ИСТИНА

Recent studies in high intensity focused ultrasound (HIFU) have shown significant interest in generating purely mechanical damage of tissue without thermal coagulation. An approach developed at the University of Washington is to use millisecond bursts of focused ultrasound shock waves and repeated localized boiling to liquefy tissue. In HIFU fields, nonlinear propagation effects lead to formation of shocks only in a small focal region. Significant enhancement of heating due to absorption at the shocks leads to boiling temperatures in tissue in milliseconds as calculated based on weak shock theory. The heated and potentially necrotized region of tissue is small compared to the volume occupied by the mm-sized boiling bubble it creates. If the HIFU pulse is only slightly longer than the time-to-boil, thermal injury is negligible compared to the mechanical injury caused by the exploding boiling bubble and its further interaction with shocks. Experiments performed in transparent gels and various ex-vivo and in-vivo tissues have confirmed the effectiveness of this method. In addition, since mm-sized boiling bubbles are highly echogenic, the treatment can be easily monitored in real-time using B-mode ultrasound imaging.