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