共查询到19条相似文献,搜索用时 62 毫秒
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声透镜对多层样品的光声层析成像 总被引:1,自引:0,他引:1
由于光声效应产生光声压分布图像,所以当强散射介质中的模拟吸光组织在受到短脉冲激光照射时,该声压分布会经声透镜成像在像平面上。在像平面上利用线性超声探测器阵列获取光声信号并传递给高速数据采集卡进行数据采集,可由程序重构出光声图像。设计的光声层析成像系统可以采集记录一定深度的数据,成像时只要在所采集到的数据中选取不同列数即可同时获得强散射介质多层样品不同层面的光声图像。实验成功地获得了强散射介质内多层样品不同层面的光声层析图像。该成像方法无需进行复杂的算法重建,且可以同时实现多层样品不同切面的光声成像。 相似文献
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报道了一种新的光声层析成像技术-光声傅里叶变换共焦扫描成像技术,并用该技术获得了强散射物质(生物组织)的层析图像,纵向分辨能力小于0.1mm,横向分辨率小于4mm。 相似文献
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光声成像是采用“光激发-超声波成像”的新型成像技术,它是检测强散射介质内部光吸收分布的一种有效医学影像技术.用短脉冲激光照射强散射介质(如生物组织),强散射介质由于光声效应产生超声信号,使用具有成像能力的声透镜把声压分布成像于像面上,然后利用具有空间分辨能力的阵列光声传感器,把同一像面上的光声信号强度记录下来,最后根据光声信号强度的空间分布进行图像重组.根据成像系统物像共轭原理,同一物平面的光声信号到达像面的时延相等,而不同物面的光声信号到达同一个探测器平面的时延各不相同,因此,利用BOXCAR的门控积分
关键词:
光声层析成像
声透镜
光声信号 相似文献
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为了进一步提高光声重建图像的质量,采用滤波反投影算法进行图像重建。实验所用的光源为YAG激光器,波长为1 064 nm,重复频率为20 Hz,脉宽为7 ns,探测器为针状的PVDF膜水听器,接收面的直径为1mm,得到了4个圆形吸收体和5根头发的光声重建图像。仿真和实验结果表明:通过对信号进行滤波,能很好地抑制噪声信号,明显提高图像的对比度和分辨率。 相似文献
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光纤型光学相干层析成像系统的研制 总被引:15,自引:7,他引:15
光学相干层析(OCT)成像技术是一新近发展的高分辨力生物医学成像手段,能非侵入性地对活体内部的结构与生理功能进行可视化观察。采用宽带近红外光源,基于迈克耳孙干涉原理和外差探测方法,建立了单模光纤型光学相干层析成像系统,相干地提取从生物体内部返回的深度分辨的弹性散射光信息,并依此构筑了自然状态下活体组织的二维光学相干层析成像图像和三维光学相干层析成像图像。光纤化设计的光学相干层析成像系统紧凑、灵活,便于与光纤导管、内窥镜和其它成像装置的有机结合,以拓展其观察范围和应用领域。 相似文献
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基于维纳滤波反卷积的光声成像 总被引:2,自引:0,他引:2
为了提高光声成像(PAT)的对比度和分辨率,需对组织样品的光声(PA)信号进行基于探头脉冲响应的滤波反卷积以恢复其频谱特性.对宽带光声信号而言,由于带通滤波的截止频率由人为确定,噪声不能得到有效抑制,很难获得稳定的反卷积结果.针对此问题,提出了基于维纳滤波反卷积的光声成像方法,利用点光声源获得超声探头的脉冲响应.利用维纳滤波抑制反卷积过程中噪声的影响,滤波器参数由离散小波变换(DWT)动态估计,样品光声图像由时域后向投影算法重建.数值模拟与成像实验均表明该方法有效地抑制了噪声对反卷积的影响,提高了光声成像的对比度和分辨率. 相似文献
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提出了基于旋转λ/2波片无色散相移器的理论模型,和实施该相移器功能的全场光学相干层析成像(Optical coherence tomography,OCT)系统,为实现快速、高分辨光学相干层析成像提供了一种有效方法。该相移器能在宽光谱范围内无色散地获得八倍于λ/2波片旋转角的相移量,避免了利用单色光相移算法提取信号时存在的系统误差。针对修正Carré算法和三步相移算法所要求的不同相移量,在240 nm波长范围内,对相移器的性能进行了数值分析。结果表明,在给定光谱范围内,相移量越大,相移误差的绝对值也越大,幅值比变化范围也越大。用于实施无色散相移器功能的全场光学相干层析成像系统结构,与现有结构相比,具有一些有益的特点。 相似文献
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We study the influence of limited-view scanning on the depth imaging of photoacoustic tomography.The situation,in which absorbers are located at different depths with respect to the limited-view scanning trajectory,is called depth imaging and is investigated in this paper.The results show that limited-view scanning causes the reconstructed intensity of deep absorbers to be weaker than that of shallow ones and that deep absorbers will be invisible if the scanning range is too small.The concept of effective scanning angle is proposed to analyse that phenomenon.We find that an effective scanning angle can well predict the relationship between scanning angle and the intensity ratio of absorbers.In addition,limited-view scanning is employed to improve image quality. 相似文献
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We study the influence of limited-view scanning on the depth imaging of photoacoustic tomography. The situation, in which absorbers are located at different depths with respect to the limited-view scanning trajectory, is called depth imaging and is investigated in this paper. The results show that limited-view scanning causes the reconstructed intensity of deep absorbers to be weaker than that of shallow ones and that deep absorbers will be invisible if the scanning range is too small. The concept of effective scanning angle is proposed to analyse that phenomenon. We find that an effective scanning angle can well predict the relationship between scanning angle and the intensity ratio of absorbers. In addition, limited-view scanning is employed to improve image quality. 相似文献
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We developed a photoacoustic imaging system that has real-time imaging capability with optical resolution. The imaging system is capable of scanning at 20 Hz over a 9 mm range and up to 40 Hz over a 1 mm scanning range. A focused laser beam provides a lateral resolution of 3.4 μm as measured in an optically nonscattering medium. Flows of micrometer-sized carbon particles or whole blood in a silicone tube and individual red blood cells (RBCs) in mouse ear capillaries were also imaged in real time, demonstrating the capability to image highly dynamic processes in vivo at a micrometer-scale resolution. 相似文献
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For the eyeball composed of membrane and liquid, the contrast of ultrasound imaging is not high due to its small variance in acoustic impedance. As a new imaging modality, photoacoustic tomography combines the advantages of pure optical and ultrasonic imaging together and can provide high resolution, high contrast images. In this paper, the feasibility of photoacoustic tomography for ophthalmology is studied experimentally. A Q-switched Nd:YAG pulsed laser with 7-ns pulse width is used to generate photoacoustic signal of a porcine eyeball in vitro. The two-dimensional (2D) optical absorption image of the entire eyeball is reconstructed by time-domain spherical back projection algorithm. The imaging results agree well with the histological structure of the eyeball and show a high imaging contrast. 相似文献
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利用前期搭建的声分辨光声系统对小鼠耳朵进行扫描成像,获取的光声图像存在部分血管不连续、分辨率较低且边界不够清晰等问题。为了有效提高声分辨光声图像质量,采用连接断点、插值、小波去噪等方法进行预处理;针对插值带来的模糊边界、损失细节等问题提出一种模糊集与分数阶微分小波增强相结合的图像增强方法,设计对比实验,结合信息熵、对比度改善指数和平均梯度等评价指标进行评价。实验结果表明增强后的图像血管连接性好、分辨率更高、高频信息表现更丰富,所提增强方法对光声图像的优化处理有应用潜力。 相似文献
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生物组织声学参数的不均匀性是光声断层成像技术面临的棘手问题,基于超声干涉测量的光声断层成像方法已被初步证明可以适用于声参数不均匀情形,但对如何取得最佳成像效果缺少深入研究。针对这一问题,该文将基于超声干涉测量的光声断层成像方法应用于同时含有声速不均匀和随机声散射现象的复杂成像媒质模型,并对如何优化成像效果开展相关研究。该文首先验证了该方法在数值模型中的有效性,随后针对相关测量参数与成像质量之间的关系开展定量研究,提出了优化成像效果的方法。结果表明,设计适合的波形滤波器、合理选择干涉测量过程中超声信号的中心频率均可优化成像效果,该文的相关研究结果可为进一步拓展基于超声干涉测量的光声断层成像的应用范围提供参考。 相似文献
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Baddour N 《The Journal of the Acoustical Society of America》2008,123(5):2577-2590
A new frequency-domain approach to photoacoustic tomography has recently been proposed, promising to overcome some of the shortcomings associated with the pulsed photoacoustic approach. This approach offers many of the benefits of pulsed photoacoustics but requires a different set of equations for modeling of the forward and inverse problems due to the longer time scales involved in the optical input signal. The theory of photoacoustic tomography with an optical input that is not necessarily a short pulse is considered in this paper. The full optical, thermal, and acoustic governing equations are derived. A transfer function approach is taken for the solution and analysis of this problem. The results and implications are compared with those of pulsed photoacoustics and traditional ultrasonic diffraction tomography. A Fourier diffraction theorem is also presented, which could be used as a basis for the development of tomographic imaging algorithms. 相似文献
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超声/光声双模态成像技术因其同时兼具超声的高分辨率结构成像和光声的高对比度功能成像优势,极大地推动了光声成像技术的临床应用推广.传统超声/光声双模态成像技术多基于超声成像所用阵列探头同时收集光声信号,系统结构紧凑且无需图像配准,操作便捷.但该类设备使用阵列探头和多通道数据采集,使得其成本较高;且成像结果易受通道一致性差异影响.本文提出了一种基于声学扫描振镜的超声/光声双模态成像技术,该技术采用单个超声换能器结合一维声学扫描振镜进行快速声束扫描,实现超声/光声双模态成像,是一种小型化、低成本的双模态快速成像技术.本文开展了系列仿体和活体成像研究,实验结果表明:系统有效成像范围为15.6 mm,超声和光声成像B扫描速度分别为1.0 s–1和0.1 s–1 (光声成像速度主要受制于脉冲激光器重复频率).基于本文所提技术研究,有助于进一步推动超声/光声双模态成像技术的临床转化和普及;也为基于超声信号检测的多模态成像技术提供了一种低成本、小型化和快速声信号检测的参考方案. 相似文献