Proton spin-lattice relaxation studies of tissue response to radiotherapy in mice.

Proton spin-lattice relaxation times were measured with pulsed NMR spectroscopy at 60 MHz for a range of tissues from healthy and tumour-bearing mice. T1 appeared to be significantly longer in the tumour than in any other tissue. Clearly distinct values of T1 were found for the vital and necrotic parts of the tumour. Non-involved tissues of tumour-bearing mice, viz. spleen, muscle, and salivary gland tissue, showed an increase in T1 relative to normal values. Irradiation of healthy mice with 6 MeV x-rays to a total-body dose of 15 Gy induced a shortening of T1 in the spleen. Similar experiments on tumour-bearing mice showed a decrease of T1 in the tumour, the spleen, the kidneys, and the liver. Attempts were made to interpret the results in terms of tissue hydration.