Figure 2
From: Direct visualization of interstitial flow distribution in aortic walls
Schematic of image analysis. (a) An image stack of fluorescent dye captured in the radial-circumferential (r–θ) plane. (b) To convert the image of the aortic wall on an arch to images of a flattened one, the chord and camber lengths were measured from any arbitrary EL (outermost layer in this figure) and the center coordinates of the arc were determined. An analysis line was drawn from the center coordinates to an arbitrary position on the left edge of the images and rotated clockwise around the center coordinates. The fluorescence intensity on each line was recorded, and the image stack was reproduced from the intensity data. (c) Identification of start time tstart and end time tend. The average fluorescence intensity \(I_{r\theta } \left( t \right)\) in the aortic region of each slice was measured (closed circles), and the minimum \(I_{r\theta ,min}\) and maximum \(I_{r\theta ,max}\) were measured. tstart was defined as the time t when \(I_{r\theta } \left( t \right)\) slightly exceeded \(I_{r\theta ,min}\) (see main text for precise definition). The moving average of the fluorescence intensity \(\overline{{I_{r\theta } }} \left( t \right)\) (open circles) was calculated, and tend was defined as the time t when \(\left\{ {\overline{{I_{r\theta } }} \left( t \right) - \overline{{I_{r\theta } }} \left( {t - 1} \right)} \right\}\) first became less than β. (d) A kymograph obtained by reslicing image (b) and averaging it on the θ-axis. (e) A normalized kymograph with 0 at tstart and 1 at tend. Normalization was performed at each r-coordinate. Further image analysis was performed in the region bordered by the broken line. (f) Magnified view of the kymograph. The differential of the intensity was calculated for each pixel. These images were taken at 80 mmHg. The graph was created using the Microsoft Excel for Microsoft 365 MSO (16.0.14326.20782). The image was created using ImageJ 1.52a.
