An apparatus for the evaluation of tissue ablation is provided. The apparatuscomprises a broadband (white multiple wavelengths) light and/or laser light(single wavelength) illumination source that delivers light to the site wherea lesion is being formed. Scattered light is collected from the ablated tissueand evaluated to obtain qualitative information regarding the newly formedlesion. The apparatus allows assessment of such parameters as, for example,catheter- tissue proximity, lesion formation, depth of penetration of thelesion, cross-sectional area of the lesion in the tissue, formation of charduring the ablation, recognition of char from non-charred tissue, formation ofcoagulum around the ablation site, differentiation of coagulated from non-coagulated blood, differentiation of ablated from healthy tissue, andrecognition of steam formation in the tissue for prevention of steam pop.These assessments are accomplished by measuring the intensity and spectrum ofdiffusely reflected light at one or more wavelengths.
