The effect of geometry on tumor thermal profile and its use in tumor functional state estimation

Abstract

Thermal differences between transplanted tumors and tumors in humans prevent the implementation of thermographic methods developed in mice models to human models and vise-versa. Transplantable tumors tend to have an extruding shape, which may affect the thermal patterns. This hypothesis was studied in phantom experiments and simulations. A correlation between tumor dimensions and relative temperature was found and used to estimate tumor functional state from previously published in vivo experiments. A correlation was found between temperature differences and tumor growth rates (tumor aggressiveness) and the effect of tumor treatment was demonstrated, showing the potential for in vivo, non-invasive tumor monitoring.

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“…It should also be noted that the calculated values of ΔT functional are low when compared to the previous research. This may be due to different settings in this experiment when compared to Tepper et al, 31 and should be explored to reduce possible errors. At the final stages of the experiment, wounds were formed on the tumor surface.…”

“…However, as shown in previous studies, the tumor temperature in animal model studies shows a different dependence on tumor volume, when compared to human model studies. 31 The tumors are cooler than their surrounding tissues and this temperature difference may increase as the tumor grows. A possible explanation for these observations was proposed and is supported by both phantom experiments and simulations: tumors in animal models are often transplanted, leading to increased tumor growth rates when compared to spontaneously occurring human tumors.…”

“…The previous research has shown that the temperature difference is partially a result of the tumor's extruding shape from the skin surface and that the expected tumor temperature difference as a result of tumor shape can be approximated using the formula E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 1 ; 1 1 6 ; 2 6 8 ΔT extruding ðh; S; V; αÞ ¼ 0.03123h þ 0.000402S þ ð25.9639∕VÞ þ 2.6522α þ 0.066αh; (1) where h is the lump's height, S is the surface area, V is the volume, and α is the aperture angle. 31 For the calculations in this study, tumor height was defined as the measured length from the deepest part of the tumor to the skin (since the tumors are very close to the skin surface). Tumor radius was assumed to be the average of the other two measurement dimensions (the length and the width).…”

“…This temperature difference approximately represents the effect of nongeometrical contributors to the temperature difference, mainly the metabolism and perfusion. 31 The model described in the literature assumes a single ellipsoid tumor. Consequently, tumors with irregular shapes or multiple cores were excluded from the thermal analysis.…”

Parametric study of different contributors to tumor thermal profile

“…This was previously speculated to be a result of poorly organized and hyperpermeable blood vessels [21]. However, it has been shown that another possible reason may be the extruding shape of the lump that causes the thermal cooling, due to enhanced radiation and convection from the tumor surface area [23].…”