Arka Bhowmik

Suitability of frequency modulated thermal wave imaging for skin cancer detection—A theoretical prediction

A theoretical study on the quantification of surface thermal response of cancerous human skin using the frequency modulated thermal wave imaging (FMTWI) technique has been presented in this article. For the first time, the use of the FMTWI technique for the detection and the differentiation of skin cancer has been demonstrated in this article. A three dimensional multilayered skin has been considered with the counter-current blood vessels in individual skin layers along with different stages of cancerous lesions based on geometrical, thermal and physical parameters available in the literature. Transient surface thermal responses of melanoma during FMTWI of skin cancer have been obtained by integrating the heat transfer model for biological tissue along with the flow model for blood vessels. It has been observed from the numerical results that, flow of blood in the subsurface region leads to a substantial alteration on the surface thermal response of the human skin. The alteration due to blood flow further causes a reduction in the performance of the thermal imaging technique during the thermal evaluation of earliest melanoma stages (small volume) compared to relatively large volume. Based on theoretical study, it has been predicted that the method is suitable for detection and differentiation of melanoma with comparatively large volume than the earliest development stages (small volume). The study has also performed phase based image analysis of the raw thermograms to resolve the different stages of melanoma volume. The phase images have been found to be clearly individuate the different development stages of melanoma compared to raw thermograms.

Thermographic evaluation of early melanoma within the vascularized skin using combined non-Newtonian blood flow and bioheat models

A theoretical study on vascularized skin model to predict the thermal evaluation criteria of early melanoma using the dynamic thermal imaging technique is presented in this article. Thermographic evaluation of melanoma has been carried out during the thermal recovery of skin from undercooled condition. During thermal recovery, the skin has been exposed to natural convection, radiation, and evaporation. The thermal responses of melanoma have been evaluated by integrating the bioheat model for multi-layered skin with the momentum as well as energy conservation equations for blood flow. Differential changes in the surface thermal response of various melanoma stages except that of the early stage have been determined. It has been predicted that the thermal response due to subsurface blood flow overpowers the response of early melanoma. Hence, the study suggests that the quantification of early melanoma diagnosis using thermography has not reached a matured stage yet. Therefore, the study presents a systematic analysis of various intermediate melanoma stages to determine the thermal evaluation criteria of early melanoma. The comprehensive modeling effort made in this work supports the prediction of the disease outcome and relates the thermal response with the variation in patho-physiological, thermal and geometrical parameters.

THERMAL ANALYSIS OF THE INCREASING SUBCUTANEOUS FAT THICKNESS WITHIN THE HUMAN SKIN—A NUMERICAL STUDY

This article reports a numerical study on the thermal response of skin with increasing fat thickness. The study considers the Pennes bioheat model for skin to simulate the thermal recovery phase after the removal of undercooled condition. Based on the surface thermal maps of a three-dimensional skin, the change in fat thickness within the skin is characterized. Sensitivity study reveals that the major variation in the thermal pattern at the skin surface is mainly due to the change in fat thickness. Possible random noise associated with background disturbances is also considered to determine the associated signal-to-noise ratio.

Inverse analysis of conductive-convective wet triangular fin for predicting thermal properties and fin dimensions

The present work deals with the application of Homotopy Analysis Method (HAM) in conjunction with Nelder–Mead simplex search method (SSM) to study a triangular wet fin. At first, analytical expression has been derived using HAM to calculate the local temperature field. Then using SSM, the important parameters, namely, thermal conductivity of the material, surface heat transfer coefficient and dimensions of the fin, have been estimated separately for attaining the prescribed temperature field. The transport phenomena involve simultaneous heat and mass transfers. It is found from the present study that many feasible solutions can satisfy a given thermal condition, which will offer the flexibility in selecting the fin material, adjusting the thermal conditions and regulating the fin dimensions. Further, it is determined that the allowable error in the temperature measurement should be limited within ± 15% and a good reconstruction of the temperature field is possible using the HAM–SSM combination.

Inverse Heat Transfer Analysis of Porous Extended Surface Using Simplex Search Method

This work deals with the application of the Nelder-Mead simplex search method (SSM) to study a porous extended surface. At first, analytical expression for calculating the local temperature field has been derived using an implicit Runge-Kutta method. The heat transfer phenomenon is assumed to be governed by conductive, naturally convective and radiative heat transfer, whereas the diffusion of mass through the porous media is also taken into account. Then, using the SSM, critical parameters such as porosity, permeability, and thermal conductivities of the extended surface have been predicted for satisfying a prescribed temperature field. It is found that many alternative solutions can meet a given thermal requirement, which is proposed to offer the flexibility in selecting the material and regulating the thermal conditions. It is observed that the allowable error in the temperature measurement should be limited within 5%. It is also found that even with few temperature measurement points, very good reconstruction of the thermal field is possible using the SSM.Copyright