Spectral sensing of ablation

A method for tissue assessment, comprising:

• ablating the tissue at a site within a body of a living subject using an invasive probe applied to the site;
• at a first stage in the ablation of the tissue, making first measurements of scattered light intensities from the site at a first wavelength, a second wavelength, and a third wavelength;
• at a second stage in the ablation of the tissue, subsequent to the first stage, making second measurements of the scattered light intensities from the site at the first wavelength, the second wavelength, and the third wavelength;
• computing a first ratio between the first measurement and the second measurement at the first wavelength, computing a second ratio between the first measurement and the second measurement at the second wavelength, and computing a third ratio between the first measurement and the second measurement at the third wavelength;
• dividing a product of the second and third ratios by the first ratio to determine an overall ratio value;
• and
• estimating a size of a lesion based on the overall ratio value.