Patent ID: 6162216
Filing Date: 2000-12-19
Classification: A61B

Abstract:
In a medical probe apparatus comprising a cannula with an exterior surface with a dielectric coating, the dielectric coating having a predominant impedance characteristic in an electrical circuit of the medical probe apparatus, an impedance sensor, a control means for adjusting an electrical current to the cannula, an RF energy generator, and a return electrode, a method for controlling or maintaining an approximately uniform current density over a surface area of the cannula in contact with tissue, the method steps comprising:(a) obtaining the following values:(i) obtaining an impedance threshold value,(ii) obtaining a starting current value, and(iii) obtaining a threshold current divided by impedance value, hereafter (I/Z); and(b) obtaining a new impedance value, comparing the impedance threshold to the new impedance value, reducing the current if the new impedance value exceeds the threshold impedance value; and(c) obtaining a new current value, dividing the new current value by the system impedance to obtain a present (I/Z), comparing the present (I/Z) to the threshold (I/Z), increasing the present current if the value of the present (I/Z) is less than the threshold (I/Z), decreasing the present current if the value of the present (I/Z) is more than the threshold (I/Z).