NMR Imaging in Dentistry: Relaxation and Diffusion Studies

U. Skaleri ¹, J. Dolinek ², J. Stepinik ², P. Cevc ², , and M. Schara ²

¹ J. Stefan Institute, E. Kardelj University of Ljubljana, 61000 Ljubljana, Jamova 39, Yugoslavia; University Dental Clinic, Medical Faculty, E. Kardelj University of Ljubljana, 61000 Ljubljana, Hrvatski trg 6, Yugoslavia
² J. Stefan Institute, E. Kardelj University of Ljubljana, 61000 Ljubljana, Jamova 39, Yugoslavia

Magnetic resonance imaging has been widely used for medical diagnosis in recent years. The knowledge of the proton spin-lattice relaxation time, T_l, represents the basis for NMR imaging. In the present study, we measured T₁ in saliva, gingival fluid, gingival blood, and inflamed gingiva by means of a pulsed NMR Fourier-transform spectrometer. From several measurements, we found the following average T₁ values: in saliva, T₁ = 2550 msec; in gingival fluid, T₁ = 2085 msec; in gingival blood, T₁ = 1515 msec; and in inflamed gingiva samples, T₁ = 840 msec.

In addition, electron paramagnetic resonance imaging was used to demonstrate the in vitro diffusion processes of spin-labeled molecules into tooth enamel by application of the linear magnetic field gradient to a conventional EPR spectrometer. The diffusion coefficient for the nitroxide spin-labeled molecules into tooth enamel was evaluated as D = 10 ^-7 cm² sec^-1.

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