Divergence Compensatory Optical Flow Method for Blood Velocimetry

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Zifeng Yang ◽  
Hongtao Yu ◽  
George P. Huang ◽  
Bryan Ludwig

Detailed blood velocity map in the vascular system can be obtained by applying the optical flow method (OFM) in processing fluoroscopic digital subtracted catheter angiographic images; however, there are still challenges with the accuracy of this method. In the present study, a divergence compensatory optical flow method (DC-OFM), in which a nonzero divergence of velocity is assumed due to the finite resolution of the image, was explored and applied to the digital subtraction angiography (DSA) images of blood flow. The objective of this study is to examine the applicability and evaluate the accuracy of DC-OFM in assessing the blood flow velocity in vessels. First, an Oseen vortex flow was simulated on the standard particle image to generate an image pair. Then, the DC-OFM was applied on the particle image pair to recover the velocity field for validation. Second, DSA images of intracranial arteries were used to examine the accuracy of the current method. For each set of images, the first image is the in vivo DSA image, and the second image is generated by superimposing a given flow field. The recovered velocity map by DC-OFM agrees well with the exact velocity for both the particle images and the angiographic images. In comparison with the traditional OFM, the present method can provide more accurate velocity estimation. The accuracy of the velocity estimation can also be improved by implementing preprocess techniques including image intensification, Gaussian filtering, and “image-shift.”

2015 ◽  
Vol 99 ◽  
pp. 918-924 ◽  
Author(s):  
Wang Hongwei ◽  
Huang Zhan ◽  
Gong Jian ◽  
Xiong Hongliang

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Tianshu Liu ◽  
David M. Salazar ◽  
Hassan Fagehi ◽  
Hassan Ghazwani ◽  
Javier Montefort ◽  
...  

Abstract A hybrid method for particle image velocimetry (PIV) is developed to overcome the limitations of the optical flow method applied to PIV images with large displacements. The main elements of the hybrid method include a cross-correlation scheme for initial estimation, a shifting scheme for generating a shifted image, and an optical flow scheme for obtaining a refined high-resolution velocity field. In addition, a preprocessing scheme is used for correcting the illumination intensity change. The accuracy of the hybrid method is evaluated through simulations in a parametric space in comparison with the typical correlation methods and optical flow method. Further quantitative comparisons are made in PIV measurements in a circular air jet.


Author(s):  
Hua Yang ◽  
Hang Shi ◽  
Jin Lu ◽  
Menggang Kang ◽  
Zhouping Yin

In this study, we present a new three-dimensional optical flow method based on volumetric segmentation for the velocity estimation of fluid flow. The proposed method uses a segmented smoothness term that is designed on the assumption that the particle velocity varies continuously in each segmented volume and discontinuously on the surfaces of the segmented volumes. Subsequently, the data term is proposed on the basis of the segmented volumes and the fluid mass conservation equation, which is derived from the Reynolds transport equation. In addition, the robust local level-set method is applied to segment the particle volume according to the velocity distribution of fluid flow. The proposed method is evaluated quantitatively on synthetic data and qualitatively on experimental data, and the velocity results are compared to the advanced 3D velocity estimation methods. The results indicate that the proposed method can obtain velocity fields with greater measurement accuracy for Tomo-PIV.


2007 ◽  
Vol 188 (3) ◽  
pp. W276-W280 ◽  
Author(s):  
Drew A. Torigian ◽  
Warren B. Gefter ◽  
John D. Affuso ◽  
Kiarash Emami ◽  
Lawrence Dougherty

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