A method of thermally inducing and monitoring changes to localized regions of tissue illuminating a volume of tissue with a first beam of X-rays, detecting the portions of the first beam of X-rays that passed through the volume of tissue, generating a first X-ray image signal from the portions of X10 rays of the first beam detected, applying heat to at least a localized region of tissue within the volume of tissue after the illuminating and after the detecting, illuminating the volume of tissue with a second beam of X-rays, detecting portions of the second beam of X-rays that passed through the volume of tissue during the illuminating with the second beam of X-rays, generating a second X-ray image signal from the portions of X-rays of the second beam detected, and generating a difference image signal based upon a comparison of the first and second X-ray image signals. The difference image signal provides information of changes in X-ray attenuation by localized regions of tissue within the volume of tissue due to the application of heat.