Fig. 4.

Videofluoroscopic swallow study (VFSS) assay. a A custom VFSS test chamber (black asterisk) is positioned in lateral view between the X-ray source (white asterisk) and image intensifier (yellow arrow) of our custom, miniaturized c-arm fluoroscope. The X-ray beam is turned on only when mice are actively drinking, identified via a webcam positioned above the test chamber. A remote-controlled positioning lift is used to readily maintain the mouse’s aerodigestive tract within the fluoroscopy field of view. b Close-up of the VFSS test chamber in image a, designed to promote voluntary drinking of liquid contrast agent by mice with minimal behavioral distractions. Note the bowl within the test chamber is filled using a syringe delivery system that is manually controlled a few feet away from the fluoroscope. c, d Representative X-ray images from a 30 fps video of a mouse drinking in lateral view. Image c shows the oropharyngeal stage of swallowing, immediately prior to triggering of the swallow reflex. Note the liquid contrast agent accumulating in the vallecula within the pharynx, which is the stereotypical swallow trigger point in mice. Image d shows the esophageal stage of swallowing. Note the swallowed bolus traversing the distal esophagus into the stomach, while liquid contrast continues to accumulate in the vallecula prior to triggering a subsequent swallow