Chairs:
jeroen van dessel
spyros damaskos
21: DETECTION OF CARIES LESIONS USING A WATER-SENSITIVE STIR SEQUENCE IN DENTAL MRI
E. Burian1,2, G. Andreisek2,3, M. Probst4
1Universitätsklinikum Ulm, Ulm, Germany, 2Kantonsspital Frauenfeld, Frauenfeld, Switzerland, 3Universitätsspital Zürich, Zürich, Switzerland, 4Abteilung für Neuroradiologie TU München, München, Germany
Aim: In clinical practice, diagnosis of suspected carious lesions is verified by using conventional dental radiography (DR), including panoramic radiography (OPT), bitewing imaging, and dental X-ray. The aim of this study was to evaluate the use of magnetic resonance imaging (MRI) for caries visualization.
Material and Methods: Fourteen patients with clinically suspected carious lesions, verified by standardized dental examination including DR and OPT, were imaged with 3D isotropic T2-weighted STIR (short tau inversion recovery) and T1 FFE Black bone sequences. Intensities of dental caries, hard tissue and pulp were measured and calculated as aSNR (apparent signal to noise ratio) and aHTMCNR (apparent hard tissue to muscle contrast to noise ratio) in both sequences. Imaging findings were then correlated to clinical examination results.
Results: In STIR as well as in T1 FFE black bone images, aSNR and aHTMCNR was significantly higher in carious lesions than in healthy hard tissue (p < 0.001). Using water-sensitive STIR sequence allowed for detecting significantly lower aSNR and aHTMCNR in carious teeth compared to healthy teeth ( p = 0.01).
Conclusion: The use of MRI for the detection of caries is a promising imaging technique that may complement clinical exams and traditional imaging.
27: DENTAL MRI – A METHOD TO MONITOR PERIODONTAL EDEMA IN PATIENTS WITH PERIODONTAL DISEASE
M. Probst1, J. Schwarting1, M. Griesbauer1, T. Robl2, E. Burian3, F. Probst4, M. Folwaczny5
1Technical University Munich / Klinikum rechts der Isar, Neuroradiology, Munich, Germany, 2LMU Munich, Oral and Maxillofacial Surgery, Munich, Germany, 3University Ulm and Kantonsspital Frauenfeld (Switzerland), Radiology, Munich, Germany, 4LMU Munich and MKG Probst, Oral and Maxillofacial Surgery, Munich, Germany, 5LMU Munich, Periodontoly, Munich, Germany
Aim: Periodontal disease can be visualized by using dental MRI. Hyperintense edema and bone loss correlate to the typical clinical findings periodontal pocket depth and bleeding on probing. Aim of this study was to investigate the reversibility of imaging findings through standard treatment in the timespan of 3 months in correlation to the clinical examination status, in order to determine whether MR imaging can be used to monitor disease activity.
Material and Methods: 36 patients with periodontitis were prospectively analyzed and recieved imaging with 3D isotropic T2-weighted STIR and Fast Field Echo T1-weighted Black bone sequences before and 3 months after non-surgical therapy. Bone edema depth was measured in 164 teeth before and after treatment. Results were compared with standardized clinical examinations according to the periodontal screening index (PSI).
Results: Periodontitis results in bone edema adjacent to affected teeth with an average depth of 1.8± 0.18mm. 3 months after therapy, mean edema depth shrunk to 1.5± 0.14 mm, p<.01. Edema reduction was observed only in patients with bleeding on probing (BOP) before treatment (2.0± 0.21 mm vs. 1.7± 0.16mm, p<.01), while there was no change in patients without BOP(0.71± 0.19mm vs. 0.75± 0.21mm). Changes were observed most prominently in patients with clinically measured periodontal pockets >5mm depth (3.4± 0.36mm vs. 2.4± 0.26 mm, p ≤ .001).
Conclusion: Periodontal osseous edema in T2 STIR MR-imaging can be used to monitor inflammation in patients with periodontal disease. This provides additional information for therapy monitoring and could be useful to validate therapy methods.
28: DEEP LEARNING NETWORKS TOWARDS SEGMENTATION OF THE LOWER AND UPPER JAW
V. Thierauf1, F. Probst2, A. Janiec1, X. Zhang3, V. Zimmer3, E. Burian4, J. Schnabel5, M. Probst1
1Technical University Munich / Klinikum rechts der Isar, Neuroradiology, Munich, Germany, 2LMU Munich and MKG Probst, Oral and Maxillofacial Surgery, Munich, Germany, 3Technical University, AI in Medicine, Munich, Germany, 4University Ulm and Kantonsspital Frauenfeld (Switzerland), Radiology, Munich, Germany, 5Technical University /Helmholtz, AI in Medicine, Munich, Germany
Aim: In dental applications, AI solutions have mainly been proposed for CBCT or X-ray data. However, MRI does offer advantages like radiation-free imaging and a higher contrast within soft tissues. In order to establish automated segmentation of the bony structures in the upper and lower jaw deep learning methods were trained on MR data.
Methods: A stepwise approach was used: networks were trained to detect bony structures of the upper and lower jaw. Therefore MR data of the viscerocranium were segmented manually representing the ground truth. Based on these data different algorithms were trained to detect osseous structures. Second, we trained the networks to track the inferior alveolar nerve (IAN).
Results: 220 MR data were acquired with similar protocols (3D STIR and 3D Short T1 FFE sequences). STIR and T1 sequences had been coregistered. We generated labels of jaw bones in 51 MR data, 60 labels of the IAN in MR data. We trained networks with the labels of the bones and the course of the IAN in MR. Congruence of manually segmented data and the AI-labled data was calculated (Dice coefficient).
Conclusion: Results show that it is possible to detect structures in MR data using deep learning networks. The established algorithm has the capability to label the upper and lower jaw on MR data correctly. Manual segmentation is time consuming so algorithms will be needed for further assessment of MR-imanging. Deep learning methods are capable to detect different structures in MR data.
29: DETECTION OF NERVE INJURY OF THE LINGUAL AND THE INFERIOR ALVEOLAR NERVE BY USING DENTAL MRI
M. Probst1, C.P. Cornelius2, E. Burian3, F. Probst4
1Technical University Munich / Klinikum rechts der Isar, Neuroradiology, Munich, Germany, 2LMU Munich, Oral and Maxillofacial Surgery, Munich, Germany, 3University Ulm and Kantonsspital Frauenfeld (Switzerland), Radiology, Munich, Germany, 4LMU Munich and MKG Probst, Oral and Maxillofacial Surgery, Munich, Germany
Aim: Dentoalveolar surgery can lead to mechanical injury of the lingual nerve (NL) or the inferior alveolar nerve (NAI). Nerve injuries might not be noticed intraoperatively, however they become apparent during follow-up examinations due to existing neurosensory deficits. Clinical neurosensory tests and neurophysiological examinations are used to determine the underlying type of lesion. In case of a complete interruption of continuity microneural reconstruction could be performed. Therefore reliable information about the extent of the injury are crucial.
Methods: MRI examinations for neurography were performed including specific high-resolution sequences (3D STIR, 3D DESS). MRI findings were further analyzed with neurosensory tests and correlated with intraoperative findings.
Results: In 15 patients with unilateral lesions of the sensory mandibular branches (NL n = 10; NAI n = 5), direct visualization of the affected nerves was possible. It was not possible to differentiate between axonal, endo- and perineurial lesions, i.e. lesions with preserved continuity (Sunderland I – IV). In contrast, a complete interruption of continuity and neuroma formation (Sunderland V & VI / Mackinnon- Dellon) could be reliably recognized, as the subsequent intraoperative correlation showed (NL n = 5 ; NAI n = 1).
Conclusion: Dental MRI allows neurographic visualization of NL and NAI lesions and can provide a basis for differentiating the extent of damage in the early phase after injury. As a consequence, MR imaging becomes a guide in the decision-making process between a wait-and-see approach versus surgical revision. MRI can chage the management concept by shortening the time before surgical intervention.
36: DENTAL-DEDICATED MRI FOR ASSESSMENT OF LOWER THIRD MOLARS: A PILOT STUDY
J. Christensen1, L.H. Matzen1, R. Spin-Neto1
1Aarhus University, Department of Dentistry and Oral Health, Section for Oral Radiology and Endodontics, Aarhus C, Denmark
Aim: To compare dental-dedicated magnetic resonance imaging (ddMRI) to CBCT as an imaging modality for assessing mandibular third molars.
Material and Methods: Twelve patients with CBCT (X1, 3Shape, Copenhagen, Denmark; FOV 4×4 cm, resolution 0.15 mm) and ddMRI of one lower third molar were selected. ddMR images were acquired on a Magnetom Free.Max (Siemens Healthineers, Erlangen, Germany) using a dental-dedicated coil (Rapid-Biomedical, Rimpar, Germany), using two sequences (6×6 cm FOV, section thickness 2 mm): PD (TSE) sagittal and coronal sections (resolution 0.3 mm) and PD-FS (TSE) sagittal sections (resolution 0.4 mm). Two observers (experienced within dentomaxillofacial radiology) assessed the images regarding angulation of the third molar, number of roots, relation to the mandibular canal, presence/absence of cortication between tooth and canal, canal positioned within a root flex, compression of the canal lumen, and pathology of the second molar: bone loss and external resorption. The ddMR images were also assessed regarding visibility and position of the lingual nerve. Interobserver agreement (Kappa statistics), and agreement between CBCT and ddMRI (non-parametric tests) were assessed.
Results: Kappa values for CBCT were substantial to almost perfect (0.83-1.0), while they varied from moderate to almost perfect (0.56-1.0) for ddMRI, except for position of the lingual nerve (0.33). There was no significant difference in assessments on CBCT and ddMRI for both observers (p>0.05 for all parameters).
Conclusion: ddMRI was comparable to CBCT regarding assessment of mandibular third molars. The visualization of the lingual nerve is an added value with ddMRI, however further education and training is needed.