Active focal zone sharpening for high-precision treatment using histotripsy.
Active focal zone sharpening for high-precision treatment using histotripsy.
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DOI：
10.1109/tuffc.2011.1808
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发表时间：
2011-02
期刊：
影响因子：
--
通讯作者：
Cain C
中科院分区：
文献类型：
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作者：
Wang TY;Xu Z;Hall T;Fowlkes J;Roberts W;Cain C
本研究的目的是开发一种聚焦区锐化策略，以产生更精确的脉冲空化超声治疗或组织摧毁术的病变。通过局部抑制治疗病灶周边的空化而不影响中心的空化，产生精确且限制良好的损伤。利用空化核预处理脉冲来主动控制焦点周围的空化，从而实现对空化的局部抑制。一个1 MHz的513元素治疗阵列被用来产生治疗和核预处理脉冲。对于治疗，以100 Hz脉冲重复频率和21/76 MPa的P-/P+压力向治疗阵列的几何焦点递送10个周期的爆发。对于核预处理，在每个治疗脉冲之前，将不同的脉冲递送到紧邻焦点周围的环形区域。在红细胞-凝胶模型中进行了预处理脉冲的有效压力、脉冲持续时间和递送时间的参数研究，其中空化损伤由局部细胞溶解引起的颜色变化指示。结果显示，在治疗脉冲之前不久（30 µs），在中等压力（P−/P+压力为7.2/13.6 MPa）下输送短持续时间（20 µ s）预处理脉冲，可显著抑制77 ± 13%的外周损伤，同时维持病灶中心的完全分离。气泡云的高速成像显示，使用聚焦区锐化，气泡云的最大宽度大幅减少48 ± 24%。在离体肝脏中的实验证实，在真实的组织中以及在幻影中产生高度受限的损伤。本研究证明了使用空化核预处理的主动聚焦区锐化的可行性，与治疗换能器的自然聚焦宽度相比，可以提高治疗精度。
The goal of this study is to develop a focal zone sharpening strategy that produces more precise lesions for pulsed cavitational ultrasound therapy, or histotripsy. Precise and well-confined lesions were produced by locally suppressing cavitation in the periphery of the treatment focus without affecting cavitation in the center. The local suppression of cavitation was achieved using cavitation nuclei preconditioning pulses to actively control cavitation in the periphery of the focus. A 1-MHz 513-element therapeutic array was used to generate both the therapy and the nuclei preconditioning pulses. For therapy, 10-cycle bursts at 100-Hz pulse repetition frequency with P−/P+ pressure of 21/76 MPa were delivered to the geometric focus of the therapeutic array. For nuclei preconditioning, a different pulse was delivered to an annular region immediately surrounding the focus before each therapy pulse. A parametric study on the effective pressure, pulse duration, and delivery time of the preconditioning pulse was conducted in red blood cell-gel phantoms, where cavitational damage was indicated by the color change resulting from local cell lysis. Results showed that a short-duration (20 µs) preconditioning pulse at a medium pressure (P−/P+ pressure of 7.2/13.6 MPa) delivered shortly before (30 µs) the therapy pulse substantially suppressed the peripheral damage by 77 ± 13% while complete fractionation in the focal center was maintained. High-speed imaging of the bubble cloud showed a substantial decrease in the maximum width of the bubble cloud by 48 ± 24% using focal zone sharpening. Experiments in ex vivo livers confirmed that highly confined lesions were produced in real tissues as well as in the phantoms. This study demonstrated the feasibility of active focal zone sharpening using cavitation nuclei preconditioning, allowing for increased treatment precision compared with the natural focal width of the therapy transducer.