Surgery – Instruments – Electrical application
Reexamination Certificate
1997-12-15
2001-08-28
Lateef, Marvin M. (Department: 3737)
Surgery
Instruments
Electrical application
C600S373000, C606S041000
Reexamination Certificate
active
06280441
ABSTRACT:
1. Field of the Invention
This relates to an apparatus and method for ablating target tissue. More particularly, a temperature controlled monopolar or bipolar device placed in target tissue to create thermal lesions in the breast or in uterine myomas or fibroids or the prostate.
2. Background of the Disclosure
U.S. Pat. No. 4,010,758 discloses an annular, flat electrode that serves as ground with a helix that bores into tissue as the active electrode. The electrode can be insulated in order to separate it from ground. The device is made to screw into the heart and it is used for cardiac pacemaking by supplying a small electrical pulse, not for lesioning as in the present invention.
U.S. Pat. No. 4,637,392 discloses a doubly wound helix that is used for coagulation of blood in a wound. It is attached to an electric motor for rotation of 150-200 RPMs for cleaning ducts or pockets of tissue. A stationary scraper is also disclosed to clean the electrode as it rotates.
U.S. Pat. No. 4,945,912 discloses a helical antenna operational in the microwave frequency range. The helix is not in direct contact with tissue and is covered by a Teflon polymer sheath. It is designed for cardiac ablation and offers intracardiac monitoring of cardiac electrical activity.
U.S. Pat. No. 5,047,026 discloses a device for tunneling into or through tissue or a blood vessel. It is flexible to fit through an endoscope and operates over-the-wire. The guide wire is active and the helix is ground. The helix is tightly wound around a plastic core, requiring many turns to maximize surface area and to minimize current density.
U.S. Pat. No. 5,047,027 discloses a device for tumor resection that is composed of a multi-winding helix on a plastic holder and a loop. The helix is ground the loop is active for cutting and resecting tissue.
U.S. Pat. No. 5,100,423 discloses an over the wire device made to clean clogged blood vessels. It is composed of helical wires that can be activated with RF energy to cut through plaque or vibrate by using ultrasound to increase the effect. It is shaped like a wire basket.
U.S. Pat. No. 5,507,743 is a combination of straight electrodes and helical electrodes on the outside of the straight electrode. Energy is activated between electrodes using an RF source. It has variable pitch deployment that allows for a compact size when undeployed. There are thermal sensors on the outside of the needles for feedback control. No frequencies or temperatures are measured. There are no thermal sensors in tissue in the target treatment area. The needles are hollow and have exit ports for drug infusion.
U.S. Pat. No. 5,431,649 discloses a catheter based helix that screws into tissue for ablation. A conductive solution is applied through side ports in the needle. The helix has variable insulation localization. There are sensors in the needle for temperature feedback control, but no sensors in tissue.
U.S. Pat. No. 4,800,395 discloses a helix as part of an antenna system operational in air. It couples to a monopole antenna for communications. U.S. Pat. No. 5,226,890 discloses a tissue gripping device with helical threads on the outside of a trocar to bore into tissue. U.S. Pat. No. 5,488,958 discloses a surgical cutting instrument where a helix bores into tissue for the purpose of providing mechanical advantage for a cutting shaft to then follow the helix and core out the tissue. U.S. Pat. No. 5,334,193 discloses a fluid cooled ablation catheter that operates by monopolar RF or by bipolar by having two helices wound around a catheter shaft. The device ablates tissue by passing over the tissue as in a lumen, rather than boring into tissue as in the present invention.
U.S. Pat. No. 5,545,193 discloses a device that is composed of a wire cage that could be helical wound for treating hollow organs and does not have temperature feedback, nor does it bore into tissue.
U.S. Pat. No. 5,662,680 discloses an irrigation and suction device that carries various needle arrangements endoscopically for tissue ablation. There is no helix configuration for boring into tissue.
As seen in the prior patents, there are many uses for helical shapes including tissue removal or tissue ablation. None of the disclosures combines all of the factors of the present invention with a helix that penetrates into tissue, temperature feedback control in the tissue instead of on the helix shaft, and the potential for closed ended fluid circulation for cooling.
Many attempts to ablate tissue percutaneously or through body orifices have been tried. The target tissue could be any contained malignancy or metastasis in the breast, liver, pelvis, or other site. The target tissue could also be a benign disease that is causing patient discomfort, bleeding or obstruction, such as prostate and myomas. The tissue could also be endometrium patches causing endometriosis or a disc herniation in the spine. The purpose of the lesioning is to ablate the tissue and defunctionalize it with subsequent fibrosis and absorption. RF delivery systems have been simply comprised of 1 needle in monopolar mode or 2 or more needles in bipolar mode. Due to the lack of significant penetration because of localized RF current, the depth of penetration of RF is limited without some sort of enhancement. This enhancement could be cooling, changing frequency or changing the electrode configuration geometry. The puncture or entry sites are of limited diameter, thus the probes must somehow have an efficient geometric shape to affect large areas for ablation without undue trauma in getting the device in place.
SUMMARY OF THE INVENTION
The current device is either a rigid or deployable design of either monopolar or bipolar design with a single entry site, not an array of needles. The rigid design is a helical shaped effector that is screwed into the tissue target. The entry consists only a small puncture site. The helical shaped effector is either a single conductor for monopolar activation or bipolar with alternating segments or alternating coils connected to a bipolar RF supply. The shaft of the helical shaped effector may be hollow to allow coolant circulation. This will enhance the heating penetration by overcoming the intense thermal gradients in the near field. Other embodiments are deployable devices that enter the target tissue in a compressed or folded state and then are expanded into the target tissue to create a devices that spreads out into the target tissue. These can also be monopolar designs or have electrically separate segments that are connected in a bipolar configuration. Cooling can enhance many of these designs and the coolant can be either air or fluid. The water cooled systems can be either pump fed or gravity fed with a pressurized IV bag. There may be a thermocouple inside of the device to provide temperature feedback and a means to control.
The current method is to place the device into the target tissue either by rotating through a small skin entry point or the surface of the target tissue. Power and/or current can be carefully controlled either by sensing temperature at the needle site or central to the helical shaped effector or at the edge of the lesion. Cooling can be added to enhance the size of the treated region. The lesion is then created over 2-12 minutes, preferably about 4-6 minutes in a gradual fashion to prevent target tissue adherence of the electrode and coring of the target tissue by removing a central block as the electrode is removed after treatment. Temperatures are limited in the central portion of the ablation volume to 95-105° C. to avoid the effects of steam formation and target tissue adherence to the device. The return pad may encompass the target organ or be placed elsewhere on the body. For precise control of the lesion, thermometry probes may be placed as follows: on or in the helical shaped effector at various locations, in the target tissue in the center of the helical shaped effector, or in the target tissue at the edge of the intended lesion.
For insertion into target tissue, especially rubber-like target tissue as found
Lateef Marvin M.
Shaw Shawna J.
Sherwood Services AG
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