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8 results on '"Castro, Simon J"'

2. Optimal Iodine Staining of Cardiac Tissue for X-ray Computed Tomography

Author

Butters, Timothy D., Castro, Simon J., Lowe, Tristan, Zhang, Yanmin, Lei, Ming, Withers, Philip J., and Zhang, Henggui

Subjects
Time Factors, Imaging Techniques, Cardiology, Iodine Compounds, Contrast Media, lcsh:Medicine, Research and Analysis Methods, Mice, Medicine and Health Sciences, Computer Based Imaging, Animals, Cardiovascular Imaging, lcsh:Science, Staining and Labeling, Myocardium, lcsh:R, Biology and Life Sciences, Reproducibility of Results, Heart, Cardiovascular Anatomy, lcsh:Q, Anatomy, Tomography, X-Ray Computed, Pericardium, Algorithms, Research Article, Iodine
Abstract

X-ray computed tomography (XCT) has been shown to be an effective imaging technique for a variety of materials. Due to the relatively low differential attenuation of X-rays in biological tissue, a high density contrast agent is often required to obtain optimal contrast. The contrast agent, iodine potassium iodide ([Formula: see text]), has been used in several biological studies to augment the use of XCT scanning. Recently I2KI was used in XCT scans of animal hearts to study cardiac structure and to generate 3D anatomical computer models. However, to date there has been no thorough study into the optimal use of I2KI as a contrast agent in cardiac muscle with respect to the staining times required, which has been shown to impact significantly upon the quality of results. In this study we address this issue by systematically scanning samples at various stages of the staining process. To achieve this, mouse hearts were stained for up to 58 hours and scanned at regular intervals of 6-7 hours throughout this process. Optimal staining was found to depend upon the thickness of the tissue; a simple empirical exponential relationship was derived to allow calculation of the required staining time for cardiac samples of an arbitrary size.

Published
2014
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3. Effects of Cardiac Structural Remodelling During Heart Failure on Cardiac Excitation – Insights from a Heterogeneous 3D Model of the Rabbit Atria

Author

Kottas, Petros, Colman, Michael A, Stephenson, Robert S, Castro, Simon J, Hart, George, Jarvis, Jonathan C, Boyett, Mark, Zhang, Henggui, Kottas, Petros, Colman, Michael A, Stephenson, Robert S, Castro, Simon J, Hart, George, Jarvis, Jonathan C, Boyett, Mark, and Zhang, Henggui

Abstract

Heart failure is a leading cause of morbidity and mortality in the western world. One of the effects of heart failure is the structural remodelling of cardiac tissue, including tissue dilation and development of fibrosis. It is therefore important to study these changes and their effect on cardiac activity, in order to gain a better understanding of the underlying mechanisms in arrhythmogenesis, which will hopefully enable us to develop better treatments for heart failure. In this study we developed biophysically detailed models of the rabbit atria for normal and heart failure conditions. These models were used to study the effects of structural remodelling of heart failure on cardiac excitation wave conduction. Anatomical reconstructions of the control and heart failure hearts were based on contrast enhanced micro-CT imaging. Fibre orientation was extracted from the control and heart failure datasets. Effects of heart failure geometry on the activation pattern of atrial excitation waves were analyzed. It was found that atrial activation time increased from the control to the heart failure case in both isotropic and anisotropic conditions, which is attributed primarily to the dilation of tissue caused by heart failure.

Published
2015

6. Extracting myofibre orientation from micro-CT images: An optimisation study.

Author

Ni, Haibo, Castro, Simon J., Stephenson, Robert S, Jarvis, Jonathan C, Lowe, Tristan, Hart, George, Boyett, Mark R, and Zhang, Henggui

Abstract

Recent studies introduced intensity based structure tensor analysis to extract the myocardium structure from micro X-ray computed tomography (micro-CT) images. The implementation of this method is empirical and encounters difficulties in validating the results. In this study, we performed series of tests using structure tensor analysis on synthetic tissue wedges with predefined fibre orientations, optimised the parameters of the method and applied it to the micro-CT images of a rabbit ventricular tissue. The accuracy of the method with several derivative filters and various parameters was investigated by quantifying the error in estimation in inclination angles. A measure of coherence was implemented to assess the coherence and reliability of the extracted orientations. We introduced Gaussian noise to investigate the robustness of this method. Our results suggest that the derivative of Gaussian and optimised Sobel derivative filter have better and balanced performances with overall mean error around 4°. The scale parameters play an important role in securing the accuracy. The algorithm is resistant to Gaussian noise. Using this method the myofibre orientation was successfully extracted from the ventricular tissue wedge images of the rabbit heart. [ABSTRACT FROM PUBLISHER]

Published
2013

7. HCN and SCN5A channel mutations: Implications for impaired atrioventricular nodal conduction in a heterogeneous computer model of the whole mouse heart.

Author

Castro, Simon J, Colman, Michael A, Kharche, Sanjay, Wang, Ruoxi, and Zhang, Henggui

Abstract

The atrioventricular (AV) node is a specialised region of the cardiac conduction system, allowing electrical excitation to propagate from the atria to the ventricles. AV block occurs when the AV node prevents electrical excitation waves reaching the ventricles, ultimately leading to a decrease in cardiac output. HCN4 and SCN5A defects have been associated with AV block, but the mechanisms underlying impaired AV node conduction remain incompletely understood. [ABSTRACT FROM PUBLISHER]

Published
2013

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