Optimized 14 + 1 receive coil array and position system for 3D high-resolution MRI of dental and maxillomandibular structures.

OBJECTIVES: The purpose of this study was to design, build and test a multielement receive coil array and position system, which is optimized for three-dimensional (3D) high-resolution dental and maxillomandibular MRI with high patient comfort. METHODS: A 14 + 1 coil array and positioning system, allowing easy handling by the technologists, reproducible positioning of the patients and high patient comfort, was tested with three healthy volunteers using a 3.0-T MRI machine (Siemens Skyra; Siemens Medical Solutions, Erlangen, Germany). High-resolution 3D T1 weighted, water excitation T1 weighted and fat-saturated T2 weighted imaging sequences were scanned, and 3D image data were reformatted in different orientations and curvatures to aid diagnosis. RESULTS: The high number of receiving coils and the comfortable positioning of the coil array close to the patient's face provided a high signal-to-noise ratio and allowed high quality, high resolution, 3D image data to be acquired within reasonable scan times owing to the possibility of parallel image acquisition acceleration. Reformatting the isotropic 3D image data in different views is helpful for diagnosis, e.g. panoramic reconstruction. The visibility of soft tissues such as the mandibular canal, nutritive canals and periodontal ligaments was exquisite. CONCLUSIONS: The optimized MRI receive coil array and positioning system for dental and oral-maxillofacial imaging provides a valuable tool for detecting and diagnosing pathologies in dental and oral-maxillofacial structures while avoiding radiation dose. The high patient comfort, as achieved by our design, is very crucial, since image artefacts due to movement or failing to complete the examination jeopardize the diagnostic value of MRI examinations.

Early detection of pulp necrosis and dental vitality after traumatic dental injuries in children and adolescents by 3-Tesla magnetic resonance imaging.

OBJECTIVES: More than 50% of all children suffer a traumatic dental injury (TDI) during childhood. In many cases, dentists apply root canal treatment (RCT), which is performed on an average of 7-10 days after replantation. Our aim was to evaluate whether RCT is necessary in many cases, and whether revitalization of affected teeth is possible and measurable by visualization using 3T magnetic resonance imaging (MRI). MATERIAL AND METHODS: Seven healthy children with TDI were treated by repositioning of the affected teeth and reduction of alveolar process fractures followed by splinting. Two weeks after initial treatment, splints were removed. After 6 weeks, all children received 3-Tesla (3T), three-dimensional, high-resolution MRI with a 20-channel standard head and neck coil. The mean age of the children (male/female = 5:2) was 10.8 years (range, 8-17 years). In addition, all children received conventional dental examination for tooth vitality and dental sensitivity to cold and tenderness on percussion. RESULTS: 3T MRI provided excellent images that allowed fine discrimination between dental pulp and adjacent tooth. Using four in-house optimized, non-contrast-enhanced sequences, including panoramic reconstruction, the assessment and analysis of the dental pulp was sufficiently feasible. We could demonstrate reperfusion and thus vitality of the affected teeth in 11 sites. In one child, MRI was able to detect nonreperfusion after TDI of the affected tooth. MRI results were confirmed by clinical examination in all cases. As a consequence of this expectant management and proof of reperfusion and tooth vitality by 3T MRI, only one child had to be treated by RCT. CONCLUSION: 3T MRI is a very promising tool for visualization and detection in the field of dental and oromaxillofacial diseases. By using new 3T MRI sequences in children with TDI, we could demonstrate that RCT are not necessary in every case, and thus could prevent unnecessary treatment of children in the future. Larger studies should follow to confirm the potential benefit in clinical practice.