Revealing and Modeling NMR Relaxation Processes in Tissues: Endometrial Cancer Tissue as an Example

These studies are intended to be a step towards the identification of characteristic markers of relaxation processes in tissues, with the aim of revealing the extent to which they are tissue and/or cancer specific, and thus to consider the potential of NMR relaxometry for diagnostic purposes. ¹H spin-lattice and spin-spin relaxation studies were carried out on 20 samples of endometrial cancer tissue. The spin-lattice relaxation experiments were performed in the frequency range from 10 kHz to 10 MHz and complemented by spin-lattice and spin-spin relaxation measurements at 18.7 MHz. It was shown that the spin-lattice relaxation data can be reproduced in the form of a power-law function with the exponent of about 0.35 over the whole frequency range, while the spin-spin relaxation process was found to be bi-exponential in all cases. The relaxation scenario has been described quantitatively, leading to a number of parameters such as the ratio between the spin-spin relaxation rates and their contributions to the total relaxation process, or the relative decay of the spin-lattice relaxation rates in the low frequency range (from 10 to 100 kHz). As a result of ¹H spin-lattice and spin-spin relaxation studies several characteristic relaxation features of endometrial cancer tissue have been revealed. The relaxation markers include the characteristic values of the relaxation rates, the shapes of the frequency dependencies of the spin-lattice relaxation rates and bi-exponentiality of the relaxation processes. The relaxation features have been compared with those for proteins and polymers.