An optical method and apparatus is utilized to evaluate the presence of tissue modification, in particular, to evaluate tissue ablation using light scattering spectroscopy realized via optical fiber(s). Such a technique allows for detection of the presence of tissue modification and provides depth information, such as, for example, depth of an ablated lesion. The method and apparatus as described herein can be used for in-vivo, real-time monitoring during predetermined procedures, such as, cardiac tissue ablation for therapeutic reasons.
 The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.