NMR proton longitudinal relaxation times in tissues of the tumour-bearing C3H mouse studied as a function of frequency.

Because of progress in NMR imaging techniques that open the feasibility of detecting cancer by recording water protein relaxation times, it is essential to elucidate the origin of the changes of this parameter by careful studies on animals. Water proton longitudinal relaxation times were measured in vitro between 7 and 90 MHz for several tissue samples of C3H male and female mice, controls and tumor-bearing. We showed that tumor and other tissues of cancerous animals gave higher T1 values than the same tissues of controls, but that this "systemic" effect of cancer was superimposed to larger genetical T1 changes. We draw conclusions for an optimum frequency around 10 MHz, giving maximum of contrast between tumor and other tissues. According to a two-site model of water in tissues, we found the "bound" water compartment to be smaller in tumor, or, preferably, that the magnitude of the water-protein interaction was smaller there.