Selection of Exposure Parameters for a HIFU Ablation System Using an Array of Thermocouples and Numerical Simulations

Image-guided High Intensity Focused Ultrasound (HIFU) technique is dynamically developing technology for treating solid tumors due to its non-invasive nature. Before a HIFU ablation system ready use, the exposure parameters of beam capable destroying treated tissue without damaging surrounding tissues should be selected ensure safety therapy. The purpose this work was select threshold acoustic power as well step and rate movement beam, generated by transducer intended used in being developed, using an array thermocouples numerical simulations. For experiments bowl-shaped 64-mm, 1.05 MHz with 62.6 mm focal length (f-number 0.98) pulsed waves propagating two-layer media: water/ex vivo pork loin (50 mm/40 mm) used. To determine creating necrotic lesion small volume within tested during less than 3 s each sample sonicated multiple parallel beams different focused at depth 12.6 below surface. Location maximum heating relaxation time were determined from temperature variations recorded after sonication five thermo-couples placed along axis obtained results enabled assess location movement. extent lesions created verified ultrasound images visual inspection cutting samples. local found 24 W, pause between sonications more 40 s. (f-number propagated (50mm/40mm). thickness water layer nonlinear propagation model. 3s samples varied (8W - 36W) spot induced these temperatures thermocouple on beam. detect scanning speed tumor means focus. ultrasonic their visible Results showed that ex structures amounted interval exposures, resulting tissue, above seconds.