Department of Medical Biotechnology, College of Life Science and Biotechnology, Dongguk University-Seoul, Republic of Korea.
Ultrasonics. 2012 Aug;52(6):730-9. doi: 10.1016/j.ultras.2012.01.016. Epub 2012 Feb 4.
In an ultrasound image-guided High Intensity Focused Ultrasound (HIFU) surgery, reflected HIFU waves received by an imaging transducer should be suppressed for real-time simultaneous imaging and therapy. In this paper, we investigate the feasibility of pulse compression scheme combined with notch filtering in order to minimize these HIFU interference signals. A chirp signal modulated by the Dolph-Chebyshev window with 3-9MHz frequency sweep range is used for B-mode imaging and 4MHz continuous wave is used for HIFU. The second order infinite impulse response notch filters are employed to suppress reflected HIFU waves whose center frequencies are 4MHz and 8MHz. The prototype integrated HIFU/imaging transducer that composed of three rectangular elements with a spherically con-focused aperture was fabricated. The center element has the ability to transmit and receive 6MHz imaging signals and two outer elements are only used for transmitting 4MHz continuous HIFU wave. When the chirp signal and 4MHz HIFU wave are simultaneously transmitted to the target, the reflected chirp signals mixed with 4MHz and 8MHz HIFU waves are detected by the imaging transducer. After the application of notch filtering with pulse compression process, HIFU interference waves in this mixed signal are significantly reduced while maintaining original imaging signal. In the single scanline test using a strong reflector, the amplitude of the reflected HIFU wave is reduced to -45dB. In vitro test, with a sliced porcine muscle shows that the speckle pattern of the restored B-mode image is close to that of the original image. These preliminary results demonstrate the potential for the pulse compression scheme with notch filtering to achieve real-time ultrasound image-guided HIFU surgery.
在超声图像引导高强度聚焦超声（HIFU）手术中，为了实现实时同步成像和治疗，应该抑制由成像换能器接收到的反射 HIFU 波。在本文中，我们研究了脉冲压缩方案与陷波滤波相结合以最小化这些 HIFU 干扰信号的可行性。使用调制有 Dolph-Chebyshev 窗的线性调频信号进行 B 模式成像，频率范围为 3-9MHz，使用 4MHz 连续波进行 HIFU。采用二阶无限脉冲响应陷波滤波器来抑制中心频率为 4MHz 和 8MHz 的反射 HIFU 波。制作了由具有球形共焦孔径的三个矩形单元组成的原型集成 HIFU/成像换能器。中心单元具有发射和接收 6MHz 成像信号的能力，两个外部单元仅用于发射 4MHz 连续 HIFU 波。当同时向目标发送线性调频信号和 4MHz HIFU 波时，由成像换能器检测到与 4MHz 和 8MHz HIFU 波混合的反射线性调频信号。在应用具有脉冲压缩处理的陷波滤波后，在保持原始成像信号的同时，显著降低了混合信号中的 HIFU 干扰波。在使用强反射器的单扫描线测试中，反射 HIFU 波的幅度降低到-45dB。在离体试验中，使用切片猪肌肉显示出恢复的 B 模式图像的斑点图案接近原始图像。这些初步结果表明，采用陷波滤波的脉冲压缩方案在实现实时超声图像引导 HIFU 手术方面具有潜力。
