舌體運動的觀測：超音波與非超音波研究綜論

Tongue is an important organ both in speech production and swallowing, yet the most difficult is to obtain a direct view. Previously, cineradiography was used almost exclusively for evaluating tongue movement. Owing to considerable x-ray exposures, the use of this technique has become limited for ethical reasons. The same limitation applies to the usage of computerize tomography (CT). Palatography is a well-known traditional method of obtaining articulatory data. However, different absorbency to the marking medium among speakers adds measurement error. Electropalatography (EPG) utilizes an artificial palate to measure tongue-palate contact during function. The involved artificial palate has to be designed individually and is expensive. The carriage of pseudo-palate during tongue movements, to some degree, is not physiological. In the case of eletromagnetic articulography (EMA) or electromagnetic midsagittal articulometer (EMMA), considerable preparation time is needed, and the procedure and subsequent signal processing is complicated. Magnetic resonance imaging (MRI) technique permits observation of vocal tract features from any angle and makes possible three-dimensional reconstruction of the entire vocal tract. However, image acquisition rates are currently still too slow by an order of magnitude to capture dynamic motion. Also the accompanied noise is disturbing. Ultrasound has the advantage of allowing visualization of the actual soft tissues of the tongue and floor of the mouth. Over the past years, an increasing number of ultrasonography examinations of tongue tumor have been carried out in an effort to improve preoperative staging and to help the surgeon to define an adequate resection margins. Many researchers used this technique to observe tongue functions, such as speaking or swallowing. However, these previous ultrasound studies are subject to potential artifacts caused by varying transducer-skin contact surfaces of the submental area due to movements during function. Additional movements also occurred readily since the ultrasound transducers in previous studies were handheld by either the examinee or the examiner. Consequently, the images depicted were misinterpreted. A dynamic tongue imaging technique, the cushion-scanning technique (CST), was developed to overcome these problems. The purpose of this study is to introduce this technique, with a brief review of other associated techniques, in the research of tongue movement.