We demonstrate a laser-generated focused ultrasound (LGFU) transducer using a perforated-photoacoustic (PA) lens and a piezoelectric probe hydrophone suitable for high-frequency ultrasound tissue characterization. The perforated-PA lens employed a centrally located hydrophone to achieve a maximum directional response at 0° from the axial direction of the lens. Under pulsed laser irradiation, the lens produced LGFU pulses with a frequency bandwidth of 6–30 MHz and high-peak pressure amplitudes of up to 46.5 MPa at a 70-µm lateral focal width. Since the hydrophone capable of covering the transmitter frequency range (∼20 MHz) was integrated with the lens, this hybrid transducer differentiated tissue elasticity by generating and detecting high-frequency ultrasound signals. Backscattered (BS) waves from excised tissues (bone, skin, muscle, and fat) were measured and also confirmed by laser-flash shadowgraphy. We characterized the LGFU-BS signals in terms of mean frequency and spectral energy in the frequency domain, enabling to clearly differentiate tissue types. Tissue characterization was also performed with respect to the LGFU penetration depth (from the surface, 1-, and 2-mm depth). Despite acoustic attenuation over the penetration depth, LGFU-BS characterization shows consistent results that can differentiate the elastic properties of tissues. We expect that the proposed transducer can be utilized for other tissue types and also for non-destructive evaluation based on the elasticity of unknown materials.

中文翻译：

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激光产生的聚焦超声换能器，使用穿孔的光声透镜进行组织表征

我们演示了使用穿孔的光声（PA）透镜和适合高频超声组织表征的压电探针水听器的激光产生的聚焦超声（LGFU）换能器。穿孔PA镜头采用了位于中央的水听器，以在距镜头轴向0°处获得最大的方向响应。在脉冲激光辐照下，该透镜产生的LGFU脉冲的带宽为6–30 MHz，在70 µm的侧向焦距上具有高达46.5 MPa的高峰值压力幅度。由于能够覆盖发射器频率范围（约20 MHz）的水听器与镜头集成在一起，因此该混合传感器通过产生和检测高频超声信号来区分组织弹性。切除的组织（骨骼，皮肤，肌肉，和脂肪）进行了测量，并通过激光闪光影印术进行了确认。我们根据频域中的平均频率和频谱能量来表征LGFU-BS信号，从而能够清楚地区分组织类型。还针对LGFU穿透深度（从表面，1毫米和2毫米深度）进行了组织表征。尽管在穿透深度上发生了声衰减，但LGFU-BS表征显示出一致的结果，可以区分组织的弹性。我们期望所提出的换能器可以用于其他组织类型，并且还可以基于未知材料的弹性进行非破坏性评估。能够清楚地区分组织类型。还针对LGFU穿透深度（从表面，1毫米和2毫米深度）进行了组织表征。尽管在穿透深度上发生了声衰减，但LGFU-BS表征显示出一致的结果，可以区分组织的弹性。我们期望所提出的换能器可以用于其他组织类型，并且还可以基于未知材料的弹性进行非破坏性评估。能够清楚地区分组织类型。还针对LGFU穿透深度（从表面，1毫米和2毫米深度）进行了组织表征。尽管在穿透深度上发生了声音衰减，但LGFU-BS表征显示出一致的结果，可以区分组织的弹性。我们期望所提出的换能器可以用于其他组织类型，并且还可以基于未知材料的弹性进行非破坏性评估。