Microwave Tomographic Imaging of the Heart in Intact Swine

Abstract

Microwave tomography is a new imaging modality based on differentiation of tissue dielectric properties. The main objective of our research project is to develop a microwave tomographic approach for non-invasive assessment of functional viability of myocardial tissue, including detection of infarcted tissue. Imaging of the heart in intact, euthanized animals is the first step towards this objective. When microwave tomography is used to image the thorax of intact animals, it faces two major problems: -the structural complexity of the rib area with high reflection of electromagnetic (EM) radiation from its boundaries, and the potential for high reflection of EM radiation from the lung, filled with air. In addition, when a targeted object (a heart in our case) is located inside of a larger high scattered object (a torso), the level of EM field scattered by the internal object has to be technically detectable from the stronger EM field Downloaded by [McGill University Library] at 07:25 17 November 2014 874 Semenov et al.scattered by torso. The goal of this research study is to evaluate the degree of complexity of these problems, to understand some technical requirements for clinically applicable MWT system and to demonstrate the feasibility of microwave tomography for imaging of the heart in intact mammals using a swine model. Experiments were conducted on pigs (Yorkshire Domestic Cross/Farm Pigs) using a modified threedimensional (3D) microwave tomographic (MWT) system operating at frequency 0.9 GHz. The presence of the heart in torso changes the amplitude of EM field by about 10-20% and changes the phase of EM field by about 7-10 degrees (mean absolute differences). Microwave tomographic images of swine torso and intact euthanized animals were obtained and discussed. Images reveal intra-torso and organ anatomy, including the heart and left ventricular chamber.

An Improved Method for Microwave Nondestructive Dielectric Measurement of Layered Media

“…Knowing these properties precisely enables scientists and engineers to use the appropriate materials for intended applications, such as the design of ferroelectrics [1,2], ceramics [3] and so forth. Understanding how dielectric material properties vary at frequencies above 1 GHz is especially important and challenging in the new areas of interest such as propagation modelling in wireless communications [4,5], aerospace ice-detection [6], radar detection of buried objects which is influenced by soil characteristics [7][8][9][10], and biomedical systems such as in the detection of cancer [11][12][13][14][15][16], and diagnosis of the functional conditions of biological tissues [17,18], where accurate data of dielectric properties is critically required. Different measurement techniques have been developed to measure dielectric properties.…”

Angular-Diversity Radar Recognition of Ships by Transformation Based Approaches --- Including Noise Effects

“…However, this is not important because our main purpose is to illustrate that the transformation based approaches can reduce the dimensions of scattering data, tolerate noise effects and achieve high recognition rate in such angular-diversity arrangements. From physical points of view, the radar recognition from RCS is basically an approximate approach of inverse scattering [9][10][11][12][13][14]. Similar to the angular-diversity reconstruction of target shape in inverse scattering, the target ships are well classified by their angular-diversity RCS characteristics in this study.…”

Radar Target Recognition by Projected Features of Frequency-Diversity RCS

“…Because the main goal of this paper is to show that projected features of frequencydiversity RCS can well identify radar targets even though there exist measured noises. From physical points of views, the RCS based recognition of radar targets is basically an approximate approach of inverse scattering [12][13][14][15][16][17][18][19][20][21][22][23]. Since frequency-diversity techniques are successful in inverse scattering, they must contain much information about targets.…”