Soft tissues are non-homogeneous deformable structures having varied structural arrangements, constituents, and composition. This chapter explains the design of a capacitance sensor array for analyzing and imaging the non-homogeneity in biological materials. Further, tissue mimicking phantoms are developed using Agar-Agar and Polyacrylamide gels for testing the developed sensor. Also, the sensor employs an unsupervised learning algorithm for automated analysis of non-homogeneity. The reconstructed capacitance image can also be sensitive to topographical and morphological variations in the sample. The proposed method is further validated using a fiberoptic-based laser imaging system and the Jaccard index. In this chapter, the design of the sensor array for smart analysis of non-homogeneity along with significant results are presented in detail.
TopIntroduction
The group of tissue that bind, support and protect our human body and organs are known as soft tissues. These soft tissues are present all over the body. The various soft tissues in the human body are fat, muscle, fibrous tissue, synovial tissue, blood vessels, lymph vessels and peripheral nerves. Every soft tissue has its own specific set of functions. They give shape to our body and support the structures of the body. These soft tissues also protect other tissues and hold them together (Marieb, 2000). Human soft tissues are deformable, viscoelastic and are complex, fiber-reinforced composite structures. Their mechanical properties vary significantly from one tissue to another tissue. Their electrical and mechanical behaviors are strongly influenced by the concentration and structural arrangements of their tissue constituents. So, soft tissues are generally non-homogeneous in composition (Holzapfel, 2001).
A biological material can be made of a single substance or combination of two or more substances. Each substance retains their own identity (Ji & Gao, 2004). A material, in general, is broadly classified as homogeneous material and non-homogeneous material. The homogeneous materials are uniform in composition and character. The particles are uniformly distributed and have the same properties at every point, without irregularities (Nasser & Hori, 2013).
Non-homogeneous materials are non-uniform in composition or character. The particles in these materials are not uniformly distributed and they also have localized regions with different properties. They have different concentration at some areas (Nasser & Hori, 2013). Few examples of non-homogeneous materials are tumor cells, sea water, blood, etc. The non-homogeneity in biological materials is mostly due to abnormal growth of malignant cells, tumor formation or the presence of foreign particles. Presence of these factors may change the regular structural arrangements or composition of the biological material, thus showing non-homogeneity in the biological tissue material (Nymeyer & Zhou, 2008). Figure 1 (a) and 1 (b) shows a pictorial representation of homogeneous arrangement and non-homogeneous arrangement in a material, respectively.
Figure 1.
A representation of (a) Homogeneous arrangement in a material (b) Non-homogeneous arrangement in a material
In recent years, capacitance sensors have been employed, for measuring many physical and electrical quantities for biomedical analysis. The two most important characteristics of capacitance sensors are low energy consumption and simple construction (Jong & Meijer, 1997). The capacitance (C) of a capacitor is determined by the following well known equation.
where,
is the dielectric permittivity of free space,
is the relative permittivity of the dielectric material,
A is the area of metallic plate and
d is the plate separation distance.