Computer-assisted estimation of lines of action of human masticatory muscles reconstructed in vivo by means of magnetic resonance imaging of parallel sections.

The orientation of these lines of action was estimated in 9 healthy subjects, by reconstructing the muscle shape from a series of parallel sections obtained by MRI. In order to gain insight into sources of error, the lines of action of the masseter and medial pterygoid were estimated from two mutually perpendicular series of sectional images. Average results were compared with anatomical data from the literature. The results indicated that the accuracy of the estimate was principally dependent on the reliability of the reconstructions; the average accuracy of the estimated orientations was about 5 degrees.