A system and method for assessing effects of ablation therapy on tissue in a body includes a) acquiring at least one ultrasound image of a region of interest； b) delivering ultrasound ablative energy from an ultrasound transducer to the region of interest； c) emitting electromagnetic radiation from an optic fiber to cause generation of a photoacoustic wave from tissue in the region of interest； d) receiving a tissue response signal from the ultrasound transducer indicative of a characteristic of tissue responsive to the electromagnetic radiation； and e) analyzing the tissue response signal to determine at least one characteristic of the tissue responsive to the ablation therapy.
