| 摘要 |
Method of operating, catheter and catherization system for measuring electrical impedances in blood vessels within an annular area around the catheter. The catheter contains excitation electrodes (T1, T2 & S1, S2) between which the impedance is measured, the measurement being a potential difference between measuring electrodes (Me1, Me2, Me3) present between those excitation electrodes. The two pairs of excitation electrodes are electrically driven in opposition to set up a controllable pattern of electric field lines (a so-called "counter current field"). By varying the amplitudes of the two excitaton currents, the electric field can be adjusted such that: a) no (or hardly any) current flows between the measuring electrodes (the "quenching relation"), and b) at a distance away from the measuring electrodes the electric field lines are substantially perpendicular to the longitudinal axis of the catheter. The average impedance of the area-to-be-measured and that of the area outside of this given area can then be measured separately. |
