Patent ID: 7505811

Claim:
A method of tissue characterization, comprising: administrating to a living body a contrast agent, formed of semiconductor particles, conjugated with a biological carrier, selectively bindable to target cells, wherein the contrast agent particles are reversibly switchable between at least two impedance modes, through reversible excitation by light illumination, and wherein the modes are: a base mode, in which electrons are in a valance band; and an increased conductivity mode, in which electrons are tansferred from the valance band to a conduction band; measuring the electrical impedance of an examined tissue, in the base and increased conductivity modes of the contrast agent, by: applying voltage pulses to the examined tissue, and measuring the electrical impedance of the examined tissue in the base mode of the contrast agent; applying optical pulses of a power density, for reversibly exciting the contrast agent, and further applying the voltage pulses to the examined tissue, and measuring the electrical impedance of the examined tissue in the increased conductivity mode of the contrast agent; detecting reversible changes in the electrical impedance, between the measurements of the base and increased conductivity modes, for the examined tissue; and utilizing the detected reversible changes, between the base and increased conductivity modes, for determining a presence of the contrast agent, hence a presence of the target cells to whom the contrast agent is selectively bound within the examined tissue, thus characterizing the tissue.