#$%^&*AU2019203666A120191219.pdf#####ABSTRACT A method includes measuring a first impedancemagnitude between a distal-electrode fitted at a distal end of a medical instrument in an organ of a patient and a 5 surface-electrode attached externally to the patient, at a first electrical frequency. A second impedance-magnitude between the distal-electrode and the surface-electrode, is measured at a second electrical frequency. A difference between the first and second measured impedance-magnitudes 10 is calculated. Based on the calculated difference, an indication of, whether the distal-electrode is in physical contact with tissue or immersed in blood is decided, and outputted. 212/2 3002 50 E o 51 En 100M 1000 3000 10k 30k 100FG.2 Frequency, Hz Measure respective sets of impedancemagnitudes at a low frequency and at a -62 FIG. 3 high frequency Calculate a respective set of differences in impedance-magnitudes between the low -64 and the high frequency sets Statistically test validity of each difference 66 within the set of differences 68 Is the N difference statistically N significant? Yes 72 Does difference No exceed Ro? 76 Y74 Update system that electrode Update system that electrode is in contact with tissue is in contact with blood
