Biomedical Engineering Reference
In-Depth Information
Fig. 7
Determining the muscle EMG signals
To exploit this relation, for each jaw-closing muscle, it was thus necessary to
determine:
-
EMGr max
, repeating isometric voluntary maximum contractions and,
-
Smax
, starting from an MRI examination.
In recording the EMG signals (Fig.
7
), the device provided several successive
functions:
- Signal capture using thread electrodes, amplification and filtering,
- Data recording and computer-assisted processing.
To reduce the strong discomfort imposed on the volunteer, the morphological
symmetry of the face was admitted. Consequently, the areas of the muscle sections
were read only on the left profile. The electrodes were distributed evenly on the left
profile and the sensor was positioned successively between the incisors (31/21), the
first premolars (34/24) and the first molars (36/26).
Admitting the perfect geometrical symmetry of the face, the situation (31/21),
corresponded to a case of plane loading. On the other hand, for an asymmetrical
loading, between premolars for example, the sensor was first positioned on tooth
34. The electrodes and the sensor were then located on the same profile and the
sensor was moved to tooth 44. The electrodes and the sensor were thus located on
different profiles. Using this technique, EMG signals of the two profiles (ipsi and
contro) could be quantified while avoiding bilateral electrode implantation.
Physiological Muscle Sections
MRI provides images with a high degree of accuracy. To determine the main muscle
section, the principal direction (or the positions of the insertion centers) needed to
