rosiland S. (Department: 3739)
Surgery
Instruments
Electrical application
C606S034000, C606S037000, C606S039000, C606S040000, C606S041000, C607S101000
Reexamination Certificate
active
06451014
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electrode device used in microwave surgery apparatus, with which coagulation, hemostasis, ablation, etc. of biotissues is performed by means of microwave, and more specifically to an electrode device in which the direction of the electrode fixed at the distal end of an elongated shaft can be controlled at a proximal site of the shaft.
BACKGROUND ART
For treatment of pathological tissues, e.g., malignant tumors, which are located deep in a body, methods which have been widely applied are those by which the body is deeply cut open through the skin to expose the lesion and then the lesion is excised together with the adjacent tissues. In recent years, however, due to a trend for benefit of patients quality of life, treatment methods that do not involve abdominal section and could thereby shorten the term of hospitalization are becoming familiar. Among them, examples of methods for treatment of hepatocellular carcinoma include transcatheter arterial embolization (TAE), percutaneous ethanol injection (PEI), microwave coagulation therapy (MCT).
In microwave coagulation therapy, selective coagulation, hemostasis, ablation, etc. of the lesion are performed utilizing the dielectric heat generated in the bio-tissues due to a localized microwave electromagnetic field created between electrodes applied to the lesion site by radiating microwave at a predetermined frequency between the electrodes. It has advantages over coagulation or ablation procedures using an electric or laser knife in hemostatic and coagulation effects, as well as in its easiness of handling. For microwave coagulation for deep region of the body, there are known methods such as percutaneous microwave coagulation therapy (PMCT) and laparoscopic microwave coagulation therapy (LMCT). In laparoscopic microwave coagulation therapy, surgery is performed by creating in the abdominal surface multiple openings usually with a diameter of several mm at proper locations surrounding the umbilicus, then inserting, through respective trocars, through one of which a laparoscope with a CCD camera equipped at its distal end, through two of which forceps, and through another of which a surgical electrode, and introducing a nontoxic gas such as carbon dioxide into the abdominal cavity to inflate the abdomen, and then manipulating the surgical electrode from outside of the body while watching the image captured by the CCD camera and displayed on a monitor.
When the electrode is being inserted through the trocar into the abdominal cavity, the electrode and the supporting shaft used for laparoscopic microwave coagulation therapy must be in generally straight configuration. Thus, the conventional electrode has an integrally attached straight shaft and the direction of its electrode tip is fixed. On the other hand, the location of a lesion to be coagulated may vary even with regard to the same organ, and there are cases in which blood vessels or the bile duct not to be coagulated lie in front of the lesion. With a conventional electrode, which is attached to the supporting shaft in a fixed, generally straight configuration, therefore, it has often been difficult to apply the electrode at an optimal angle to the lesion.
To solve this problem, it is necessary to design an electrode such that, after insertion of it into the abdominal cavity, the direction of the electrode can be changed to a desired angle by operation at a proximal site. However, unlike an electric or laser knife, one of the characteristics of an electrode for microwave coagulation therapy is that it contains inside a microwave coaxial cable up to the distal end of the electrode. Due to this, there has been proposed no electrode usable in laparoscopic microwave coagulation therapy in which the direction of its electrode tip can be controlled at its proximal site.
That is, there is a difficulty with an electrode for microwave coagulation therapy in providing within its support shaft a complex mechanism for controlling the angle of the electrode, for a coaxial cable occupies main space in the cross section of the support shaft's lumen.
In addition, it is one of the characteristics of a microwave coaxial cable that if there is a region curved at an acute angle, the microwave being conducted is partly reflected at the region to create a standing wave, thus causing generation of heat and a loss of energy, and the forward conduction of microwave energy beyond that region is eventually impeded. Therefore, even when the electrode is bent near its distal end, its curve must not be acute so that the curve of the interior coaxial cable can have as large a radius of curvature as possible.
Furthermore, a microwave coaxial cable extending contained within the shaft includes a inner conductor, an insulating medium covering the inner conductor, and an outer conductor surrounding the insulating medium. Thus, as a coaxial cable has substantial thickness and therefore resists deformation, a mechanism that can apply a sufficient force on it is required for bending it.
Furthermore, as the electrode is inserted into or pressed against a lesional tissue, the electrode must be so constructed that the angle of the electrode can be retained even when the electrode receives a reaction force from the tissue.
Still further, as tissue coagulation with microwave generally takes about 60 seconds per site, the electrode once applied to the lesion site must be held at the predetermined angle during the period. Therefore, it is preferable that the electrode is so designed that the angle is fixed without imposing extra burden on the hand of the operator once the direction of electrode is set at an desired angle.
In addition, further problem was noticed that while the support shaft containing a coaxial cable is being bent, the interior coaxial cable caused to curve is often distorted along the longitudinal axis, thus creating stress in the direction of the longitudinal axis, and this stress could prevent smooth bending of the shaft beyond a certain amount of bending.
The objective of the present invention is to solve the above mentioned problems and provide an electrode for microwave coagulation therapy, in which the direction of the electrode tip can be controlled as desired through operation at its proximal region.
DISCLOSURE OF INVENTION
The present inventors found that, according to a planned maximal angle with the distal end of the electrode, by separating the distal part of support shaft of the electrode into one or more links whose angles can be altered in a single plane, and arranging them so that the most distal one of the links can be pulled and pushed back on its deflection side from a proximal region by means of an elongated resilient member along the inner surface of the support shaft, the direction of the distal end of the electrode containing a coaxial cable can be easily and reliably controlled from the proximal region of the electrode, and, even where multiple links are included, all of the links can be moved in concert retaining their mutual balance and therefore an acute curve will not created in any region along the coaxial cable contained therein even when the angle of the electrode is changed a great deal.
Thus, the present invention provides an electrode device for microwave surgery which allows to control the angle of the electrode thereof comprising: a handpiece provided with a rigid hollow support shaft extending toward a distal end, a movable support provided at the distal end of the support shaft and carrying thereon an electrode for microwave surgery, a microwave coaxial cable which is connected at the proximal end thereof to a microwave coaxial connector and connected in the movable support to corresponding portions of the electrode for microwave surgery, said cable extending through the handpiece and the support shaft, wherein:
(a) the movable support comprises one or more links surrounding the coaxial cable and longitudinally connected to the distal end of the support shaft so that the movable support can be bent and stretched,
Kitada Suminori
Wakikaido Koichi
Azwell Inc.
Kearney Rosiland S.
Millen White Zelano & Branigan P.C.
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