Abstract Phased arrays are increasingly employed in clinical high-intensity focused ultrasound (HIFU) systems for treatment of uterine fibroids. However, the electronic steering range of current phased arrays is insufficient to cover a symptomatic uterine fibroid. This study proposes a method to augment the focal steering range for HIFU treatment of uterine fibroids. Geometric focus can be shifted by tilting HIFU phased array around two orthogonal axes with a rotating platform, and both rotating angles can be adjusted up to 15° with tilt radius of 277 mm according to the shift of geometric focus. A three-layer (skin, fat and muscle) tissue model was used as the beam propagation path. The acoustic fields with and without tilting HIFU phased array were characterized by numerical simulation and hydrophone measurement. Focal accuracy was evaluated in phantoms and targeting areas were ablated in in vivo pigs’ thighs. In combination with the electronic focal steering, the steering range in the focal plane has been augmented to ±53 mm from ±6 mm. In the phantoms, the mean focal error has been increased from 0.2 mm to 0.9 mm with the geometric focus shift ranged from 10 mm to 40 mm. In vivo experimental results have proved that it is safe and effective to ablate the 25 mm × 25 mm square area. Tilting the HIFU phased array is feasible to safely augment the focal steering range, which can potentially improve the efficacy of HIFU treatment.

中文翻译：

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倾斜高强度聚焦超声相控阵扩大焦点转向范围治疗子宫肌瘤

摘要 相控阵越来越多地用于治疗子宫肌瘤的临床高强度聚焦超声 (HIFU) 系统。然而，当前相控阵的电子控制范围不足以覆盖有症状的子宫肌瘤。本研究提出了一种增加 HIFU 治疗子宫肌瘤的焦点转向范围的方法。HIFU相控阵通过旋转平台围绕两个正交轴倾斜，可以实现几何焦点的偏移，根据几何焦点的偏移，两个旋转角度都可以调整到15°，倾斜半径为277mm。三层（皮肤、脂肪和肌肉）组织模型用作光束传播路径。通过数值模拟和水听器测量来表征有和没有倾斜HIFU相控阵的声场。在体模中评估焦距准确性，并在体内猪大腿中消融靶向区域。结合电子焦点转向，焦平面内的转向范围从±6mm扩大到±53mm。在体模中，平均焦距误差从 0.2 毫米增加到 0.9 毫米，几何焦点偏移范围从 10 毫米到 40 毫米。体内实验结果证明，对25mm×25mm正方形区域进行消融是安全有效的。倾斜 HIFU 相控阵可以安全地增加焦点转向范围，这可能会提高 HIFU 治疗的疗效。平均焦距误差从 0.2 毫米增加到 0.9 毫米，几何焦点偏移范围从 10 毫米到 40 毫米。体内实验结果证明，对25mm×25mm正方形区域进行消融是安全有效的。倾斜 HIFU 相控阵可以安全地增加焦点转向范围，这可能会提高 HIFU 治疗的功效。平均焦距误差从 0.2 毫米增加到 0.9 毫米，几何焦点偏移范围从 10 毫米到 40 毫米。体内实验结果证明，对25mm×25mm正方形区域进行消融是安全有效的。倾斜 HIFU 相控阵可以安全地增加焦点转向范围，这可能会提高 HIFU 治疗的功效。