Clinical application of tagging snapshot MRI

The present study was to determine the contraction of the tongue-related muscles during the production of 5 Japanese vowels by tagging snapshot MRI. The tagging snapshot pulse sequence had three components: a contrast preparation pulse, subsequent tagging pulses and a data acquisition phase. When a vowel was uttered, the stripes were displaced, indicating the displacement of the tissues. The subjects were a 35-year-old and a 30-year-old Japanese men. Images of 5 vowels and the reference position were acquired. Six lines were imposed with their anatomical meanings on MRI, representing fibers of the anterior, middle and posterior parts of the genioglossus muscles (GGa, GGm, GGp), superior-longitudinalis muscle (SL), inferior-longitudinalis muscle (IL) and verticalis muscle (V). The lengths of these lines were measured for the contractions of the muscles along these lines. During the utterance of /a/, the contraction of GGa, V and SL seemed to cause the shortening of the tongue in the vertical axis. During the utterance of /i/, GGm and GGp seemed to contract to pull the tongue toward the chin to make the tongue shorter in the longitudinal axis. During the utterance of /u/, the contraction of GGa, GGp and IL made the tongue shorter in the vertical and longitudinal axes. During the utterance of /e/, GGp contracted as of /i/, although the tongue position was lower for /e/ than /i/. During the utterance of /o/, GGp contracted to pull the bottom of the tongue against the contraction of SG to pull back the upper part of the tongue. A newly developed tagging snapshot MRI is capable of imaging the 'inner' construction of the tongue and the contraction of the muscles during speech production. (N.K.)