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Feasibility Study of Ex Ovo Chick Chorioallantoic Artery Model for Investigating Pulsatile Variation of Arterial Geometry.

Nam KH, Kim J, Ra G, Lee CH, Paeng DG - PLoS ONE (2015)

Bottom Line: The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results.In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images.The CAM artery model with the spectral analysis method is a useful in vivo experimental model for studying pulsatile variation in arterial geometry.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Postgraduate Program in Biomedical Engineering, Jeju National University, Jeju, South Korea.

ABSTRACT
Despite considerable research efforts on the relationship between arterial geometry and cardiovascular pathology, information is lacking on the pulsatile geometrical variation caused by arterial distensibility and cardiomotility because of the lack of suitable in vivo experimental models and the methodological difficulties in examining the arterial dynamics. We aimed to investigate the feasibility of using a chick embryo system as an experimental model for basic research on the pulsatile variation of arterial geometry. Optical microscope video images of various arterial shapes in chick chorioallantoic circulation were recorded from different locations and different embryo samples. The high optical transparency of the chorioallantoic membrane (CAM) allowed clear observation of tiny vessels and their movements. Systolic and diastolic changes in arterial geometry were visualized by detecting the wall boundaries from binary images. Several to hundreds of microns of wall displacement variations were recognized during a pulsatile cycle. The spatial maps of the wall motion harmonics and magnitude ratio of harmonic components were obtained by analyzing the temporal brightness variation at each pixel in sequential grayscale images using spectral analysis techniques. The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results. In addition, mapping the phase angle of the fundamental frequency identified the regional variations in the wall motion directivity and phase shift. Regional variations in wall motion phase angle and fundamental-to-second harmonic ratio were remarkable near the bifurcation area. In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images. The CAM artery model with the spectral analysis method is a useful in vivo experimental model for studying pulsatile variation in arterial geometry.

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RMS amplitude maps and waveform analysis.(A) Local variations of RMS amplitude corresponding to artery images in Fig 3 are presented in false color maps. (B) Time-amplitude plots and frequency spectra obtained from FFT analysis at selected points in RMS amplitude maps are displayed.
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pone.0145969.g004: RMS amplitude maps and waveform analysis.(A) Local variations of RMS amplitude corresponding to artery images in Fig 3 are presented in false color maps. (B) Time-amplitude plots and frequency spectra obtained from FFT analysis at selected points in RMS amplitude maps are displayed.

Mentions: The changes in the brightness of each pixel in the video clips of the artery images in Fig 3 were analyzed by the FFT method. The analysis results are presented as false color image maps in Figs 4 and 5. The maps of the RMS amplitude in Fig 4A reflected the regional variation of wall motion because the RMS amplitude was higher near the vessel boundary with stronger wall motion. The RMS amplitude was not qualitatively correlated with the displacement of the wall movement in physical dimension, but it was possible to estimate relative variation of the wall movement, as shown in Figs 3A and 4A. In the case of the curved artery in which marked regional variations were observed, the RMS amplitude map well reflected the systolic and diastolic variation of arterial boundary. Fig 4B shows the brightness waveforms at the pixels of the vessel edges pointed by arrows in Fig 4A and the corresponding frequency spectra analyzed through the FFT technique. In the brightness waveform with outward wall motion at the systolic phase (cases #1 and #2), the ascending slope was less steep than the descending slope, but the opposite was observed for the inward wall motion at the systolic phase (case #3). These observations were caused by the combined effect of more rapid wall movement at systole and darker color in blood vessels than the surrounding medium. The obtained frequency spectra showed the fundamental and second or higher harmonic components. The fundamental frequency corresponded to the heart beat rate of the chick embryos. The appearance and magnitude of the higher harmonics varied among the measurement locations and embryo samples. The magnitude maps of the fundamental and second harmonic components are shown in Fig 5A and 5B, respectively, and their ratios in the regions above 6 dB for the maximum RMS amplitude are shown in Fig 5C. The maps of the fundamental to second harmonic ratios showed limited regional and individual differences in wall motion harmonics. The phase angle maps of the fundamental component in Fig 6A well presented directional information on wall movement. The angular difference (purple and yellowish green) observed in case #1 indicated that the translational motion in the lateral direction is dominant in this artery, but the same angle (purple color) in both sides of the same artery (case #2) indicated that arterial expansion and contraction are the dominant wall motions in this region. The curved region shown in case #3 had a complex wall motion accompanied by a cyclic change in radius of arterial curvature. The histograms in Fig 6B show that the phase angle maps had two main groups that were almost 180° out of phase, thereby suggesting that wall motion in the arteries had two main directivities, which were in opposite directions, during a pulsatile cycle.


Feasibility Study of Ex Ovo Chick Chorioallantoic Artery Model for Investigating Pulsatile Variation of Arterial Geometry.

Nam KH, Kim J, Ra G, Lee CH, Paeng DG - PLoS ONE (2015)

RMS amplitude maps and waveform analysis.(A) Local variations of RMS amplitude corresponding to artery images in Fig 3 are presented in false color maps. (B) Time-amplitude plots and frequency spectra obtained from FFT analysis at selected points in RMS amplitude maps are displayed.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696805&req=5

pone.0145969.g004: RMS amplitude maps and waveform analysis.(A) Local variations of RMS amplitude corresponding to artery images in Fig 3 are presented in false color maps. (B) Time-amplitude plots and frequency spectra obtained from FFT analysis at selected points in RMS amplitude maps are displayed.
Mentions: The changes in the brightness of each pixel in the video clips of the artery images in Fig 3 were analyzed by the FFT method. The analysis results are presented as false color image maps in Figs 4 and 5. The maps of the RMS amplitude in Fig 4A reflected the regional variation of wall motion because the RMS amplitude was higher near the vessel boundary with stronger wall motion. The RMS amplitude was not qualitatively correlated with the displacement of the wall movement in physical dimension, but it was possible to estimate relative variation of the wall movement, as shown in Figs 3A and 4A. In the case of the curved artery in which marked regional variations were observed, the RMS amplitude map well reflected the systolic and diastolic variation of arterial boundary. Fig 4B shows the brightness waveforms at the pixels of the vessel edges pointed by arrows in Fig 4A and the corresponding frequency spectra analyzed through the FFT technique. In the brightness waveform with outward wall motion at the systolic phase (cases #1 and #2), the ascending slope was less steep than the descending slope, but the opposite was observed for the inward wall motion at the systolic phase (case #3). These observations were caused by the combined effect of more rapid wall movement at systole and darker color in blood vessels than the surrounding medium. The obtained frequency spectra showed the fundamental and second or higher harmonic components. The fundamental frequency corresponded to the heart beat rate of the chick embryos. The appearance and magnitude of the higher harmonics varied among the measurement locations and embryo samples. The magnitude maps of the fundamental and second harmonic components are shown in Fig 5A and 5B, respectively, and their ratios in the regions above 6 dB for the maximum RMS amplitude are shown in Fig 5C. The maps of the fundamental to second harmonic ratios showed limited regional and individual differences in wall motion harmonics. The phase angle maps of the fundamental component in Fig 6A well presented directional information on wall movement. The angular difference (purple and yellowish green) observed in case #1 indicated that the translational motion in the lateral direction is dominant in this artery, but the same angle (purple color) in both sides of the same artery (case #2) indicated that arterial expansion and contraction are the dominant wall motions in this region. The curved region shown in case #3 had a complex wall motion accompanied by a cyclic change in radius of arterial curvature. The histograms in Fig 6B show that the phase angle maps had two main groups that were almost 180° out of phase, thereby suggesting that wall motion in the arteries had two main directivities, which were in opposite directions, during a pulsatile cycle.

Bottom Line: The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results.In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images.The CAM artery model with the spectral analysis method is a useful in vivo experimental model for studying pulsatile variation in arterial geometry.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Postgraduate Program in Biomedical Engineering, Jeju National University, Jeju, South Korea.

ABSTRACT
Despite considerable research efforts on the relationship between arterial geometry and cardiovascular pathology, information is lacking on the pulsatile geometrical variation caused by arterial distensibility and cardiomotility because of the lack of suitable in vivo experimental models and the methodological difficulties in examining the arterial dynamics. We aimed to investigate the feasibility of using a chick embryo system as an experimental model for basic research on the pulsatile variation of arterial geometry. Optical microscope video images of various arterial shapes in chick chorioallantoic circulation were recorded from different locations and different embryo samples. The high optical transparency of the chorioallantoic membrane (CAM) allowed clear observation of tiny vessels and their movements. Systolic and diastolic changes in arterial geometry were visualized by detecting the wall boundaries from binary images. Several to hundreds of microns of wall displacement variations were recognized during a pulsatile cycle. The spatial maps of the wall motion harmonics and magnitude ratio of harmonic components were obtained by analyzing the temporal brightness variation at each pixel in sequential grayscale images using spectral analysis techniques. The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results. In addition, mapping the phase angle of the fundamental frequency identified the regional variations in the wall motion directivity and phase shift. Regional variations in wall motion phase angle and fundamental-to-second harmonic ratio were remarkable near the bifurcation area. In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images. The CAM artery model with the spectral analysis method is a useful in vivo experimental model for studying pulsatile variation in arterial geometry.

Show MeSH
Related in: MedlinePlus