Abstract
Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects.
Highlights
Over the last several years, Magnetic Resonance Imaging (MRI) has improved the analysis method of dynamic processes of the vocal tract, such as swallowing [1,2], singing voice [3,4,5] and speech [6,7,8,9,10].These studies used clinically available high field MR scanners, because they allow a sagittal slice of the whole vocal tract to be recorded without ionizing radiation
The present study aims to analyze the feasibility of an openconfiguration, weight-bearing 0.25 T MRI system with a rotatable examination bed in order to compare untrained subjects’ singing voice production in upright and supine positions
This study demonstrates the feasibility of using an openconfiguration, tilting, 0.25 T MRI system for vocal tract imaging in untrained subjects and presents quantitative data of vocal tract modifications in the upright and the supine body positions
Summary
Over the last several years, Magnetic Resonance Imaging (MRI) has improved the analysis method of dynamic processes of the vocal tract (including the oral cavity, pharynx and epilaryngeal tube), such as swallowing [1,2], singing voice [3,4,5] and speech [6,7,8,9,10].These studies used clinically available high field MR scanners, because they allow a sagittal slice of the whole vocal tract to be recorded without ionizing radiation. Takemoto et al described differences between formant frequencies (i.e. spectral peaks in the sound spectrum of the voice) from acoustical analysis of natural speech sounds in the supine position and area functions derived from stable and cine 3D MR images [12]. The authors assigned these differences to changes of the vocal tract geometry caused by the different impact of gravitational forces in the supine position between stable phonation and continuous utterance. The authors noted that a tongue retraction due to gravity, could be observed
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