ABSTRACT
Objective To investigate the difference of apparent diffusion coefficients (ADCs) changes in three major salivary glands after gustatory stimulation using two different stimuli. Methods Thirty healthy volunteers were examined with a 1.5 T MR unit. A diffusion-weighted MR imaging (MR DWI) sequence was performed once at rest and continuously repeated 13 times after gustatory stimulation using a commercially available lemon juice and vitamin C tablets in the same volunteer by using self-controlled method. The subsequence of two stimuli was random. In addition, the salivary flow rates at rest and after stimulation were measured. Characteristics and differences in ADCs curves of three salivary glands before and after stimulation between two stimuli were analyzed. Comparison of maximum ADCs, maximum ADCs increase rates (IRs) and times to maximum ADCs(Tmax) between two stimuli was performed by using independent-samples t test. Correlation analysis between rest salivary flow rates and rest ADCs, the maximum salivary flow rates and ADCs after stimulation, the maximum salivary flow IRs and ADC IRs after stimulation were performed by using Pearson correlation test. Results In lemon juice stimulation group, the mean ADCs mostly showed a steady increase to peak values during the first DW MRI scan after stimulation in all glands, followed by a gradually decrease fluctuating slightly around the baseline values. In vitamin C stimulation group, the mean ADCs were significantly increased in all glands during the first DW MRI scan after stimulation, followed by a gradual upward trend till peak values. In lemon juice stimulation group, the mean Tmax of submandibular and sublingual glands[(184±122)s, (345±232)s, respectively] were significantly earlier than those[(454 ± 301)s, (528 ± 297)s, respectively] in vitamin C stimulation group (t=-3.517 and-2.548 respectively, P0.05). Conclusion MR DWI with transient stimulation using lemon juice is more stable for evaluating the physiologic changes of salivary glands in vivo.