| 摘要 |
According to the present invention, a device for detecting metal is provided with a sparking electrosurgical instrument and comprises a metal detector, thereby reliably differentiating the operation of the instrument on metal from the operation of the instrument on body tissue. The metal detector determines whether a spark (18) generated by the instrument touches body tissue (11) or a metal component (19) on the basis of an electric current (and voltage) transferred to the instrument. Preferably, the determination is performed by determining the component of an electric current which does not correspond to a linear equivalent circuit. Components of the linear equivalent circuit are determined previously or during the operation of regression calculation. As a first standard of determination, a spark characteristic variable, Frel, is determined from an electric current. As a second standard of determination, a resistance characteristic variable, R, characterizing tissue resistance is determined. The two characteristic variables are compared with critical values. When the tissue resistance is reduced below a critical value of resistance and the spark characteristic variable exceeds a critical value of spark size, a signal characterizing the activation of the spark (18) regarding the metal component (19) is generated. |
