Understanding water properties in tumorous murine cells using field-cycling NMR relaxometry

Abstract

Abstract The fixed high magnetic fields (1–7 Tesla) used for magnetic resonance imaging produce resolution suitable for oncology but image contrast is insufficient to determine tumour stage. Fast field cycling nuclear magnetic resonance (FFC NMR) measurements spanning low fields (0.24 mT–0.24 T) provide frequency-dependent longitudinal relaxation rate $$R_1(f)$$ profiles which allow healthy and pathological tissue to be differentiated. In vivo FFC NMR measurements from healthy and tumorous murine tissue spanning a range of tumour fractions have been interpreted using the 3-Tau model (3TM). Each 3TM fit yields six physically meaningful fit parameters. Statistically significant correlation with tumour fraction is found for two of these parameters, namely the surface-to-volume ratio and bulk water dynamic time constant. These fit parameters therefore act as biomarkers. The sensitivity of the biomarkers to tumour fraction is explained by the net water ingress into tumour cells. The sensitivity of $$R_1(f)$$ at the lowest field ( $$f=0.01$$  MHz) is explained by changes in the surface-to-volume ratio. $$R_1(f=0.01)$$ is also a biomarker. The water dynamics at solid surfaces are found to change with tumour fraction probably due to differences in cell wall structure between healthy and pathological tissue. FFC NMR measurements interpreted with the 3TM have the potential to estimate tumour fraction from biopsy samples from humans.