ABSTRACT
Objective To establish a three-dimensional (3D) dynamic model of temporomandibular joint (TMJ) based on data collected from the TMJ movement with multi-level two-dimensional (2D) dynamic magnetic resonance imaging (MRI) and make biomechanical analysis. Methods GE Signa 1.5T TwinSpeed superconductive magnetic resonance scanner was used. TMJs of 2 asymptomatic male volunteers were chosen to be examined with MRI. All the images were imported to the Mimics software. 3D dynamic model of the TMJ was built, and the relationship between the magnitude of mouth opening and the disc transverse diameter was analyzed using linear fitting. Results The 3D dynamic model of TMJ was successfully established. The disc-condyle relationship and the dynamic morphological change of the TMJ disc were showed clearly in this model. The linear fitting equations were y=-0.03x+14.44 (R2=0.591) and y=-0.061x+13.48 (R2=0.306) from volunteers 1 and 2, respectively. A linear trend was observed regarding the relationship between mouth opening position and articular disc transverse diameter. The contact of the condyle surrounded by the TMJ disc varied inversely with the magnitude of mouth opening; the longitudinal diameter of TMJ disc changed along with the magnitude of mouth opening. In the process of mouth opening, the thickest longitudinal diameter of the joint disc was at the middle part of post-zone. The most remarkable changes of the longitudinal diameter of TMJ disc were found at the outer part of the post-zone and the inner part of the mid-zone. Conclusions The 3D dynamic model of TMJ was built successfully to observe the TMJ movement dynamically with 2D dynamic MRI. The model showed the disc-condyle relationship intuitively and precisely, and could be used as an alternative method to make up for the shortage of the 2D static MRI.
ABSTRACT
<p><b>OBJECTIVE</b>To determine the characteristics and diagnostic value of dynamic contrast enhanced MRI (DCE-MRI) in differentiating benign soft tissue lesions from malignant tumors affecting the masticator space (MS).</p><p><b>METHODS</b>Prior to managements, conventional MRI and DCE-MRI were performed in 53 patients who suffered from primary or secondary soft tissue lesions affecting the MS. The time to peak (TTP), relative maximum enhancement (RME) and relative washout ratio (RWO) were separately calculated.</p><p><b>RESULTS</b>Mean TTP of benign and malignant lesions were (130.3 ± 13.2) and (69.6 ± 6.9) s, respectively. Mean RWO of benign and malignant lesions were (29.7 ± 5.5)% and (8.7 ± 2.1)%, respectively. Malignant lesions had a significantly shorter TTP(P = 0.001) and lower RWO (P = 0.003) than benign lesions. When TTP was less than 92.2 s and RWO less than or equal to 16.0%, malignant tumors were considered. DCE-MRI had a sensitivity of 72.3%, specificity of 93.5%, accuracy of 84.9%, positive predictive value of 88.9%, and negative predictive value of 82.9%.</p><p><b>CONCLUSIONS</b>As a non-invasive imaging technique, DCE-MRI is valuable to differentiate benign soft tissue lesions from malignant tumors affecting the MS.</p>