Panoramic Reconstruction Research Articles

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

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. 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. 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. 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

ObjectivesMore 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 methodsSeven 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. Results3T 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. Conclusion3T 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.

A Panoramic 3D Reconstruction System Based on the Projection of Patterns

This work presents the implementation of a 3D reconstruction system capable of reconstructing a 360-degree scene with a single acquisition using a projection of patterns. The system is formed by two modules: the first module is a CCD camera with a parabolic mirror that allows the acquisition of catadioptric images. The second module consists of a light projector and a parabolic mirror that is used to generate the pattern projections over the object that will be reconstructed. The projection system has a 360-degree field of view and both modules were calibrated to obtain the extrinsic parameters. To validate the functionality of the system, we performed 3D reconstructions of three objects, and show the reconstruction error analysis.

A comparison of the mandibular index on panoramic and cross-sectional images from CBCT exams from osteoporosis risk group

Osteoporosis is a degenerative disease that primarily affects postmenopausal women. Based on panoramic radiographs, several assessment methods have been proposed for the diagnosis and evaluation of bone changes and as a predictor of osteoporosis for example the mandibular index. The purpose of this study is to compare the assessment of mandibular indices on panoramic and cross-sectional images. Forty-four cone beam computed tomography (CBCT) images from postmenopausal female subjects aged more than 45years without systemic changes were selected for this study. From those images, cross-sectional and panoramic reconstruction images were assembled into a template for evaluation. The evaluation was conducted by observing the panoramic images and parasagittal sections. The appearance of the inferior cortex of the mandible was classified according to the mandibular index: C1, the endosteal margin of the cortex was even and sharp; C2, the endosteal margin presented semilunar defects or appeared to form endosteal cortical residues; or C3, the cortical layer formed heavy endosteal cortical residues and was clearly porous. Based on Wilcoxon statistical test (p > 0.01), the data showed no statistically significant difference between the exams. The mandibular index assigned in tomographic images is comparable to that obtained in panoramic images, indicating a valid use of the index in CBCT images, which can lead to the identification of patients with bone mass loss and a premature referral to further exams and treatment.

Comparative study of Puricelli’s panorametry in conventional panoramic radiography and cone beam computed tomography panoramic reconstruction

Objectives: to compare the reproducibility of Puricelli’s panorametry on conventional panoramic radiography and on CBCT reformatted panoramic images, acquired in MIP mode. This study also compared linear and angular measurements between both exams. Methods: were evaluated 54 pairs of conventional panoramic radiography and CBCT panoramic MIP reconstructions. panorametry was manually traced, in both films, by three examiners. The originally proposed linear and angular, dental and skeletal measurements where tabulated and compared between imaging methods. Inter-examiner reproducibility was tested by intraclass correlation coefficient, and the differences between measurements of both methods were analyzed by Student’s t test. Results: the inter-examiner correlation was high for both the conventional panoramic radiography and CBCT panoramic MIP reconstructions (0.86±0.07 and 0.88±0.07, respectively). Total magnification of pano-ramic radiograph, for the studied measurements, was of 4.3%, being vertically higher (12%) and to the horizontal inferior line (11.5%) comparing to the angular measurements of straight lines (6.7%) and to the horizontal superior lines (1.9%). The conventional panoramic radiography, in comparison to the CBCT, presented lower values for most angular measurements. Conclusions: Puricelli’s panorametry presents a high degree of reproducibility in both conventional panoramic radiography and CBCT reformatted panoramic images. Conventional panoramic radiography presents augmented linear and angular skeletal measurements and reduced dental angular measurements when compared to CBCT reformatted panoramic images. Conventional panoramic radiographs seem to present a consistent augmentation of the right side of the mandibular image.

Uncommon trajectory variations of the mandibular canal and of the mandibular incisive canal: case report

This paper aims to report and discuss a case in which unusual anatomical variations were observed in the mandibular canal (MC) and the mandibular incisive canal (MIC) in a same patient. A 49-year-old healthy female was referred for mandibular dental implant placement. Panoramic radiography and cone beam computed tomography (CBCT) were performed. Cross-sections, axial, coronal, panoramic reconstructions and volume rendering were obtained. The panoramic radiograph did not show any evidence of abnormality. CBCT showed a bifid MC on the right side. It extended to the buccal cortex, exteriorized for 6mm and returned to its conventional trajectory to reach the mental foramen. On the left side, the MIC initially followed its normal trajectory for 4mm but, in the canine region, it also extended to the buccal cortex and exteriorized. The advent of CBCT in Dentistry allowed a greater accuracy in the diagnosis of anatomical variations in the jaws, preventing injury to the neurovascular bundle and enabling an adequate surgical planning in the region.

An ellipse detection method for 3D head image fusion based on color-coded mark points

In this paper, we proposed a new kind of mark points coded by color and a new quasi-ellipse detector on pixel level. This method is especially applicable to three-dimensional (3D) head panoramic reconstruction. Images of adjacent perspectives can be stitched by matching pasted color-coded mark points in overlap area to calculate the transformation matrix. This paper focuses on how the color-coded mark points work and how to detect and match corresponding points from different perspectives. Tests are performed to show the efficiency and accuracy of this method based on the original data obtained by structured light projection.

Cone Beam Computed Tomography in Veterinary Dentistry

The purpose of this study was to assess the feasibility of cone beam computed tomography (CBCT) in imaging dogs and cats for diagnostic dental veterinary applications. CBCT scans of heads of six dogs and two cats were made. Dental panoramic and multi-planar reformatted (MPR) para-sagittal reconstructions were created using specialized software. Image quality and visibility of anatomical landmarks were subjectively assessed by two observers. Good image quality was obtained for the MPR para-sagittal reconstructions through multiple teeth. The image quality of the panoramic reconstructions of dogs was moderate while the panoramic reconstructions of cats were poor since the images were associated with an increased noise level. Segmental panoramic reconstructions of the mouth seem to be useful for studying the dental anatomy especially in dogs. The results of this study using human dental CBCT technology demonstrate the potential of this scanning technology in veterinary medicine. Unfortunately, the moderate image quality obtained with the CBCT technique reported here seems to be inferior to the diagnostic image quality obtained from 2-dimensional dental radiographs. Further research is required to optimize scanning and reconstruction protocols for veterinary applications.

Design and preliminary study of custom laser scanning cystoscope for automated bladder surveillance

Background: The current gold standard of bladder cancer surveillance, endoscopic visualization, is manually manipulated and still has significant room for improvement in performance and controls. Methods: This paper reports our developments toward automated bladder surveillance that employs a shape memory alloy-based machine-controlled scanning mechanism. In conjunction with the electro-mechanical advances, we use modified commercial post-processing computer vision software capable of converting cystoscopic video of the bladder into stitched panoramas. Results: Experimental results conducted on a synthetic bladder demonstrate that this computer-aided scanning tool can help 82% of the entire bladder surface being scanned. Although the panoramic stitching algorithm increases the field of view and generates reasonable results in many cases, some image matching failures result in incompleteness in its full panoramic reconstruction. Conclusion: Our current study ensures that the automated steering mechanism can follow the desired trajectory to scan the surface of the bladder but must be improved. The current reconstruction algorithm needs further modification. Our methodology may constitute a first step in suggesting a new automated and computer-aided bladder surveillance system.

Adaptive panoramic tomography with a circular rotational movement for the formation of multifocal image layers

Panoramic radiography with which only structures within a certain image layer are in focus and others out of focus on the panoramic image has become a popular imaging technique especially in dentistry. However, the major drawback to the technique is a mismatch between the structures to be focused and the predefined image layer mainly due to the various shapes and sizes of dental arches and/or to malpositioning of the patient. These result in image quality typically inferior to that obtained using intraoral radiographic techniques. In this paper, to overcome these difficulties, we suggest a new panoramic reconstruction algorithm, the so-called adaptive panoramic tomography (APT), capable of reconstructing multifocal image layers with no additional exposure. In order to verify the effectiveness of the proposed algorithm, we performed systematic simulation studies with a circular rotational movement and investigated the image performance.

Direct 3D Information Determination in an Uncalibrated Stereovision System by Using Evolutionary Algorithms

This paper proposes a 3D panoramic shape reconstruction method based on an uncalibrated stereovision system (USS) composed of five cameras circularly located around the object to be analysed. First, some interesting points are detected from markers placed on the object such that they are visible by two successive cameras of the USS. These points are then matched on both images acquired by a couple of successive cameras. This process is repeated for all the couples of cameras. Second, by using an evolutionary algorithm, the depth values of the different interesting points are calculated. A comparison with a traditional method based on calibrated cameras validates the accuracy of 3D information provided by the proposed method. Finally, by combining all the interesting points, a panoramic view of the object is obtained.

Evolutionary-based 3D reconstruction using an uncalibrated stereovision system: application of building a panoramic object view

In this paper, we propose an original evolutionary-based method for 3D panoramic reconstruction from an uncalibrated stereovision system (USS). The USS is composed of five cameras located on an arc of a circle around the object to be analyzed. The main originality of this work concerns the process of the calculation of the 3D information. Actually, with our method, 3D coordinates are directly obtained without any prior estimation of the fundamental matrix. The method operates in two steps. Firstly, points of interest are detected in pairs of images acquired by two consecutive cameras of the USS are matched. And secondly, using evolutionary algorithms, we jointly compute the transformed matrix between the two images and the respective depth of the points of interest. The accuracy of the proposed method is validated through a comparison with the depth values obtained using a traditional method. In order to perform 3D panoramic object reconstruction, the process is repeated for all the pairs of consecutive cameras. The 3D points thus obtained throughout the successive steps of the process which correspond to the different points of interest, are combined in order to obtain a set of 3D points all around the analyzed object.

PANORAMIC 3D RECONSTRUCTION USING STEREO MULTI-PERSPECTIVE PANORAMA

In this paper, we present a novel approach to imaging a panoramic (360°) environment and computing its dense depth map. Our approach adopts a multi-baseline stereo strategy using a set of multi-perspective panoramas where large baseline lengths are available. We design two image acquisition rigs for capturing such multi-perspective panoramas. The first one is composed of two parallel stereo cameras. By rotating the rig about a vertical axis, we generate four multi-perspective panoramas by resampling the regular perspective images captured by the stereo cameras. Then a depth map is estimated from the four multi-perspective panoramas and an original perspective image using a multi-baseline matching technique with different types of epipolar constraints. The second one is composed of a single camera and two mirrors. By rotating the rig, we acquire a spatio-temporal volume that is made up of the sequential images captured by the camera. Then we estimate a depth map by extracting trajectories from the spatio-temporal volume by using a multi-baseline stereo technique by considering occlusions. We can consider both rotating rigs as a single rotating camera with a very large field of view (FOV), that offers a large baseline length in depth estimation. In addition, compared with a previous approach using two multi-perspective panoramas from a single rotating camera, our approach can reduce matching errors due to image noise, repeated patterns, and occlusions by multi-baseline stereo techniques. Experimental results using both synthetic and real images show that our approach produces high quality panoramic 3D reconstruction.

Detection of periodontal bone loss using digital intraoral and cone beam computed tomography images: anin vitroassessment of bony and/or infrabony defects

To explore the diagnostic values of digital intraoral radiography and cone beam CT (CBCT) in the determination of periodontal bone loss, infrabony craters and furcation involvements. Accuracy assessment of the imaging modalities was conducted through bone level measurements, infrabony crater and furcation involvement classifications. For CBCT, images were obtained at 120 kV and 23.87 mAs, and observations were made on a 5.2 mm panoramic reconstruction view and on 0.4 mm thick cross-sectional slices. Intraoral radiographs of a size 2 charge-coupled device (CCD) sensor were obtained using the paralleling technique, at 60 kV (DC) and 0.28 mAs exposure. 71 human cadaver and dry skull bony defects were measured and evaluated by 3 observers. Comparison was made with the gold standard. The mean error (gold standard deviation) of bone level measurements was 0.56 mm for intraoral radiography and 0.47 mm for the CBCT panoramic 5.2 mm reconstruction view. There were no significant differences (P = 0.165) between the two methods. However, on 0.4 mm thick cross-sections, the mean error was 0.29 mm and the Wilcoxon signed-rank test indicated a significant difference when compared with the CCD (P = 0.006). The detection of crater and furcation involvements failed in 29% and 44% for the CCD, respectively, in contrast to 100% detectability for both defects with CBCT. CBCT on the panoramic 5.2 mm reconstruction view allowed comparable measurements of periodontal bone levels and defects as with intraoral radiography. CBCT with 0.4 mm thick cross-sections demonstrated values closer to the gold standard, indicating more accurate assessment of periodontal bone loss. Further research is needed to explore these results in vivo and to determine the use of CBCT in periodontal diagnosis.

Accuracy of measurements of mandibular anatomy in cone beam computed tomography images

Cone beam computed tomography (CBCT) images of ideally positioned and systematically mispositioned dry skulls were measured using two-dimensional and three-dimensional software measurement techniques. Image measurements were compared with caliper measurements of the skulls. Cone beam computed tomography volumes of 28 skulls in ideal, shifted, and rotated positions were assessed by measuring distances between anatomic points and reference wires by using panoramic reconstructions (two-dimensional) and direct measurements from axial slices (three-dimensional). Differences between caliper measurements on skulls and software measurements in images were assessed with paired t tests and analysis of variance (ANOVA). Accuracy of measurement was not significantly affected by alterations in skull position or measurement of right or left sides. For easily visualized orthodontic wires, measurement accuracy was expressed by average errors less than 1.2% for two-dimensional measurement techniques and less than 0.6% for three-dimensional measurement techniques. Anatomic measurements were significantly more variable regardless of measurement technique. Both two-dimensional and three-dimensional techniques provide acceptably accurate measurement of mandibular anatomy. Cone beam computed tomography measurement was not significantly influenced by variation in skull orientation during image acquisition.

Panoramic Reconstruction of the Sea Floor Environment, Using Underwater Photography, Direct Observations, and Field Sketches

Graphic illustration by a scientifically trained artist provides a panoramic view of the sea floor unobtainable directly by photography. Detailed photographs, direct observations, and field sketches are combined to produce a photographically documented hypsographic reconstruction of the sea floor. Dry submersible or diver traverses show only a sequence of closeup photographs because of the visibility limitations presented by the ocean environment. At present the large scale aspects of the topography are best developed from direct observations. The underwater photographs arranged in traverse sequence serve to refresh the memory and provide topographic, geologic, and biologic detail. The resulting detailed illustration gives a three dimensional composite panorama of the sea floor. This combined artist-photographic technique has been applied to: submarine cable routing, habitat emplacement, and geological and biological reconnaissance.

Localization of the mandibular neurovascular bundle using dental magnetic resonance imaging.

To assess the reliability of a commercially available 3D-MPR MRI program for the jaws for imaging the mandibular neurovascular bundle. A gradient echo sequence (TR: 49 ms/TE: 6.3 ms/flip angle: 25 degrees/excitations: 3) with a spectral fat suppression pre-impulse and a voxel size of 0.9 x 0.9 x 0.8 mm was designed. Cross-sectional and panoramic reconstruction of the whole mandible were performed from the axial scans using Easy Vision (Philips, Best, The Netherlands) software package. The ability of differentiate the mandibular neurovascular bundle was assessed in 11 patients. The mandibular neurovascular bundle was clearly visualized in all cases. Dental MRI is a possible alternative to plain films or CT for patients requiring surgery near the mandibular canal.