Studies of temporomandibular joint sounds Part 3. The clinical usefulness of TMJ Doppler.

Doppler auscultation as applied to internal derangements of the TMJ has been developed in recent years. Possible clinical use of TMJ Doppler auscultation was examined by separating the signals into their spectral components, and comparing the results with those of the conventional sound amplification system (CSAS). Observing frequency component changes with time, similar observations were made using CSAS and TMJ Doppler. However, noises found in TMJ Doppler sonograms were markedly reduced in comparison with those found using CSAS. Ultrasonic waves have high directivity, and pass through soft tissue and fluid; however they have difficulty passing through air, and this may decrease the recording noise. TMJ Doppler can be applied to record movements of the condyle because changes in the receiving frequency indicate the movement of an observed object with precision.