[Assessment with magnetic resonance of laryngeal and oropharyngeal movements during phonation].
The latest MR units are provided with the Turbo-Field-Echo technique which permits gradient-echo imaging with very short TE and TR and is optimized to yield the highest possible image quality within a very short acquisition time--i.e., less than 5 seconds. This dynamic study was aimed at depicting normal laryngeal and oropharyngeal movements during maximal inspiration and the prolonged uttering of vowels, in both a normal and a loud voice. We examined 10 healthy volunteers (7 men and 3 women) with an 0.5-T superconductive unit (Gyroscan T5 III, Philips Medical System). We used Turbo-Field-Echo sequences with the following acquisition parameters: TR 12 ms, TE 6 ms, flip angle 30 degrees, 4 acquisitions, acquisition time: 5 seconds. A single coronal scan was acquired at the larynx, while a midsagittal scan and 2 coronal scans were acquired at the oropharynx. The volunteers were asked to breathe in long and deep, to prolong the emission of the vowel [i] during laryngeal studies and to prolong the emission of the fundamental vowels [a], [i] and [u] in a normal (50 db) and a loud (70 db) voice during oropharyngeal studies. The movements of true and false vocal cords were clearly depicted in all the volunteers, and the activity of the different anatomical structures of the oropharyngeal cavity (lips, tongue, hard and soft palate, pharynx and epiglottis) was also demonstrated. During vowel production in a loud voice, the vocal tract was enlarged at the oral cavity for the vowels [a] and [u] and at the pharynx for the vowel [i]. To conclude, fast MRI with midsagittal scans is the best imaging modality to study different vocal tract patterns during speech and can thus replace midsagittal radiography and xeroradiography in the study of vowel production.