Kulthida Nunthayanon1, Ei-ichi Honda2, Kazuo Shimazaki3, Hiroko Ohmori4, Maristela Sayuri Inoue-Arai5, Tohru Kurabayashi6, Takashi Ono7. 1. Graduate student, Graduate School, Orthodontic Science, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan; Lecturer, Faculty of Dentistry, Naresuan University, Phitsanulok, 65000, Thailand. Electronic address: kulthida.ort@gmail.com. 2. Professor, Graduate School, Oral and Maxillofacial Radiology, University of Tokushima, 3-18-15, Kuramoto-cho, Tokushima, 770-8504, Japan; Lecturer, Graduate School, Oral and Maxillofacial Radiology, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan. 3. Assistant professor, Graduate School, Orthodontic Science, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan. 4. Staff, Graduate School, Orthodontic Science, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan. 5. Lecturer, Maxillofacial Orthognathics, Graduate School, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan. 6. Professor, Graduate School, Oral and Maxillofacial Radiology, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8549, Japan. 7. Professor, Graduate School, Orthodontic Science, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, 113-8549, Tokyo, Japan.
Abstract
OBJECTIVE: To develop a magnetic resonance imaging (MRI) movie to reveal the dynamic movement of articulators and teeth. STUDY DESIGN: Five healthy females with normal occlusion participated in this study. Various concentrations of MRI contrast media (ferric ammonium citrate [FAC]) were tested for visualization of teeth, according to facial markers and with the use of a gel. Custom-made circuitry was connected to synchronize pronunciation of fricative sounds (/asa/) with scans. Three gradient echo sequences (True fast imaging with steady state precession [true FISP], FISP, and fast low angle shot [FLASH]) with a segmented cine were tested with the use of repetition times (TRs) of 9 ms and 31.5 ms. The MRI movie images were superimposed over the boundaries of teeth. The images produced during pronunciation, using the two different TRs (9 ms and 31 ms), were compared to assess the position of the lips and the tongue. RESULTS: Images obtained using the FLASH sequence, with a TR of 9 ms or 31.5 ms, can be used for diagnostic purposes. A TR of 9 ms, with 161 continuous images acquired, produced the highest-quality images of teeth, with few artifacts present. Pronunciation of the consonant "s" was clearly discernable. CONCLUSIONS: Our 3-T MRI movie system, with a temporal resolution less than 9 ms, can provide detailed information pertaining to variations in speech or oropharyngeal function.
OBJECTIVE: To develop a magnetic resonance imaging (MRI) movie to reveal the dynamic movement of articulators and teeth. STUDY DESIGN: Five healthy females with normal occlusion participated in this study. Various concentrations of MRI contrast media (ferric ammonium citrate [FAC]) were tested for visualization of teeth, according to facial markers and with the use of a gel. Custom-made circuitry was connected to synchronize pronunciation of fricative sounds (/asa/) with scans. Three gradient echo sequences (True fast imaging with steady state precession [true FISP], FISP, and fast low angle shot [FLASH]) with a segmented cine were tested with the use of repetition times (TRs) of 9 ms and 31.5 ms. The MRI movie images were superimposed over the boundaries of teeth. The images produced during pronunciation, using the two different TRs (9 ms and 31 ms), were compared to assess the position of the lips and the tongue. RESULTS: Images obtained using the FLASH sequence, with a TR of 9 ms or 31.5 ms, can be used for diagnostic purposes. A TR of 9 ms, with 161 continuous images acquired, produced the highest-quality images of teeth, with few artifacts present. Pronunciation of the consonant "s" was clearly discernable. CONCLUSIONS: Our 3-T MRI movie system, with a temporal resolution less than 9 ms, can provide detailed information pertaining to variations in speech or oropharyngeal function.