Diffusion-Weighted Magnetic Resonance Imaging of the Parotid glands in healthy volunteers before and after a gustatory stimulation to quantify relative function

Diffusion weighted imaging (DWI) can be employed in head and neck MRI to quantify function of salivary glands. Currently, parotid function is measured using radio-isotope scintigraphy and an invasive needle biopsy. In this study a non-invasive, non-ionising DWI sequence was tested in healthy volunteers. In-vivo measurements of spin-lattice T1 and spin-spin T2 relaxation times were made using Driven Equilibrium Single Pulse Observation of T1 (DESPOT1) and Turbo Spin Echo (TSE) multi-echo sequences respectively. These were used to set echo time (TE) and repetition time (TR) of the final DWI sequence. Diffusion b-values were chosen to incorporate both perfusion and diffusion regimes. Five healthy volunteers (31.6 ± 9.6 yrs.) underwent two MRI scans one week apart on a 3 T Philips Achieva (Philips, Best, the Netherlands) using an 8 channel SENSE coil. Each scan consisted of a baseline DWI measurement, stimulus of 5 ml lemon juice and a repeat of the DWI measurement. Functional parameters were extracted using ROI analysis on co-registered DWI and T2 anatomical images. The DWI sequence used, consisted of six b-Values covering perfusion and diffusion regimes b = [0, 20,50,100,250,500 s/mm^2]. T1 and T2 relaxation times were (T1 : 1599.2 ± 252.5 ms) and (T2: 64.9 ± 5.2 ms). Statistically significant differences were seen when comparing parameters pre and post stimulus across the subject group (n = 5) ; (p < 0.025). No significant differences were seen when comparing right and left glands across the subject group. Scans were shown to be more reproducible pre stimulus than post. This sequence and analysis process is effective in identifying functional changes in salivary glands pre and post stimulus, with future applications in radiotherapy treatment monitoring and early identification of gland pathologies.