3D-visualization of the temporomandibular joint with focus on the articular disc based on clinical T1-, T2-, and proton density weighted MR images

Diagnostic accuracy of MRI-CBCT fused images in assessment of clinically diagnosed internal derangement of the temporomandibular joint

OBJECTIVES

To evaluate the diagnostic accuracy of Fused (MRI)-CBCT images in the assessment of internal derangement of the temporomandibular joint.

METHODS

MRI and CBCT images of the TMJ were evaluated bilaterally in 10 patients with clinically diagnosed internal derangement. Image fusion was performed using Amira 3D Software (version 5.4.3, Thermo Fisher Scientific Inc.).

RESULTS

The AUC index for MRI-CBCT fused images was 0.83, which was significantly different from the null hypothesis value of 0.5. This was confirmed by inter-examiner reliability index of 0.87, which is statistically significant.

CONCLUSION

MRI-CBCT fused images can significantly improve the accuracy and inter-examiner reliability in the evaluation of clinically diagnosed cases with internal derangement.

Evaluating the temporomandibular joint disc using calcium-suppressed technique in dual-layer detector computed tomography

Objectives

To investigate the application value of the calcium-suppressed (CaSupp) images of dual-layer detector computed tomography (DLCT) in the evaluation of the temporomandibular joint (TMJ) discs.

Methods

Thirty-three healthy subjects underwent DLCT and magnetic resonance imaging (MRI) examinations. CaSupp images were reconstructed from the spectral-based images using a calcium suppression algorithm. The location, morphology, and thickness of the posterior band of the TMJ discs were evaluated on the oblique sagittal proton-density weighted images and CaSupp images.

Results

Of the 66 TMJ discs, anterior displacement was observed on 9 TMJ discs on MR images and 6 TMJ discs on CaSupp images, and posterior displacement was present on 3 TMJ discs on MR and CaSupp images. No significant difference was observed in TMJ disc displacement between MR images and CaSupp images (P value = 0.730). The TMJ discs without displacement had no significant difference in the thickness of the posterior band between the MR and CaSupp images (P value = 0.401).

Conclusions

The calcium-suppressed technique in DLCT may be a simple and preliminary way to evaluate the TMJ disc displacement and structure.

Are morphologic and topographic alterations of the mandibular fossa after fixed functional treatment detectable on tomograms? Visual classification and morphometric analysis

AIM

The goal was to evaluate if changes in morphology and topography of the mandibular fossa after Functional Mandibular Advancer (FMA) treatment are detectable on tomograms. Furthermore, the suitability of digital tomograms (DT) over magnetic resonance imaging (MRI) for this particular question was investigated.

MATERIALS AND METHODS

In all, 25 patients (14 female, 11 male) with a skeletal class II malocclusion received treatment with a FMA. DTs were available prior to (T1) and after (T2) FMA treatment. A total of 50 temporomandibular joints were investigated. The mandibular fossae were evaluated metrically and visually regarding treatment-induced alterations. A p < 0.05 was set as the level for statistical significance for all tests. Results were compared to the results of a recent MRI study.

RESULTS

Visual inspection of all 50 joints in the DT at T1 and T2 revealed no alterations of the fossa shape in the sagittal plane; 24 patients showed identical morphology of right and left joints. The metrical analysis revealed no significant changes regarding width, depth and ratio thereof between T1 and T2. There also were no bilateral differences. Another 18 different distance measurements between porion, mandibular fossa, articular eminence and pterygoid fossa showed no significant changes. There was no detectable proof of a fossa shift.

CONCLUSIONS

No changes in the sagittal plane, mandibular fossa, the articular tubercle, or a possible fossa shift were found in the DT of class II patients after FMA treatment. DT and MRI measurements and the visual inspection revealed identical findings; thus, DT appears to be a valuable research tool for sagittal analysis of mandibular fossa changes.

Mandibular fossa morphology during therapy with a fixed functional orthodontic appliance : A magnetic resonance imaging study

OBJECTIVE

During therapy of distoclusion entailing a rigid, fixed orthodontic appliance, the mandibular fossa and condyle are ideally remodeled, while dentoalveolar effects occur through adaptive mechanisms. Adaptive processes, especially in the fossa region, have not been adequately investigated. Our magnetic resonance imaging (MRI) investigation aimed to assess the effects of therapy with a functional mandibular advancer (FMA) on mandibular fossa morphology.

PATIENTS AND METHODS

We monitored via MRI the therapeutic course of 25 patients at three time points. Visual findings and metric assessments were carried out in the sagittal plane. Three-dimensional (3D) reconstructions of the joint structure of two exemplary patients were also made.

RESULTS

Visual examinations of the MRI slices at the three time points revealed no changes in fossa shape in any of the 50 temporomandibular joints. Lateral comparisons showed that the morphology of the fossae of all 25 patients was identical. Metric analysis demonstrated no significant alterations in width, depth, or in their ratio, not even laterally. Nine measurements of the distances between the porion, mandibular fossa, and articular eminence revealed no significant changes in total or on the left and right sides, or intralaterally.

CONCLUSION

The visual findings and metric analyses of parasagittal MRI slices did not indicate any morphological changes in the mandibular fossa or articular eminence in patients with distoclusion treated via a rigid, fixed orthodontic appliance. However, special reworking of the MRI data facilitated reconstruction of the surfaces of joint structures in 3D. This new method makes it possible to depict more accurately and noninvasively the adaptive mechanisms not ascertainable via metric methods and to assess them as 3D structures.

Three-Dimensional Assessment of Temporomandibular Joint Using MRI-CBCT Image Registration

Purpose

To introduce a new approach to reconstruct a 3D model of the TMJ using magnetic resonance imaging (MRI) and cone-beam computed tomography (CBCT) registered images, and to evaluate the intra-examiner reproducibility values of reconstructing the 3D models of the TMJ.

Methods

MRI and CBCT images of five patients (10 TMJs) were obtained. Multiple MRIs and CBCT images were registered using a mutual information based algorithm. The articular disc, condylar head and glenoid fossa were segmented at two different occasions, at least one-week apart, by one investigator, and 3D models were reconstructed. Differences between the segmentation at two occasions were automatically measured using the surface contours (Average Perpendicular Distance) and the volume overlap (Dice Similarity Index) of the 3D models. Descriptive analysis of the changes at 2 occasions, including means and standard deviation (SD) were reported to describe the intra-examiner reproducibility.

Results

The automatic segmentation of the condyle revealed maximum distance change of 1.9±0.93 mm, similarity index of 98% and root mean squared distance of 0.1±0.08 mm, and the glenoid fossa revealed maximum distance change of 2±0.52 mm, similarity index of 96% and root mean squared distance of 0.2±0.04 mm. The manual segmentation of the articular disc revealed maximum distance change of 3.6±0.32 mm, similarity index of 80% and root mean squared distance of 0.3±0.1 mm.

Conclusion

The MRI-CBCT registration provides a reliable tool to reconstruct 3D models of the TMJ’s soft and hard tissues, allows quantification of the articular disc morphology and position changes with associated differences of the condylar head and glenoid fossa, and facilitates measuring tissue changes over time.