手持偏振光声计算层析成像探头设计及应用研究

Design and Application of Handheld Polarized Photoacoustic Computational Tomography Probe

光声成像技术(PAT)通常将生物组织对光的吸收系数视为标量,然而大多数生物组织具有各向异性,对不同偏振态的光的吸收系数是不同的,这限制了光声成像技术在一些有偏振需求的临床诊疗中的应用。基于此,设计了一种基于光纤引导的激发光手持偏振角度可调的光声计算层析成像(PACT)探头,并搭建了偏振PACT系统,旨在为术中偏振组织检测提供影像学依据。激发光由非保偏光纤引导传输,经过一系列透镜整形后,由起偏器起偏并用半波片调节激发光的偏振角度进行声信号的激发。实验中,通过对不同光轴方向和位于散射介质不同深度偏光片进行多次偏振光声成像实验,成功地实现偏光片的光轴方向检测和深度成像。此外,通过使用两个正交偏振角度的激发光对牛肌腱进行光声成像,成功地提取了牛肌腱的结构信息,验证了所设计的手持偏振光声成像探头及偏振PACT系统的成像能力和各向异性检测性能,有望为具有各向异性生物组织(如神经和肌腱)的术中诊断和治疗提供影像学依据。

Photoacoustic imaging technology(PAT)usually regards the absorption coefficient of biological tissue to light as a scalar.However,most biological tissues are anisotropic,and the absorption coefficients of light with different polarization states differ,limiting the use of photoacoustic imaging technology in some clinical diagnosis and treatment with polarization requirements.Based on this,a photoacoustic computed tomography(PACT)probe with an adjustable polarization angle is designed,and a polarization PACT system is built to provide an imaging basis for intraoperative polarization tissue detection.Nonpolarization maintaining fiber guides and transmits the excitation light.It is polarized by a polarizer after a series of lens shapings,and the polarization angle of the excitation light is adjusted by a halfwave plate to excite the acoustic signal.In the experiment,through multiple polarized photoacoustic imaging experiments on polarizers with different optical axis directions and different depths in scattering media,the optical axis direction detection and depth imaging of polarizers are successfully realized.Furthermore,the structural information of the bovine tendon is successfully extracted by using the excitation light of two orthogonal polarization angles to the photoacoustic image of the bovine tendon,and the imaging ability and anisotropy detection performance of the designed handheld polarized photoacoustic imaging probe and polarization pact system are verified.It is expected to provide an imaging basis for the intraoperative diagnosis and treatment of anisotropic biological tissues(such as nerves and tendons).