Monitoring of gustatory stimulation of salivary glands by diffusion-weighted MR imaging: comparison of 1.5T and 3T.

Background and Purpose: Our aim was to compare different field strengths monitoring physiologic changes due to oral stimulation of parotid glands by using diffusion-weighted (DW) echo-planar imaging (EPI).
Materials and Methods: Twenty-seven healthy volunteers were examined with a DW-EPI sequence at 1.5T and 3T before and after oral stimulation with commercially available lemon juice. The b factors used were 0, 500, and 1000 s/mm(2). Apparent diffusion coefficient (ADC) maps were evaluated with a manually placed region of interest including the entire parotid gland. For comparison of results, a Student t test was used on the basis of the mean of the volunteer median values. To compare both field strengths, we calculated the Pearson correlation coefficient (r).
Results: DW-EPI MR imaging visualized the parotid glands of all volunteers. With 1.5T, the mean ADC before stimulation was 1.12 x 10(-3) mm(2)/s +/- 0.08 x 10(-3) mm(2)/s. After stimulation with lemon juice, the ADC increased to 1.18 x 10(-3) mm(2)/s +/- 0.09 x 10(-3) mm(2)/s. For 3T, the ADC before stimulation was 1.14 x 10(-3) mm(2)/s +/- 0.04 x 10(-3) mm(2)/s, with an increase to 1.17 x 10(-3) mm(2)/s +/- 0.05 x 10(-3) mm(2)/s after stimulation. For both field strengths, the increase in ADC after stimulation was significant (P < .001). High correlations between both field strengths were found pre- and poststimulation (r = 0.955, and 0.936, respectively).
Conclusion: DW-EPI MR imaging allows monitoring of physiologic changes due to oral stimulation of parotid glands by using DW imaging with high correlation between 1.5T and 3T.