A novel fault-tolerant computation technique based on array Belief Propagation (BP)-decodable XOR (BP-XOR) codes is proposed for distributed matrix-matrix multiplication. The proposed scheme is shown ...to be configurable and suited for modern hierarchical compute architectures such as Graphical Processing Units (GPUs) equipped with multiple nodes, whereby each has many small independent processing units with increased core-to-core communications. The proposed scheme is shown to outperform a few of the well-known earlier strategies in terms of total end-to-end execution time while in presence of slow nodes, called stragglers . This performance advantage is due to the careful design of array codes which distributes the encoding operation over the cluster (slave) nodes at the expense of increased master-slave communication. An interesting trade-off between end-to-end latency and total communication cost is precisely described. In addition, to be able to address an identified problem of scaling stragglers, an asymptotic version of array BP-XOR codes based on projection geometry is proposed at the expense of some computation overhead. A thorough latency analysis is conducted for all schemes to demonstrate that the proposed scheme achieves order-optimal computation in both the sublinear as well as the linear regimes in the size of the computed product from an end-to-end delay perspective.
This paper presents the implementing multiple fan beam projection technique using optical fibre sensors for a tomography system. From the dynamic experiment of solid/gas flow using plastic beads in a ...gravity flow rig, the designed optical fibre sensors are reliable in measuring the mass flow rate below 40% of flow. Another important matter that has been discussed is the image processing rate or IPR. Generally, the applied image reconstruction algorithms, the construction of the sensor and also the designed software are considered to be reliable and suitable to perform real-time image reconstruction and mass flow rate measurements.
The purpose of this study was to quantify the existing (inevitable) angle which in intraoral radiology appears between tooth length axis and receptor caused by the anatomical situation. Especially in ...the upper jaw, due to its arched anatomy, a true “paralleling technique” is not achievable. The angulation necessarily causes distortion and a foreshortening of the image; hence, the foreshortened image leads to misinterpretations in diagnostics. We investigated the effects of the realistic angulation on these image deteriorating factors. Two hundred ninety-four plaster models of the upper jaw were collected, and the angles between a dummy receptor and the axes of the central incisor or the first molar were measured. For evaluation, a rigid dummy of an intraoral charge-coupled device (CCD) receptor (30 mm × 40 mm) was used. The mean angulation evaluated for central incisors was 36.7° (range 19–56°) and for first molars 42.5° (range 26–56°). This leads to a foreshortening of the tooth ranging from 5.4% to 44.1% in the image, when magnification is neglected. Large angles of up to 56°, in both incisor and molar region, result in a relevant underestimation of true tooth length up to 44%. It is important to note that this error cannot be simply corrected by means of local magnification correction. Techniques should be developed that allow for automated assessment of the effective angle to provide information for distortion correction.
A reference-based radiographic “reference sphere method” (RSM) for accurate length measurements in (dental) projection radiographs for the assessment of tooth length in dry human mandible sections is ...evaluated. RSM determines the depth coordinates of reference spheres placed in the object plane from the elliptical distortion of their shadows. Two segments (one canine and one molar) of dry human mandibles were exposed 95 times at different angulations (0–40°) on a dental charge-coupled device receptor. Three steel spheres (diameters
d
1
= 2.00 mm,
d
2
= 3.00 mm) were attached roughly coplanar with the tooth’s main axis. Radiographs were assessed once by visual inspection plus manual landmark identification with a mouse-driven cursor. The results were compared to the true tooth length assessed after extraction and to a conventional method (C), i.e., the rule of proportion based on magnification of the sphere shadows. Mean relative length error was 2.28% (
d
1
) and 0.46% (
d
2
) for RSM and −13.58% (
d
1
) and −9.90% (
d
2
) for C. For both methods, length errors were significantly (
p
< 0.0001) correlated with the inclination relative to the receptor. RSM allows for complete a posteriori determination of the imaging geometry under the assumption of a known source-to-receptor distance. One specific application is foreshortening correction of objects coplanar with the reference spheres. Remaining errors are mainly due to incorrect landmark definition. In our setup, these were exaggerated by the visual/manual image-evaluation process. Automated image analysis has been shown for similar tasks to minimize these errors considerably.
For successful endodontic treatment, it's imperative to locate and obturate all root canals. As concluded by Ingle, the major cause for failure of root canal therapy is in ability to recognize all ...theexisting canals and subsequent failure in their obturation.
To analyze the canal configuration of the mesio-buccal root of maxillary first permanent molar teeth.
A total of 30 recently extracted human permanent maxillary first molars were collected and stored in a container with 5% Sodium Chloride solution for four days. Teeth with open apices, external resorption, improperly formed roots and teeth with previous restorations were excluded. Using the dental modeling wax, teeth were arranged in a 'U' shaped arch with roots embedded inside the wax and occlusal surface remaining free. 10 teeth were arranged in each arch and three such sample plates were prepared. Flat surface of the base encasing enabled the plate to be mounted on flat plastic bite plate. With bite plate roughly centered in the focal trough area Axial, Coronal and Sagittal section Cone-Beam Computed Tomography (CBCT) images were taken with Kodak 9000 Extra-oral Imaging System. Images displayed on a monitor were inspected by two endodontists using Kodak Dental Imaging Software 3D Module V2.2.
When the data was observed, it was found that 24 teeth out of total 30 teeth examined showed some variation (i.e. possible additional canal) along the length of the mesio-buccal root canal. Out of these 24 teeth, 13 showed presence of additional canal at coronal third, 7 showed presence of additional canal at middle third and four showed presence of additional canal in apical third level. Percentage analysis was done as there was no group comparison to be done.
Cone-Beam Volumetric Tomography (CBVT) evaluation positively identified the variations in mesio-buccal canal in 80% of samples. Out of these, 54.16% were in coronal 3(rd), 29.16% in middle 3(rd) and 16.66% were in apical 3(rd).
Within the limitations of this study, it can be concluded that- (1) more than half of maxillary first molars have four canals and (2) most of the additional canals were located in the MBR and CBVT is a good diagnostic tool to help diagnose these additional canals. Further investigations using larger sample sizes would be helpful.
Three-dimensional tomographic reconstruction using intra-operative mobile C-arms could provide physicians with new and exciting tools for image-guided surgery. Recovery of the projection geometry of ...mobile X-ray systems is a crucial step for such reconstruction procedures. Recent work on medical imaging describes the use of optical or electro-magnetic sensor systems in order to navigate surgical instruments. These systems can also be used for the estimation of C-arm motion, and therefore for the recovery of the projection geometry of the X-ray C-arm. In this case, the mathematical problem that needs to be solved is equivalent to the hand–eye calibration well studied by both the computer vision and robotics community. We first study the recovery of the motion and projection geometry using five different hand–eye calibration methods proposed in the literature. The optical navigation system POLARIS from Northern Digital Inc. was used in our experiments. The results of the estimated motion and projection geometry using the five hand–eye calibration methods are compared with the same results obtained using an off-the-shelf CCD camera attached to the mobile C-arm. The experimental results include three-dimensional tomographic reconstruction results using our mobile C-arm. We show that even though the motion of the C-arm is more precisely recovered using the navigation system, the projection geometry is better estimated using the attached CCD camera.
Three resection–intersection algorithms were applied to simulated projections and clinical data from radiostereometric patients. On simulated data, the more advanced bundle-adjustment-based ...algorithms outperformed the classical Selvik algorithm, even if the error reductions were small for some parameters. On clinical data, the results were inconclusive.
The two different projection geometries had a much larger influence on the error size and distribution. For the biplanar configuration, the position and motion errors were small and almost isotropic. For the uniplanar configuration, the position errors were comparably high and anisotropic, but still resulted in a high accuracy for some motion parameters at the expense of others.
The simplified resection–intersection algorithm by Selvik may still be considered a good and robust algorithm for radiostereometry. More studies will have to be performed to find out how the theoretical advantages of the bundle methods can be utilized in clinical radiostereometry.
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