The　microwave　ablation　has　become　an　important　manner　for　tumor　treatment.　In　this　paper,　we　proposed　a　new　method　for　evaluation　of　microwave-induced　thermal　lesions　using　the　wavelet　analysis　of　the　mean　scatterer　spacing　(MSS).　First,　the　ultrasonic　radiofrequency　(RF)　data　of　normal　and　coagulated　porcine　liver　tissues　was　collected　through　the　temperature-controlled　water　bath　heating　experiments.　The　convex　array　ultrasound　probe　with　a　center　frequency　of　3.5　MHz　was　used.　Second,　the　wavelet　analysis　was　used　to　compute　the　MSS　of　normal　and　coagulated　porcine　liver　tissues,　respectively.　Finally,　the　microwave-induced　thermal　lesions　were　detected　based　on　the　differences　in　the　MSS　between　normal　tissues　and　thermal　lesions.　Eighteen　cases　of　microwave　ablation　experiments　and　20　cases　of　water　bath　heating　experiments　were　conducted　on　fresh　porcine　liver　samples.　The　MSS　of　normal　porcine　liver　tissues　was　1.15　+/-　0.12　mm,　and　the　MSS　of　coagulated　porcine　liver　tissues　was　0.93　+/-　0.07　mm.　Six　cases　of　thermal　lesions　were　compared　between　the　MSS-detected　area　and　the　caliper-measured　area,　and　the　MSS-detected　area　had　an　error　of　(13.55　+/-　5.29)　%.　The　experimental　results　indicated　that　the　proposed　method　could　be　used　in　preliminary　detection　and　evaluation　of　microwave-induced　thermal　lesions.　(C)　2013　Elsevier　B.　V.　All　rights　reserved.