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Johns Hopkins University
Heat and mass transfer analysis has its application in various fields including automobile, steam-electric power generation, energy systems, HVAC, electronic device cooling and in characterizing and diagnosing diseases. Here we have focused on applying the principles of heat and mass transfer to biological tissue and materials. In the first part we introduce a computational method to simultaneously estimate size, location and blood perfusion of model cancerous breast lesions from surface temperature data. A 2-dimensional computational phantom of axisymmetric tumorous breast with six tissue layers, epidermis, papillary dermis, reticular dermis, fat, gland, muscle layer and spherical tumor was used to generate surface temperature distributions and estimate tumor characteristics iteratively using an inverse algorithm based on the Levenberg-Marquardt method. However, similar steady state temperature profiles for different tumors are insufficient to simultaneously estimate blood perfusion, size and location of tumor. This becomes possible when transient temperature data are used along with steady state data. Thus, in addition to the steady state temperature data, we modified and expanded the inverse algorithm to include transient data that can be captured by dynamic infrared imaging. Blood perfusion is an indicator of the growth rate of the tumor and therefore its evaluation can lead to assessment of tumor malignancy. In the second part we treat X-ray computed tomography (CT) perfusion. The goal was to reduce the total radiation exposure by reducing the number of scans without compromising information integrity. CT scan images obtained from a rabbit model of liver and tumors were processed using the maximum slope (MS) method to estimate blood perfusion in the liver. Limitations of MS method are also discussed. The MS method makes use of key time points, forming the basis of the rationale to explore optimization strategies that utilize variable time intervals, rather than the more common approach of fixed time intervals. Results show that this leads to significant improvement, without compromising diagnostic information. In the last section we explore the magnetic shielding efficacy of superconducting materials and methods to mitigate the effect of necessary discontinuities in superconducting shield.
Bio heat transfer, inverse heat transfer, CT Perfusion, Breast Cancer, Liver Cancer