PHOTOACOUSTIC ULTRASOUND - PULSE PRODUCTION AND DETECTION IN 0.5-PERCENT LIPOSYN
PHOTOACOUSTIC ULTRASOUND - PULSE PRODUCTION AND DETECTION IN 0.5-PERCENT LIPOSYN
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DOI：
10.1118/1.597399
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发表时间：
1994-07-01
期刊：
影响因子：
3.8
通讯作者：
LIU, PY
中科院分区：
文献类型：
--
作者：
KRUGER, RA;LIU, PY
本文报道了在0.5%的Liposyn（一种高散射光传播介质）溶液中产生光声脉冲的理论预测和实验测量结果。一个简单的模型，预测光声信号的压力作为一个混浊介质内的深度的函数，从红外光源的表面照射。该模型适用于很短的辐照时间。该模型预测，在距离一个小的，高度吸收半径为R的球体的中心r处产生的声压包括两个，极性相反的脉冲，一个来自近侧和一个来自远侧的球体。预期这些双相脉冲的幅度与入射到球体表面上的能量通量（E）和比率R/r成比例。此外，到达球体的能量注量（E）大致与e（-ueffZ）成比例，其中mu（eff）是混浊介质的有效衰减系数，Z是被照射表面下方的嵌入球体的深度。实验验证了在吸声体内E随深度的变化和双相声脉冲的产生。进一步的实验表明，一个小的（3毫米直径），高吸收球可以检测和定位在37.5毫米的深度内的0.5%的Liposyn溶液的空间分辨率为1 × 6 mm 2，使用生物安全水平的红外辐射（λ =1064 nm）和传统的超声换能器（频率=2.25 MHz）。这些结果表明，光声超声成像可能有生物系统，如人类乳房的应用。
Theoretical predictions and experimental measurements of photoacoustic pulse production within a 0.5% solution of Liposyn, a highly scattering, optical propagation medium, are reported. A simple model for photoacoustic energetics is developed that predicts photoacoustic signal pressure as a function of depth within a turbid medium following surface irradiation from an infrared source. The model is valid for very short irradiation duration. The model predicts that the acoustic pressure produced at a distance r from the center of a small, highly absorbing sphere of radius R consists of two, opposite polarity pulses, one originating from the near and one from the far side of the sphere. The magnitude of these biphasic pulses is expected to be proportional to the energy fluence (E) incident on the surface of the sphere and to the ratio, R/r. Furthermore, the energy fluence (E) that reaches the sphere is roughly proportional to e(-ueffZ), where mu(eff) is the effective attenuation coefficient of the turbid medium and Z is the depth of the embedded sphere below the irradiated surface. The variation of E with depth within the absorber and biphasic acoustic pulse production have been verified experimentally. Further experiments demonstrate that a small (3-mm diameter), highly absorbing sphere can be detected and localized at a depth of 37.5 mm within a 0.5% solution of Liposyn with a spatial resolution of 1 x 6 mm2, using a biologically safe level of infrared irradiation (lambda=1064 nm) and a conventional ultrasound transducer (frequency=2.25 MHz). These results suggest that photoacoustic ultrasound imaging may have application to biologic systems such as the human breast.