A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results

TLDR

The arrays were engineered to integrate co‑aligned diagnostic transducers for precise targeting and monitoring during therapeutic ultrasound. The study modeled flat, λ/2‑spaced phased arrays composed of 64‑element modules with 1.5 mm spacing, assembling six 1024‑element (16‑module) and four 6144‑element (96‑module) arrays and evaluating peak pressure, focal size, off‑axis steerability, and grating lobe amplitude. Two 1024‑element prototypes delivered over 100 W acoustic power, matched simulation predictions, maintained only 24–25 % pressure loss at 40 mm off‑axis at 30–50 mm depths, and 6144‑element designs showed <20 % loss when steered 100 mm off‑axis with 20 % grating lobes, indicating sufficient power for rapid, large‑volume ablations without mechanical translation.

Abstract

Flat, λ/2-spaced phased arrays for therapeutic ultrasound were examined in silico and in vitro. All arrays were made by combining modules made of 64 square elements with 1.5 mm inter-element spacing along both major axes. The arrays were designed to accommodate integrated, co-aligned diagnostic transducers for targeting and monitoring. Six arrays of 1024 elements (16 modules) and four arrays of 6144 elements (96 modules) were modelled and compared according to metrics such as peak pressure amplitude, focal size, ability to be electronically-steered far off-axis and grating lobe amplitude. Two 1024 element prototypes were built and measured in vitro, producing over 100 W of acoustic power. In both cases, the simulation model of the pressure amplitude field was in good agreement with values measured by hydrophone. Using one of the arrays, it was shown that the peak pressure amplitude dropped by only 24% and 25% of the on-axis peak pressure amplitude when steered to the edge of the array (40 mm) at depths of 30 mm and 50 mm. For the 6144 element arrays studied in in silico only, similarly high steerability was found: even when steered 100 mm off-axis, the pressure amplitude decrease at the focus was less than 20%, while the maximum pressure grating lobe was only 20%. Thermal simulations indicate that the modules produce more than enough acoustic power to perform rapid ablations at physiologically relevant depths and steering angles. Arrays such as proposed and tested in this study have enormous potential: their high electronic steerability suggests that they will be able to perform ablations of large volumes without the need for any mechanical translation.