The aim of this study was to analyze the three-dimensional deformational changes in the tongue base during natural chewing in a minipig model. Eight 7-8-month-old Yucatan minipigs were used in this study. Under anesthesia, eight 2mm ultrasonic piezoelectric crystals were implanted in the tongue base forming a cubic-shaped configuration, representing the right/left dorsal (RDL-LDL) and ventral (RVL-LVL) lengths, anterior/posterior dorsal (ADW-PDW) and ventral (AVW-PVW) widths, right/left anterior (RAT-LAT) and posterior (RPT-LPT) thicknesses. After the minipig was awakened after anesthesia withdrawal, unrestrained feeding was offered for 10-15 minutes. The amplitudes and onsets for each dimensional change of the crystal-circumscribed region were measured from the start of the jaw opening phase of chewing, and up to 21 concessive chewing cycles were measured. The phases of jaw opening-closing/power stroke during chewing were determined from the simultaneous electromyographic recordings. The duration measurements represented the chewing cycle lengths. The ADW was set up as the reference dimension for the onset calculation (zero point) due to its most stable nature during chewing. All measured dimensions showed either increased (peak/elongation) or decreased (valley/shortening) signals from the baseline. Overall, lengths (RDL-LDL and RVL-LVL) are either shortened or elongated depending upon a given chewing side. The widths (ADW-AVW and PDW-PVW) increased, and the RPT-LAT thickness increased while RAT-LPT thickness reduced during jaw opening of chewing. RDL showed the largest shortening (-42.28% valley-amplitude) while LDL showed the largest elongation (21.15% peak-amplitude, p ≤ 0.05). Earlier onsets occurred in shortening and later onsets in elongation (1.41% to 10.53%) in relation to the reference. Last, the duration of the chewing cycle was 0.45-0.58 seconds. The findings of this study showed a specific kinematic pattern of the tongue base in chewing. This will contribute to a better understanding of the biomechanics of the oropharyngeal function.

Ultrasound elastography (USE) is an emerging technique used to measure in vivo tissue elasticity, or stiffness. The present study applies USE to examine tissue property of the tongue in a minipig animal model. The long-term goal of this research is to examine the association between tongue stiffness in relation to obesity and obstructive sleep apnea (OSA). Eight Yucatan minipigs, 7-8 months-old, were used for this study. USE data were collected for the caudal tongue from the submandibular region with sagittal orientation and for the left masseter muscle when the pig was under sedated sleep in the lateral position. The USE data are collected as video clips, and image frames are extracted and then analyzed with custom-developed software that converts image pixel colors to stiffness values. Multiple video clips are recorded at each site for each study. For each video clip the USE values in extracted ROIs are averaged over 10-20 frames, producing an average circular elastography ROI. The USE pixel values are then averaged over the video clips acquired in each region of the tongue and the left neck muscles. I have processed the tongue video clips to extract blocks of USE measurements that will be compiled to summarize the tissue stiffness and USE data quality for each animal. This procedure will also be applied to the masseter muscle images to produce reference tissue stiffness values for each animal. These data will provide a set of normal baseline stiffness values that can be compared to animals with obesity and OSA in ongoing research studies.