Ultrasound Imaging and Swallowing

Abstract

Ultrasound technology has advanced substantially, providing clinicians and researchers with vastly expanded noninvasive opportunities to study the dynamics of the oral pharyngeal system and the muscles and other soft tissues of the oropharynx during swallowing. In the current climate of cost containment and efficiency, ultrasound imaging presents a viable alternative to videofluorography to examine the oropharyngeal swallow. Because ultrasound imaging is uniquely suited for investigating soft tissue structures, it is used to view the abdomen, fetus, heart, bladder, genitalia, breast, and to visualize tumors and masses throughout the body (1--3). Ultrasound can be used to identify normal and abnormal oropharyngeal tissues such as the thyroid and salivary glands, tongue, palate, and floor of the mouth in various diseases, infections, and genetic conditions (4,5). Because of its inherent advantages (Table 8.1), ultrasound has been successfully adapted for viewing the oral cavity during swallowing (6--9). Real-time ultrasound is totally noninvasive, dynamic, and has no known bioeffects and minimal risk to the patient. Studies can therefore be performed repeatedly or for extended periods of time without risk of future tissue change from effects of long-term radiation. This property is especially relevant when one is studying infants and children who are at greater risk than adults for showing the cumulative effects of ionizing radiation. The air interface at the surface of the tongue is a nearly perfect reflector of sound, thus clearly displaying the lingual musculature and vessels both at rest and during oral motion. Ultrasound imaging is ideally suited to identifying the various soft tissues that compose the upper aerodigestive tract. In addition, the transduction properties of sound waves allow these soft tissues to be distinguished from ingested fluids, semisolids, and solid materials. Since no contrast material is needed to visualize the oropharynx and the bolus during swallowing, any type of food commonly ingested by the patient can be used during a study. The ultrasound examination is conducted with the adult or child patient seated in a comfortable position, while an infant is held on the mother's lap. All ultrasound systems are portable, have built-in video systems, online computerized image processing and measurement programs, a computer keyboard, display screen, and hard copy printout capacity. Ultrasound is easy to use and provides reliable diagnostic information. Because of these advantages, ultrasound technology is well suited to evaluate individuals of any age from infancy to senescence, and any neurological, systemic, genetic, traumatic, developmental, or progressive condition that affects oral physiology.