Abstract
High intensity focused ultrasound (HIFU) has been used as a non-invasive tool for thermal ablation treatments. Typically, HIFU can ablate a small region (2 × 10 mm2) depending on the frequency and transducer dimensions. Cavitation-induced bubbles or injected microbubbles have been shown to enhance tissue heating during HIFU at lower acoustic intensities. The formed lesion is limited to the focal region, necessitating prolonged time of treatment to expose the entire target. To solve this problem, we designed a non-planar diffraction lens that mounts onto the surface of a 900kHz focused transducer (64 mm diameter and 62 mm focus) to enlarge the focal region. The lens was designed with an iterative angular spectrum approach to achieve a lateral beamwidth of 8 mm while maintaining a similar axial beamwidth. The focal beam size (transverse × axial) increased from 2.5 × 15.8 mm2 to 8 × 20 mm2 which also resulted in a corresponding increase in thermal lesion. We plan to expand this work to matrix phased arrays for application to mild hyperthermia for enhanced drug delivery.
Published Version
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