The impedivity of freshly excised human breast tissue.

A set of 120 impedivity spectra was collected in breast tissue immediately after excision from 64 patients undergoing breast surgery. The measurements were made at 12 discrete frequencies halving from 1 MHz to 488 Hz. The spectra were sorted into three groups of normal tissue, mammary gland, connective tissue and adipose tissue, and three groups of pathological tissue, mastopathy, fibroadenoma and carcinoma. Intergroup multiple comparisons of the components of impedivity and admittivity were systematically carried out at every measurement frequency. The low-frequency-limit resistivity, the fractional power and characteristic frequencies were calculated from the experimental data. No significant correlation between impedivity and admittivity and patient's age was observed, except for mastopathy. No significant difference between groups of normal tissue and benign pathology (mammary gland, mastopathy and fibroadenoma) was found. The group of carcinoma differed from all the other groups principally by the low-frequency-limit resistivity, the fractional power and the phase angle at frequency above 125 kHz. These results indicate that impedance spectroscopy is appropriate for the detection of breast cancer.