Measurements Of Hemodynamic Parameters In Chick Embryonic Hearts Based On Optical Coherence Tomography

The internal metabolic characteristics of biological tissues can be reflected by the function parameters of different tissues and organs, so in medicine some parameter information of biological tissues is often used as the reference in the early diagnosis of disease. In this paper, combined with Spectrum Domain Optical Coherence (SDOCT) and Doppler flow velocity measurement technology, the structural image and blood flow velocity distribution for highly scattering biological tissue can be obtained simultaneously, on the basis of that the hemodynamic parameters for early chick embryonic hearts were measured, including absolute blood flow velocity, myocardial radial strain and blood stress shear.Firstly, the fast high-resolution SDOCT system in our laboratory was introduced in the article. The system was based on a 2×2 fiber coupler (10/90) to construct the whole interference light path. The SDOCT system used Super Luminescent Diode (SLD) as the broadband light source with the bandwidth of 52nm centered at 1312.5nm. In sample arm, the light was focused onto the sample via a 2D optical scanning galvanometer. Spectrometer was composed of ultra high-speed line array CCD camera and diffraction grating (1145 lines/mm), and was used for data acquisition, then the spectrum data was transferred to the computer by the IMAQ grabber. Based on the needs of phase-resolved flow measurement experiment, the hardware system was improved. A fast line array CCD camera (92K lines/s) was used for making the flow measurement range increased effectively instead of the original line array CCD camera (47K lines/s). In order to meet the needs of fast acquisition, the software system was also improved appropriately. In the detection unit, the focusing lens with a long focal length was used for making the spectral resolution improved and making the theoretical depth of investigation increased, thereby making the imaging contrast ratio of the area of interest increased.The structural imaging of early chick embryonic hearts could be obtained by the SDOCT system, and the relevant hemodynamic parameters also could be measured by the SDOCT system. Combined with SDOCT and Doppler flow velocity measurement technology, the projected velocity of flowing particle motion could be calculated by the phase difference between two adjacent A-scans. Combined with imaging processing procedure, the measurement method of absolute blood flow velocity was proposed, and experimental verification and results analysis were subsequently made. Based on the relationship between the vessel wall thickness and radial strain in the outflow tract (OFT) of the chick embryonic hearts, OFT radial strain was measured, and the strain changes between the normal OFT and the banding OFT were compared. Under the premise of assuming that the blood was nearly Newtonian fluid, the blood shear stress was proportional to the flow velocity gradient, and then the feasible measurement method of blood shear stress was pointed out.In summary, we built a fast high-resolution SDOCT system which had the advantages of fast imaging speed, high resolution and large flow measurement range. We completed the measurements of hemodynamic basic parameters of chick embryonic hearts, and laid the foundation for the subsequent study of chick embryonic hearts.