Abstract
Accurate knowledge of the hyperthermia induced power deposition and temperature patterns are necessary to optimize the hyperthermia dose. A critical factor influencing the hyperthermia induced temperature distribution is the tumor blood perfusion. Hence, perfusion information must be available to optimize the hyperthermia therapy dose. Previous efforts to describe the tumor blood perfusion distribution for thermal analysis have relied upon the “classical” perfusion model of a highly perfused periphery and a necrotic core. However, biological structures, i.e. tumor perfusion, often cannot be described with such a straightforward Euclidean framework. To describe the irregular and fragmented non-Euclidean patterns of the tumor blood perfusion, fractal geometry is used. In particular, it has been shown that the fractal dimension of two-dimensional vascular networks resembles that of percolation clusters. In this paper, dynamic contrast-enhanced MRI is used to obtain two- and tree-dimensional images of the perfusion distribution in six canine tumors. The wash-in component of the MRI contrast signal intensity is depicted as a percolation cluster. Fractal characteristics are determined for each two- and three-dimensional percolation cluster. It is concluded that the blood perfusion in a two-dimensional tumor vessel network has a fractal structure, regardless of the tumor type and size. A preliminary three-dimensional analysis is presented that also shows a fractal structure.
