Effect of meal ingestion on parotid gland T2 values.

Parotid T2 mapping is used for quantitative evaluation, for example to assess early radiation‑induced changes in the parotid gland. However, the effects of pre-scan meals on parotid gland T2 values have not yet been reported. We investigated the temporal changes in parotid T2 values induced by meal ingestion. This prospective, single-center repeated-measures study included sixteen healthy volunteers. 3.0 T axial multi-slice multi-echo TSE T2 mapping was performed with and without fat suppression. Measurements were performed at fasting (baseline) and then alternated between 10 and 30 min after meal ingestion. T2 values at each time point were calculated by averaging the measurements obtained from six ROIs, which were drawn to avoid Stensen's duct and major vessels. Repeated-measures ANOVA with Greenhouse-Geisser correction and Bonferroni adjustment was applied. Without fat suppression, the mean parotid T2 value increased from 63.4 ± 4.63 ms at baseline to 65.8 ± 4.52 ms at 26 min after the start of meal ingestion, with no significant differences from baseline in the pairwise comparisons at any time point. With fat suppression, the mean T2 value increased from 55.7 ± 3.10 ms to 58.6 ± 3.01 ms; significant differences were observed from 16 min onward and persisted through the final time point (p < 0.05). These findings suggest the importance of standardizing pre-scan meal status for quantitative parotid T2 mapping.