A blockage of the middle cerebral artery (MCA) on the cortical branch will seriously affect the blood supply of the cerebral cortex. Real-time monitoring of MCA hemodynamic parameters is critical for therapy and rehabilitation. Optical coherence tomography (OCT) is a powerful imaging modality that can produce not only structural images but also functional information on the tissue. We use OCT to detect hemodynamic changes after MCA branch occlusion. We injected a selected dose of endothelin-1 (ET-1) at a depth of 1 mm near the MCA and let the blood vessels follow a process first of occlusion and then of slow reperfusion as realistically as possible to simulate local cerebral ischemia. During this period, we used optical microangiography and Doppler OCT to obtain multiple hemodynamic MCA parameters. The change trend of these parameters from before to after ET-1 injection clearly reflects the dynamic regularity of the MCA. These results show the mechanism of the cerebral ischemia-reperfusion process after a transient middle cerebral artery occlusion and confirm that OCT can be used to monitor hemodynamic parameters.
Activity of brain neurons will lead to changes in local blood flow rate (BFR). Thus, it is important to measure the local BFR of cerebral cortex on research of neuron activity in vivo, such as rehabilitation evaluation after stroke, etc. Currently, laser Doppler flowmetry is commonly used for blood flow measurement, however, relatively low resolution limits its application. Optical coherence tomography (OCT) is a powerful noninvasive 3D imaging modality with high temporal and spatial resolutions. Furthermore, OCT can provide flow distribution image by calculating Doppler frequency shift which makes it possible for blood flow rate measurement. In this paper, we applied OCT to measure the blood flow rate of the primary motor cortex in rats. The animal was immobilized and anesthetized with isoflurane, an incision was made along the sagittal suture, and bone was exposed. A skull window was opened on the primary motor cortex. Then, blood flow rate changes in the primary motor cortex were monitored by our homemade spectral domain OCT with a stimulation of the passive movement of the front legs. Finally, we established the relationship between blood flow rate and the test design. The aim is to demonstrate the potential of OCT in the evaluation of cerebral cortex function.
It is important to measure embryonic heart myocardial wall strain and strain rate for understanding the mechanisms of embryonic heart development. Optical coherence tomography (OCT) can provide depth resolved images with high spatial and temporal resolution, which makes it have the potential to reveal the complex myocardial activity in the early stage embryonic heart. We develop a novel method to measure strain in embryonic chick heart based on spectral domain OCT images and subsequent image processing. We perform 4D(x,y,z,t) scanning on the outflow tract (OFT) of chick embryonic hearts in HH18 stage (~3 days of incubation). Only one image sequence acquired at the special position is selected based on the Doppler blood flow information where the probe beam penetrates through the OFT perpendicularly. For each image of the selected sequence, the cross-section of the myocardial wall can be approximated as an annulus. The OFT is segmented with a semi-automatic boundary detection algorithm, thus the area and mean circumference of the annular myocardial wall can be achieved. The myocardial wall thickness was calculated using the area divided by the mean circumference, and then the strain was obtained. The results demonstrate that OCT can be a useful tool to describe the biomechanical characteristics of the embryonic heart.
The cardiac development is a complicated process affected by genetic and environmental factors. Wall shear stress (WSS) is one of the components which have been proved to influence the morphogenesis during early stages of cardiac development. To study the mechanism, WSS measurement is a step with significant importance. WSS is caused by blood flow imposed on the inner surface of the heart wall and it can be determined by calculating velocity gradients of blood flow in a direction perpendicular to the wall. However, the WSS of the early stage embryonic heart is difficult to measure since the embryonic heart is tiny and beating fast. Optical coherence tomography (OCT) is a non-invasive imaging modality with high spatial and temporal resolution, which is uniquely suitable for the study of early stage embryonic heart development. In this paper, we introduce a method to measure the WSS of early stage chick embryonic heart based on high speed spectral domain optical coherence tomography (SDOCT). 4D (x,y,z,t) scan was performed on the outflow tract (OFT) of HH18 (~3 days of incubation) chick embryonic heart. After phase synchronization, OFT boundary segmentation, and OFT center line calculation, Doppler angle of the blood flow in the OFT can be achieved (This method has been described in previous publications). Combining with the Doppler OCT results, we calculate absolute blood flow velocity distribution in the OFT. The boundary of the OFT was segmented at each cross-sectional structural image, then geometrical center of the OFT can be calculated. Thus, the gradients of blood flow in radial direction can be calculated. This velocity gradient near the wall is termed wall shear rate and the WSS value is proportional to the wall shear rate. Based on this method, the WSS at different heart beating phase are compare. The result demonstrates that OCT is capable of early stage chicken embryonic heart WSS study.
KEYWORDS: Heart, Optical coherence tomography, Blood circulation, Mathematical modeling, Doppler effect, Finite element methods, In vivo imaging, Animal model studies, Systems modeling, Molybdenum
The heart undergoes remarkable changes during embryonic development due to genetic programming and epigenetic influences, in which mechanical loads is a key factor. As embryonic research development, an important goal is to develop mathematical models that describe the influence of mechanics on embryonic heart development. However, basic parameters for the modeling are difficult to acquire since the embryonic heart is tiny and beating fast in the early stages. Optical coherence tomography (OCT) technique provides depth-resolved image with high resolution and high acquisition speed in a noninvasive manner. In this paper, we performed 4D[(x,y,z) + t] scan on the outflow tract (OFT) of the chick embryonic heart at stage of HH18(~ 3 days of incubation) in vivo using spectral domain OCT (SDOCT). Parameters such as displacement and geometrical size of the OFT were extracted from the structural images of the SDOCT. Two-dimensional strain vector were solved using strain-displacement relations in curvilinear cylindrical coordinates based on kinetic theory of elasticity. Based on the geometrical size and other initial conditions, two-dimensional elasticity finite element model of the OFT myocardial wall deformation were established and then solved by direct frequency response method. Comparison between experimental data and simulation result shows the utility of the finite element models. Our results demonstrate that mathematical modeling based on parameters provided by SDOCT is a useful approach for studying cardiac development in early stage.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.