Method for biopsy and ablation of tumor cells

Abstract

A medical instrument including a cannula or probe used to penetrate tissue to a target area to perform a medical procedure including biopsy and RF ablation of undesirable tissues or cells for treatment, or to prevent the spread of cancer cells during a biopsy procedure. The probe is preferably shape changeable. The probe may be hollow or solid having an exterior surface coated with a dielectric material, a preferably sharpened beveled tip at a distal end coated with a resistor material, and means for coupling the probe to an RF generator and control device. The RF generator provides current to the probe. The dielectric material provides a predominant impedance characteristic of the probe in contact with tissue, thus changes in impedance will vary primarily based on the area of the probe in contact with tissue. The control device monitors the impedance of the probe and based thereon calculates the area of the probe in contact with tissue, then adjusts the current in order to maintain an approximately constant current density over the area of the probe in contact with tissue, thereby preventing hot spots and fulguration. A thermocouple may be formed at the tip of the probe, or other temperature sensing device may be used. If a temperature sensing device is used, the control device may also monitor the temperature to determine the efficacy of treatment. RF energy directors may be used with the invention to control the shape of the RF energy field.