You may be referring to MRIgFUS which is a technique used in recurrent gliomas. This is a high intensity focused ultrasound that is used to apply thermocoagulation to intracranial lesions. It’s the use of “sound waves” to kill tumors by the heat that is generated. You might also be referring to the use of a cavitron ultrasound aspirator which is a surgical tool used during open surgery to help in tumor resections. This technology allows us to “vaporize” tumors with ultrasound with extreme precision.