Proton relaxation times and interstitial fluid pressure in human melanoma xenografts

The interstitial fluid pressure (IFP) and the proton spin-lattice and spin-spin relaxation times (T-1 and T-2) of some experimental tumours have been shown to be related to tumour water content. These observations have led to the hypothesis that magnetic resonance imaging (MRI) might be a clinically useful non-invasive method for assessment of tumour IFP. The purpose of the work reported here was to examine the general validity of this hypothesis. R-18 human melanoma xenografts grown intradermally in Balb/c nu/nu mice were used as the tumour model system. Median T-1 and T-2 were determined by spin-echo MRI using a 1.5-T clinical whole-body tomograph. IFP was measured using the wick-in-needle technique. Na correlation was found between tumour IFP and fractional tumour water content. Moreover, there was no correlation between median T-1 or T-2 and IFP, suggesting that proton T-1 and T-2 values determined by MRI cannot be used clinically to assess tumour IFP and thereby to predict the uptake of macromolecular therapeutic agents.