Mitigating pre-focal heating using a spherical Fibonacci lattice high-intensity focused ultrasound array and a near-field focusing strategy

Focus steering technique plays a crucial role in various high-intensity focused ultrasound (HIFU) treatment scenarios. However, due to current technological limitations, the focus quality degrades rapidly and prefocal grating lobes arise with increasing focus-shifting distance, which may adversely affect the safety of the treatment. To enlarge the focal steering range of a phased array, a novel method for array element arrangement is proposed in this study, which can increase both the safety and the efficient steering range of the focus. Additionally, a “near-field focusing” strategy for ablation using an HIFU phased array is introduced. Experimental results demonstrate that this strategy not only effectively reduces the average acoustic intensity at the medium’s surface but also inhibits temperature elevation in the prefocal region. Thus, this approach could mitigate the risks of skin burn and abdominal edema during clinical HIFU therapy.