Dynamic MRI for the upper airway

Although the conventional airway observations have been performed mainly using fluoroscopy and endoscopy, they both have defects and provide no satisfactory results in a single examination. Therefore, utilizing ultra-fast magnetic resonance imaging (MRI), a study was carried out for kinetic observations around an airway, directly via excellent tissue contrast images. Turbo-fast low-angle shot (FLASH) with T1-weighted 180deg preparation pulse was used during scanning. The study was also subjected to variable inversion time (TI) and flip angle (FA). Kinetic observation could be scanned in a second or so, and the dynamic study was carried out under a condition of supposed best tissue contrast. Turbo-FLASH, which is unique ultra-fast MRI in clinical use did not always have good tissue contrast. In the present study, the prolongation of TI and enlargement of FA were confirmed to give much better tissue contrast. Due to the simultaneous prolongation of the scanning time with that of TI, however, TI was set up at 300 msec to allow for a kinetic observation (TR=8.5 msec, TE=4 msec, FA=12deg, slice thickness, 8 mm). Clinically, good tissue contrast images around the airway was obtained and a direct observation could be made via the free sections. We are applying the present approach to observations of deglutition and the sleep-apnea syndrome. Regarding deglutition, the present approach is excellent in that easy observations can be made via swallowing saliva while confirming the position and for the sleep-apnea syndrome, it is very good for grasping the obstruction site. Thus, the dynamic study of the airway using turbo-FLASH was shown also to be clinically useful. (author)