A method is described for determining
biological tissue type based on a complex impedance spectra obtained from a probe with a conducting part adjacent a tissue
region of interest, wherein the impedance spectra includes data from a number of frequencies. The method may include: obtaining, from the complex impedance spectra, a first
data set representative of impedance modulus values, or equivalent
admittance values, at one or more frequencies, obtaining, from the complex impedance spectra, a second
data set representative of impedance
phase angle values, or equivalent
admittance values, at one or more different frequencies, applying a first discrimination criterion to the first
data set, applying a second discrimination criterion to the second data set, and thereby determining if the tissue
region of interest is a
tissue type characterised by the discrimination criteria.