High Intensity Focused Ultrasound Pressure Field Characterization

One of the innovative methods in cancer treatment is to use high intensity focused ultrasound (HIFU) technology. HIFU transducers create a very high acoustic pressure (tens of MPa) area at the focal point of the tissue inside the body. The HIFU transducer pressure area should be characterized for effective and safe use in applications in cancer treatment. A system was established in TUBITAK Ultrasound Laboratory for the characterization of acoustic pressure field produced by HIFU systems. The system is controlled by a LabVIEW-based data processing program. A signal generator card was used to drive the HIFU converter and an oscilloscope card was used to process the signal received from the hydrophone. HIFU pressure area scanning measurements were performed at pressure levels of approximately 1 MPa - 3 MPa. The theoretical model, based on the Khokhlov- Zabolotskaya-Kuznetsov equation, was not initially analyzed for periodic wave clusters with a homogeneous amplitude distribution. Numerical solutions have been shown to be compatible with experimental data. The choice of the PZT type to manufacture the HIFU transducer was modeled theoretically and its effect on the field structure was also emphasized.