Co-registration method for photoacoustic imaging and laser speckle imaging

Combining photoacoustic (PA) imaging with laser speckle (LS) imaging (LSI) can simultaneously determine total hemoglobin concentration (HbT), hemoglobin oxygen saturation (SO2), and blood flow rates. Thus,the co-registration of PA and LS images is important in physiological studies and pathological diagnosis.This letter presents a co-registration algorithm combining mutual information with the maximum betweenclass variance segmentation method (Otsu method). The mutual information and Otsu method are used to provide the registration measure criterion and image feature recognition, respectively. The evaluation results show that the registration function possesses a single maximum peak and high smoothness across the global co-registration district, indicating a robust behavior. Moreover, this method has good registration accuracy, and the fusion result simultaneously visualizes the separate functional information of two kindsof images.     

High-resolution photoacoustic microscope for rat brain imaging in vivo

<正>A reflection-mode photoacoustic microscope(PAM) for rat brain imaging in vivo is constructed.A pulsed laser is used as an excitation source,and a focused ultrasound transducer is adopted to collect the photoacoustic signal.Raster scanning is applied to acquire three-dimensional(3D) data.The obtained measurements of the lateral and axial resolutions of the microscope are 45 and 15μm,respectively.The imaging depth in the chicken breast tissue is 3.1 mm at a signal-to-noise ratio(SNR) of 20 dB without any signal averaging.The imaging speed is 30 A-line/s.Experimental results in vivo demonstrate the capability of 3D imaging of the brain vessels of the rat after removing the skull.     

Micro CT中混叠伪影的消除

Micro CT系统是近几年发展起来的具有极高空间分辨率和探测灵敏度的一种成像技术,专门用于对小动物进行成像,并被广泛应用于药物开发,肿瘤检测.Micro CT的这种高分辨率使存在于CT中的混叠伪影在Micro CT中更为突出,成为影响图像质量,降低图像分辨率的主要因素.本文模拟分析了伪影产生的机理,并提出了一种直接对重构的切片图进行伪影分析及消除的算法,能快速有效的消除Micro CT切片图像里的混叠伪影,伪影消除率达70%以上,并且使图像的对比度提高. 关键词： Micro CT 混叠伪影 自适应滤波     

Fluorescence molecular tomography system for in vivo tumor imaging in small animals

A fluorescence molecular tomography system for in vivo tumor imaging is developed using a 748-nm continuous wave diode laser as an excitation source.A high sensitivity cooled charge-coupled device (CCD) camera with excitation and emission filters is utilized to obtain the excitation and fluorescence images.The laser beam performs fast raster scanning using a dual-axis galvanometric scanner.The accuracy of the laser spot position at the source window is within ±200 μm.Based on the phantom experimental results,the spatial resolution is less than 1.7 mm,and the relative quantitation error is about 10%.In vivo imaging of a tumor-bearing nude mouse tagged with near-infrared dye demonstrates the feasibility of the system.     

滑动焦点光声显微成像方法

在高分辨光声显微成像系统中,只有在有限焦深范围内的吸收体可以获得高分辨率高信噪比的成像,而实际的生物组织往往具有不规则的轮廓,导致成像结果分辨率和信噪比不均匀。提出了一种基于稀疏扫描轮廓的滑动焦点光声显微成像方法,首先在固定的焦点上稀疏扫描轮廓,人工选择轮廓点获取轮廓的稀疏矩阵,然后通过双调和(Biharmonic)插值获取完整的轮廓矩阵,并将轮廓矩阵转化为焦点位置移动矩阵,最后进行二次扫描,根据焦点位置移动矩阵在每次扫描之前调整焦点位置,使得在整个扫描过程中,样品始终处于焦深的范围,从而获得分辨率和信噪比均匀的光声显微图像。通过模型实验和在体皮下血管成像、颅下血管成像,证明了该方法可以有效地提高光声成像的质量。     

融合结构先验信息的稳态扩散光学断层成像重建算法研究

扩散光学断层成像作为一种无辐射损伤、低成本的光学在体成像技术,有着良好的应用前景,但具有空间分辨率低、难以定量的缺陷.为了提高扩散光学断层成像的分辨率,实现光学参数分布的精确重建,基于有限元方法,提出了融合结构先验信息的稳态扩散光学断层成像重建算法.该算法以扩散近似作为成像模型,通过软先验的Laplace 正则化方法引入由MicroCT提供的空间结构信息.采用伴随法计算Jacobian矩阵,Levenberg-Marquardt方法用来进行迭代优化.仿真结果表明该算法不仅能获得精确的光学参数值分布,而且显著地提高了迭代收敛的速度.