Comparison between the use of magnetic resonance imaging and conebeam computed tomography for mandibular nerve identification

Objective: Conebeam computed tomography (CBCT) and magnetic resonance imaging (MRI) have been used to identify the mandibular nerve but a comparison of the reliabilities of the two imaging modalities has not been performed. It was hypothesized that the reliabilities were not different between the two. Materials and methods: Twelve dental postgraduates in five disciplines were recruited to assess two sets of reformatted oblique images (CBCT and MRI) of 11 patients who were scanned before wisdom teeth extraction. The variance of the identified locations of mandibular nerve, the mental foramen and the mandibular foramen between two sets of images of each patient was compared. Each set of images was rated by assessors to reveal the satisfaction in determining the structures. Results: It was found that by using MRI images, significantly lesser variances and significantly higher satisfactory scores were given by the assessors than by using CBCT images in the identification of the structures. Conclusions: We concluded that MRI is a promising imaging modality that can be used to identify the mandibular nerve when it cannot be found in CBCT images. To cite this article:
Chau A, Comparison between the use of MRI and CBCT for mandibular nerve identification.
Clin. Oral Impl. Res. 23 , 2012; 253–256.
doi: 10.1111/j.1600‐0501.2011.02188.x     

MR imaging of maxillomandibular lesions

This paper addresses maxillomandibular lesions including cyst, tumor and osteomyelitis in terms of their general features and discusses the use of MR imaging techniques, interpretation of images and their characteristic findings. MR imaging of odontogenic keratocyst improved the visualization of a cystic pattern, regularly thin walls, weak enhancement of cyst walls and inhomogeneous intensity of fluid contents. However, some of them could be misdiagnosed as mixed or solid patterns by non-contrast study alone. Ameloblastoma showed mixed solid and cystic components, irregularly thick walls, papillary projections, and marked enhancement of the walls. In mandibular osteomyelitis, MR imaging could give us more detailed information regarding residual activity of infection and the extent of involvement. MR findings were suggestive to differentiate between tumors and cysts and characterize many cystic entities in the maxillomandibular region.     

Advances in imaging: impact on studying craniofacial bone structure

Methods for measuring the structure of craniofacial bones are discussed in this paper. In addition to the three-dimensional macro-structure of the craniofacial skeleton, there is considerable interest in imaging the bone at a microscopic resolution in order to depict the micro-architecture of the trabecular bone itself. In addition to the density of the bone, the microarchitecture reflects bone quality. An understanding of bone quality and density changes has implications for a number of craniofacial pathologies, as well as for implant design and understanding the biomechanical function and loading of the jaw. Trabecular bone micro-architecture has been recently imaged using imaging methods such as micro-computed tomography, magnetic resonance imaging, and the images have been used in finite element models to assess bone mechanical properties. In this paper, some of the recent advances in micro-computed tomography and magnetic resonance imaging are reviewed, and their potential for imaging the trabecular bone in mandibular bones is presented. Examples of in vitro and in vivo images are presented.     

MR imaging as a precise technique to evaluate skull-base tumor volume: Comparison of CT,MR imaging and FDG PET from murine and clinical data

In spite of the many imaging modalities used in clinics, the one that best reflects the true delineation of skull-base (infratemporal fossa, ITF) malignancies is still unknown. In order to compare the tumor recognition capabilities of different imaging modalities, established murine models and patients with skull-base tumors were evaluated by computer tomography (CT), magnetic resonance (MR) imaging, and fluorine-18 fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) for delineation of gross tumor volume (GTV).PET, MR imaging, and CT enhanced by iodine staining were all sensitive to, and able to recognize, the skull-base tumor in the murine model. No significant difference (p > 0.9999) was observed between average GTV according to MR imaging (176.67 ± 19.6 mm³) and the histological measurement result (170.23 ± 22.24 mm³) for the murine model. In contrast, the GTVs according to CT (88.77 ± 13.03 mm³, p < 0.0001) and ¹⁸FDG PET (35.67 ± 6.56 mm³, p < 0.0001) were much smaller.In nine patients for whom the three modalities were available, tumor volume comparisons tended to be consistent with the murine model data. According to both the established murine model and clinical patient data, MR imaging possessed the optimal ability to recognize tumor contours.     

Soft Tissue Images from Cephalograms Compared With Those from a 3D Surface Acquisition System

Objective:To assess whether 2D cephalometrics is comparable with 3D imaging devices and whether 3D technology could replace traditional 2D image capture in posttreatment evaluation.Materials and Methods:The study is a prospective evaluation of superimposition techniques obtained from a cohort of 40 patients who underwent orthognathic surgery in a private practice environment. Surgical records were obtained from lateral cephalometric radiographs taken by a Kodak 8000C machine, and the 3D images were obtained from the 3dMD stereo photogrammetric camera capture system. Pre- and postlateral cephalometric records were superimposed on the cranial base (SN line) while pre- and post-3D surgical records were superimposed on the regional best-fit method. A mathematical algorithm, or best-fit calculation, was carried out on the selected surfaces. Each set of superimposed records was analyzed, and five soft tissue landmarks were plotted. The differences between the five surface points were analyzed for each set of records.Results:The final sample consisted of 34 subjects with full records. A total of 680 surface landmarks were plotted and analyzed. The mean differences of the soft tissue landmarks were analyzed for each pair of data sets and were found to range between 1.06 and 8.07 mm and 1.26 and 7.34 mm for lateral cephalometric and 3D readings, respectively. Paired t-tests were carried out using the SPSS 15.0 software, and they showed that the results were not statistically significant between the superimposition techniques on the image capture systems (P > .05).Conclusions:The types of superimposition techniques used in the imaging modalities studied were comparable with one another.