A portion of a concentric bipolar microelectrode sensor is attached to an inflatable balloon of a catheter. Another portion of the concentric bipolar microelectrode sensor is also attached to a body of the catheter. The inflatable balloon is guided to become in proximity of a tissue. The inflatable balloon is then inflated. The inflation increases the likelihood of contact between microelectrodes of the concentric bipolar microelectrode sensor with the tissue. A voltage is supplied to the microelectrodes. The tissue's impedance is accordingly measured over a frequency range. A disease of the tissue, such as a lesion, is diagnosed based on the measured impedance.
