Koushik Das

Numerical analysis for determination of the presence of a tumor and estimation of its size and location in a tissue.

This article deals with the numerical analysis to ascertain the presence of a tumor and to estimate its size and location in a tissue. Heat transfer in the tissue is modeled using the Pennes bioheat transfer equation, and is solved using the finite volume method. Consideration is given to 1-D brain and breast tissues. Temperature distributions in the tissues are specific to the tumor grades, its locations and sizes, and these are different than that of a normal tissue. With temperature distribution known a priori, estimations of the position and the size of a tumor are done using the inverse analysis. The proposed approach gives a correct estimation of the presence of a tumor and its location and size.

Laser-induced hyperthermia of nanoshell mediated vascularized tissue - a numerical study.

Laser-induced hyperthermia treatment of tumor in a 2-D axisymmetric tissue embedded with moderate size (100-150µm) blood vessels is studied. Laser absorption is enhanced by embedding gold-silica nanoshells in the tumor. Heat transfer in the tissue is modeled using Weinbaum-Jiji bioheat transfer equation. With laser irradiation, the volumetric radiation is accounted in the governing bioheat equation. Radiative information needed in the bioheat equation is calculated using the discrete ordinate method, and the coupled bioheat-radiation equation is solved using the finite volume method. Effects of power density, laser exposure time, beam radius, diameter of blood vessel and volume fractions of nanoshells on temperature spread in the tissue are analyzed.

Simultaneous estimation of size, radial and angular locations of a malignant tumor in a 3-D human breast – A numerical study

This article reports a numerical study pertaining to simultaneous estimation of size, radial location and angular location of a malignant tumor in a 3-D human breast. The breast skin surface temperature profile is specific to a tumor of specific size and location. The temperature profiles are always the Gaussian one, though their peak magnitudes and areas differ according to the size and location of the tumor. The temperature profiles are obtained by solving the Pennes bioheat equation using the finite element method based solver COMSOL 4.3a. With temperature profiles known, simultaneous estimation of size, radial location and angular location of the tumor is done using the curve fitting method. Effect of measurement errors is also included in the study. Estimations are accurate, and since in the inverse analysis, the curve fitting method does not require solution of the governing bioheat equation, the estimation is very fast.

Study of thermal behavior of a biological tissue: an equivalence of Pennes bioheat equation and Wulff continuum model.

Equivalence of Pennes bioheat equation (PBHE) and Wulff continuum model (WCM) is established for a 1-D planar tissue. The derived condition of equivalence is specific to tissue without metabolic heat generation. Mathematical analysis is carried out to relate blood perfusion rate and local mean blood velocity that are needed in the analysis of WCM. It is found that the local mean blood velocity in a tissue is a direct function of square root of blood perfusion rate. This functional dependence is also established numerically by having same solution obtained from PBHE and WCM. Analysis is also done to check how closely the derived relation can be used for practical cases of breast tissue with and without a tumor. Blood velocity is a very important physiological quantity. Its measurement is a difficult process and requires a state-of-the-art technique. The proposed relation allows its computation merely from the knowledge of blood perfusion rate.

A Comparative Analysis of Heat Transfer in Extended Surfaces with and Without Holes

The current fin industries are working with a prime goal to reduce the overall dimensions of the fins with enhancement of the heat transfer rate per unit weight of the fins. To meet the industrial demands it has become mandatory to optimize the shape and the size of the conventional fin systems. Introduction of an extended surface on a heated plate does not always ensures increased rate of heat transfer to the surroundings. An effective utilization of the wetted surface area is major factor in this perspective. Use of fins with different configurations of holes, over a heated surface is found to have very less effect on the average convective heat flux. However, with the considered system of holes, the weight of the fins can be hugely reduced without much lowering of the outlet convective heat flux. With air as the working fluid, a 3-D system of aluminum fins has been numerically modeled in the present work, simulating a conduction-convection scenario.