Science.gov

Sample records for reduce dental artifacts

  1. Monoenergetic computed tomography reconstructions reduce beam hardening artifacts from dental restorations.

    PubMed

    Stolzmann, Paul; Winklhofer, Sebastian; Schwendener, Nicole; Alkadhi, Hatem; Thali, Michael J; Ruder, Thomas D

    2013-09-01

    The aim of this study was to assess the potential of monoenergetic computed tomography (CT) images to reduce beam hardening artifacts in comparison to standard CT images of dental restoration on dental post-mortem CT (PMCT). Thirty human decedents (15 male, 58 ± 22 years) with dental restorations were examined using standard single-energy CT (SECT) and dual-energy CT (DECT). DECT data were used to generate monoenergetic CT images, reflecting the X-ray attenuation at energy levels of 64, 69, 88 keV, and at an individually adjusted optimal energy level called OPTkeV. Artifact reduction and image quality of SECT and monoenergetic CT were assessed objectively and subjectively by two blinded readers. Subjectively, beam artifacts decreased visibly in 28/30 cases after monoenergetic CT reconstruction. Inter- and intra-reader agreement was good (k = 0.72, and k = 0.73 respectively). Beam hardening artifacts decreased significantly with increasing monoenergies (repeated-measures ANOVA p < 0.001). Artifact reduction was greatest on monoenergetic CT images at OPTkeV. Mean OPTkeV was 108 ± 17 keV. OPTkeV yielded the lowest difference between CT numbers of streak artifacts and reference tissues (-163 HU). Monoenergetic CT reconstructions significantly reduce beam hardening artifacts from dental restorations and improve image quality of post-mortem dental CT.

  2. An opposite view data replacement approach for reducing artifacts due to metallic dental objects

    SciTech Connect

    Yazdi, Mehran; Lari, Meghdad Asadi; Bernier, Gaston; Beaulieu, Luc

    2011-04-15

    Purpose: To present a conceptually new method for metal artifact reduction (MAR) that can be used on patients with multiple objects within the scan plane that are also of small sized along the longitudinal (scanning) direction, such as dental fillings. Methods: The proposed algorithm, named opposite view replacement, achieves MAR by first detecting the projection data affected by metal objects and then replacing the affected projections by the corresponding opposite view projections, which are not affected by metal objects. The authors also applied a fading process to avoid producing any discontinuities in the boundary of the affected projection areas in the sinogram. A skull phantom with and without a variety of dental metal inserts was made to extract the performance metric of the algorithm. A head and neck case, typical of IMRT planning, was also tested. Results: The reconstructed CT images based on this new replacement scheme show a significant improvement in image quality for patients with metallic dental objects compared to the MAR algorithms based on the interpolation scheme. For the phantom, the authors showed that the artifact reduction algorithm can efficiently recover the CT numbers in the area next to the metallic objects. Conclusions: The authors presented a new and efficient method for artifact reduction due to multiple small metallic objects. The obtained results from phantoms and clinical cases fully validate the proposed approach.

  3. Dental material artifacts on MR images.

    PubMed

    Hinshaw, D B; Holshouser, B A; Engstrom, H I; Tjan, A H; Christiansen, E L; Catelli, W F

    1988-03-01

    Magnetic resonance (MR) imaging of the head and neck is becoming an important aid in evaluating pathologic conditions of the brain, midface, and pharynx. Certain dental materials cause artifacts during MR imaging of the lower midface. These artifacts can obscure the normal anatomy. This study describes the degree of artifact production caused by various materials commonly used in dental restorations. Of the materials tested, those causing artifacts were made of stainless steel, such as orthodontic bands used for braces, and pins or posts that are commonly drilled into teeth to provide structure or stability before filling. Materials used as temporary or permanent fillings or crowns--such as amalgam, gold alloy, aluminum, microfilled resin, and polyvinyl acrylics--did not cause artifacts in the images.

  4. Reducing Artifacts in TMS-Evoked EEG

    NASA Astrophysics Data System (ADS)

    Fuertes, Juan José; Travieso, Carlos M.; Álvarez, A.; Ferrer, M. A.; Alonso, J. B.

    Transcranial magnetic stimulation induces weak currents within the cranium to activate neuronal firing and its response is recorded using electroencephalography in order to study the brain directly. However, different artifacts contaminate the results. The goal of this study is to process these artifacts and reduce them digitally. Electromagnetic, blink and auditory artifacts are considered, and Signal-Space Projection, Independent Component Analysis and Wiener Filtering methods are used to reduce them. These last two produce a successful solution for electromagnetic artifacts. Regarding the other artifacts, processed with Signal-Space Projection, the method reduces the artifact but modifies the signal as well. Nonetheless, they are modified in an exactly known way and the vector used for the projection is conserved to be taken into account when analyzing the resulting signals. A system which combines the proposed methods would improve the quality of the information presented to physicians.

  5. Automatic correction of dental artifacts in PET/MRI

    PubMed Central

    Ladefoged, Claes N.; Andersen, Flemming L.; Keller, Sune. H.; Beyer, Thomas; Law, Ian; Højgaard, Liselotte; Darkner, Sune; Lauze, Francois

    2015-01-01

    Abstract. A challenge when using current magnetic resonance (MR)-based attenuation correction in positron emission tomography/MR imaging (PET/MRI) is that the MRIs can have a signal void around the dental fillings that is segmented as artificial air-regions in the attenuation map. For artifacts connected to the background, we propose an extension to an existing active contour algorithm to delineate the outer contour using the nonattenuation corrected PET image and the original attenuation map. We propose a combination of two different methods for differentiating the artifacts within the body from the anatomical air-regions by first using a template of artifact regions, and second, representing the artifact regions with a combination of active shape models and k-nearest-neighbors. The accuracy of the combined method has been evaluated using 25 F18-fluorodeoxyglucose PET/MR patients. Results showed that the approach was able to correct an average of 97±3% of the artifact areas. PMID:26158104

  6. Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials

    PubMed Central

    Klinke, Thomas; Daboul, Amro; Maron, Juliane; Gredes, Tomasz; Puls, Ralf; Jaghsi, Ahmad; Biffar, Reiner

    2012-01-01

    Background Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a common problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the artifacts produced by different dental restoration materials in CT and MRI images. Methods Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and embedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples and evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software. Results In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts produced in both MRI and CT images were categorized according to the size of the artifact. Significance Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth elements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings would help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and CT images. PMID:22384071

  7. Metal artifact reduction in dental CT images using polar mathematical morphology.

    PubMed

    Naranjo, Valery; Lloréns, Roberto; Alcañiz, Mariano; López-Mir, Fernando

    2011-04-01

    Most dental implant planning systems use a 3D representation of the CT scan of the patient under study as it provides a more intuitive view of the human jaw. The presence of metallic objects in human jaws, such as amalgam or gold fillings, provokes several artifacts like streaking and beam hardening which makes the reconstruction process difficult. In order to reduce these artifacts, several methods have been proposed using the raw data, directly obtained from the tomographs, in different ways. However, in DICOM-based applications this information is not available, and thus the need of a new method that handles this task in the DICOM domain. The presented method performs a morphological filtering in the polar domain yielding output images less affected by artifacts (even in cases of multiple metallic objects) without causing significant smoothing of the anatomic structures, which allows a great improvement in the 3D reconstruction. The algorithm has been automated and compared to other image denoising methods with successful results. PMID:21227532

  8. Method for reducing windmill artifacts in multislice CT images

    NASA Astrophysics Data System (ADS)

    Brown, Kevin M.; Žabic, Stanislav

    2011-03-01

    Thin-slice images reconstructed from helical multi-slice CT scans typically display artifacts known as windmill artifacts, which arise from not satisfying the Nyquist sampling criteria in the patient longitudinal direction. Since these are essentially aliasing artifacts, they can be reduced or removed by trading off resolution, either globally (by reconstructing thicker slices) or locally (by local smoothing of the strong gradients). The obvious drawback to this approach is the associated loss in resolution. Another approach is to utilize an x-ray tube with the capability to modulate the focal spot in the z-direction, to effectively improve the sampling rate. This work presents a new method for windmill artifact reduction based on total variation minimization in the image domain, which is capable of removing windmill artifacts while at the same time preserving the resolution of anatomic structures within the images. This is a big improvement over previous reconstruction methods that sacrifice resolution, and it provides practically the same benefits as a z-switching x-ray tube with a much simpler impact to the overall CT system.

  9. A fast algorithm to reduce gibbs ringing artifact in MRI.

    PubMed

    Huang, Xin; Chen, Wufan

    2005-01-01

    In magnetic resonance imaging, a finite number of k-space data are often collected in order to decrease the acquisition time. The partial k-space data lead to the famous Gibbs ringing artifact with Fourier transform method. The Gegenbauer reconstruction method has been shown to effectively eliminate the Gibbs ringing artifact and restore high resolution. However, the disadvantages of using the Gegenbauer method are more computational time and complicated the choice of parameters. In this paper, we improve the Gegenbauer method by introducing the inverse polynomial reconstruction method and replacing the Gegenbauer polynomials with the Chebyshev polynomials. The new method effectively reduces the reconstructed error and computational cost without any requirement for selection of parameters. Additionally, we present an improved edge detection method which can achieve more accurate edge and make our new reconstruction method more efficient. The proposed method is verified with experiment of the artifact removal. PMID:17282451

  10. Interpolation strategies for reducing IFOV artifacts in microgrid polarimeter imagery.

    PubMed

    Ratliff, Bradley M; LaCasse, Charles F; Tyo, J Scott

    2009-05-25

    Microgrid polarimeters are composed of an array of micro-polarizing elements overlaid upon an FPA sensor. In the past decade systems have been designed and built in all regions of the optical spectrum. These systems have rugged, compact designs and the ability to obtain a complete set of polarimetric measurements during a single image capture. However, these systems acquire the polarization measurements through spatial modulation and each measurement has a varying instantaneous field-of-view (IFOV). When these measurements are combined to estimate the polarization images, strong edge artifacts are present that severely degrade the estimated polarization imagery. These artifacts can be reduced when interpolation strategies are first applied to the intensity data prior to Stokes vector estimation. Here we formally study IFOV error and the performance of several bilinear interpolation strategies used for reducing it. PMID:19466161

  11. Artifacts

    NASA Technical Reports Server (NTRS)

    Harris, Samantha

    2009-01-01

    NASA Headquarters sent a list of items to KSC that were deemed potential artifacts. These items played arole in the Shuttle Program's development and maintenance. Because these items are national assets, many are of interest to museums, schools, other government entities, etc. upon the Space Shuttle's retirement. The list contains over 500 items. All of these items need to be located, photographed, and catalogued with accompanying specific data that needs to be gathered. Initial research suggests that this is a time, labor, and cost intensive project. The purpose of my project was to focus on 20-60 of these 500 items, gather the necessary data, and compile them in a way that can be added to by other users when/if the project goes into full effect.

  12. Metal Artifact Reduction and Segmentation of Dental Computerized Tomography Images Using Least Square Support Vector Machine and Mean Shift Algorithm

    PubMed Central

    Mortaheb, Parinaz; Rezaeian, Mehdi

    2016-01-01

    Segmentation and three-dimensional (3D) visualization of teeth in dental computerized tomography (CT) images are of dentists’ requirements for both abnormalities diagnosis and the treatments such as dental implant and orthodontic planning. On the other hand, dental CT image segmentation is a difficult process because of the specific characteristics of the tooth's structure. This paper presents a method for automatic segmentation of dental CT images. We present a multi-step method, which starts with a preprocessing phase to reduce the metal artifact using the least square support vector machine. Integral intensity profile is then applied to detect each tooth's region candidates. Finally, the mean shift algorithm is used to partition the region of each tooth, and all these segmented slices are then applied for 3D visualization of teeth. Examining the performance of our proposed approach, a set of reliable assessment metrics is utilized. We applied the segmentation method on 14 cone-beam CT datasets. Functionality analysis of the proposed method demonstrated precise segmentation results on different sample slices. Accuracy analysis of the proposed method indicates that we can increase the sensitivity, specificity, precision, and accuracy of the segmentation results by 83.24%, 98.35%, 72.77%, and 97.62% and decrease the error rate by 2.34%. The experimental results show that the proposed approach performs well on different types of CT images and has better performance than all existing approaches. Moreover, segmentation results can be more accurate by using the proposed algorithm of metal artifact reduction in the preprocessing phase. PMID:27014607

  13. Improved image decompression for reduced transform coding artifacts

    NASA Technical Reports Server (NTRS)

    Orourke, Thomas P.; Stevenson, Robert L.

    1994-01-01

    The perceived quality of images reconstructed from low bit rate compression is severely degraded by the appearance of transform coding artifacts. This paper proposes a method for producing higher quality reconstructed images based on a stochastic model for the image data. Quantization (scalar or vector) partitions the transform coefficient space and maps all points in a partition cell to a representative reconstruction point, usually taken as the centroid of the cell. The proposed image estimation technique selects the reconstruction point within the quantization partition cell which results in a reconstructed image which best fits a non-Gaussian Markov random field (MRF) image model. This approach results in a convex constrained optimization problem which can be solved iteratively. At each iteration, the gradient projection method is used to update the estimate based on the image model. In the transform domain, the resulting coefficient reconstruction points are projected to the particular quantization partition cells defined by the compressed image. Experimental results will be shown for images compressed using scalar quantization of block DCT and using vector quantization of subband wavelet transform. The proposed image decompression provides a reconstructed image with reduced visibility of transform coding artifacts and superior perceived quality.

  14. Local regularization of tilt projections reduces artifacts in electron tomography.

    PubMed

    Maiorca, Mauro; Millet, Coralie; Hanssen, Eric; Abbey, Brian; Kazmierczak, Edmund; Tilley, Leann

    2014-04-01

    Electron tomography produces very high resolution 3D image volumes useful for investigating the structure and function of cellular components. Unfortunately, unavoidable discontinuities and physical constraints in the acquisition geometry lead to a range of artifacts that can affect the reconstructed image. In particular, highly electron dense regions, such as gold nanoparticles, can hide proximal biological structures and degrade the overall quality of the reconstructed tomograms. In this work we introduce a pre-reconstruction non-conservative non-linear isotropic diffusion (NID) filter that automatically identifies and reduces local irregularities in the tilt projections. We illustrate the improvement in quality obtained using this approach for reconstructed tomograms generated from samples of malaria parasite-infected red blood cells. A quantitative and qualitative evaluation for our approach on both simulated and real data is provided.

  15. Adaptive motion artifact reducing algorithm for wrist photoplethysmography application

    NASA Astrophysics Data System (ADS)

    Zhao, Jingwei; Wang, Guijin; Shi, Chenbo

    2016-04-01

    Photoplethysmography (PPG) technology is widely used in wearable heart pulse rate monitoring. It might reveal the potential risks of heart condition and cardiopulmonary function by detecting the cardiac rhythms in physical exercise. However the quality of wrist photoelectric signal is very sensitive to motion artifact since the thicker tissues and the fewer amount of capillaries. Therefore, motion artifact is the major factor that impede the heart rate measurement in the high intensity exercising. One accelerometer and three channels of light with different wavelengths are used in this research to analyze the coupled form of motion artifact. A novel approach is proposed to separate the pulse signal from motion artifact by exploiting their mixing ratio in different optical paths. There are four major steps of our method: preprocessing, motion artifact estimation, adaptive filtering and heart rate calculation. Five healthy young men are participated in the experiment. The speeder in the treadmill is configured as 12km/h, and all subjects would run for 3-10 minutes by swinging the arms naturally. The final result is compared with chest strap. The average of mean square error (MSE) is less than 3 beats per minute (BPM/min). Proposed method performed well in intense physical exercise and shows the great robustness to individuals with different running style and posture.

  16. A novel method of removing artifacts because of metallic dental restorations in 3-D CT images of jaw bone.

    PubMed

    Sohmura, Taiji; Hojoh, Hirokazu; Kusumoto, Naoki; Nishida, Masahiko; Wakabayashi, Kazumichi; Takahashi, Junzo

    2005-12-01

    CT images, especially in a three-dimensional (3-D) mode, give valuable information for oral implant surgery. However, image quality is often severely compromised by artifacts originating from metallic dental restorations, and an effective solution for artifacts is being sought. This study attempts to substitute the damaged areas of the jaw bone images with dental cast model images obtained by CT. The position of the dental cast images was registered to that of the jaw bone images using a devised interface that is composed of an occlusal bite made of self-curing acrylic resin and a marker plate made of gypsum. The patient adapted this interface, and CT images of the stomatognathic system were filmed. On the other hand, this interface was placed between the upper and lower cast models and filmed by CT together with the cast models. The position of the marker plate imaged with the dental casts was registered to those adapted by the patient. The error of registration was examined to be 0.25 mm, which was satisfactory for clinical application. The damaged region in the cranial bone images as an obstacle for implant surgery was removed and substituted with the trimmed images of the dental cast. In the method developed here, the images around the metallic compounds severely damaged by artifacts were successfully reconstructed, and the stomatognathic system images became clear, and this is useful for implant surgery.

  17. Using an injection signal to reduce motion artifacts in capacitive ECG measurements.

    PubMed

    Serteyn, Aline; Vullings, Rik; Meftah, Mohammed; Bergmans, Jan

    2013-01-01

    Capacitive electrodes are a promising alternative to the conventional adhesive ECG electrodes. They provide more comfort to the patient when integrated in everyday objects (e.g. beds or seats) for long-term monitoring. However, the application of such electrodes is limited by their high sensitivity to motion artifacts. Artifacts caused by variation of the coupling capacitance are studied here. An injection signal is proposed to track these variations in real-time. An adaptive filter then estimates the motion artifact and cancels it from the recorded ECG. The amplitude of the motion artifact is reduced in average by 29 dB in simulation and by 20 dB in a lab environment. Our method has the advantages that it is able to reduce motion artifacts occurring in the frequency band of the ECG and that it does not require knowledge about the measurement system.

  18. Potential hazards and artifacts of ferromagnetic and nonferromagnetic surgical and dental materials and devices in nuclear magnetic resonance imaging

    SciTech Connect

    New, P.F.J.; Rosen, B.R.; Brady, T.J.; Buonanno, F.S.; Kistler, J.P.; Burt, C.T.; Hinshaw, W.S.; Newhouse, J.H.; Pohost, G.M.; Taveras, J.M.

    1983-04-01

    The risks to patients with metal surgical implants who are undergoing nuclear magnetic resonance (NMR) imaging and the artifacts caused by such implants were studied. Twenty-one aneurysm and other hemostatic clips and a variety of other materials (e.g., dental amalgam, 14 karat gold) were used. Longitudinal forces and torques were found to be exerted upon 16 of the 21 clips. With five aneurysm clips, forces and torques sufficient to produce risk of hemorrhage from dislocation of the clip from the vessel or aneurysm, or cerebral injury by clip displacement without dislodgement were identified. The induced ferromagnetism was shown to be related to the composition of the alloys from which the clips were manufactured. Clips with 10-14% nickel are evidently without sufficient induced ferromagnetism to cause hazard. The extent of NMR imaging artifacts was greater for materials with measurable ferromagnetic properties, but metals without measurable ferromagnetism in our tests also resulted in significant artifacts. Dental amalgam and 14 karat gold produced no imaging artifacts, but stainless steels in dentures and orthodontic braces produced extensive artifacts in the facial region.

  19. Evaluation of 4D CT acquisition methods designed to reduce artifacts.

    PubMed

    Castillo, Sarah J; Castillo, Richard; Castillo, Edward; Pan, Tinsu; Ibbott, Geoffrey; Balter, Peter; Hobbs, Brian; Guerrero, Thomas

    2015-03-08

    Four-dimensional computed tomography (4D CT) is used to account for respiratory motion in radiation treatment planning, but artifacts resulting from the acquisition and postprocessing limit its accuracy. We investigated the efficacy of three experimental 4D CT acquisition methods to reduce artifacts in a prospective institutional review board approved study. Eighteen thoracic patients scheduled to undergo radiation therapy received standard clinical 4D CT scans followed by each of the alternative 4D CT acquisitions: 1) data oversampling, 2) beam gating with breathing irregularities, and 3) rescanning the clinical acquisition acquired during irregular breathing. Relative values of a validated correlation-based artifact metric (CM) determined the best acquisition method per patient. Each 4D CT was processed by an extended phase sorting approach that optimizes the quantitative artifact metric (CM sorting). The clinical acquisitions were also postprocessed by phase sorting for artifact comparison of our current clinical implementation with the experimental methods. The oversampling acquisition achieved the lowest artifact presence among all acquisitions, achieving a 27% reduction from the current clinical 4D CT implementation (95% confidence interval = 34-20). The rescan method presented a significantly higher artifact presence from the clinical acquisition (37%; p < 0.002), the gating acquisition (26%; p < 0.005), and the oversampling acquisition (31%; p < 0.001), while the data lacked evidence of a significant difference between the clinical, gating, and oversampling methods. The oversampling acquisition reduced artifact presence from the current clinical 4D CT implementation to the largest degree and provided the simplest and most reproducible implementation. The rescan acquisition increased artifact presence significantly, compared to all acquisitions, and suffered from combination of data from independent scans over which large internal anatomic shifts occurred.

  20. Dual energy CT: How well can pseudo-monochromatic imaging reduce metal artifacts?

    SciTech Connect

    Kuchenbecker, Stefan Faby, Sebastian; Sawall, Stefan; Kachelrieß, Marc; Lell, Michael

    2015-02-15

    Purpose: Dual Energy CT (DECT) provides so-called monoenergetic images based on a linear combination of the original polychromatic images. At certain patient-specific energy levels, corresponding to certain patient- and slice-dependent linear combination weights, e.g., E = 160 keV corresponds to α = 1.57, a significant reduction of metal artifacts may be observed. The authors aimed at analyzing the method for its artifact reduction capabilities to identify its limitations. The results are compared with raw data-based processing. Methods: Clinical DECT uses a simplified version of monochromatic imaging by linearly combining the low and the high kV images and by assigning an energy to that linear combination. Those pseudo-monochromatic images can be used by radiologists to obtain images with reduced metal artifacts. The authors analyzed the underlying physics and carried out a series expansion of the polychromatic attenuation equations. The resulting nonlinear terms are responsible for the artifacts, but they are not linearly related between the low and the high kV scan: A linear combination of both images cannot eliminate the nonlinearities, it can only reduce their impact. Scattered radiation yields additional noncanceling nonlinearities. This method is compared to raw data-based artifact correction methods. To quantify the artifact reduction potential of pseudo-monochromatic images, they simulated the FORBILD abdomen phantom with metal implants, and they assessed patient data sets of a clinical dual source CT system (100, 140 kV Sn) containing artifacts induced by a highly concentrated contrast agent bolus and by metal. In each case, they manually selected an optimal α and compared it to a raw data-based material decomposition in case of simulation, to raw data-based material decomposition of inconsistent rays in case of the patient data set containing contrast agent, and to the frequency split normalized metal artifact reduction in case of the metal

  1. Approximation error method can reduce artifacts due to scalp blood flow in optical brain activation imaging

    NASA Astrophysics Data System (ADS)

    Heiskala, Juha; Kolehmainen, Ville; Tarvainen, Tanja; Kaipio, Jari. P.; Arridge, Simon R.

    2012-09-01

    Diffuse optical tomography can image the hemodynamic response to an activation in the human brain by measuring changes in optical absorption of near-infrared light. Since optodes placed on the scalp are used, the measurements are very sensitive to changes in optical attenuation in the scalp, making optical brain activation imaging susceptible to artifacts due to effects of systemic circulation and local circulation of the scalp. We propose to use the Bayesian approximation error approach to reduce these artifacts. The feasibility of the approach is evaluated using simulated brain activations. When a localized cortical activation occurs simultaneously with changes in the scalp blood flow, these changes can mask the cortical activity causing spurious artifacts. We show that the proposed approach is able to recover from these artifacts even when the nominal tissue properties are not well known.

  2. Correction of dental artifacts within the anatomical surface in PET/MRI using active shape models and k-nearest-neighbors

    NASA Astrophysics Data System (ADS)

    Ladefoged, Claes N.; Andersen, Flemming L.; Keller, Sune H.; Beyer, Thomas; Højgaard, Liselotte; Lauze, François

    2014-03-01

    In combined PET/MR, attenuation correction (AC) is performed indirectly based on the available MR image information. Metal implant-induced susceptibility artifacts and subsequent signal voids challenge MR-based AC. Several papers acknowledge the problem in PET attenuation correction when dental artifacts are ignored, but none of them attempts to solve the problem. We propose a clinically feasible correction method which combines Active Shape Models (ASM) and k- Nearest-Neighbors (kNN) into a simple approach which finds and corrects the dental artifacts within the surface boundaries of the patient anatomy. ASM is used to locate a number of landmarks in the T1-weighted MR-image of a new patient. We calculate a vector of offsets from each voxel within a signal void to each of the landmarks. We then use kNN to classify each voxel as belonging to an artifact or an actual signal void using this offset vector, and fill the artifact voxels with a value representing soft tissue. We tested the method using fourteen patients without artifacts, and eighteen patients with dental artifacts of varying sizes within the anatomical surface of the head/neck region. Though the method wrongly filled a small volume in the bottom part of a maxillary sinus in two patients without any artifacts, due to their abnormal location, it succeeded in filling all dental artifact regions in all patients. In conclusion, we propose a method, which combines ASM and kNN into a simple approach which, as the results show, succeeds to find and correct the dental artifacts within the anatomical surface.

  3. Reduced aliasing artifacts using variable-density k-space sampling trajectories.

    PubMed

    Tsai, C M; Nishimura, D G

    2000-03-01

    A variable-density k-space sampling method is proposed to reduce aliasing artifacts in MR images. Because most of the energy of an image is concentrated around the k-space center, aliasing artifacts will contain mostly low-frequency components if the k-space is uniformly undersampled. On the other hand, because the outer k-space region contains little energy, undersampling that region will not contribute severe aliasing artifacts. Therefore, a variable-density trajectory may sufficiently sample the central k-space region to reduce low-frequency aliasing artifacts and may undersample the outer k-space region to reduce scan time and to increase resolution. In this paper, the variable-density sampling method was implemented for both spiral imaging and two-dimensional Fourier transform (2DFT) imaging. Simulations, phantom images and in vivo cardiac images show that this method can significantly reduce the total energy of aliasing artifacts. In general, this method can be applied to all types of k-space sampling trajectories.

  4. Reducing metal artifacts in cone-beam CT images by preprocessing projection data

    SciTech Connect

    Zhang Yongbin; Zhang Lifei; Zhu, X. Ronald; Lee, Andrew K.; Chambers, Mark; Dong Lei . E-mail: ldong@mdanderson.org

    2007-03-01

    Purpose: Computed tomography (CT) streak artifacts caused by metallic implants remain a challenge for the automatic processing of image data. The impact of metal artifacts in the soft-tissue region is magnified in cone-beam CT (CBCT), because the soft-tissue contrast is usually lower in CBCT images. The goal of this study was to develop an effective offline processing technique to minimize the effect. Methods and Materials: The geometry calibration cue of the CBCT system was used to track the position of the metal object in projection views. The three-dimensional (3D) representation of the object can be established from only two user-selected viewing angles. The position of the shadowed region in other views can be tracked by projecting the 3D coordinates of the object. Automatic image segmentation was used followed by a Laplacian diffusion method to replace the pixels inside the metal object with the boundary pixels. The modified projection data were then used to reconstruct a new CBCT image. The procedure was tested in phantoms, prostate cancer patients with implanted gold markers and metal prosthesis, and a head-and-neck patient with dental amalgam in the teeth. Results: Both phantom and patient studies demonstrated that the procedure was able to minimize the metal artifacts. Soft-tissue visibility was improved near or away from the metal object. The processing time was 1-2 s per projection. Conclusion: We have implemented an effective metal artifact-suppressing algorithm to improve the quality of CBCT images.

  5. Functionalized bio-artifact fabricated via selective slurry extrusion. Part 2: Fabrication of ceramic dental crown.

    PubMed

    Zhu, D B; Liang, J P; Qu, Y X; Duan, G L

    2014-05-01

    Functionalized ceramic dental crown was successfully fabricated through selective slurry extrusion (SSE) based technique of solid freeform fabrication (also known as rapid prototyping). After sintering, the decomposed tourmaline powders were embedded in ZrO2 matrix. The far infrared emission properties of the ceramic dental crown were improved due to the increase of the numbers of infrared active bonds from tourmaline. This new dental restoration process presents potential to provide dental patients with functionalized artificial teeth, which benefits the body health by the way of emitting far infrared rays in ambient temperatures. PMID:24734617

  6. Functionalized bio-artifact fabricated via selective slurry extrusion. Part 2: Fabrication of ceramic dental crown.

    PubMed

    Zhu, D B; Liang, J P; Qu, Y X; Duan, G L

    2014-05-01

    Functionalized ceramic dental crown was successfully fabricated through selective slurry extrusion (SSE) based technique of solid freeform fabrication (also known as rapid prototyping). After sintering, the decomposed tourmaline powders were embedded in ZrO2 matrix. The far infrared emission properties of the ceramic dental crown were improved due to the increase of the numbers of infrared active bonds from tourmaline. This new dental restoration process presents potential to provide dental patients with functionalized artificial teeth, which benefits the body health by the way of emitting far infrared rays in ambient temperatures.

  7. An improved correction method for reducing off-focal artifacts in CT imaging.

    PubMed

    Sun, Haining; Qiu, Shaokun; Lou, Shanshan; Li, Changjun; Liu, Jinjun; Li, Shuangxue; Jiang, Genmiao

    2005-01-01

    This paper presents a new method to reduce halo artifacts in Computed Tomography (CT) images, which blur the image edges and descend the image quality. Off-focal radiation is main ill factor leading to these halo artifacts. To reduce the off-focal effects, we adopt a pre-processing method to filter the sampling data directly before reconstruction, instead of post-processing method such as edge enhancing on the reconstructed images. Different from the prior pre-processing method, we also present a new and more practical method to obtain convolution kernel and a simpler formula in this paper. Results show that after calibration by the new practical method, the off-focal radiation effects were reduced efficiently, the edges were enhanced and the image quality was improved without increasing noise. PMID:17281695

  8. The effectiveness of dental floss in reducing gingival inflammation.

    PubMed

    Finkelstein, P; Grossman, E

    1979-03-01

    Unwaxed and waxed dental floss were clinically evaluated for effectiveness in reducing gingival inflammation. Two different scoring methods were employed. Both types of floss, when administered by a dental hygienist, were very effective, but no significant differences between them could be found. Both scoring methods led to the same conclusions, but one was more sensitive and provided more detailed information.

  9. SU-E-T-365: Dosimetric Impact of Dental Amalgam CT Image Artifacts On IMRT and VMAT Head and Neck Plans

    SciTech Connect

    Cao, N; Young, L; Parvathaneni, U; Liao, J; Richard, P; Ford, E; Sandison, G

    2014-06-01

    Purpose: The presence of high density dental amalgam in patient CT image data sets causes dose calculation errors for head and neck (HN) treatment planning. This study assesses and compares dosimetric variations in IMRT and VMAT treatment plans due to dental artifacts. Methods: Sixteen HN patients with similar treatment sites (oropharynx), tumor volume and extensive dental artifacts were divided into two groups: IMRT (n=8, 6 to 9 beams) and VMAT (n=8, 2 arcs with 352° rotation). All cases were planned with the Pinnacle 9.2 treatment planning software using the collapsed cone convolution superposition algorithm and a range of prescription dose from 60 to 72Gy. Two different treatment plans were produced, each based on one of two image sets: (a)uncorrected; (b)dental artifacts density overridden (set to 1.0g/cm{sup 3}). Differences between the two treatment plans for each of the IMRT and VMAT techniques were quantified by the following dosimetric parameters: maximum point dose, maximum spinal cord and brainstem dose, mean left and right parotid dose, and PTV coverage (V95%Rx). Average differences generated for these dosimetric parameters were compared between IMRT and VMAT plans. Results: The average absolute dose differences (plan a minus plan b) for the VMAT and IMRT techniques, respectively, caused by dental artifacts were: 2.2±3.3cGy vs. 37.6±57.5cGy (maximum point dose, P=0.15); 1.2±0.9cGy vs. 7.9±6.7cGy (maximum spinal cord dose, P=0.026); 2.2±2.4cGy vs. 12.1±13.0cGy (maximum brainstem dose, P=0.077); 0.9±1.1cGy vs. 4.1±3.5cGy (mean left parotid dose, P=0.038); 0.9±0.8cGy vs. 7.8±11.9cGy (mean right parotid dose, P=0.136); 0.021%±0.014% vs. 0.803%±1.44% (PTV coverage, P=0.17). Conclusion: For the HN plans studied, dental artifacts demonstrated a greater dose calculation error for IMRT plans compared to VMAT plans. Rotational arcs appear on the average to compensate dose calculation errors induced by dental artifacts. Thus, compared to VMAT, density

  10. An aliasing artifacts reducing approach with random undersampling for spatiotemporally encoded single-shot MRI.

    PubMed

    Chen, Lin; Bao, Lijun; Li, Jing; Cai, Shuhui; Cai, Congbo; Chen, Zhong

    2013-12-01

    Compared to the echo planar imaging (EPI), spatiotemporally encoded (SPEN) single-shot MRI holds better immunity to the field inhomogeneity, while retaining comparable spatial and temporal resolutions after the super-resolved reconstruction. Though various reconstruction methods have been proposed, the reconstructed SPEN images usually contain aliasing artifacts because of vast undersampling. A hybrid scheme based on random sampling, singular value decomposition (SVD) and compressed sensing (CS) was introduced to reduce these aliasing artifacts and improve the image quality. The efficiency of this hybrid scheme was demonstrated by numerical simulations and experiments on water phantom and in vivo rat brain. The hybrid scheme provided herein would benefit the SPEN approach in vast undersampling situation.

  11. A conventional procedure to reduce Asn deamidation artifacts during trypsin peptide mapping.

    PubMed

    Kori, Yekaterina; Patel, Rekha; Neill, Alyssa; Liu, Hongcheng

    2016-01-15

    Asn deamidation is a common post-translational modification of proteins with significant biological consequences. Asn deamidation can cause changes in structure, stability and function of proteins. LC-MS peptide mapping is the most widely used method to detect and quantify Asn deamidation. However, a significant amount of deamidation can occur during sample preparation for peptide mapping, making it challenging to accurately determine the original level of deamidation. Although several protocols to reduce procedure-induced deamidation have been reported, they either require special procedural steps or are not optimal for maintaining trypsin activity. In the current study, several commonly used buffers that are optimal for trypsin activity were evaluated. The results demonstrated that much lower levels of Asn deamidation artifacts were observed when Tris buffer was used, especially at lower concentrations. The addition of 10% acetonitrile further reduced the levels of Asn deamidation artifacts. The utility of the optimized procedure was demonstrated by the digestion of a recombinant monoclonal antibody. The proposed procedure can be readily applied to any laboratory settings as it does not require any special reagents or procedures. PMID:26720699

  12. Reconcilable differences: the use of reference material to reduce methodological artifacts in the reporting of organochlorine pesticides and polychlorinated biphenyls.

    PubMed

    de Solla, Shane R; Weseloh, D V Chip; Letcher, Robert J; Hebert, Craig E

    2010-01-01

    Numerous long-term monitoring programs have assessed spatial and temporal trends of organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Changes in analytical approaches (e.g., gas chromatography coupled with electron capture detection [GC-ECD] versus mass spectrometric detection [GC-MSD]) can reveal artifacts in the reported concentrations. In-house reference material (RM) was used to determine the analytical artifacts in the measurement of OCs and PCBs in Great Lake herring gull eggs previously analyzed from 1994 to 1996 (GC-ECD) and 1997 to 1999 (GC-MSD). Approximately 19.0% of the variability of PCB congeners in gull eggs was associated with analytical artifacts, and differences among colonies were obscured. Although the discrepancy in sum PCBs (SigmaPCBs) was fairly small (2.1%), some congeners varied considerably between methods (> 60%). After statistically removing the artifacts, only 1.4% of the variability in PCBs of herring gull eggs was associated with artifacts, and differences among gull colonies became apparent. After excluding OCs near the detection limit in the RM, statistically removing the artifacts reduced some of the differences between methods for OCs. Analytical artifacts may potentially render inferences difficult, confounded, and erroneous. When combining contaminant data obtained using different methods, the methods should be assumed to give different results unless demonstrated otherwise. Assessments of the compatibility of analytical methodologies should be made using an appropriate RM.

  13. Reconcilable differences: the use of reference material to reduce methodological artifacts in the reporting of organochlorine pesticides and polychlorinated biphenyls.

    PubMed

    de Solla, Shane R; Weseloh, D V Chip; Letcher, Robert J; Hebert, Craig E

    2010-01-01

    Numerous long-term monitoring programs have assessed spatial and temporal trends of organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Changes in analytical approaches (e.g., gas chromatography coupled with electron capture detection [GC-ECD] versus mass spectrometric detection [GC-MSD]) can reveal artifacts in the reported concentrations. In-house reference material (RM) was used to determine the analytical artifacts in the measurement of OCs and PCBs in Great Lake herring gull eggs previously analyzed from 1994 to 1996 (GC-ECD) and 1997 to 1999 (GC-MSD). Approximately 19.0% of the variability of PCB congeners in gull eggs was associated with analytical artifacts, and differences among colonies were obscured. Although the discrepancy in sum PCBs (SigmaPCBs) was fairly small (2.1%), some congeners varied considerably between methods (> 60%). After statistically removing the artifacts, only 1.4% of the variability in PCBs of herring gull eggs was associated with artifacts, and differences among gull colonies became apparent. After excluding OCs near the detection limit in the RM, statistically removing the artifacts reduced some of the differences between methods for OCs. Analytical artifacts may potentially render inferences difficult, confounded, and erroneous. When combining contaminant data obtained using different methods, the methods should be assumed to give different results unless demonstrated otherwise. Assessments of the compatibility of analytical methodologies should be made using an appropriate RM. PMID:20821415

  14. Using data redundancy gained by patch overlaps to reduce truncation artifacts in magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Ahlborg, M.; Kaethner, C.; Knopp, T.; Szwargulski, P.; Buzug, T. M.

    2016-06-01

    The imaging technology magnetic particle imaging allows the detection of magnetic material, in particular superparamagnetic nanoparticles, by remagnetization of the material via magnetic fields. The application is aimed at medical imaging where the particles are applied as tracer directly into the blood stream. Medical safety considerations such as peripheral nerve stimulation limit the maximal amplitude of the magnetic fields and in turn the field of view size. To handle this constraint the concept of patches was introduced, which allows a shift of a field of view to different positions in order to enlarge the imaging area. If this is done statically an overlap of patches can be used to reduce truncation artifacts occurring at the adjacent edges. In this contribution, a differentiation of two different kinds of patch overlaps, i.e. a trajectory and a system matrix overlap, is made. Further, different concepts to combine the resulting redundant information are investigated with respect to the reduction of truncation artifacts. The methods are analyzed in detail in a simulation study and validated on experimental data.

  15. Reducing multiplexing artifacts in multi-pinhole SPECT with a stacked silicon-germanium system: a simulation study.

    PubMed

    Johnson, Lindsay C; Shokouhi, Sepideh; Peterson, Todd E

    2014-12-01

    In pinhole single photon emission computed tomography (SPECT), multi-pinhole collimators can increase sensitivity but may lead to projection overlap, or multiplexing, which can cause image artifacts. In this work, we explore whether a stacked-detector configuration with a germanium and a silicon detector, used with 123I (27-32, 159 keV), where little multiplexing occurs in the Si projections, can reduce image artifacts caused by highly-multiplexed Ge projections. Simulations are first used to determine a reconstruction method that combines the Si and Ge projections to maximize image quality. Next, simulations of different pinhole configurations (varying projection multiplexing) in conjunction with digital phantoms are used to examine whether additional Si projections mitigate artifacts from the multiplexing in the Ge projections. Reconstructed images using both Si and Ge data are compared to those using Ge data alone. Normalized mean-square error and normalized standard deviation provide a quantitative evaluation of reconstructed images' error and noise, respectively, and are used to evaluate the impact of the additional nonmultiplexed data on image quality. For a qualitative comparison, the differential point response function is used to examine multiplexing artifacts. Results show that in cases of highly-multiplexed Ge projections, the addition of low-multiplexed Si projections helps to reduce image artifacts both quantitatively and qualitatively.

  16. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals.

    PubMed

    Peng, Fulai; Liu, Hongyun; Wang, Weidong

    2015-10-01

    A photoplethysmographic (PPG) signal can provide very useful information about a subject's cardiovascular status. Motion artifacts (MAs), which usually deteriorate the waveform of a PPG signal, severely obstruct its applications in the clinical diagnosis and healthcare area. To reduce the MAs from a PPG signal, in the present study we present a comb filter based signal processing method. Firstly, wavelet de-noising was implemented to preliminarily suppress a part of the MAs. Then, the PPG signal in the time domain was transformed into the frequency domain by a fast Fourier transform (FFT). Thirdly, the PPG signal period was estimated from the frequency domain by tracking the fundamental frequency peak of the PPG signal. Lastly, the MAs were removed by the comb filter which was designed based on the obtained PPG signal period. Experiments with synthetic and real-world datasets were implemented to validate the performance of the method. Results show that the proposed method can effectively restore the PPG signals from the MA corrupted signals. Also, the accuracy of blood oxygen saturation (SpO2), calculated from red and infrared PPG signals, was significantly improved after the MA reduction by the proposed method. Our study demonstrates that the comb filter can effectively reduce the MAs from a PPG signal provided that the PPG signal period is obtained. PMID:26334000

  17. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals.

    PubMed

    Peng, Fulai; Liu, Hongyun; Wang, Weidong

    2015-10-01

    A photoplethysmographic (PPG) signal can provide very useful information about a subject's cardiovascular status. Motion artifacts (MAs), which usually deteriorate the waveform of a PPG signal, severely obstruct its applications in the clinical diagnosis and healthcare area. To reduce the MAs from a PPG signal, in the present study we present a comb filter based signal processing method. Firstly, wavelet de-noising was implemented to preliminarily suppress a part of the MAs. Then, the PPG signal in the time domain was transformed into the frequency domain by a fast Fourier transform (FFT). Thirdly, the PPG signal period was estimated from the frequency domain by tracking the fundamental frequency peak of the PPG signal. Lastly, the MAs were removed by the comb filter which was designed based on the obtained PPG signal period. Experiments with synthetic and real-world datasets were implemented to validate the performance of the method. Results show that the proposed method can effectively restore the PPG signals from the MA corrupted signals. Also, the accuracy of blood oxygen saturation (SpO2), calculated from red and infrared PPG signals, was significantly improved after the MA reduction by the proposed method. Our study demonstrates that the comb filter can effectively reduce the MAs from a PPG signal provided that the PPG signal period is obtained.

  18. 21 CFR 872.5580 - Oral rinse to reduce the adhesion of dental plaque.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Oral rinse to reduce the adhesion of dental plaque... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Therapeutic Devices § 872.5580 Oral rinse to reduce the adhesion of dental plaque. (a) Identification. The device is assigned the generic name oral rinse to...

  19. 21 CFR 872.5580 - Oral rinse to reduce the adhesion of dental plaque.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Oral rinse to reduce the adhesion of dental plaque... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Therapeutic Devices § 872.5580 Oral rinse to reduce the adhesion of dental plaque. (a) Identification. The device is assigned the generic name oral rinse to...

  20. 21 CFR 872.5580 - Oral rinse to reduce the adhesion of dental plaque.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Oral rinse to reduce the adhesion of dental plaque... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Therapeutic Devices § 872.5580 Oral rinse to reduce the adhesion of dental plaque. (a) Identification. The device is assigned the generic name oral rinse to...

  1. 21 CFR 872.5580 - Oral rinse to reduce the adhesion of dental plaque.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Oral rinse to reduce the adhesion of dental plaque... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Therapeutic Devices § 872.5580 Oral rinse to reduce the adhesion of dental plaque. (a) Identification. The device is assigned the generic name oral rinse to...

  2. 21 CFR 872.5580 - Oral rinse to reduce the adhesion of dental plaque.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Oral rinse to reduce the adhesion of dental plaque... SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Therapeutic Devices § 872.5580 Oral rinse to reduce the adhesion of dental plaque. (a) Identification. The device is assigned the generic name oral rinse to...

  3. A decomposition-based CT reconstruction formulation for reducing blooming artifacts.

    PubMed

    Do, Synho; Karl, W Clem; Liang, Zhuangli; Kalra, Mannudeep; Brady, Thomas J; Pien, Homer H

    2011-11-21

    Cardiac computed tomography represents an important advancement in the ability to assess coronary vessels. The accuracy of these non-invasive imaging studies is limited, however, by the presence of calcium, since calcium blooming artifacts lead to an over-estimation of the degree of luminal narrowing. To address this problem, we have developed a unified decomposition-based iterative reconstruction formulation, where different penalty functions are imposed on dense objects (i.e. calcium) and soft tissue. The result is a quantifiable reduction in blooming artifacts without the introduction of new distortions away from the blooming observed in other methods. Results are shown for simulations, phantoms, ex vivo, and in vivo studies.

  4. A method to reduce the Gibbs ringing artifact in MRI scans while keeping tissue boundary integrity.

    PubMed

    Archibald, Rick; Gelb, Anne

    2002-04-01

    Gibbs ringing is a well known artifact that effects reconstruction of images having discontinuities. This is a problem in the reconstruction of magnetic resonance imaging (MRI) data due to the many different tissues normally present in each scan. The Gibbs ringing artifact manifests itself at the boundaries of the tissues, making it difficult to determine the structure of the brain tissue. The Gegenbauer reconstruction method has been shown to effectively eliminate the effects of Gibbs ringing in other applications. This paper presents the application of the Gegenbauer reconstruction method to neuro-imaging. PMID:12022619

  5. Diffusion-weighted line-scan echo-planar spectroscopic imaging technique to reduce motion artifacts in metabolite diffusion imaging.

    PubMed

    Bito, Yoshitaka; Hirata, Koji; Ebisu, Toshihiko; Kawai, Yuko; Otake, Yosuke; Hirata, Satoshi; Shirai, Toru; Soutome, Yoshihisa; Ochi, Hisaaki; Yamamoto, Etsuji; Umeda, Masahiro; Higuchi, Toshihiro; Tanaka, Chuzo

    2015-01-01

    Metabolite diffusion is expected to provide more specific microstructural and functional information than water diffusion. However, highly accurate measurement techniques have still not been developed, especially for reducing motion artifacts caused by cardiac pulsation and respiration. We developed a diffusion-weighted line-scan echo-planar spectroscopic imaging (DW-LSEPSI) technique to reduce such motion artifacts in measuring diffusion-weighted images (DWI) of metabolites. Our technique uses line-scan and echo-planar techniques to reduce phase errors induced by such motion during diffusion time. The phase errors are corrected using residual water signals in water suppression for each acquisition and at each spatial pixel specified by combining the line-scan and echo-planar techniques. We apply this technique to a moving phantom and a rat brain in vivo to demonstrate the reduction of motion artifacts in DWI and apparent diffusion coefficient (ADC) maps of metabolites. DW-LSEPSI will be useful for investigating a cellular diffusion environment using metabolites as probes.

  6. Possible ways of reducing dental erosive potential of acidic beverages.

    PubMed

    Stefański, T; Postek-Stefańska, L

    2014-09-01

    Frequent consumption of acidic beverages is related to excessive tooth wear, namely dental erosion. Preventive measures may involve reduction or elimination of acidic drink consumption. However, the success of this approach is difficult to achieve as it is highly dependent on patient compliance. Therefore, a practical way of minimizing the erosive potential of popular acidic drinks may be their chemical modification. The aim of this article was to review the different methods of modification and their shortcomings. The available literature demonstrates that the erosive potential of most acidic beverages could be reduced. To date, the effectiveness of soluble calcium salts supplementation is the best established. However, modification can reduce the sensorial quality of the drink and shorten its shelf-life. There is also a need to evaluate the lowest effective and safe dose of the additive.

  7. Reducing motion artifacts for long-term clinical NIRS monitoring using collodion-fixed prism-based optical fibers.

    PubMed

    Yücel, Meryem A; Selb, Juliette; Boas, David A; Cash, Sydney S; Cooper, Robert J

    2014-01-15

    As the applications of near-infrared spectroscopy (NIRS) continue to broaden and long-term clinical monitoring becomes more common, minimizing signal artifacts due to patient movement becomes more pressing. This is particularly true in applications where clinically and physiologically interesting events are intrinsically linked to patient movement, as is the case in the study of epileptic seizures. In this study, we apply an approach common in the application of EEG electrodes to the application of specialized NIRS optical fibers. The method provides improved optode-scalp coupling through the use of miniaturized optical fiber tips fixed to the scalp using collodion, a clinical adhesive. We investigate and quantify the performance of this new method in minimizing motion artifacts in healthy subjects, and apply the technique to allow continuous NIRS monitoring throughout epileptic seizures in two epileptic in-patients. Using collodion-fixed fibers reduces the percent signal change of motion artifacts by 90% and increases the SNR by 6 and 3 fold at 690 and 830 nm wavelengths respectively when compared to a standard Velcro-based array of optical fibers. The SNR has also increased by 2 fold during rest conditions without motion with the new probe design because of better light coupling between the fiber and scalp. The change in both HbO and HbR during motion artifacts is found to be statistically lower for the collodion-fixed fiber probe. The collodion-fixed optical fiber approach has also allowed us to obtain good quality NIRS recording of three epileptic seizures in two patients despite excessive motion in each case.

  8. Cell morphology classification in phase contrast microscopy image reducing halo artifact

    NASA Astrophysics Data System (ADS)

    Kang, Mi-Sun; Song, Soo-Min; Lee, Hana; Kim, Myoung-Hee

    2012-03-01

    Since the morphology of tumor cells is a good indicator of their invasiveness, we used time-lapse phase-contrast microscopy to examine the morphology of tumor cells. This technique enables long-term observation of the activity of live cells without photobleaching and phototoxicity which is common in other fluorescence-labeled microscopy. However, it does have certain drawbacks in terms of imaging. Therefore, we first corrected for non-uniform illumination artifacts and then we use intensity distribution information to detect cell boundary. In phase contrast microscopy image, cell is normally appeared as dark region surrounded by bright halo ring. Due to halo artifact is minimal around the cell body and has non-symmetric diffusion pattern, we calculate cross sectional plane which intersects center of each cell and orthogonal to first principal axis. Then, we extract dark cell region by analyzing intensity profile curve considering local bright peak as halo area. Finally, we examined cell morphology to classify tumor cells as malignant and benign.

  9. A Bayesian approach for the estimation and transmission of regularization parameters for reducing blocking artifacts.

    PubMed

    Mateos, J; Katsaggelos, A K; Molina, R

    2000-01-01

    With block-based compression approaches for both still images and sequences of images annoying blocking artifacts are exhibited, primarily at high compression ratios. They are due to the independent processing (quantization) of the block transformed values of the intensity or the displaced frame difference. We propose the application of the hierarchical Bayesian paradigm to the reconstruction of block discrete cosine transform (BDCT) compressed images and the estimation of the required parameters. We derive expressions for the iterative evaluation of these parameters applying the evidence analysis within the hierarchical Bayesian paradigm. The proposed method allows for the combination of parameters estimated at the coder and decoder. The performance of the proposed algorithms is demonstrated experimentally. PMID:18262958

  10. Noise cancellation model validation for reduced motion artifact wearable PPG sensors using MEMS accelerometers.

    PubMed

    Wood, Levi B; Asada, H Harry

    2006-01-01

    This paper investigates the validity of utilizing Widrow's Active Noise Cancellation (ANC) in the context of motion artifact reduction for photoplethysmogram (PPG) sensors. The ANC approach has previously been applied to the PPG problem, but little consideration has been given to the validity of the ANC signal corruption assumptions and in what motion range the algorithm works. The ANC validity testing is done in the form of impact (approximate impulse) testing of the physical PPG system and comparing with the modeled response for a range of motion amplitudes. The testing reveals that the identified corruption model does not generally represent the true physical system, but locally approximates the true system. Testing shows that if a similar motion amplitude is used for model tuning as the impact test, an average peak deviation of 5.2% is obtained, but if motion amplitude that is smaller than the impact amplitude by a factor of 5, the peak deviation is 15%. Finally, after ANC filtering motion corrupted data, heart rate can be estimated with less than 1.6% error.

  11. MR Image Based Approach for Metal Artifact Reduction in X-Ray CT

    PubMed Central

    2013-01-01

    For decades, computed tomography (CT) images have been widely used to discover valuable anatomical information. Metallic implants such as dental fillings cause severe streaking artifacts which significantly degrade the quality of CT images. In this paper, we propose a new method for metal-artifact reduction using complementary magnetic resonance (MR) images. The method exploits the possibilities which arise from the use of emergent trimodality systems. The proposed algorithm corrects reconstructed CT images. The projected data which is affected by dental fillings is detected and the missing projections are replaced with data obtained from a corresponding MR image. A simulation study was conducted in order to compare the reconstructed images with images reconstructed through linear interpolation, which is a common metal-artifact reduction technique. The results show that the proposed method is successful in reducing severe metal artifacts without introducing significant amount of secondary artifacts. PMID:24302860

  12. Ambient odors of orange and lavender reduce anxiety and improve mood in a dental office.

    PubMed

    Lehrner, J; Marwinski, G; Lehr, S; Johren, P; Deecke, L

    2005-09-15

    The goal of this study was to investigate the impact of the essential oils of orange and lavender on anxiety, mood, alertness and calmness in dental patients. Two hundred patients between the ages of 18 and 77 years (half women, half men) were assigned to one of four independent groups. While waiting for dental procedures patients were either stimulated with ambient odor of orange or ambient odor of lavender. These conditions were compared to a music condition and a control condition (no odor, no music). Anxiety, mood, alertness and calmness were assessed while patients waited for dental treatment. Statistical analyses revealed that compared to control condition both ambient odors of orange and lavender reduced anxiety and improved mood in patients waiting for dental treatment. These findings support the previous opinion that odors are capable of altering emotional states and may indicate that the use of odors is helpful in reducing anxiety in dental patients.

  13. Does atraumatic restorative treatment reduce dental anxiety in children? A systematic review and meta-analysis

    PubMed Central

    Simon, Arun K.; Bhumika, T. V.; Nair, N. Sreekumaran

    2015-01-01

    Dental anxiety is one of the major problems affecting children, which impairs the rendering of dental care, leading to impaired quality of life. It often leads to occupational stress in dental personnel and conflict between parents/caregivers. The objective of this study was to conduct a systematic review and meta-analysis of randomized controlled trials done in children, to synthesize evidence of the effectiveness of atraumatic restorative treatment (ART) in reducing dental anxiety in children compared to conventional restorative treatments. The databases searched included PubMed, Google Scholar and The Cochrane Oral Health Group's Trials Register. Eligible studies reporting dental anxiety by a variety of psychometric scales were tabulated. The review was conducted and reported in accordance with the guidelines provided by the Cochrane Collaboration. Among 416 studies retrieved through literature search, six studies matched the inclusion criteria. Due to lack of data, only three studies were included for meta-analysis using RevMan software (Review Manager, Version 5.3;The Cochrane Collaboration, Copenhagen, 2014). The pooled meta-analysis data, (standardized mean difference − 2.12 [95% confidence interval: −4.52, 0.27]) failed to show any difference between ART group and the conventional treatment group. In conclusion, ART was not more beneficial in reducing dental anxiety among pediatric dental patients. The findings are relevant in the field of clinical practice in dentistry in the management of the anxious pediatric dental patient. PMID:26038668

  14. Prosthetic Treatment Concepts for the Reduced Dentition in German Dental Schools.

    PubMed

    Passia, Nicole; Kern, Matthias

    2015-01-01

    This survey of German dental schools sought to gain insight into the present prosthetic treatment concepts and their application in student and postgraduate education, as well as to compare the results to those from an identical 2002 survey. A questionnaire, based on this issue, was sent via email to the chairpersons of all prosthetic departments of the German dental schools, and 93.1% of the departments completed the questionnaire. Within the limitations of this survey, almost all treatment concepts for the reduced dentition are taught intensively at dental schools in Germany while some therapy forms are preferred.

  15. Recursive approach of EEG-segment-based principal component analysis substantially reduces cryogenic pump artifacts in simultaneous EEG-fMRI data.

    PubMed

    Kim, Hyun-Chul; Yoo, Seung-Schik; Lee, Jong-Hwan

    2015-01-01

    Electroencephalography (EEG) data simultaneously acquired with functional magnetic resonance imaging (fMRI) data are preprocessed to remove gradient artifacts (GAs) and ballistocardiographic artifacts (BCAs). Nonetheless, these data, especially in the gamma frequency range, can be contaminated by residual artifacts produced by mechanical vibrations in the MRI system, in particular the cryogenic pump that compresses and transports the helium that chills the magnet (the helium-pump). However, few options are available for the removal of helium-pump artifacts. In this study, we propose a recursive approach of EEG-segment-based principal component analysis (rsPCA) that enables the removal of these helium-pump artifacts. Using the rsPCA method, feature vectors representing helium-pump artifacts were successfully extracted as eigenvectors, and the reconstructed signals of the feature vectors were subsequently removed. A test using simultaneous EEG-fMRI data acquired from left-hand (LH) and right-hand (RH) clenching tasks performed by volunteers found that the proposed rsPCA method substantially reduced helium-pump artifacts in the EEG data and significantly enhanced task-related gamma band activity levels (p=0.0038 and 0.0363 for LH and RH tasks, respectively) in EEG data that have had GAs and BCAs removed. The spatial patterns of the fMRI data were estimated using a hemodynamic response function (HRF) modeled from the estimated gamma band activity in a general linear model (GLM) framework. Active voxel clusters were identified in the post-/pre-central gyri of motor area, only from the rsPCA method (uncorrected p<0.001 for both LH/RH tasks). In addition, the superior temporal pole areas were consistently observed (uncorrected p<0.001 for the LH task and uncorrected p<0.05 for the RH task) in the spatial patterns of the HRF model for gamma band activity when the task paradigm and movement were also included in the GLM.

  16. Motion artifacts in capacitive ECG measurements: reducing the combined effect of DC voltages and capacitance changes using an injection signal.

    PubMed

    Serteyn, A; Vullings, R; Meftah, M; Bergmans, J W M

    2015-01-01

    Capacitive electrodes are a promising alternative to the conventional adhesive electrodes for ECG measurements. They provide more comfort to the patient when integrated in everyday objects (e.g., beds or seats) for long-term monitoring. However, the application of capacitive sensors is limited by their high sensitivity to motion artifacts. For example, motion at the body-electrode interface causes variations of the coupling capacitance which, in the presence of a dc voltage across the coupling capacitor, create strong artifacts in the measurements. The origin, relevance, and reduction of this specific and important type of artifacts are studied here. An injection signal is exploited to track the variations of the coupling capacitance in real time. This information is then used by an identification scheme to estimate the artifacts and subtract them from the measurements. The method was evaluated in simulations, lab environments, and in a real-life recording on an adult's chest. For the type of artifact under study, a strong artifact reduction ranging from 40 dB for simulated data to 9 dB for a given real-life recording was achieved. The proposed method is automated, does not require any knowledge about the measurement system parameters, and provides an online estimate for the dc voltage across the coupling capacitor.

  17. Reduction of metal artifacts: beam hardening and photon starvation effects

    NASA Astrophysics Data System (ADS)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  18. Pretreatment modeling. A technique for reducing children's fear in the dental operatory.

    PubMed

    Greenbaum, P E; Melamed, B G

    1988-10-01

    Research on modeling indicates that this technique offers dentists a means of reducing fear in child patients of all ages. As a preventive measure used with children who have had no prior exposure to dental treatment, it can be particularly efficacious. Based on the assumption that much of adult dental avoidance is based on dental fears acquired in childhood treatment, the reduction of children's dental fear would have a positive effect on the individual's tendency to seek out dental health care throughout his or her lifespan. For the dentist, there are also short- and long-term benefits. Dental management of the child is prerequisite to providing good dental care. Pedodontics as a specialty recognizes behavioral management of the child cannot be separated from the quality of the dentist's work. Fear has been identified as an important factor in disruptive behavior of school age children in the dental office. Practicing dentists consider the fearful, disruptive child to be among the most troublesome of problems in their clinical work. The child must cooperate or at least passively comply with the dentist's procedures in order to have the technical work completed. By reducing disruptive patient behavior (crying, screaming children whose peripheral and gross motor movements often make direct contact with the dentist or his equipment) the most unpalatable aspect of pediatric dentistry is minimized. Further, the actual time for treatment becomes shorter rather than longer. Although modeling is not restricted to videotape media, the emergence of current videotape technology provides the practitioner with the means for incorporating patient viewing of prerecorded modeling tapes as part of the usual waiting period. Such a procedure would mean that in the long run, the dentist will spend more time doing dentistry and less in behavioral management tasks.

  19. A study on a method to reduce the effect of the cross-talk artifact in a simultaneous, multiple-slice, plane, oblique MRI scan

    NASA Astrophysics Data System (ADS)

    Lee, Sun-Yeob; Cho, Jae-Hwan; Lee, Hae-Kag; Cho, Moo-Seong; Park, Cheol-Soo; Kim, Eng-Chan; Kim, Sung-Kyu; Dong, Kyung-Rae; Chung, Woon-Kwan; Shin, Jae-Woo; Kim, Young-Jae; Cho, Young-Kuk

    2012-09-01

    The aim of this study was to reduce the effect of cross-talk artifacts on the region of interest (ROI) and to improve the diagnostic value of an image by conducting an examination using the linear (series) method, rather than the interleave method, based on the time concept, which is a basic principle of MRI, with a focus on the T1-weighted image, which has a strong effect on the cross-talk artifact. A water phantom was placed in the center of a brain coil before using the interleave method and the linear method to obtain cross-sectional images. A sagittal oblique scan was conducted to ensure that the slice groups intersected one another. A reference image was also acquired at TR (time of repetition) = 500 msec. Subsequently, the TR was changed to 600 and 700 msec to conduct scans. The analysis method was to use the interleave method and the linear method to compare the effects of the cross-talk artifacts and the TR. As scanned images were suggested, the SNR (signal to noise ratio) for the ROI was measured. According to the study results, the effects of cross-talk artifacts were reduced more significantly in the image scanned using the linear method than in that using the interleave method. When the SNRs of the images scanned in the interleave method and the linear method were compared, the image scanned in the linear method showed higher SNRs for the anterior and the posterior parts at TR = 500, 600, and 700 msec. On the other hand, the image scanned in the interleave method showed an increase in the SNR for the middle part, where the cross-talk artifacts did not appear. This means that the cross-talk artifacts were reduced in the image scanned using the linear method, which resulted in an increase in the SNR. Overall, the SNRs of each image for the interleave method and the linear method were highest at TR = 700 msec. In conclusion, the linear method is selected to reduce the effects of cross-talk artifacts in a simultaneous and multiple slice plane oblique scan

  20. Estimation of resting-state functional connectivity using random subspace based partial correlation: a novel method for reducing global artifacts.

    PubMed

    Chen, Tianwen; Ryali, Srikanth; Qin, Shaozheng; Menon, Vinod

    2013-11-15

    Intrinsic functional connectivity analysis using resting-state functional magnetic resonance imaging (rsfMRI) has become a powerful tool for examining brain functional organization. Global artifacts such as physiological noise pose a significant problem in estimation of intrinsic functional connectivity. Here we develop and test a novel random subspace method for functional connectivity (RSMFC) that effectively removes global artifacts in rsfMRI data. RSMFC estimates the partial correlation between a seed region and each target brain voxel using multiple subsets of voxels sampled randomly across the whole brain. We evaluated RSMFC on both simulated and experimental rsfMRI data and compared its performance with standard methods that rely on global mean regression (GSReg) which are widely used to remove global artifacts. Using extensive simulations we demonstrate that RSMFC is effective in removing global artifacts in rsfMRI data. Critically, using a novel simulated dataset we demonstrate that, unlike GSReg, RSMFC does not artificially introduce anti-correlations between inherently uncorrelated networks, a result of paramount importance for reliably estimating functional connectivity. Furthermore, we show that the overall sensitivity, specificity and accuracy of RSMFC are superior to GSReg. Analysis of posterior cingulate cortex connectivity in experimental rsfMRI data from 22 healthy adults revealed strong functional connectivity in the default mode network, including more reliable identification of connectivity with left and right medial temporal lobe regions that were missed by GSReg. Notably, compared to GSReg, negative correlations with lateral fronto-parietal regions were significantly weaker in RSMFC. Our results suggest that RSMFC is an effective method for minimizing the effects of global artifacts and artificial negative correlations, while accurately recovering intrinsic functional brain networks.

  1. Epigallocatechin-3-Gallate Reduces Cytotoxic Effects Caused by Dental Monomers: A Hypothesis

    PubMed Central

    Jiao, Yang; Ma, Sai; Wang, Yirong; Li, Jing; Shan, Lequn; Chen, Jihua

    2015-01-01

    Resin monomers from dental composite materials leached due to incomplete polymerization or biodegradation may cause contact allergies and damage dental pulp. The cytotoxicity of dental resin monomers is due to a disturbance of intracellular redox equilibrium, characterized by an overproduction of reactive oxygen species (ROS) and depletion of reduced glutathione (GSH). Oxidative stress caused by dental resin monomers leads to the disturbance of vital cell functions and induction of cell apoptosis in affected cells. The nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway plays a key role in the cellular defense system against oxidative and electrophilic stress. Epigallocatechin-3-gallate (EGCG) can activate the Nrf2 pathway and induce expression of a multitude of antioxidants and phase II enzymes that can restore redox homeostasis. Therefore, here, we tested the hypothesis that EGCG-mediated protection against resin monomer cytotoxicity is mediated by activation of the Nrf2 pathway. This study will help to elucidate the mechanism of resin monomer cytotoxicity and provide information that will be helpful in improving the biocompatibility of dental resin materials. PMID:26489899

  2. A technique to reduce motion artifact for externally triggered cine-MRI(EC-MRI) based on detecting the onset of the articulated word with spectral analysis.

    PubMed

    Shimada, Yasuhiro; Nishimoto, Hironori; Kochiyama, Takanori; Fujimoto, Ichiro; Mano, Hiroaki; Masaki, Shinobu; Murase, Kenya

    2012-01-01

    One issue in externally triggered cine-magnetic resonance imaging (EC-MRI) for the dynamic observation of speech organs is motion artifact in the phase-encoding direction caused by unstable repetitions of speech during data acquisition. We propose a technique to reduce such artifact by rearranging the k-space data used to reconstruct MR images based on the analysis of recorded speech sounds. We recorded the subject's speech sounds during EC-MRI and used post hoc acoustical processing to reduce scanning noise and detect the onset of each utterance based on analysis of the recorded sounds. We selected each line of k-space from several data acquisition sessions and rearranged them to reconstruct a new series of dynamic MR images according to the analyzed time of utterance onset. Comparative evaluation showed significant reduction in motion artifact signal in the dynamic MR images reconstructed by the proposed method. The quality of the reconstructed images was sufficient to observe the dynamic aspects of speech production mechanisms.

  3. Collecting Artifacts

    ERIC Educational Resources Information Center

    Coffey, Natalie

    2004-01-01

    Fresh out of college, the author had only a handful of items worthy of displaying, which included some fossils she had collected in her paleontology class. She had binders filled with great science information, but kids want to see "real" science, not paper science. Then it came to her: she could fill the shelves with science artifacts with the…

  4. Dental Procedures.

    PubMed

    Ramponi, Denise R

    2016-01-01

    Dental problems are a common complaint in emergency departments in the United States. There are a wide variety of dental issues addressed in emergency department visits such as dental caries, loose teeth, dental trauma, gingival infections, and dry socket syndrome. Review of the most common dental blocks and dental procedures will allow the practitioner the opportunity to make the patient more comfortable and reduce the amount of analgesia the patient will need upon discharge. Familiarity with the dental equipment, tooth, and mouth anatomy will help prepare the practitioner for to perform these dental procedures. PMID:27482994

  5. Aluminum-free low-modulus Ti-C composites that exhibit reduced image artifacts during MRI.

    PubMed

    Kim, Sung-Chul; Lee, Hong-Jun; Son, Seong-Guk; Seok, Hyun-Kwang; Lee, Kang-Sik; Shin, Seung-Young; Lee, Jae-Chul

    2015-01-01

    Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti-C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10(-6)), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young's modulus was low (E=81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful. PMID:25449916

  6. Aluminum-free low-modulus Ti-C composites that exhibit reduced image artifacts during MRI.

    PubMed

    Kim, Sung-Chul; Lee, Hong-Jun; Son, Seong-Guk; Seok, Hyun-Kwang; Lee, Kang-Sik; Shin, Seung-Young; Lee, Jae-Chul

    2015-01-01

    Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti-C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10(-6)), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young's modulus was low (E=81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful.

  7. The Benefits of Prone SPECT Myocardial Perfusion Imaging in Reducing Both Artifact Defects and Patient Radiation Exposure

    PubMed Central

    Stathaki, Maria; Koukouraki, Sophia; Papadaki, Emmanouela; Tsaroucha, Angeliki; Karkavitsas, Nikolaos

    2015-01-01

    Background Prone imaging has been demonstrated to minimize diaphragmatic and breast tissue attenuation. Objectives To determine the role of prone imaging on the reduction of unnecessary rest perfusion studies and coronary angiographies performed, thus decreasing investigation time and radiation exposure. Methods We examined 139 patients, 120 with an inferior wall and 19 with an anterior wall perfusion defect that might represented attenuation artifact. Post-stress images were acquired in both the supine and prone position. Coronary angiography was used as the “gold standard” for evaluating coronary artery patency. The study was terminated and rest imaging was obviated in the presence of complete improvement of the defect in the prone position. Quantitative interpretation was performed. Results were compared with clinical data and coronary angiographic findings. Results Prone acquisition correctly revealed defect improvement in 89 patients (89/120) with inferior wall and 12 patients (12/19) with anterior wall attenuation artifact. Quantitative analysis demonstrated statistically significant difference in the mean summed stress scores (SSS) of supine and mean SSS of prone studies in patients with disappearing inferior wall defect in the prone position and patent right coronary artery (true negative results). The mean difference between SSS in supine and in prone position was higher with disappearing than with remaining defects. Conclusion Technetium-99m (Tc-99m) tetrofosmin myocardial perfusion imaging with the patient in the prone position overcomes soft tissue attenuation; moreover it provides an inexpensive, accurate approach to limit the number of unnecessary rest perfusion studies and coronary angiographies performed. PMID:26559981

  8. The use of a respiratory rate biofeedback device to reduce dental anxiety: an exploratory investigation.

    PubMed

    Morarend, Quinn A; Spector, Michael L; Dawson, Deborah V; Clark, Steven H; Holmes, David C

    2011-06-01

    Anxiety experienced by individuals visiting the dental office to receive treatment is common. Evidence has shown biofeedback to be a useful modality of treatment for numerous maladies associated with anxiety. The purpose of the current pilot study was to investigate the use of a novel biofeedback device (RESPeRATE™) to reduce patients' pre-operative general anxiety levels and consequently reduce the pain associated with dental injections. Eighty-one subjects participated in this study, forty in the experimental group and forty-one in the control group. Subjects in the experimental group used the biofeedback technique, while those in the control group were not exposed to any biofeedback. All subjects filled out a pre-injection anxiety survey, then received an inferior alveolar injection of local anesthetic. Post-injection, both groups were given an anxiety survey and asked to respond to four questions regarding the injection experience using a Visual Analog Scale (VAS). With the use of the respiratory rate biofeedback device, there was a significant reduction of negative feelings regarding the overall injection experience, as measured by a VAS. Our findings demonstrate that this novel biofeedback technique may be helpful in the amelioration of dental anxiety, and may help produce a more pleasant overall experience for the patient. PMID:21365307

  9. Artifacts in magnetic resonance imaging.

    PubMed

    Krupa, Katarzyna; Bekiesińska-Figatowska, Monika

    2015-01-01

    Artifacts in magnetic resonance imaging and foreign bodies within the patient's body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients' bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature.

  10. Artifacts in Magnetic Resonance Imaging

    PubMed Central

    Krupa, Katarzyna; Bekiesińska-Figatowska, Monika

    2015-01-01

    Summary Artifacts in magnetic resonance imaging and foreign bodies within the patient’s body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients’ bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature. PMID:25745524

  11. Toothpastes containing abrasive and chemical whitening agents: efficacy in reducing extrinsic dental staining.

    PubMed

    Soares, Cristina Neves Girao Salgado; Amaral, Flavia Lucisano Botelho do; Mesquita, Marcelo Ferraz; Franca, Fabiana Mantovani Gomes; Basting, Roberta Tarkany; Turssi, Cecilia Pedroso

    2015-01-01

    This in vitro study evaluated the efficacy of toothpastes containing abrasive and chemical whitening agents in reducing the extrinsic discoloration of dental enamel. Sixty slabs of dentin from human teeth were sealed so that only the enamel surface was exposed. The enamel surfaces were photographed for initial color assessment. Staining was performed by immersing the dental slabs in 0.2% chlorhexidine solution for 2 minutes and then in black tea for 60 minutes. This process was repeated 15 times. Photographs were taken at the end of the staining process, and the slabs were divided into 5 groups (n = 12), 3 to be brushed with toothpastes containing chemical whitening agents (2 containing phosphate salts and 1 containing phosphate salts plus hydrogen peroxide) and 2 to represent control groups (ordinary/nonwhitening toothpaste and distilled water). The dental slabs were subjected to mechanical toothbrushing with toothpaste slurry or distilled water, according to each group's specifications. After brushing, more photographs were taken for color analysis. The results showed a significant reduction in luminosity after the staining process in addition to an increase in the colors red and yellow (P < 0.001). After brushing, there was a significant increase in luminosity and a reduction in both red and yellow (P < 0.001). However, there was no observed difference between the changes in color values in dental enamel slabs brushed with whitening toothpastes and the changes found in slabs brushed with ordinary toothpaste. The whitening toothpastes did not outperform an ordinary toothpaste in the removal of extrinsic staining. PMID:26545284

  12. Clinical Use of Virtual Reality Distraction System to Reduce Anxiety and Pain in Dental Procedures

    PubMed Central

    Gao, Kenneth; Wiederhold, Brenda K.

    2014-01-01

    Abstract Virtual reality (VR) has been used by clinicians to manage pain in clinical populations. This study examines the use of VR as a form of distraction for dental patients using both subjective and objective measures to determine how a VR system affects patients' reported anxiety level, pain level, and physiological factors. As predicted, results of self-evaluation questionnaires showed that patients experienced less anxiety and pain after undergoing VR treatment. Physiological data reported similar trends in decreased anxiety. Overall, the favorable subjective and objective responses suggest that VR distraction systems can reduce discomfort and pain for patients with mild to moderate fear and anxiety. PMID:24892198

  13. Clinical use of virtual reality distraction system to reduce anxiety and pain in dental procedures.

    PubMed

    Wiederhold, Mark D; Gao, Kenneth; Wiederhold, Brenda K

    2014-06-01

    Virtual reality (VR) has been used by clinicians to manage pain in clinical populations. This study examines the use of VR as a form of distraction for dental patients using both subjective and objective measures to determine how a VR system affects patients' reported anxiety level, pain level, and physiological factors. As predicted, results of self-evaluation questionnaires showed that patients experienced less anxiety and pain after undergoing VR treatment. Physiological data reported similar trends in decreased anxiety. Overall, the favorable subjective and objective responses suggest that VR distraction systems can reduce discomfort and pain for patients with mild to moderate fear and anxiety.

  14. Contrast adaptive total p-norm variation minimization approach to CT reconstruction for artifact reduction in reduced-view brain perfusion CT

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Won; Kim, Jong-Hyo

    2011-03-01

    Perfusion CT (PCT) examinations are getting more frequently used for diagnosis of acute brain diseases such as hemorrhage and infarction, because the functional map images it produces such as regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV), and mean transit time (MTT) may provide critical information in the emergency work-up of patient care. However, a typical PCT scans the same slices several tens of times after injection of contrast agent, which leads to much increased radiation dose and is inevitability of growing concern for radiation-induced cancer risk. Reducing the number of views in projection in combination of TV minimization reconstruction technique is being regarded as an option for radiation reduction. However, reconstruction artifacts due to insufficient number of X-ray projections become problematic especially when high contrast enhancement signals are present or patient's motion occurred. In this study, we present a novel reconstruction technique using contrast-adaptive TpV minimization that can reduce reconstruction artifacts effectively by using different p-norms in high contrast and low contrast objects. In the proposed method, high contrast components are first reconstructed using thresholded projection data and low p-norm total variation to reflect sparseness in both projection and reconstruction spaces. Next, projection data are modified to contain only low contrast objects by creating projection data of reconstructed high contrast components and subtracting them from original projection data. Then, the low contrast projection data are reconstructed by using relatively high p-norm TV minimization technique, and are combined with the reconstructed high contrast component images to produce final reconstructed images. The proposed algorithm was applied to numerical phantom and a clinical data set of brain PCT exam, and the resultant images were compared with those using filtered back projection (FBP) and conventional TV

  15. Metal artifact reduction in CT using tissue-class modeling and adaptive prefiltering

    SciTech Connect

    Bal, Matthieu; Spies, Lothar

    2006-08-15

    High-density objects such as metal prostheses, surgical clips, or dental fillings generate streak-like artifacts in computed tomography images. We present a novel method for metal artifact reduction by in-painting missing information into the corrupted sinogram. The information is provided by a tissue-class model extracted from the distorted image. To this end the image is first adaptively filtered to reduce the noise content and to smooth out streak artifacts. Consecutively, the image is segmented into different material classes using a clustering algorithm. The corrupted and missing information in the original sinogram is completed using the forward projected information from the tissue-class model. The performance of the correction method is assessed on phantom images. Clinical images featuring a broad spectrum of metal artifacts are studied. Phantom and clinical studies show that metal artifacts, such as streaks, are significantly reduced and shadows in the image are eliminated. Furthermore, the novel approach improves detectability of organ contours. This can be of great relevance, for instance, in radiation therapy planning, where images affected by metal artifacts may lead to suboptimal treatment plans.

  16. A review of the role of solar ultraviolet-B irradiance and vitamin D in reducing risk of dental caries

    PubMed Central

    2011-01-01

    Large geographical variations in dental health and tooth loss among US adolescents and young adults have been reported since the mid-1800s. Studies in the 1920s and 1930s noted that vitamin D and ultraviolet-B (UVB) irradiance reduced caries formation, the proposed mechanism being improved calcium absorption and metabolism. This paper reviews the history of studies of dental caries with respect to vitamin D, geographical location and available solar UVB doses. In addition, data on mean dental health rank by state for US servicemen from three periods, 1918, 1934 and 1943, were used in regression analyses with respect to summertime solar UVB doses and an index for mottled enamel, a proxy for natural fluoridation of drinking water, for 1935. There was a significant inverse correlation for dental health rank with respect to solar UVB from doses of 4.0 to 6.5 kJ/m2 with little change thereafter. Adding data for mottled enamel rates for the states with UvB doses <6.6 kJ/m2 improved the adjusted R2 from 0.45 to 0.52. The mechanism whereby UVB reduces risk of dental caries is likely through production of vitamin D, followed by induction of cathelicidin and defensins, which have antimicrobial properties. Serum 25-hydroxyvitamin D concentrations at or above 30–40 ng/ml should significantly reduce the formation of dental caries. It is unfortunate that the UVB and vitamin D findings were not given more consideration in the 1950s as a way to reduce the risk of dental caries when water fluoridation was being proposed. PMID:22110779

  17. Postprocessing algorithms to minimize fixed-pattern artifact and reduce trigger jitter in swept source optical coherence tomography

    PubMed Central

    Liu, Gangjun; Tan, Ou; Gao, Simon S.; Pechauer, Alex D.; Lee, ByungKun; Lu, Chen D.; Fujimoto, James G.; Huang, David

    2015-01-01

    We propose methods to align interferograms affected by trigger jitter to a reference interferogram based on the information (amplitude/phase) at a fixed-pattern noise location to reduce residual fixed-pattern noise and improve the phase stability of swept source optical coherence tomography (SS-OCT) systems. One proposed method achieved this by introducing a wavenumber shift (k-shift) in the interferograms of interest and searching for the k-shift that minimized the fixed-pattern noise amplitude. The other method calculated the relative k-shift using the phase information at the residual fixed-pattern noise location. Repeating this wavenumber alignment procedure for all A-lines of interest produced fixed-pattern noise free and phase stable OCT images. A system incorporating these correction routines was used for human retina OCT and Doppler OCT imaging. The results from the two methods were compared, and it was found that the intensity-based method provided better results. PMID:25969023

  18. Artifacts as Conventional Objects

    ERIC Educational Resources Information Center

    Siegel, Deborah R.; Callanan, Maureen A.

    2007-01-01

    What underlies children's understanding of artifacts? Studies suggest that beginning around age 7, people reason about artifacts in terms of the inventor's purpose--termed "the design stance." Our two studies emphasize another component of artifact understanding--the cultural nature of artifacts--by demonstrating people's sensitivity to an…

  19. PET/CT artifacts.

    PubMed

    Blodgett, Todd M; Mehta, Ajeet S; Mehta, Amar S; Laymon, Charles M; Carney, Jonathan; Townsend, David W

    2011-01-01

    There are several artifacts encountered in positron emission tomography/computed tomographic (PET/CT) imaging, including attenuation correction (AC) artifacts associated with using CT for AC. Several artifacts can mimic a 2-deoxy-2-[18F] fluoro-d-glucose (FDG) avid malignant lesions and therefore recognition of these artifacts is clinically relevant. Our goal was to identify and characterize these artifacts and also discuss some protocol variables that may affect image quality in PET/CT.

  20. Mesoscale hybrid calibration artifact

    DOEpatents

    Tran, Hy D.; Claudet, Andre A.; Oliver, Andrew D.

    2010-09-07

    A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.

  1. DENTAL MINERALIZATION AND SALIVARY ACTIVITY ARE REDUCED IN OFFSPRING OF SPONTANEOUSLY HYPERTENSIVE RATS (SHR)

    PubMed Central

    Elias, Gracieli Prado; dos Santos, Otoniel Antonio Macedo; Sassaki, Kikue Takebayashi; Delbem, Alberto Carlos Botazzo; Antoniali, Cristina

    2006-01-01

    Several pathologies have been diagnosed in children of hypertensive mothers; however, some studies that evaluated the alterations in their oral health are not conclusive. This study analyzed the salivary gland activity and dental mineralization of offsprings of spontaneously hypertensive rats (SHR). Thirty-day-old SHR males and Wistar rats were studied. The salivary flow was evaluated by injection of pilocarpine, the protein concentration and salivary amylase activity, by the Lowry method and kinetic method at 405 nm, respectively. Enamel and dentin mineralization of the mandibular incisors was quantified with aid of the microhardness meter. The results were analyzed by the ANOVA or Student's t test (p<0.05). It was noticed that the salivary flow rate (0.026 mL/min/100 g ± 0.002) and salivary protein concentration (2.26 mg/mL ± 0.14) of SHR offspring were reduced compared to Wistar normotensive offspring (0.036 mL/min/100 g ± 0.003 and 2.91 mg/mL ± 0.27, respectively), yet there was no alteration in amylase activity (SHR: 242.4 U/mL ± 36.9; Wistar: 163.8 U/mL ± 14.1). Microhardness was lower both in enamel (255.8 KHN ± 2.6) and dentin (59.9 KHN ± 0.8) for the SHR teeth compared to the Wistar teeth (enamel: 328.7 KHN ± 3.3 and dentin: 67.1 KHN ± 1.0). These results suggest that the SHR offspring are more susceptible to development of pathologies impairing oral health, once they presented lesser flow and salivary protein concentration and lower dental mineralization. PMID:19089272

  2. Effectiveness of benzocaine in reducing deep cavity restoration and post-extraction stress in dental patients

    PubMed Central

    Al-Samadani, Khalid H.; Gazal, Giath

    2015-01-01

    Objectives: To investigate the effectiveness of topical anesthetic, 20% benzocaine in relieving pain and stress in patients following deep cavity restoration and extraction of teeth under local anesthesia (LA). Methods: A prospective clinical trial was conducted from October 2014 until April 2015 at Taibah University, Al Madinah Al Munawarah, Kingdom of Saudi Arabia. Forty-five patients were included in the 20% benzocaine group, and 46 in the normal saline group. Evaluation of the dental stress was made pre-operatively and immediately post-operative treatment using the visual analogue scale (VAS). Furthermore, discomfort of the injections were recorded by the patients after each treatment on standard 100 mm VAS, tagged at the endpoints with “no pain” (0 mm) and “unbearable pain” (100 mm). Results: There were statistically significant differences between the mean stress scores for patients in the benzocaine and normal saline groups post-operatively (p=0.002). There were significant differences between the mean pain scores for patients in the post buccal injection (p=0.001), post palatal injection (p=0.01), and the post inferior alveolar nerve block groups (p=0.02). Buccal, palatal, and inferior alveolar nerve block injections were more painful for patients in the normal saline group than the benzocaine group. Conclusion: This investigation has demonstrated that post-operative stress associated with deep cavity restoration and dental extractions under LA can be reduced by the application of topical anesthetic (20% benzocaine) at the operative site for intra-oral injections. PMID:26593169

  3. A rubber-covered ceramic weapon reduces the incidence of dental trauma in recruits during combat basic training.

    PubMed

    Becker, Talia; Ashkenazi, Malka

    2011-10-01

    The effect of a rubber-covered ceramic weapon was assessed on the incidence of dental trauma during basic training, since soldiers are more at risk of impact from a personal weapon. Dental files of soldiers (n = 4,542), who completed 8 months of training during 2008, were analyzed for incidence and type of dental trauma from a personal weapon. A rubber-covered ceramic weapon (n = 2,972) or a conventional one (n = 1,570, control) was used. Dental trauma was 0.4% per 8 months (0.6% per year) from the ceramic weapon and 1.5% per 8 months (2.3% per year) from the conventional one (p<0.001). The most prevalent type of injury was a simple/noncomplicated crown fracture (82% in study group, 75% in control group). The ceramic weapon significantly reduced dental trauma by diminishing the impact while in direct contact with the teeth or by absorbing and/or distributing the impact force. In conclusion, when possible a rubber-covered ceramic weapon should be preferred for basic combat training.

  4. Detection of Sulphate-Reducing Bacteria and Others Cultivable Facultative Bacteria in Dental Tissues

    PubMed Central

    Gonçalves, Lúcio de Souza; Dias, Eliane Pedra; Heggendorn, Christiane; Lutterbach, Márcia T. S.

    2014-01-01

    Aim To detect for the presence of sulphate-reducing bacteria (SRB) and evaluate the possible association between SRB and cultivable facultative bacterial of oral sites with different periodontal conditions. Methods The study was carried out on 9 samples from different oral sites in 8 patients (two samples were collected from the same patient). Material was collected using modified Postgate E culture medium, indicated for the growth and isolation of SRB. In addition, a reducing solution for anaerobic bacteria was used as a transport solution for facultative bacteria and identified by polymerase chain reaction amplification (PCR) and sequencing of the 16S rRNA gene. Results SRB was found in 3 patient samples: the first in a root fragment, the second in a root fragment and a healthy tooth with vertical bone loss and a mobility degree of 3; and the third in a healthy tooth extracted for orthodontic treatment. In the final patient, the cultivable facultative species Lactobacillus casei was identified. Other facultative bacterial species were identified in patient 5 (Kurthia Gibsonii) and patient 7 (Pseudomonas aeruginosa). Conclusions The detection of SRB in different dental tissues with distinct periodontal features demonstrated that new studies need to be developed in order to determine the true role of SRB in the oral microbiota. In addition, it was possible to verify the presence of Lactobacillus casei together with SRB in one sample.

  5. Breast Imaging Artifacts.

    PubMed

    Odle, Teresa G

    2015-01-01

    Artifacts appear on breast images for a number of reasons. Radiologic technologists play an important role in identifying artifacts that can help or hinder breast cancer diagnosis and in minimizing artifacts that degrade image quality. This article describes various artifacts that occur in breast imaging, along with their causes. The article focuses on artifacts in mammography, with a heavy emphasis on digital mammography, and on magnetic resonance imaging of the breast. Artifacts in ultrasonography of the breast, digital breast tomosynthesis, and positron emission mammography also are discussed.

  6. Cleaning MEG artifacts using external cues.

    PubMed

    Tal, I; Abeles, M

    2013-07-15

    Using EEG, ECoG, MEG, and microelectrodes to record brain activity is prone to multiple artifacts. The main power line (mains line), video equipment, mechanical vibrations and activities outside the brain are the most common sources of artifacts. MEG amplitudes are low, and even small artifacts distort recordings. In this study, we show how these artifacts can be efficiently removed by recording external cues during MEG recordings. These external cues are subsequently used to register the precise times or spectra of the artifacts. The results indicate that these procedures preserve both the spectra and the time domain wave-shapes of the neuromagnetic signal, while successfully reducing the contribution of the artifacts to the target signals without reducing the rank of the data.

  7. Artifacts, Tools, and Classrooms

    ERIC Educational Resources Information Center

    McDonald, Geraldine; Le, Huong; Higgins, Joanna; Podmore, Valerie

    2005-01-01

    Although schools contain many material artifacts, studies in classrooms have tended to focus on discourse and quality of social interaction even when artifacts are being used. Responding to Engstrom's (1999) invitation to take artifacts seriously, three studies are described in which a material object was essential to a classroom activity. The…

  8. Reducing child uncooperative behavior during dental treatment through modeling and reinforcement.

    PubMed

    Stokes, T F; Kennedy, S H

    1980-01-01

    The uncooperative behavior of grade-school children during dental treatment was examined. Forty children enrolled in a government dental program were observed during treatment conditions involving instructions concerning the appropriate behavior required by the dental practitioner, description of the objective procedures and subjective experience the child could expect, praise for appropriate behavior, and a colorful stamp for coming to the clinic. Eight of these children whose behavior was still too disruptive for effective dentistry were formally introduced to additional intervention procedures of tangible consequences for cooperative behavior, and observation of peers and by peers during actual dental treatment. Within a multiple baseline design, the intervention conditions were effective in decreasing the children's uncooperative behavior to acceptable levels.

  9. Root Canal Therapy Reduces Multiple Dimensions of Pain: A National Dental PBRN Study

    PubMed Central

    Law, Alan S.; Nixdorf, Donald R.; Rabinowitz, Ira; Reams, Gregory J.; Smith, James A.; Torres, Anibal V.; Harris, D. Robert

    2014-01-01

    Background Initial orthograde root canal therapy (RCT) is used to treat dentoalveolar pathosis. The affect RCT has on pain intensity has been frequently reported, but the affect on other dimensions of pain has not. Also, the lack of large prospective studies involving diverse groups of patients and practitioners that are not involved in data collection suggest that there are multiple opportunities for bias to be introduced when this data is systematically aggregated. Method This prospective observational study assessed pain intensity, duration, and its interference with daily activities among RCT patients. Sixty-two practitioners (46 general dentists, 16 endodontists) in the National Dental Practice-Based Research Network enrolled patients requiring RCT. Patient reported data were collected before, immediately following, and one week after treatment using the Graded Chronic Pain Scale. Results Enrollment of 708 patients was completed over 6 months with 655 patients (93%) providing one-week follow-up data. Prior to treatment, patients reported a mean (±standard deviation) worst pain intensity of 5.3±3.8 (0-10 scale), 50% had “severe” pain (≥7), and mean days in pain and days pain interfered with activities were 3.6±2.7 and 0.5±1.2, respectively. Following treatment, patients reported a mean worst pain intensity of 3.0±3.2, 19% had “severe” pain, and mean days in pain and days with pain interference were 2.1±2.4 and 0.4±1.1, respectively. All changes were statistically significant (p<0.0001). Conclusions RCT is an effective treatment for patients experiencing pain, significantly reducing pain intensity, duration, and related interference. Further research is needed to reduce the proportion of patients reporting “severe” post-operative pain. PMID:25190605

  10. Frequent Dental Scaling Is Associated with a Reduced Risk of Periprosthetic Infection following Total Knee Arthroplasty: A Nationwide Population-Based Nested Case-Control Study

    PubMed Central

    Tai, Ta-Wei; Lin, Tzu-Chieh; Ho, Chia-Jung; Kao Yang, Yea-Huei; Yang, Chyun-Yu

    2016-01-01

    Oral bacteremia has been presumed to be an important risk factor for total knee arthroplasty (TKA) infection. We aimed to investigate whether dental scaling could reduce the risk of TKA infection. A nested case-control study was conducted to compare 1,291 TKA patients who underwent resection arthroplasty for infected TKA and 5,004 matched controls without infection in the TKA cohort of Taiwan’s National Health Insurance Research Database (NHIRD). The frequency of dental scaling was analyzed. Multiple conditional logistic regression was used to assess the frequency of dental scaling and the risk of TKA infection. The percentage of patients who received dental scaling was higher in the control group than in the TKA infection group. The risk for TKA infection was 20% lower for patients who received dental scaling at least once within a 3-year period than for patients who never received dental scaling. Moreover, the risk of TKA infection was reduced by 31% among patients who underwent more frequent dental scaling (5–6 times within 3 years). Frequent and regular dental scaling is associated with a reduced risk of TKA infection. PMID:27336912

  11. Frequent Dental Scaling Is Associated with a Reduced Risk of Periprosthetic Infection following Total Knee Arthroplasty: A Nationwide Population-Based Nested Case-Control Study.

    PubMed

    Tai, Ta-Wei; Lin, Tzu-Chieh; Ho, Chia-Jung; Kao Yang, Yea-Huei; Yang, Chyun-Yu

    2016-01-01

    Oral bacteremia has been presumed to be an important risk factor for total knee arthroplasty (TKA) infection. We aimed to investigate whether dental scaling could reduce the risk of TKA infection. A nested case-control study was conducted to compare 1,291 TKA patients who underwent resection arthroplasty for infected TKA and 5,004 matched controls without infection in the TKA cohort of Taiwan's National Health Insurance Research Database (NHIRD). The frequency of dental scaling was analyzed. Multiple conditional logistic regression was used to assess the frequency of dental scaling and the risk of TKA infection. The percentage of patients who received dental scaling was higher in the control group than in the TKA infection group. The risk for TKA infection was 20% lower for patients who received dental scaling at least once within a 3-year period than for patients who never received dental scaling. Moreover, the risk of TKA infection was reduced by 31% among patients who underwent more frequent dental scaling (5-6 times within 3 years). Frequent and regular dental scaling is associated with a reduced risk of TKA infection. PMID:27336912

  12. Cytological artifacts masquerading interpretation

    PubMed Central

    Sahay, Khushboo; Mehendiratta, Monica; Rehani, Shweta; Kumra, Madhumani; Sharma, Rashi; Kardam, Priyanka

    2013-01-01

    Background: Cytological artifacts are important to learn because an error in routine laboratory practice can bring out an erroneous result. Aims: The aim of this study was to analyze the effects of delayed fixation and morphological discrepancies created by deliberate addition of extraneous factors on the interpretation and/or diagnosis of an oral cytosmear. Materials and Methods: A prospective study was carried out using papanicolaou and hematoxylin and eosin-stained oral smears, 6 each from 66 volunteer dental students with deliberate variation in fixation delay timings, with and without changes in temperature, undue pressure while smear making and intentional addition of contaminants. The fixation delay at room temperature was carried out at an interval of every 30 minutes, 1 day and 1 week and was continued till the end of 1 day, 1 week, and 1 month, respectively. The temperature variations included 60 to 70°C and 3 to 4°C. Results: Light microscopically, the effect of delayed fixation at room temperature appeared first on cytoplasm followed by nucleus within the first 2 hours and on the 4th day, respectively, till complete cytoplasmic degeneration on the 23rd day. However, delayed fixation at variable temperature brought faster degenerative changes at higher temperature than lower temperature. Effect of extraneous factors revealed some interesting facts. Conclusions: In order to justify a cytosmear interpretation, a cytologist must be well acquainted with delayed fixation-induced cellular changes and microscopic appearances of common contaminants so as to implicate better prognosis and therapy. PMID:24648667

  13. MADR: metal artifact detection and reduction

    NASA Astrophysics Data System (ADS)

    Jaiswal, Sunil Prasad; Ha, Sungsoo; Mueller, Klaus

    2016-04-01

    Metal in CT-imaged objects drastically reduces the quality of these images due to the severe artifacts it can cause. Most metal artifacts reduction (MAR) algorithms consider the metal-affected sinogram portions as the corrupted data and replace them via sophisticated interpolation methods. While these schemes are successful in removing the metal artifacts, they fail to recover some of the edge information. To address these problems, the frequency shift metal artifact reduction algorithm (FSMAR) was recently proposed. It exploits the information hidden in the uncorrected image and combines the high frequency (edge) components of the uncorrected image with the low frequency components of the corrected image. Although this can effectively transfer the edge information of the uncorrected image, it also introduces some unwanted artifacts. The essential problem of these algorithms is that they lack the capability of detecting the artifacts and as a result cannot discriminate between desired and undesired edges. We propose a scheme that does better in these respects. Our Metal Artifact Detection and Reduction (MADR) scheme constructs a weight map which stores whether a pixel in the uncorrected image belongs to an artifact region or a non-artifact region. This weight matrix is optimal in the Linear Minimum Mean Square Sense (LMMSE). Our results demonstrate that MADR outperforms the existing algorithms and ensures that the anatomical structures close to metal implants are better preserved.

  14. Edge-preserving metal artifact reduction

    NASA Astrophysics Data System (ADS)

    Meyer, Esther; Raupach, Rainer; Lell, Michael; Schmidt, Bernhard; Kachelriess, Marc

    2012-03-01

    Metal implants in the field of measurement lead to strong artifacts in CT images and reduce the image quality and the diagnostic value severely. We introduce frequency split metal artifact reduction (FSMAR), a conceptually new MAR method which is designed to reduce metal artifacts and preserve details and edges of structures even close to metal implants. There are many MAR methods which simply replace unreliable parts of the projection data by inpainting. FSMAR is a combination of an inpainting-based MAR method with a frequency split approach. Normalized metal artifact reduction (NMAR) is chosen as the inpainting-based MAR method in this work. The high frequencies of the original image, where all rawdata were used for the reconstruction, are combined with an NMAR-corrected image. NMAR uses a normalization step to reduce metal artifacts without introducing severe new artifacts. Algorithms using a frequency split were already used in CT for example to reduce cone-beam artifacts. FSMAR is tested for patient datasets with different metal implants. The study includes patients with hip prostheses, a neuro coil, and a spine fixation. All datasets were scanned with modern clinical dual source CT scanners. In contrast to other MAR methods, FSMAR yields images without the usual blurring close to metal implants.

  15. Corrosion and Preservation of Bronze Artifacts.

    ERIC Educational Resources Information Center

    Walker, Robert

    1980-01-01

    Reviews chemical information relating to the corrosion of bronze artifacts. Properties of copper alloys are reviewed, with a thorough discussion of the specialized properties of bronze. Techniques to reduce or eliminate corrosion are listed. (CS)

  16. Evidence summary: which dental liners under amalgam restorations are more effective in reducing postoperative sensitivity?

    PubMed

    Nasser, Mona

    2011-06-10

    Since August 2009, members of the Primary Care Dentistry Research Forum (www.dentistryresearch.org) have taken part in an online vote to identify questions in day-to-day practice that they felt most needed to be answered with conclusive research. The question that receives the most votes each month forms the subject of a critical appraisal of the relevant literature. Each month a new round of voting takes place to decide which further questions will be reviewed. Dental practitioners and dental care professionals are encouraged to take part in the voting and submit their own questions to be included in the vote by joining the website. The paper below details a summary of the findings of the ninth critical appraisal. In order to address the question raised by dentistry research forum, first a search was conducted for systematic reviews on the topic. There was one systematic review retrieved comparing bonded amalgam restorations versus non-bonded amalgam restorations. However, there was no other systematic review identified assessing the effectiveness of dental liners under amalgam restorations in general. Therefore, a search was conducted for any randomised controlled trial (RCT) comparing use of a lining under amalgam restorations versus no lining or RCTs comparing differing lining materials under amalgam against each other. There were eight relevant RCTs identified. Due to the low quality, small sample sizes or lack of adequate reporting of the outcome data, the evidence is inadequate to claim or refute a difference in postoperative sensitivity between different dental liners. Further well-conducted RCTs are needed to answer this question. These RCTs would be preferably included and synthesised in a systematic review.

  17. Imaging Artifacts in Echocardiography.

    PubMed

    Le, Huong T; Hangiandreou, Nicholas; Timmerman, Robert; Rice, Mark J; Smith, W Brit; Deitte, Lori; Janelle, Gregory M

    2016-03-01

    Artifacts are frequently encountered during echocardiographic examinations. An understanding of the physics and underlying assumptions of ultrasound processing involved with image generation is important for accurate interpretation of 2D grayscale, spectral Doppler, color flow Doppler, and 3D artifacts and their clinical implications.

  18. Artifacts in musculoskeletal ultrasonography.

    PubMed

    Taljanovic, Mihra S; Melville, David M; Scalcione, Luke R; Gimber, Lana H; Lorenz, Eileen J; Witte, Russell S

    2014-02-01

    During the past 2 decades, high-resolution ultrasonography (US) has been increasingly utilized in the diagnosis of musculoskeletal trauma and diseases with results comparable with MR imaging. US has an advantage over other cross-sectional modalities in many circumstances due to its superior spatial resolution and ability to allow dynamic assessment. When performing musculoskeletal US, the examiner has to be knowledgeable in the complex anatomy of the musculoskeletal system and US imaging technique. Additionally, he or she must be familiar with several common imaging artifacts in musculoskeletal US that may be mistaken for pathology, as well as several artifacts that frequently accompany pathologic conditions. These artifacts may occur with both B-mode gray-scale and Doppler imaging. In this article, we discuss common artifacts seen in musculoskeletal US and techniques to avoid or minimize these artifacts during clinical US examinations.

  19. WE-D-18A-01: Evaluation of Three Commercial Metal Artifact Reduction Methods for CT Simulations in Radiation Therapy Treatment Planning

    SciTech Connect

    Huang, J; Kerns, J; Nute, J; Liu, X; Stingo, F; Followill, D; Mirkovic, D; Howell, R; Kry, S

    2014-06-15

    Purpose: To evaluate three commercial metal artifact reduction methods (MAR) in the context of radiation therapy treatment planning. Methods: Three MAR strategies were evaluated: Philips O-MAR, monochromatic imaging using Gemstone Spectral Imaging (GSI) dual energy CT, and monochromatic imaging with metal artifact reduction software (GSIMARs). The Gammex RMI 467 tissue characterization phantom with several metal rods and two anthropomorphic phantoms (pelvic phantom with hip prosthesis and head phantom with dental fillings), were scanned with and without (baseline) metals. Each MAR method was evaluated based on CT number accuracy, metal size accuracy, and reduction in the severity of streak artifacts. CT number difference maps between the baseline and metal scan images were calculated, and the severity of streak artifacts was quantified using the percentage of pixels with >40 HU error (“bad pixels”). Results: Philips O-MAR generally reduced HU errors in the RMI phantom. However, increased errors and induced artifacts were observed for lung materials. GSI monochromatic 70keV images generally showed similar HU errors as 120kVp imaging, while 140keV images reduced errors. GSI-MARs systematically reduced errors compared to GSI monochromatic imaging. All imaging techniques preserved the diameter of a stainless steel rod to within ±1.6mm (2 pixels). For the hip prosthesis, O-MAR reduced the average % bad pixels from 47% to 32%. For GSI 140keV imaging, the percent of bad pixels was reduced from 37% to 29% compared to 120kVp imaging, while GSI-MARs further reduced it to 12%. For the head phantom, none of the MAR methods were particularly successful. Conclusion: The three MAR methods all improve CT images for treatment planning to some degree, but none of them are globally effective for all conditions. The MAR methods were successful for large metal implants in a homogeneous environment (hip prosthesis) but were not successful for the more complicated case of dental

  20. Artifacts and essentialism

    PubMed Central

    Gelman, Susan A.

    2013-01-01

    Psychological essentialism is an intuitive folk belief positing that certain categories have a non-obvious inner “essence” that gives rise to observable features. Although this belief most commonly characterizes natural kind categories, I argue that psychological essentialism can also be extended in important ways to artifact concepts. Specifically, concepts of individual artifacts include the non-obvious feature of object history, which is evident when making judgments regarding authenticity and ownership. Classic examples include famous works of art (e.g., the Mona Lisa is authentic because of its provenance), but ordinary artifacts likewise receive value from their history (e.g., a worn and tattered blanket may have special value if it was one's childhood possession). Moreover, in some cases, object history may be thought to have causal effects on individual artifacts, much as an animal essence has causal effects. I review empirical support for these claims and consider the implications for both artifact concepts and essentialism. This perspective suggests that artifact concepts cannot be contained in a theoretical framework that focuses exclusively on similarity or even function. Furthermore, although there are significant differences between essentialism of natural kinds and essentialism of artifact individuals, the commonalities suggest that psychological essentialism may not derive from folk biology but instead may reflect more domain-general perspectives on the world. PMID:23976903

  1. An evaluation of a commercial chewing gum in combination with normal toothbrushing for reducing dental plaque and gingivitis.

    PubMed

    Sharma, N C; Galustians, J H; Qaqish, J G

    2001-07-01

    New evidence suggests a beneficial outcome to chewing a sugarless gum as an added component to a regular, twice-daily toothbrushing regimen. Results of a 4-week study performed on 78 adults with preexisting gingivitis showed a significant reduction of dental plaque and gingivitis when the test group of 39 adults chewed 2 pieces of ARM & HAMMER Dental Care The Baking Soda Gum (AHDC)--a sugar-free chewing gum containing sorbitol, malitol, xylitol, and sodium bicarbonate--for 20 minutes twice a day in conjunction with once-daily toothbrushing for 60 seconds. The control group, also comprised of 39 adults, used breath mints (the study placebo) twice a day in conjunction with the same toothbrushing regimen. There were no statistically significant differences in plaque and gingivitis scores at the baseline examination. Using the Quigley-Hein Plaque Index, the test group experienced a 17% reduction in plaque over 4 weeks, while the control group reduced their plaque amounts by approximately 9% over the same period. Lobene's Mean Gingivitis Index scores were equally significant: a nearly 10% decline for the test group compared to almost 2% for the control group. This article describes the 4-week study and its promising results. PMID:11913304

  2. An evaluation of a commercial chewing gum in combination with normal toothbrushing for reducing dental plaque and gingivitis.

    PubMed

    Sharma, N C; Galustians, J H; Qaqish, J G

    2001-07-01

    New evidence suggests a beneficial outcome to chewing a sugarless gum as an added component to a regular, twice-daily toothbrushing regimen. Results of a 4-week study performed on 78 adults with preexisting gingivitis showed a significant reduction of dental plaque and gingivitis when the test group of 39 adults chewed 2 pieces of ARM & HAMMER Dental Care The Baking Soda Gum (AHDC)--a sugar-free chewing gum containing sorbitol, malitol, xylitol, and sodium bicarbonate--for 20 minutes twice a day in conjunction with once-daily toothbrushing for 60 seconds. The control group, also comprised of 39 adults, used breath mints (the study placebo) twice a day in conjunction with the same toothbrushing regimen. There were no statistically significant differences in plaque and gingivitis scores at the baseline examination. Using the Quigley-Hein Plaque Index, the test group experienced a 17% reduction in plaque over 4 weeks, while the control group reduced their plaque amounts by approximately 9% over the same period. Lobene's Mean Gingivitis Index scores were equally significant: a nearly 10% decline for the test group compared to almost 2% for the control group. This article describes the 4-week study and its promising results.

  3. Reference Artifacts for NDE

    SciTech Connect

    Bono, M; Hibbard, R; Martz, H E

    2003-02-11

    Two reference artifacts will be fabricated for this study. One of the artifacts will have a cylindrical geometry and will contain features similar to those on an SNRT target. The second artifact will have a spherical geometry and will contain features similar to those on a Double Shell target. The artifacts were designed for manufacturability and to provide a range of features that can be measured using NDE methods. The cylindrical reference artifact is illustrated in Figure 1. This artifact consists of a polystyrene body containing two steps and a machined slot, into which will fit a tracer made of doped polystyrene. The polystyrene body contains several grooves and can be fabricated entirely on a diamond turning machine. The body can be machined by turning a PS rod to a diameter slightly greater than the finished diameter of 2 mm. The part can be moved off-axis to face it off and to machine the steps, slot, and grooves. The tracer contains a drilled hole and a milled slot, which could be machined with a single setup on a milling machine. Once assembled, the artifact could be placed in a Be tube or other structure relevant to target assemblies. The assembled artifact will contain many features that could be measured using various NDE methods. Some of these features are: Diameter; Maximum height; Step height; Dimensions of upper step; Radius at the union of the bottom of step and the vertical wall; Sizes of the grooves; Distance from step to groove; Slot width; Slot height; Location of the groove beneath the tracer; Diameter and location of drilled hole in tracer; and Size and location of slot in tracer. The spherical reference artifact is illustrated in Figure 2. This artifact is intended to replicate a double shell target, which consists of concentric polymer spheres separated by aerogel. The artifact consists of an upper hemispherical shell composed of 1% BrCH, which mates via a step joint with a hemispherical component made of polystyrene. This lower component

  4. Influence of metallic artifact filtering on MEG signals for source localization during interictal epileptiform activity

    NASA Astrophysics Data System (ADS)

    Migliorelli, Carolina; Alonso, Joan F.; Romero, Sergio; Mañanas, Miguel A.; Nowak, Rafał; Russi, Antonio

    2016-04-01

    Objective. Medical intractable epilepsy is a common condition that affects 40% of epileptic patients that generally have to undergo resective surgery. Magnetoencephalography (MEG) has been increasingly used to identify the epileptogenic foci through equivalent current dipole (ECD) modeling, one of the most accepted methods to obtain an accurate localization of interictal epileptiform discharges (IEDs). Modeling requires that MEG signals are adequately preprocessed to reduce interferences, a task that has been greatly improved by the use of blind source separation (BSS) methods. MEG recordings are highly sensitive to metallic interferences originated inside the head by implanted intracranial electrodes, dental prosthesis, etc and also coming from external sources such as pacemakers or vagal stimulators. To reduce these artifacts, a BSS-based fully automatic procedure was recently developed and validated, showing an effective reduction of metallic artifacts in simulated and real signals (Migliorelli et al 2015 J. Neural Eng. 12 046001). The main objective of this study was to evaluate its effects in the detection of IEDs and ECD modeling of patients with focal epilepsy and metallic interference. Approach. A comparison between the resulting positions of ECDs was performed: without removing metallic interference; rejecting only channels with large metallic artifacts; and after BSS-based reduction. Measures of dispersion and distance of ECDs were defined to analyze the results. Main results. The relationship between the artifact-to-signal ratio and ECD fitting showed that higher values of metallic interference produced highly scattered dipoles. Results revealed a significant reduction on dispersion using the BSS-based reduction procedure, yielding feasible locations of ECDs in contrast to the other two approaches. Significance. The automatic BSS-based method can be applied to MEG datasets affected by metallic artifacts as a processing step to improve the localization of

  5. Reduced dental calcium expression and dental mass in chronic sleep deprived rats: Combined EDS, TOF-SIMS, and micro-CT analysis

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Jie; Huang, Yung-Kai; Chou, Hsiu-Chu; Pai, Man-Hui; Lee, Ai-Wei; Mai, Fu-Der; Chang, Hung-Ming

    2015-08-01

    Teeth are the hardest tissue in the body. The growth of teeth is closely regulated by circadian rhythmicity. Considering that sleep deprivation (SD) is a severe condition that disrupts normal circadian rhythmicity, this study was conducted to determine whether calcium expression (the major element participating in teeth constitution), and dental mass would be significantly impaired following SD. Adolescent rats subjected to 3 weeks of SD were processed for energy dispersive spectrum (EDS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and micro-computed tomography (micro-CT) analyses. The EDS and TOF-SIMS results indicated that high calcium intensity was detected in both the upper and lower incisors of untreated rats. Micro-CT analysis corresponded closely with spectral data in which an enhanced dental mass was calculated in intact animals. However, following SD, both calcium expression and the dental mass were remarkably decreased to nearly half those of the untreated values. Because SD plays a detrimental role in impairing dental structure, establishing satisfactory sleep behavior would therefore serve as a crucial strategy for preventing or improving prevalent dental dysfunctions.

  6. Facts in artifacts

    PubMed Central

    Bindhu, PR; Krishnapillai, Rekha; Thomas, Priya; Jayanthi, P

    2013-01-01

    Examination of microscopic sections of animal tissues reveals facts which are not always related to its normal histology or pathology. Processing of tissue specimens consists of lengthy procedures from the stage of surgical removal to the stained and mounted microscopic sections. Defects are common in tissue sections as a result of faulty procedures. These defects are referred to as artifacts. They lead to misinterpretation of histopathological diagnosis but at times they throw limelight into diagnosis. This paper attempts to put together all the facts regarding the various artifacts that are encountered in histopathology. PMID:24574659

  7. Facts in artifacts.

    PubMed

    Bindhu, Pr; Krishnapillai, Rekha; Thomas, Priya; Jayanthi, P

    2013-09-01

    Examination of microscopic sections of animal tissues reveals facts which are not always related to its normal histology or pathology. Processing of tissue specimens consists of lengthy procedures from the stage of surgical removal to the stained and mounted microscopic sections. Defects are common in tissue sections as a result of faulty procedures. These defects are referred to as artifacts. They lead to misinterpretation of histopathological diagnosis but at times they throw limelight into diagnosis. This paper attempts to put together all the facts regarding the various artifacts that are encountered in histopathology.

  8. ORGANIC SPECIATION SAMPLING ARTIFACTS

    EPA Science Inventory

    Sampling artifacts for molecular markers from organic speciation of particulate matter were investigated by analyzing forty-one samples collected in Philadelphia as a part of the Northeast Oxidant and Particulate Study (NEOPS). Samples were collected using a high volume sampler ...

  9. Characterization of mucosa-associated bacterial communities of the mouse intestine by terminal restriction fragment length polymorphism: Utility of sampling strategies and methods to reduce single-stranded DNA artifacts.

    PubMed

    Costa, Estela; Puhl, Nathan J; Selinger, L Brent; Inglis, G Douglas

    2009-08-01

    Terminal restriction fragment length polymorphism (T-RFLP) is a molecular technique used for comparative analysis of microbial community structure and dynamics. We evaluated three sampling methods for recovering bacterial community DNA associated with intestinal mucosa of mice (i.e. mechanical agitation with PBS, hand washing with PBS containing Tween 80, and direct DNA extraction from mucosal plugs). In addition, the utility of two methods (i.e. Klenow fragment and mung-bean nuclease) to reduce single-stranded DNA artifacts was tested. T-RFLP analysis indicated that diverse communities of bacteria are associated with mucosa of the ileum, cecum, and descending colon of mice. Although there was no significant difference in bacterial community structure between the mechanical agitation and direct DNA extraction methods regardless of intestinal location, community diversity was reduced for the hand wash method in the colon. The use of Klenow fragment and mung-bean nuclease have been reported to eliminate single-stranded DNA artifacts (i.e. pseudo-T-restriction fragments), but neither method was beneficial for characterizing mucosa-associated bacterial communities of the mouse cecum. Our study showed that the mechanical agitation and direct plug extraction methods yielded equivalent bacterial community DNA from the mucosa of the small and large intestines of mice, but the latter method was superior for logistical reasons. We also applied a combination of different statistical approaches to analyze T-RFLP data, including statistical detection of true peaks, analysis of variance for peak number, and group significance test, which provided a quantitative improvement for the interpretation of the T-RFLP data.

  10. Dental Amalgam

    MedlinePlus

    ... Products and Medical Procedures Dental Devices Dental Amalgam Dental Amalgam Share Tweet Linkedin Pin it More sharing options Linkedin Pin it Email Print Dental amalgam is a dental filling material which is ...

  11. Effectiveness of 2 scavenger mask systems for reducing exposure to nitrous oxide in a hospital-based pediatric dental clinic: a pilot study.

    PubMed

    Freilich, Marshall M; Alexander, Laura; Sándor, George K B; Judd, Peter

    2007-09-01

    Chronic exposure to elevated ambient air levels of nitrous oxide during nitrous oxide/ oxygen (N2O/2) sedation can result in deleterious side effects to dentists and auxiliary staff. A sampling survey was done in the outpatient dental clinic at the Hospital for Sick Children to determine whether airborne nitrous oxide (N2O) gas concentrations were within established regulatory limits. The effectiveness of 2 scavenger mask systems, the Matrix Medical single-mask system and the Porter/Brown double-mask system, for reducing airborne contamination in a clinical environment during the treatment of pediatric dental patients was compared in a pilot study. The results indicated that the double-mask system more effectively minimized N2O exposure during N2O/O2 sedation of outpatients for a variety of clinical pediatric dental procedures.

  12. An evaluation of three commercially available metal artifact reduction methods for CT imaging

    PubMed Central

    Huang, Jessie Y; Kerns, James R; Nute, Jessica L; Liu, Xinming; Balter, Peter A; Stingo, Francesco C; Followill, David S; Mirkovic, Dragan; Howell, Rebecca M; Kry, Stephen F

    2015-01-01

    Three commercial metal artifact reduction methods were evaluated for use in computed tomography (CT) imaging in the presence of clinically realistic metal implants: Philips O-MAR, GE's monochromatic Gemstone Spectral Imaging (GSI) using dual-energy CT, and GSI monochromatic imaging with metal artifact reduction software applied (MARs). Each method was evaluated according to CT number accuracy, metal size accuracy, and streak artifact severity reduction by using several phantoms, including three anthropomorphic phantoms containing metal implants (hip prosthesis, dental fillings, and spinal fixation rods). All three methods showed varying degrees of success for the hip prosthesis and spinal fixation rod cases, while none were particularly beneficial for dental artifacts. Limitations of the methods were also observed. MARs underestimated the size of metal implants and introduced new artifacts in imaging planes beyond the metal implant when applied to dental artifacts, and both the O-MAR and MARs algorithms induced artifacts for spinal fixation rods in a thoracic phantom. Our findings suggest that all three artifact mitigation methods may benefit patients with metal implants, though they should be used with caution in certain scenarios. PMID:25585685

  13. An evaluation of three commercially available metal artifact reduction methods for CT imaging

    NASA Astrophysics Data System (ADS)

    Huang, Jessie Y.; Kerns, James R.; Nute, Jessica L.; Liu, Xinming; Balter, Peter A.; Stingo, Francesco C.; Followill, David S.; Mirkovic, Dragan; Howell, Rebecca M.; Kry, Stephen F.

    2015-02-01

    Three commercial metal artifact reduction methods were evaluated for use in computed tomography (CT) imaging in the presence of clinically realistic metal implants: Philips O-MAR, GE’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI monochromatic imaging with metal artifact reduction software applied (MARs). Each method was evaluated according to CT number accuracy, metal size accuracy, and streak artifact severity reduction by using several phantoms, including three anthropomorphic phantoms containing metal implants (hip prosthesis, dental fillings and spinal fixation rods). All three methods showed varying degrees of success for the hip prosthesis and spinal fixation rod cases, while none were particularly beneficial for dental artifacts. Limitations of the methods were also observed. MARs underestimated the size of metal implants and introduced new artifacts in imaging planes beyond the metal implant when applied to dental artifacts, and both the O-MAR and MARs algorithms induced artifacts for spinal fixation rods in a thoracic phantom. Our findings suggest that all three artifact mitigation methods may benefit patients with metal implants, though they should be used with caution in certain scenarios.

  14. Hand hygiene in the dental setting: reducing the risk of infection.

    PubMed

    Fluent, Marie T

    2013-09-01

    Hand hygiene remains the single most important measure for reducing the risk of healthcare-associated infections. In the past 20 years, hand-washing recommendations and guidelines have become increasingly complex, and a plethora of products have become available. This article aims to discuss and clarify the fundamentals of appropriate hand hygiene in dentistry. PMID:24564616

  15. Teaching Social Studies with Artifacts.

    ERIC Educational Resources Information Center

    Morris, Ronald Vaughan

    2000-01-01

    Considers the reasons for utilizing artifacts when teaching social studies to children. Describes seven artifact kits: (1) an object box; (2) resource kit; (3) primary source enhancement kit; (4) symbol kits; (5) economic process kit; (6) packs; and (7) a kit for an archaeology dig. Provides an appendix for sources of artifacts. (CMK)

  16. Metrological multispherical freeform artifact

    NASA Astrophysics Data System (ADS)

    Blobel, Gernot; Wiegmann, Axel; Siepmann, Jens; Schulz, Michael

    2016-07-01

    Precisely known artifacts are required to characterize the accuracy of asphere and freeform measuring instruments. To this end the best knowledge of the surface characteristics in conjunction with a low measurement uncertainty are necessary. Because this is a challenging task for typical freeform surfaces used in optical systems, the concept of "metrological" artifacts is introduced. We have developed a multispherical freeform artifact for performance tests of tactile touch probe and contact-free optical measuring systems. The measurement accuracy of the complete form and the deviation from calibrated spherical sections can thus be determined. The radius calibration of multiple spherical sections is performed with an extended radius measuring procedure by interferometry. Evaluated surface forms of different measuring methods and the radii determined can be compared to each other. In this study, a multispherical freeform specimen made of copper, with two differing radii, has been measured by two optical measuring methods, a full field measuring tilted-wave interferometer and a high accuracy cylinder coordinate measuring machine with an optical probe. The surface form measurements are evaluated and compared, and the radii determined are compared to the results of a radius measurement bench.

  17. Artifacts in magnetic measurements of fluid samples

    NASA Astrophysics Data System (ADS)

    Boekelheide, Z.; Dennis, C. L.

    2016-08-01

    Applications of magnetic fluids are ever increasing, as well as the corresponding need to be able to characterize these fluids in situ. Commercial magnetometers are accurate and well-characterized for solid and powder samples, but their use with fluid samples is more limited. Here, we describe artifacts which can occur in magnetic measurements of fluid samples and their impact. The most critical problem in the measurement of fluid samples is the dynamic nature of the sample position and size/shape. Methods to reduce these artifacts are also discussed, such as removal of air bubbles and dynamic centering.

  18. An Additive Manufacturing Test Artifact.

    PubMed

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039

  19. An Additive Manufacturing Test Artifact

    PubMed Central

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039

  20. An Additive Manufacturing Test Artifact.

    PubMed

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system.

  1. Post-cremation taphonomy and artifact preservation.

    PubMed

    Warren, Michael W; Schultz, John J

    2002-05-01

    Contemporary commercial cremation is a reductive taphonomic process that represents one of the most extreme examples of postmortem human alteration of bone. The thorough reduction and fragmentation of cremated human remains often leaves little biological evidence of diagnostic value. Instead, non-osseous artifacts often provide the best evidence of the origin of the cremated remains, the identity of the decedent, and commingling of the remains of more than one individual. Once human remains have been cremated they are most commonly placed into a processor and reduced into small fragments and fine ash suitable for inurnment or scattering. The type of processor determines the size and utility of the particulates and artifacts available for analysis. The newest type of processors have changed the manner and degree of postmortem bone modification and altered the preservation of diagnostic bone fragments and cremation artifacts. This paper addresses the impact of the newest cremation procedures on forensic analysis of cremated remains.

  2. Dental office ergonomics: how to reduce stress factors and increase efficiency.

    PubMed

    Pollack, R

    1996-06-01

    Ergonomics, the science that studies human stress and strain related to activities, has one primary objective-to prevent work related musculoskeletal disorders, or symptoms that aggravate these disorders. Smart business owners have adopted the practice of ergonomics as an integral element in their ongoing strategies to increase productivity and ensure reduced workers' compensation liability. In British Columbia, however, potentially expensive ergonomic draft regulations created by the province's Workers' Compensation Board in 1993, have been put on hold. These ergonomic standards-described as the stiffest in the world -were to have been implemented across the province in early 1995. Nonetheless, ergonomic practices are alive and thriving in Canadian businesses that are devoted to ensuring a reduction in work-related injuries and salvaging potentially lost productivity. Although it is difficult to document lost productivity, Ontario's Workers' Compensation Board reported that it received 707 repetitive stress injury claims from office workers in 1992, with a per person cost of $7,703. In addition to these costs, each claimant took about 93 days off work. In dentistry, poor working habits, along with repetitive tasks, such as scaling and root planing, contribute greatly to musculoskeletal disorders, stress claims and lost productivity. Our tendency is to adapt awkward and illogical physical postures to access the oral cavity. The key objective for clinicians is to find a position that allows them to achieve optimum access, visibility, comfort and control at all times. With the professional goal to deliver the highest quality of care for a reasonable profit, the practice of ergonomics becomes a core focus in determining how to achieve practice success with less stress.

  3. Redox cycling compounds generate H2O2 in HTS buffers containing strong reducing reagents – real hits or promiscuous artifacts?

    PubMed Central

    Johnston, Paul A.

    2010-01-01

    Redox cycling compounds (RCCs) generate µM concentrations of hydrogen peroxide (H2O2) in the presence of strong reducing agents, common buffer components used to maintain the catalytic activity and/or folding of target proteins for high throughput screening (HTS) assays. H2O2 generated by RCCs can indirectly inhibit the catalytic activity of proteins by oxidizing accessible cysteine, tryptophan, methionine, histidine or selenocysteine residues, and indeed several important classes of protein targets are susceptible to H2O2-mediated inactivation; protein tyrosine phosphatases, cysteine proteases, and metalloenzymes. The main sources of H2O2 in cells are the Nox enzyme/SOD systems, peroxisome metabolism, and the autoxidation of reactive chemicals by enzyme mediated redox cycling at both the microsomal and mitochondrial sites of electron transport. Given the role of H2O2 as a second messenger involved in the regulation of many signaling pathways it is hardly surprising that compounds which can generate intracellular H2O2 by enzyme mediated redox cycling would have pleiotropic effects. RCCs can therefore have serious negative consequences for the probe and/or lead generation process: primary HTS assay hit rates may be inflated by RCC false positives; critical resources will be diverted to develop and implement follow up assays to distinguish RCCs from real hits; and screening databases will become annotated with the promiscuous activity of RCCs. In an attempt to mitigate the serious impact of RCCs on probe and lead generation, two groups have independently developed assays to indentify RCCs. PMID:21075044

  4. Redox cycling compounds generate H2O2 in HTS buffers containing strong reducing reagents--real hits or promiscuous artifacts?

    PubMed

    Johnston, Paul A

    2011-02-01

    Redox cycling compounds (RCCs) generate μM concentrations of hydrogen peroxide (H(2)O(2)) in the presence of strong reducing agents, common buffer components used to maintain the catalytic activity and/or folding of target proteins for high throughput screening (HTS) assays. H(2)O(2) generated by RCCs can indirectly inhibit the catalytic activity of proteins by oxidizing accessible cysteine, tryptophan, methionine, histidine, or selenocysteine residues, and indeed several important classes of protein targets are susceptible to H(2)O(2)-mediated inactivation; protein tyrosine phosphatases, cysteine proteases, and metalloenzymes. The main sources of H(2)O(2) in cells are the Nox enzyme/SOD systems, peroxisome metabolism, and the autoxidation of reactive chemicals by enzyme mediated redox cycling at both the microsomal and mitochondrial sites of electron transport. Given the role of H(2)O(2) as a second messenger involved in the regulation of many signaling pathways it is hardly surprising that compounds that can generate intracellular H(2)O(2) by enzyme mediated redox cycling would have pleiotropic effects. RCCs can therefore have serious negative consequences for the probe and/or lead generation process: primary HTS assay hit rates may be inflated by RCC false positives; crucial resources will be diverted to develop and implement follow up assays to distinguish RCCs from real hits; and screening databases will become annotated with the promiscuous activity of RCCs. In an attempt to mitigate the serious impact of RCCs on probe and lead generation, two groups have independently developed assays to indentify RCCs.

  5. Clinical Evaluation of Normalized Metal Artifact Reduction in kVCT Using MVCT Prior Images (MVCT-NMAR) for Radiation Therapy Treatment Planning

    SciTech Connect

    Paudel, Moti Raj; Mackenzie, Marc; Fallone, B. Gino; Rathee, Satyapal

    2014-07-01

    Purpose: To evaluate the metal artifacts in diagnostic kilovoltage computed tomography (kVCT) images of patients that are corrected by use of a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images: MVCT-NMAR. Methods and Materials: MVCT-NMAR was applied to images from 5 patients: 3 with dual hip prostheses, 1 with a single hip prosthesis, and 1 with dental fillings. The corrected images were evaluated for visualization of tissue structures and their interfaces and for radiation therapy dose calculations. They were compared against the corresponding images corrected by the commercial orthopedic metal artifact reduction algorithm in a Phillips CT scanner. Results: The use of MVCT images for correcting kVCT images in the MVCT-NMAR technique greatly reduces metal artifacts, avoids secondary artifacts, and makes patient images more useful for correct dose calculation in radiation therapy. These improvements are significant, provided the MVCT and kVCT images are correctly registered. The remaining and the secondary artifacts (soft tissue blurring, eroded bones, false bones or air pockets, CT number cupping within the metal) present in orthopedic metal artifact reduction corrected images are removed in the MVCT-NMAR corrected images. A large dose reduction was possible outside the planning target volume (eg, 59.2 Gy to 52.5 Gy in pubic bone) when these MVCT-NMAR corrected images were used in TomoTherapy treatment plans without directional blocks for a prostate cancer patient. Conclusions: The use of MVCT-NMAR corrected images in radiation therapy treatment planning could improve the treatment plan quality for patients with metallic implants.

  6. WE-G-18A-07: Clinical Evaluation of Normalized Metal Artifact Reduction in KVCT Using MVCT Prior Images (MVCT-NMAR) Technique in Radiotherapy

    SciTech Connect

    Paudel, M; MacKenzie, M; Fallone, B; Rathee, S

    2014-06-15

    Purpose: To evaluate the metal artifacts in diagnostic kVCT images of patients that are corrected using a normalized metal artifact reduction method with MVCT prior images, MVCT-NMAR. Methods: An MVCTNMAR algorithm was developed and applied to five patients: three with bilateral hip prostheses, one with unilateral hip prosthesis and one with dental fillings. The corrected images were evaluated for visualization of tissue structures and their interfaces, and for radiotherapy dose calculations. They were also compared against the corresponding images corrected by a commercial metal artifact reduction technique, O-MAR, on a Phillips™ CT scanner. Results: The use of MVCT images for correcting kVCT images in the MVCT-NMAR technique greatly reduces metal artifacts, avoids secondary artifacts, and makes patient images more useful for correct dose calculation in radiotherapy. These improvements are significant over the commercial correction method, provided the MVCT and kVCT images are correctly registered. The remaining and the secondary artifacts (soft tissue blurring, eroded bones, false bones or air pockets, CT number cupping within the metal) present in O-MAR corrected images are removed in the MVCT-NMAR corrected images. Large dose reduction is possible outside the planning target volume (e.g., 59.2 Gy in comparison to 52.5 Gy in pubic bone) when these MVCT-NMAR corrected images are used in TomoTherapy™ treatment plans, as the corrected images no longer require directional blocks for prostate plans in order to avoid the image artifact regions. Conclusion: The use of MVCT-NMAR corrected images in radiotherapy treatment planning could improve the treatment plan quality for cancer patients with metallic implants. Moti Raj Paudel is supported by the Vanier Canada Graduate Scholarship, the Endowed Graduate Scholarship in Oncology and the Dissertation Fellowship at the University of Alberta. The authors acknowledge the CIHR operating grant number MOP 53254.

  7. Effect of 0.12% chlorhexidine in reducing microorganisms found in aerosol used for dental prophylaxis of patients submitted to fixed orthodontic treatment

    PubMed Central

    dos Santos, Isis Rodrigues Menezes; Moreira, Ana Cristina Azevedo; Costa, Myrela Galvão Cardoso; Barbosa, Marcelo de Castellucci e

    2014-01-01

    Objective This study aimed at assessing, in vivo, whether the prior use of 0.12% chlorhexidine as mouthwash would decrease air contamination caused by aerosolized sodium bicarbonate during dental prophylaxis. The study was conducted with 23 patients aged between 10 and 40 years old who were randomly selected and undergoing fixed orthodontic treatment. Methods The study was divided into two phases (T1 and T2) with a 30-day interval in between. In both phases, dental prophylaxis was performed with aerosolized sodium bicarbonate jetted to the upper and lower arches for 4 minutes. In T1, 10 minutes before the prophylaxis procedure, the participants used distilled water as mouthwash for one minute; whereas in T2, mouthwash was performed with 0.12% chlorhexidine. Microbial samples were collected in BHI agar plates for microbiological analysis. Two dishes were positioned on the clinician (10 cm from the mouth) and a third one at 15 cm from the patient's mouth. The samples were incubated for 48 hours at 37°C. Results were expressed in colony-forming units (CFU). Results Statistical analysis carried out by means of Student's t test, as well as Wilconxon and Kruskal-Wallis tests revealed that the prior use of 0.12% chlorhexidine as mouthwash significantly reduced CFU in the three positions studied (P < 0.001). Conclusion The prior use of 0.12% chlorhexidine as mouthwash significantly reduced contamination caused by aerosolized sodium bicarbonate during dental prophylaxis in the orthodontic clinic. PMID:25162572

  8. Prior-based artifact correction (PBAC) in computed tomography

    SciTech Connect

    Heußer, Thorsten Brehm, Marcus; Ritschl, Ludwig; Sawall, Stefan; Kachelrieß, Marc

    2014-02-15

    Purpose: Image quality in computed tomography (CT) often suffers from artifacts which may reduce the diagnostic value of the image. In many cases, these artifacts result from missing or corrupt regions in the projection data, e.g., in the case of metal, truncation, and limited angle artifacts. The authors propose a generalized correction method for different kinds of artifacts resulting from missing or corrupt data by making use of available prior knowledge to perform data completion. Methods: The proposed prior-based artifact correction (PBAC) method requires prior knowledge in form of a planning CT of the same patient or in form of a CT scan of a different patient showing the same body region. In both cases, the prior image is registered to the patient image using a deformable transformation. The registered prior is forward projected and data completion of the patient projections is performed using smooth sinogram inpainting. The obtained projection data are used to reconstruct the corrected image. Results: The authors investigate metal and truncation artifacts in patient data sets acquired with a clinical CT and limited angle artifacts in an anthropomorphic head phantom data set acquired with a gantry-based flat detector CT device. In all cases, the corrected images obtained by PBAC are nearly artifact-free. Compared to conventional correction methods, PBAC achieves better artifact suppression while preserving the patient-specific anatomy at the same time. Further, the authors show that prominent anatomical details in the prior image seem to have only minor impact on the correction result. Conclusions: The results show that PBAC has the potential to effectively correct for metal, truncation, and limited angle artifacts if adequate prior data are available. Since the proposed method makes use of a generalized algorithm, PBAC may also be applicable to other artifacts resulting from missing or corrupt data.

  9. Sound as artifact

    NASA Astrophysics Data System (ADS)

    Benjamin, Jeffrey L.

    A distinguishing feature of the discipline of archaeology is its reliance upon sensory dependant investigation. As perceived by all of the senses, the felt environment is a unique area of archaeological knowledge. It is generally accepted that the emergence of industrial processes in the recent past has been accompanied by unprecedented sonic extremes. The work of environmental historians has provided ample evidence that the introduction of much of this unwanted sound, or "noise" was an area of contestation. More recent research in the history of sound has called for more nuanced distinctions than the noisy/quiet dichotomy. Acoustic archaeology tends to focus upon a reconstruction of sound producing instruments and spaces with a primary goal of ascertaining intentionality. Most archaeoacoustic research is focused on learning more about the sonic world of people within prehistoric timeframes while some research has been done on historic sites. In this thesis, by way of a meditation on industrial sound and the physical remains of the Quincy Mining Company blacksmith shop (Hancock, MI) in particular, I argue for an acceptance and inclusion of sound as artifact in and of itself. I am introducing the concept of an individual sound-form, or sonifact , as a reproducible, repeatable, representable physical entity, created by tangible, perhaps even visible, host-artifacts. A sonifact is a sound that endures through time, with negligible variability. Through the piecing together of historical and archaeological evidence, in this thesis I present a plausible sonifactual assemblage at the blacksmith shop in April 1916 as it may have been experienced by an individual traversing the vicinity on foot: an 'historic soundwalk.' The sensory apprehension of abandoned industrial sites is multi-faceted. In this thesis I hope to make the case for an acceptance of sound as a primary heritage value when thinking about the industrial past, and also for an increased awareness and acceptance

  10. Reducing dental plaque formation and caries development. A review of current methods and implications for novel pharmaceuticals.

    PubMed

    Kalesinskas, Povilas; Kačergius, Tomas; Ambrozaitis, Arvydas; Pečiulienė, Vytautė; Ericson, Dan

    2014-01-01

    Dental caries is an oral disease, which has a high worldwide prevalence despite the availability of various prophylactic means, including the daily use of fluoride toothpastes, water fluoridation, dental sealants, oral health educational programs and various antiseptic mouth-rinses. One important reason for this is uncontrolled increase in consumption of foods containing considerable sucrose concentration, especially among children. Sucrose is easily metabolized by oral bacteria (mostly streptococci) to acids and, subsequently, causing tooth decay or dental caries. In the oral ecosystem, streptococci principally reside on tooth surfaces forming biofilm. Important structural and binding materials of biofilm are glucan polymers synthesized by several isoforms of glucosyltransferase enzyme present in certain species of oral bacteria, including mutans group streptococci - Streptococcus mutans and Streptococcus sobrinus, which preferably colonize humans. Thus, there is a constant need to develop the methods and chemotherapeutics for improving oral health care and decreasing teeth decay through the suppression of cariogenic biofilm formation in the oral cavity. The aim of this paper was to review literature related to the pathogenesis of dental caries as well as currently existing and experimental pharmaceutical substances used for prevention of this process. PMID:25209226

  11. Volume-of-interest reconstruction from severely truncated data in dental cone-beam CT

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Kusnoto, Budi; Han, Xiao; Sidky, E. Y.; Pan, Xiaochuan

    2015-03-01

    As cone-beam computed tomography (CBCT) has gained popularity rapidly in dental imaging applications in the past two decades, radiation dose in CBCT imaging remains a potential, health concern to the patients. It is a common practice in dental CBCT imaging that only a small volume of interest (VOI) containing the teeth of interest is illuminated, thus substantially lowering imaging radiation dose. However, this would yield data with severe truncations along both transverse and longitudinal directions. Although images within the VOI reconstructed from truncated data can be of some practical utility, they often are compromised significantly by truncation artifacts. In this work, we investigate optimization-based reconstruction algorithms for VOI image reconstruction from CBCT data of dental patients containing severe truncations. In an attempt to further reduce imaging dose, we also investigate optimization-based image reconstruction from severely truncated data collected at projection views substantially fewer than those used in clinical dental applications. Results of our study show that appropriately designed optimization-based reconstruction can yield VOI images with reduced truncation artifacts, and that, when reconstructing from only one half, or even one quarter, of clinical data, it can also produce VOI images comparable to that of clinical images.

  12. Artifacts in musculoskeletal MR imaging.

    PubMed

    Singh, Dinesh R; Chin, Michael S M; Peh, Wilfred C G

    2014-02-01

    MR imaging has become an important diagnostic tool in the evaluation of a vast number of pathologies and is of foremost importance in the evaluation of spine, joints, and soft tissue structures of the musculoskeletal system. MR imaging is susceptible to various artifacts that may affect the image quality or even simulate pathologies. Some of these artifacts have gained special importance with the use of higher field strength magnets and with the increasing need for MR imaging in postoperative patients, especially those with previous joint replacements or metallic implants. Artifacts may arise from patient motion or could be due to periodic motion, such as vascular and cardiac pulsation. Artifacts could also arise from various protocol errors including saturation, wraparound, truncation, shading, partial volume averaging, and radiofrequency interference artifacts. Susceptibility artifact occurs at interfaces with different magnetic susceptibilities and is of special importance with increasing use of metallic joint replacement prostheses. Magic angle phenomenon is a special type of artifact that occurs in musculoskeletal MR imaging. It is essential to recognize these artifacts and to correct them because they may produce pitfalls in image interpretation.

  13. Camera artifacts in IUE spectra

    NASA Technical Reports Server (NTRS)

    Bruegman, O. W.; Crenshaw, D. M.

    1994-01-01

    This study of emission line mimicking features in the IUE cameras has produced an atlas of artifiacts in high-dispersion images with an accompanying table of prominent artifacts and a table of prominent artifacts in the raw images along with a medium image of the sky background for each IUE camera.

  14. Intention, History, and Artifact Concepts.

    ERIC Educational Resources Information Center

    Bloom, Paul

    1996-01-01

    Claims that people determine whether something is a member of a given artifact kind by inferring that it was successfully created with the intention that it belong to that kind. Discusses function-based and intentional-historical accounts of artifact concepts. Concludes that a rich set of inferential capacities is needed to constitute a theory of…

  15. Iterative scatter correction based on artifact assessment

    NASA Astrophysics Data System (ADS)

    Wiegert, Jens; Hohmann, Steffen; Bertram, Matthias

    2008-03-01

    In this paper we propose a novel scatter correction methodology for X-ray based cone-beam CT that allows to combine the advantages of projection-based and volume-based correction approaches. The basic idea is to use a potentially non-optimal projection-based scatter correction method and to iteratively optimize its performance by repeatedly assessing remaining scatter-induced artifacts in intermediately reconstructed volumes. The novel approach exploits the fact that due to the flatness of the scatter-background, compensation itself is most easily performed in the projection-domain, while the scatter-induced artifacts can be better observed in the reconstructed volume. The presented method foresees to evaluate the scatter correction efficiency after each iteration by means of a quantitative measure characterizing the amount of residual cupping and to adjust the parameters of the projection-based scatter correction for the next iteration accordingly. The potential of this iterative scatter correction approach is demonstrated using voxelized Monte Carlo scatter simulations as ground truth. Using the proposed iterative scatter correction method, remarkable scatter correction performance was achieved both using simple parametric heuristic techniques as well as by optimizing previously published scatter estimation schemes. For the human head, scatter induced artifacts were reduced from initially 148 HU to less than 8.1 HU to 9.1 HU for different studied methods, corresponding to an artifact reduction exceeding 93%.

  16. The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergetic extrapolation with a DECT scanner.

    PubMed

    Schwahofer, Andrea; Bär, Esther; Kuchenbecker, Stefan; Grossmann, J Günter; Kachelrieß, Marc; Sterzing, Florian

    2015-12-01

    % to 20%. Thus, the improvement is not significant for radiotherapy planning. For amalgam with a density between steel and tungsten, monoenergetic data sets of a patient do not show substantial artifact reduction. The local dose uncertainties around the metal artifact determined for a static field are of the order of 5%. Although dental fillings are smaller than the phantom inserts, metal artifacts could not be reduced effectively. In conclusion, the image based monoenergetic extrapolation method does not provide efficient reduction of the consequences of CT-generated metal artifacts for radiation therapy planning, but the suitability of other MAR methods will be subsequently studied.

  17. The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergetic extrapolation with a DECT scanner.

    PubMed

    Schwahofer, Andrea; Bär, Esther; Kuchenbecker, Stefan; Grossmann, J Günter; Kachelrieß, Marc; Sterzing, Florian

    2015-12-01

    % to 20%. Thus, the improvement is not significant for radiotherapy planning. For amalgam with a density between steel and tungsten, monoenergetic data sets of a patient do not show substantial artifact reduction. The local dose uncertainties around the metal artifact determined for a static field are of the order of 5%. Although dental fillings are smaller than the phantom inserts, metal artifacts could not be reduced effectively. In conclusion, the image based monoenergetic extrapolation method does not provide efficient reduction of the consequences of CT-generated metal artifacts for radiation therapy planning, but the suitability of other MAR methods will be subsequently studied. PMID:26144602

  18. Turquoise Artifact from Teotihuacan

    SciTech Connect

    Spence, Michael W.; Harbottle, Garman; Weigand, Phil C.

    1999-07-01

    Turquoise artifacts appeared sporadically in Mesoamerica as early as the Formative period (Merry de Morales 1987:100, Figure 8.4; Weigand 1989:43). Most occurrences, however, postdate the collapse of Teotihuacan. In the Late Classic and Postclassic periods increasing quantities are found, often in the form of elaborate mosaics, in a wide variety of contexts in central, west and northwest Mexico. Neutron activation analysis has determined that much of this turquoise derives from sources in the southwestern United States (Weigand et al. 1977; Harbottle and Weigand 1992; Weigand and Harbottle 1993). Teotihuacan played a major role in Mesoamerica during the Terminal Formative and Early-Middle Classic periods. It was the dominant power in central Mexico from about the time of Christ to its collapse at about A.D. 650 (Millon 1988, 1992; Cowgill 1996). Throughout this period goods flowed into Teotihuacan from many parts of the Mesoamerican world. Despite this widespread economic interaction, only two pieces of turquoise have been recovered in the city. In the following pages, the context and implications of one of these finds will be examined.

  19. Correction of CT artifacts and its influence on Monte Carlo dose calculations

    SciTech Connect

    Bazalova, Magdalena; Beaulieu, Luc; Palefsky, Steven; Verhaegen, Frank

    2007-06-15

    Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts.

  20. Dental Sealants

    MedlinePlus

    ... Data & Statistics > Find Data by Topic > Dental Sealants Dental Sealants Main Content Dental sealants are thin plastic coatings that protect the chewing surfaces of children’s back teeth from tooth decay. Overall, the prevalence of sealants ...

  1. Archaic artifacts resembling celestial spheres

    NASA Astrophysics Data System (ADS)

    Dimitrakoudis, S.; Papaspyrou, P.; Petoussis, V.; Moussas, X.

    We present several bronze artifacts from the Archaic Age in Greece (750-480 BC) that resemble celestial spheres or forms of other astronomical significance. They are studied in the context of the Dark Age transition from Mycenaean Age astronomical themes to the philosophical and practical revival of astronomy in the Classical Age with its plethora of astronomical devices. These artifacts, mostly votive in nature are spherical in shape and appear in a variety of forms their most striking characteristic being the depiction of meridians and/or an equator. Most of those artifacts come from Thessaly, and more specifically from the temple of Itonia Athena at Philia, a religious center of pan-Hellenic significance. Celestial spheres, similar in form to the small artifacts presented in this study, could be used to measure latitudes, or estimate the time at a known place, and were thus very useful in navigation.

  2. Redox artifacts in electrophysiological recordings

    PubMed Central

    Berman, Jonathan M.

    2013-01-01

    Electrophysiological techniques make use of Ag/AgCl electrodes that are in direct contact with cells or bath. In the bath, electrodes are exposed to numerous experimental conditions and chemical reagents that can modify electrode voltage. We examined voltage offsets created in Ag/AgCl electrodes by exposure to redox reagents used in electrophysiological studies. Voltage offsets were measured in reference to an electrode separated from the solution by an agar bridge. The reducing reagents Tris-2-carboxyethly-phosphine, dithiothreitol (DTT), and glutathione, as well as the oxidizing agent H2O2 used at experimentally relevant concentrations reacted with Ag in the electrodes to produce voltage offsets. Chloride ions and strong acids and bases produced offsets at millimolar concentrations. Electrolytic depletion of the AgCl layer, to replicate voltage clamp and sustained use, resulted in increased sensitivity to flow and DTT. Offsets were sensitive to electrode silver purity and to the amount and method of chloride deposition. For example, exposure to 10 μM DTT produced a voltage offset between 10 and 284 mV depending on the chloride deposition method. Currents generated by these offsets are significant and dependent on membrane conductance and by extension the expression of ion channels and may therefore appear to be biological in origin. These data demonstrate a new source of artifacts in electrophysiological recordings that can affect measurements obtained from a variety of experimental techniques from patch clamp to two-electrode voltage clamp. PMID:23344161

  3. Motion artifact detection in four-dimensional computed tomography images

    NASA Astrophysics Data System (ADS)

    Bouilhol, G.; Ayadi, M.; Pinho, R.; Rit, S.; Sarrut, D.

    2014-03-01

    Motion artifacts appear in four-dimensional computed tomography (4DCT) images because of suboptimal acquisition parameters or patient breathing irregularities. Frequency of motion artifacts is high and they may introduce errors in radiation therapy treatment planning. Motion artifact detection can be useful for image quality assessment and 4D reconstruction improvement but manual detection in many images is a tedious process. We propose a novel method to evaluate the quality of 4DCT images by automatic detection of motion artifacts. The method was used to evaluate the impact of the optimization of acquisition parameters on image quality at our institute. 4DCT images of 114 lung cancer patients were analyzed. Acquisitions were performed with a rotation period of 0.5 seconds and a pitch of 0.1 (74 patients) or 0.081 (40 patients). A sensitivity of 0.70 and a specificity of 0.97 were observed. End-exhale phases were less prone to motion artifacts. In phases where motion speed is high, the number of detected artifacts was systematically reduced with a pitch of 0.081 instead of 0.1 and the mean reduction was 0.79. The increase of the number of patients with no artifact detected was statistically significant for the 10%, 70% and 80% respiratory phases, indicating a substantial image quality improvement.

  4. Metal artifacts correction in cone-beam CT bone imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Ning, Ruola; Conover, David

    2007-03-01

    Cone-beam CT (CBCT) technique is needed by orthopaedists in their new studies to monitor bone volume growth and blood vessel growth of structural bone grafts used in reconstruction surgery. However, titanium plate and screws, which are commonly used to connect bone grafts to host bones, can cause severe streaking artifacts and shading artifact in the reconstructed images due to their high attenuation of x-rays. These metal artifacts will distort the information of the bone and cause difficulties when measuring bone volume growth and the inside blood vessel growth. To solve this problem and help orthopaedists quantitatively record the growth of bone grafts, we present a three-dimensional metal artifact correction technique to correct the streaking artifacts generated by titanium implants. In this project not only the artifacts need to be corrected but also the correct information of the bone is required in the image for the quantitative measurements. Both phantom studies and animal studies were conducted to test this correction method. Images without metal correction and images with metal correction were compared together, as well as the reference bone images acquired without metal. It's shown the streaking and shading artifacts were greatly reduced after metal correction. The accuracy of bone volume measurements was also greatly increased by 79% for phantom studies and 53% for animal studies.

  5. An illustrative review to understand and manage metal-induced artifacts in musculoskeletal MRI: a primer and updates.

    PubMed

    Dillenseger, J P; Molière, S; Choquet, P; Goetz, C; Ehlinger, M; Bierry, G

    2016-05-01

    This article reviews and explains the basic physical principles of metal-induced MRI artifacts, describes simple ways to reduce them, and presents specific reduction solutions. Artifacts include signal loss, pile-up artifacts, geometric distortion, and failure of fat suppression. Their nature and origins are reviewed and explained though schematic representations that ease the understanding. Then, optimization of simple acquisition parameters is detailed. Lastly, dedicated sequences and options specifically developed to reduce metal artifacts (VAT, SEMAC, and MAVRIC) are explained.

  6. MR-driven metal artifact reduction in PET/CT.

    PubMed

    Delso, G; Wollenweber, S; Lonn, A; Wiesinger, F; Veit-Haibach, P

    2013-04-01

    Among the proposed system architectures capable of delivering positron emission tomography/magnetic resonance (PET/MR) datasets, tri-modality systems open an interesting field in which the synergies between these modalities can be exploited to address some of the problems encountered in standalone systems. In this paper we present a feasibility study of the correction of dental streak artifacts in computed tomography (CT)-based attenuation correction images using complementary MR data. The frequency and severity of metal artifacts in oncology patients was studied by inspecting the CT scans of 152 patients examined at our hospital. A prospective correction algorithm using CT and MR information to automatically locate and edit the region affected by metal artifacts was developed and tested retrospectively on data from 15 oncology patients referred for a PET/CT scan. In datasets without malignancies, the activity in Waldeyer's ring was used to measure the maximum uptake variation when the proposed correction was applied. The measured bias ranged from 10% to 30%. In datasets with malignancies on the slices affected by artifacts, the correction led to lesion uptake variations of 6.1% for a lesion 3 cm away from the implant, 1.5% for a lesion 7 cm away and <1% for a lesion 8 cm away.

  7. Striping artifact reduction in lunar orbiter mosaic images

    USGS Publications Warehouse

    Mlsna, P.A.; Becker, T.

    2006-01-01

    Photographic images of the moon from the 1960s Lunar Orbiter missions are being processed into maps for visual use. The analog nature of the images has produced numerous artifacts, the chief of which causes a vertical striping pattern in mosaic images formed from a series of filmstrips. Previous methods of stripe removal tended to introduce ringing and aliasing problems in the image data. This paper describes a recently developed alternative approach that succeeds at greatly reducing the striping artifacts while avoiding the creation of ringing and aliasing artifacts. The algorithm uses a one dimensional frequency domain step to deal with the periodic component of the striping artifact and a spatial domain step to handle the aperiodic residue. Several variations of the algorithm have been explored. Results, strengths, and remaining challenges are presented. ?? 2006 IEEE.

  8. Metal artifact reduction sequence: early clinical applications.

    PubMed

    Olsen, R V; Munk, P L; Lee, M J; Janzen, D L; MacKay, A L; Xiang, Q S; Masri, B

    2000-01-01

    Artifact arising from metal hardware remains a significant problem in orthopedic magnetic resonance imaging. The metal artifact reduction sequence (MARS) reduces the size and intensity of susceptibility artifacts from magnetic field distortion. The sequence, which is based on view angle tilting in combination with increased gradient strength, can be conveniently used in conjunction with any spin-echo sequence and requires no additional imaging time. In patients with persistent pain after femoral neck fracture, the MARS technique allows visualization of marrow adjacent to hip screws, thus enabling diagnosis or exclusion of avascular necrosis. Other applications in the hip include assessment of periprosthetic soft tissues after hip joint replacement surgery, postoperative assessment after resection of bone tumors and reconstruction, and localization of unopacified methyl methacrylate cement prior to hip arthroplasty revision surgery. In the knee, the MARS technique allows visualization of structures adjacent to implanted metal staples, pins, or screws. The technique can significantly improve visualization of periprosthetic bone and soft-tissue structures even in patients who have undergone total knee arthroplasty. In patients with spinal fixation hardware, the MARS technique frequently allows visualization of the vertebral bodies and spinal canal contents. The technique can be helpful after wrist fusion or screw fixation of scaphoid fractures.

  9. Fast image restoration without boundary artifacts.

    PubMed

    Reeves, Stanley J

    2005-10-01

    Fast Fourier transform (FFT)-based restorations are fast, but at the expense of assuming that the blurring and deblurring are based on circular convolution. Unfortunately, when the opposite sides of the image do not match up well in intensity, this assumption can create significant artifacts across the image. If the pixels outside the measured image window are modeled as unknown values in the restored image, boundary artifacts are avoided. However, this approach destroys the structure that makes the use of the FFT directly applicable, since the unknown image is no longer the same size as the measured image. Thus, the restoration methods available for this problem no longer have the computational efficiency of the FFT. We propose a new restoration method for the unknown boundary approach that can be implemented in a fast and flexible manner. We decompose the restoration into a sum of two independent restorations. One restoration yields an image that comes directly from a modified FFT-based approach. The other restoration involves a set of unknowns whose number equals that of the unknown boundary values. By summing the two, the artifacts are canceled. Because the second restoration has a significantly reduced set of unknowns, it can be calculated very efficiently even though no circular convolution structure exists. PMID:16238051

  10. Intention, history, and artifact concepts.

    PubMed

    Bloom, P

    1996-07-01

    What determines our intuitions as to which objects are members of specific artifact kinds? Prior research suggests that factors such as physical appearance, current use, and intended function are not at the core of concepts such as chair, clock and pawn. The theory presented here, based on Levinson's (1993) intentional-historical theory of our concept of art, is that we determine that something is a member of a given artifact kind by inferring that it was successfully created with the intention to belong to that kind. This theory can explain why some properties (such as shape) are more important than others (such as color) when we determine kind membership and can account for why certain objects are judged to be members of artifact kinds even though they are highly dissimilar from other members of the kinds. It can also provide a framework for explaining the conditions under which broken objects cease to be members of their kinds and new artifacts can come into existence. This account of our understanding of artifact concepts is argued to be consistent with more general "essentialist" theories of our understanding of concepts corresponding to proper names and natural kind terms.

  11. Reduction of motion blurring artifacts using respiratory gated CT in sinogram space: A quantitative evaluation

    SciTech Connect

    Lu Wei; Parikh, Parag J.; Hubenschmidt, James P.; Politte, David G.; Whiting, Bruce R.; Bradley, Jeffrey D.; Mutic, Sasa; Low, Daniel A.

    2005-11-15

    Techniques have been developed for reducing motion blurring artifacts by using respiratory gated computed tomography (CT) in sinogram space and quantitatively evaluating the artifact reduction. A synthetic sinogram was built from multiple scans intercepting a respiratory gating window. A gated CT image was then reconstructed using the filtered back-projection algorithm. Wedge phantoms, developed for quantifying the motion artifact reduction, were scanned while being moved using a computer-controlled linear stage. The resulting artifacts appeared between the high and low density regions as an apparent feature with a Hounsfield value that was the average of the two regions. A CT profile through these regions was fit using two error functions, each modeling the partial-volume averaging characteristics for the unmoving phantom. The motion artifact was quantified by determining the apparent distance between the two functions. The blurring artifact had a linear relationship with both the speed and the tangent of the wedge angles. When gating was employed, the blurring artifact was reduced systematically at the air-phantom interface. The gated image of phantoms moving at 20 mm/s showed similar blurring artifacts as the nongated image of phantoms moving at 10 mm/s. Nine patients were also scanned using the synchronized respiratory motion technique. Image artifacts were evaluated in the diaphragm, where high contrast interfaces intercepted the imaging plane. For patients, this respiratory gating technique reduced the blurring artifacts by 9%-41% at the lung-diaphragm interface.

  12. Comparison of cone beam artifacts reduction: two pass algorithm vs TV-based CS algorithm

    NASA Astrophysics Data System (ADS)

    Choi, Shinkook; Baek, Jongduk

    2015-03-01

    In a cone beam computed tomography (CBCT), the severity of the cone beam artifacts is increased as the cone angle increases. To reduce the cone beam artifacts, several modified FDK algorithms and compressed sensing based iterative algorithms have been proposed. In this paper, we used two pass algorithm and Gradient-Projection-Barzilai-Borwein (GPBB) algorithm to reduce the cone beam artifacts, and compared their performance using structural similarity (SSIM) index. In two pass algorithm, it is assumed that the cone beam artifacts are mainly caused by extreme-density(ED) objects, and therefore the algorithm reproduces the cone beam artifacts(i.e., error image) produced by ED objects, and then subtract it from the original image. GPBB algorithm is a compressed sensing based iterative algorithm which minimizes an energy function for calculating the gradient projection with the step size determined by the Barzilai- Borwein formulation, therefore it can estimate missing data caused by the cone beam artifacts. To evaluate the performance of two algorithms, we used testing objects consisting of 7 ellipsoids separated along the z direction and cone beam artifacts were generated using 30 degree cone angle. Even though the FDK algorithm produced severe cone beam artifacts with a large cone angle, two pass algorithm reduced the cone beam artifacts with small residual errors caused by inaccuracy of ED objects. In contrast, GPBB algorithm completely removed the cone beam artifacts and restored the original shape of the objects.

  13. Artifacts in ambient toxicity testing

    SciTech Connect

    Kszos, L.A.; Stewart, A.J.

    1992-01-01

    Short-term toxicity tests with fathead minnow (Pimephales promelas) larvae and Ceriodaphnia dubia can be used to estimate the acute or chronic toxicity of effluents or receiving water. The results of effluent toxicity tests may need to be interpreted differently from the results of ambient toxicity tests. In this paper we provide examples of common artifacts, which can cause either false positives or false negatives, that we have encountered when these tests are used in ambient assessments. The examples we provide are drawn from diverse effluent and ambient water toxicity tests conducted at the Oak Ridge National Laboratory from March, 1985 through November, 1991. Three types of artifacts which have been encountered when using these tests in ambient applications are explored here. One type involves unusual replicate-specific variance in survival of fathead minnow larvae. The second and third types of artifacts affect the C. dubia test and appear to be related to food availability.

  14. Artifacts in ambient toxicity testing

    SciTech Connect

    Kszos, L.A.; Stewart, A.J.

    1992-10-01

    Short-term toxicity tests with fathead minnow (Pimephales promelas) larvae and Ceriodaphnia dubia can be used to estimate the acute or chronic toxicity of effluents or receiving water. The results of effluent toxicity tests may need to be interpreted differently from the results of ambient toxicity tests. In this paper we provide examples of common artifacts, which can cause either false positives or false negatives, that we have encountered when these tests are used in ambient assessments. The examples we provide are drawn from diverse effluent and ambient water toxicity tests conducted at the Oak Ridge National Laboratory from March, 1985 through November, 1991. Three types of artifacts which have been encountered when using these tests in ambient applications are explored here. One type involves unusual replicate-specific variance in survival of fathead minnow larvae. The second and third types of artifacts affect the C. dubia test and appear to be related to food availability.

  15. Artifact reduction in HARP strain maps using anisotropic smoothing

    NASA Astrophysics Data System (ADS)

    Abd-Elmoniem, Khaled Z.; Parthasarathy, Vijay; Prince, Jerry L.

    2006-03-01

    Harmonic phase (HARP) MRI is used to measure myocardial motion and strain from tagged MR images. HARP MRI uses limited number of samples from the spectrum of the tagged images to reconstruct motion and strain. The HARP strain maps, however, suffer from artifacts that limit the accuracy of the computations and degrade the appearance of the strain maps. Causes of these, so called 'zebra', artifacts include image noise, Gibbs ringing, and interference from other Fourier spectral peaks. Computing derivatives of the HARP phase, which are needed to estimate strain, further accentuates these artifacts. Previous methods to reduce these artifacts include 1-D and 2-D nonlinear filtering of the HARP derivatives, and a 2-D linear filtering of unwrapped HARP phase. A common drawback among these methods is the lack of proper segmentation of the myocardium from the blood pool. Because of the lack of segmentation, the noisy phase values from the blood pool enter into the computation in the smoothed strain maps, which causes artifacts. In this work, we propose a smoothing method based on anisotropic diffusion that filters the HARP derivatives strictly within the myocardium without the need for prior segmentation. The information about tissue geometry and the strain distribution is used to restrict the smoothing to within the myocardium, thereby ensuring minimum distortion of the final strain map. Preliminary results demonstrate the ability of anisotropic diffusion for better artifact reduction and lesser strain distortion than the existing methods.

  16. Combined method for artifact reduction in surface electroenterogram.

    PubMed

    Ye, Y; Garcia-Casado, J; Martinez-de-Juan, J L; Alvarez, D; Prats-Boluda, G; Ponce, J L

    2007-01-01

    Surface electroenterogram (EEnG) is a non-invasive method for monitoring the intestinal motility. However, surface EEnG recordings are contaminated by movement artifact, cardiac activity, respiratory artifact and other interferences. The aim of this work is to remove movement artifacts by means of a combined method of empirical mode decomposition (EMD) and independent component analysis (ICA). Four recording sessions were conducted on canine model. Surface signals from 4 different channels are decomposed using EMD. Resulting intrinsic mode functions are the inputs of ICA analysis which permits to separate and identify the activities of different origin. Signal components associated to movement artifacts are removed and the original signals are reconstructed by means of an inverse procedure. The results show that the proposed method allows extracting and cancelling movement artifacts from surface EEnG, avoiding the presence of irregular peaks in external intestinal motility indexes. Therefore, the proposed method could be useful to reduce artifacts in EEnG recording and to provide more robust non-invasive intestinal motility indicators.

  17. Filter and electrostatic samplers for semivolatile aerosols: physical artifacts.

    PubMed

    Volckens, John; Leith, David

    2002-11-01

    Adsorptive and evaporative artifacts often bias measurements of semivolatile aerosols. Adsorption occurs when the sampling method disrupts the gas-particle partitioning equilibrium. Evaporation occurs because concentrations of semivolatiles are rarely constant over time. Filtration is subject to both adsorptive and evaporative artifacts. By comparison, electrostatic precipitation reduces these artifacts by minimizing the surface area of collected particles without substantially disrupting the gas-particle equilibrium. The extent of these artifacts was determined for filter samplers and electrostatic precipitator samplers for semivolatile alkane aerosols in the laboratory. Adsorption of gas-phase semivolatiles was lower in electrostatic precipitators by factors of 5-100 compared to the filter method. Particle evaporation from the electrostatic sampler was 2.3 times lower than that from TFE-coated glass-fiber filters. Use of a backup filter to correct for compound-specific adsorption artifacts can introduce positive or negative errors to the measured particle-phase concentration due to competition among the adsorbates for available adsorption sites. Adsorption of evaporated particles from the front filter onto the backup filter increased the measured evaporative artifact by a factor of 1.5-2.

  18. Schistosome resistance to praziquantel: Fact or artifact?

    PubMed

    Fallon, P G; Tao, L F; Ismail, M M; Bennett, J L

    1996-08-01

    Praziquantel is the current drug of choice for human schistosomiasis. Recent reports from laboratory and field studies concerning reduced praziquantel efficacy against Schistosoma mansoni have generated some controversy. The prevailing question is whether the emergence of strains of schistosome resistant to praziquantel is a fact, or an artifact resulting from erroneous field or laboratory experimentation. In this article, Padraic Fallon, Liang-feng Tao, Magdi Ismail and James Bennett examine the available evidence for schistosome resistance to praziquantel. Contributory factors to the schistosomicidal activity of praziquantel, which may interfere with evaluation of drug efficacy or resistance, are also considered.

  19. Toddlers View Artifact Function Normatively

    ERIC Educational Resources Information Center

    Casler, Krista; Terziyan, Treysi; Greene, Kimberly

    2009-01-01

    When children use objects like adults, are they simply tracking regularities in others' object use, or are they demonstrating a normatively defined awareness that there are right and wrong ways to act? This study provides the first evidence for the latter possibility. Young 2- and 3-year-olds (n = 32) learned functions of 6 artifacts, both…

  20. Text Signals Influence Team Artifacts

    ERIC Educational Resources Information Center

    Clariana, Roy B.; Rysavy, Monica D.; Taricani, Ellen

    2015-01-01

    This exploratory quasi-experimental investigation describes the influence of text signals on team visual map artifacts. In two course sections, four-member teams were given one of two print-based text passage versions on the course-related topic "Social influence in groups" downloaded from Wikipedia; this text had two paragraphs, each…

  1. Joint correction of Nyquist artifact and minuscule motion-induced aliasing artifact in interleaved diffusion weighted EPI data using a composite two-dimensional phase correction procedure.

    PubMed

    Chang, Hing-Chiu; Chen, Nan-Kuei

    2016-09-01

    Diffusion-weighted imaging (DWI) obtained with interleaved echo-planar imaging (EPI) pulse sequence has great potential of characterizing brain tissue properties at high spatial-resolution. However, interleaved EPI based DWI data may be corrupted by various types of aliasing artifacts. First, inconsistencies in k-space data obtained with opposite readout gradient polarities result in Nyquist artifact, which is usually reduced with 1D phase correction in post-processing. When there exist eddy current cross terms (e.g., in oblique-plane EPI), 2D phase correction is needed to effectively reduce Nyquist artifact. Second, minuscule motion induced phase inconsistencies in interleaved DWI scans result in image-domain aliasing artifact, which can be removed with reconstruction procedures that take shot-to-shot phase variations into consideration. In existing interleaved DWI reconstruction procedures, Nyquist artifact and minuscule motion-induced aliasing artifact are typically removed subsequently in two stages. Although the two-stage phase correction generally performs well for non-oblique plane EPI data obtained from well-calibrated system, the residual artifacts may still be pronounced in oblique-plane EPI data or when there exist eddy current cross terms. To address this challenge, here we report a new composite 2D phase correction procedure, which effective removes Nyquist artifact and minuscule motion induced aliasing artifact jointly in a single step. Our experimental results demonstrate that the new 2D phase correction method can much more effectively reduce artifacts in interleaved EPI based DWI data as compared with the existing two-stage artifact correction procedures. The new method robustly enables high-resolution DWI, and should prove highly valuable for clinical uses and research studies of DWI.

  2. TH-C-BRD-06: A Novel MRI Based CT Artifact Correction Method for Improving Proton Range Calculation in the Presence of Severe CT Artifacts

    SciTech Connect

    Park, P; Schreibmann, E; Fox, T; Roper, J; Elder, E; Tejani, M; Crocker, I; Curran, W; Dhabaan, A

    2014-06-15

    Purpose: Severe CT artifacts can impair our ability to accurately calculate proton range thereby resulting in a clinically unacceptable treatment plan. In this work, we investigated a novel CT artifact correction method based on a coregistered MRI and investigated its ability to estimate CT HU and proton range in the presence of severe CT artifacts. Methods: The proposed method corrects corrupted CT data using a coregistered MRI to guide the mapping of CT values from a nearby artifact-free region. First patient MRI and CT images were registered using 3D deformable image registration software based on B-spline and mutual information. The CT slice with severe artifacts was selected as well as a nearby slice free of artifacts (e.g. 1cm away from the artifact). The two sets of paired MRI and CT images at different slice locations were further registered by applying 2D deformable image registration. Based on the artifact free paired MRI and CT images, a comprehensive geospatial analysis was performed to predict the correct CT HU of the CT image with severe artifact. For a proof of concept, a known artifact was introduced that changed the ground truth CT HU value up to 30% and up to 5cm error in proton range. The ability of the proposed method to recover the ground truth was quantified using a selected head and neck case. Results: A significant improvement in image quality was observed visually. Our proof of concept study showed that 90% of area that had 30% errors in CT HU was corrected to 3% of its ground truth value. Furthermore, the maximum proton range error up to 5cm was reduced to 4mm error. Conclusion: MRI based CT artifact correction method can improve CT image quality and proton range calculation for patients with severe CT artifacts.

  3. Application of digital tomosynthesis (DTS) of optimal deblurring filters for dental X-ray imaging

    NASA Astrophysics Data System (ADS)

    Oh, J. E.; Cho, H. S.; Kim, D. S.; Choi, S. I.; Je, U. K.

    2012-04-01

    Digital tomosynthesis (DTS) is a limited-angle tomographic technique that provides some of the tomographic benefits of computed tomography (CT) but at reduced dose and cost. Thus, the potential for application of DTS to dental X-ray imaging seems promising. As a continuation of our dental radiography R&D, we developed an effective DTS reconstruction algorithm and implemented it in conjunction with a commercial dental CT system for potential use in dental implant placement. The reconstruction algorithm employed a backprojection filtering (BPF) method based upon optimal deblurring filters to suppress effectively both the blur artifacts originating from the out-focus planes and the high-frequency noise. To verify the usefulness of the reconstruction algorithm, we performed systematic simulation works and evaluated the image characteristics. We also performed experimental works in which DTS images of enhanced anatomical resolution were successfully obtained by using the algorithm and were promising to our ongoing applications to dental X-ray imaging. In this paper, our approach to the development of the DTS reconstruction algorithm and the results are described in detail.

  4. Dental Hygienists

    MedlinePlus

    ... anatomy, patient management, and periodontics, which is the study of gum disease. High school students interested in becoming dental hygienists should take courses in biology, chemistry, and math. Most dental hygiene programs also require applicants to have completed at ...

  5. Dental sealants

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants Are Applied Your dentist applies sealants on ...

  6. Grid artifact reduction for direct digital radiography detectors based on rotated stationary grids with homomorphic filtering

    SciTech Connect

    Kim, Dong Sik; Lee, Sanggyun

    2013-06-15

    Purpose: Grid artifacts are caused when using the antiscatter grid in obtaining digital x-ray images. In this paper, research on grid artifact reduction techniques is conducted especially for the direct detectors, which are based on amorphous selenium. Methods: In order to analyze and reduce the grid artifacts, the authors consider a multiplicative grid image model and propose a homomorphic filtering technique. For minimal damage due to filters, which are used to suppress the grid artifacts, rotated grids with respect to the sampling direction are employed, and min-max optimization problems for searching optimal grid frequencies and angles for given sampling frequencies are established. The authors then propose algorithms for the grid artifact reduction based on the band-stop filters as well as low-pass filters. Results: The proposed algorithms are experimentally tested for digital x-ray images, which are obtained from direct detectors with the rotated grids, and are compared with other algorithms. It is shown that the proposed algorithms can successfully reduce the grid artifacts for direct detectors. Conclusions: By employing the homomorphic filtering technique, the authors can considerably suppress the strong grid artifacts with relatively narrow-bandwidth filters compared to the normal filtering case. Using rotated grids also significantly reduces the ringing artifact. Furthermore, for specific grid frequencies and angles, the authors can use simple homomorphic low-pass filters in the spatial domain, and thus alleviate the grid artifacts with very low implementation complexity.

  7. Allergy or Tolerance: Reduced Inflammatory Cytokine Response and Concomitant IL-10 Production of Lymphocytes and Monocytes in Symptom-Free Titanium Dental Implant Patients

    PubMed Central

    Thomas, Peter; Wollenberg, Andreas

    2013-01-01

    Hypersensitivity reactions to titanium (Ti) are very rare. Thus, we assessed the proinflammatory response and also potential tolerance favoring in vitro reactivity of human blood lymphocytes and monocytes (PBMC) to Ti in healthy individuals (14 without, 6 with complication-free dental Ti implants). The proliferation index (SI) in lymphocyte transformation test (LTT) and production of cytokines linked to innate immune response (IL-1β, IL-6, and TNFα) or immune regulation (IL-10) were assessed in response to TiO2 particles or Ti discs. In both groups, the Ti-LTT reactivity was not enhanced (e.g., SI < 3). The control antigen tetanus toxoid (TT) gave adequate reactivity (median SI individuals without/with implant: 20.6 ± 5.97/19.58 ± 2.99). Individuals without implant showed higher cytokine response to Ti materials than individuals with symptom-free implants; for example, TiO2 rutile particle induced increase of IL-1β 70.27-fold/8.49-fold versus control medium culture. PBMC of 5 of the 6 individuals with complication-free Ti implants showed an ex vivo ongoing production of IL-10 (mean 4.18 ± 2.98 pg/mL)-but none of the 14 controls showed such IL-10 production. Thus in vitro IL-1β-, IL-6-, and TNF-α production reflects “normal” unspecific immune response to Ti. This might be reduced by production of tolerogenic IL-10 in individuals with symptom-free Ti dental implants. PMID:24106709

  8. Reflection-artifact-free photoacoustic imaging using PAFUSion (photoacoustic-guided focused ultrasound)

    NASA Astrophysics Data System (ADS)

    Kuniyil Ajith Singh, Mithun; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-03-01

    Reflection artifacts caused by acoustic inhomogeneities are a main challenge to deep-tissue photoacoustic imaging. Photoacoustic transients generated by the skin surface and superficial vasculature will propagate into the tissue and reflect back from echogenic structures to generate reflection artifacts. These artifacts can cause problems in image interpretation and limit imaging depth. In its basic version, PAFUSion mimics the inward travelling wave-field from blood vessel-like PA sources by applying focused ultrasound pulses, and thus provides a way to identify reflection artifacts. In this work, we demonstrate reflection artifact correction in addition to identification, towards obtaining an artifact-free photoacoustic image. In view of clinical applications, we implemented an improved version of PAFUSion in which photoacoustic data is backpropagated to imitate the inward travelling wave-field and thus the reflection artifacts of a more arbitrary distribution of PA sources that also includes the skin melanin layer. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. We present a phantom experiment and initial in vivo measurements on human volunteers where we demonstrate significant reflection artifact reduction using our technique. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can reduce these artifacts significantly to improve the deep-tissue photoacoustic imaging.

  9. SU-E-I-38: Improved Metal Artifact Correction Using Adaptive Dual Energy Calibration

    SciTech Connect

    Dong, X; Elder, E; Roper, J; Dhabaan, A

    2015-06-15

    Purpose: The empirical dual energy calibration (EDEC) method corrects for beam-hardening artifacts, but shows limited performance on metal artifact correction. In this work, we propose an adaptive dual energy calibration (ADEC) method to correct for metal artifacts. Methods: The empirical dual energy calibration (EDEC) method corrects for beam-hardening artifacts, but shows limited performance on metal artifact correction. In this work, we propose an adaptive dual energy calibration (ADEC) method to correct for metal artifacts. Results: Highly attenuating copper rods cause severe streaking artifacts on standard CT images. EDEC improves the image quality, but cannot eliminate the streaking artifacts. Compared to EDEC, the proposed ADEC method further reduces the streaking resulting from metallic inserts and beam-hardening effects and obtains material decomposition images with significantly improved accuracy. Conclusion: We propose an adaptive dual energy calibration method to correct for metal artifacts. ADEC is evaluated with the Shepp-Logan phantom, and shows superior metal artifact correction performance. In the future, we will further evaluate the performance of the proposed method with phantom and patient data.

  10. Dental operatory water lines.

    PubMed

    Beierle, J W

    1993-02-01

    Water samples were collected from dental handpiece and air-water syringe lines at various times during the day and cultured for the presence and prevalence of various microbes. It was found that the longer a dental unit was out of use, the greater the microbial build-up in water lines. However, purging lines for two to three minutes at the start of the day and between patients significantly reduced microbial presence.

  11. Dental care demand among children with dental insurance.

    PubMed Central

    Grembowski, D; Conrad, D A; Milgrom, P

    1987-01-01

    As the number of families with dental insurance and expenditures for dental care has increased over the past two decades, so has interest in determining cost-sharing effects on dental demand among insureds. Using a representative sample of Pennsylvania Blue Shield children insureds during 1980, we estimate cost-sharing effects on dental demand for basic (diagnostic, preventive, restorative, endodontic, and extraction services) and orthodontic care. Results indicate that cost-sharing has little influence on the probability of using any dental services and basic expenditures. However, the probability of using orthodontic services decreases 2.1 percent when the proportion of orthodontic expenditures paid by the parent increases 10 percent. By reducing the cost of care, cost-sharing reduces social class differences in dental demand common in unisured populations, likely producing public oral health benefits. PMID:2952622

  12. Reduction of motion artifacts in electrocardiogram monitoring using an optical sensor.

    PubMed

    Liu, Yan; Pecht, Michael G

    2011-01-01

    The effectiveness of electrocardiogram (ECG) monitors can be significantly impaired by motion artifacts, which can trigger false alarms, cause misdiagnoses, and lead to inappropriate treatment decisions. Skin stretch associated with patient motion is the most significant source of motion artifacts in current ECG monitoring. In this study, motion artifacts are adaptively filtered by using skin strain as the reference variable, measured noninvasively using an optical sensor incorporated into an ECG electrode. The results demonstrate that this new device and method can significantly reduce motion induced ECG artifacts in continuous ambulatory ECG monitoring.

  13. Reduction of skin stretch induced motion artifacts in electrocardiogram monitoring using adaptive filtering.

    PubMed

    Liu, Yan; Pecht, Michael G

    2006-01-01

    The effectiveness of electrocardiogram (ECG) monitors can be significantly impaired by motion artifacts which can cause misdiagnoses, lead to inappropriate treatment decisions, and trigger false alarms. Skin stretch associated with patient motion is a significant source of motion artifacts in current ECG monitoring. In this study, motion artifacts are adaptively filtered by using skin strain as the reference variable. Skin strain is measured non-invasively using a light emitting diode (LED) and an optical sensor incorporated in an ECG electrode. The results demonstrate that this device and method can significantly reduce skin strain induced ECG artifacts.

  14. HEAVENS system for software artifacts

    NASA Technical Reports Server (NTRS)

    Matthews, Paul

    1990-01-01

    The HEAVENS system is a workstation-based collection of software for analyzing, organizing, and viewing software artifacts. As a prototype, the system was used for visualizing source code structure, analyzing dependencies, and reconstructing to simplify maintenance. The system was also used in the early stages of software design to organize and relate design objects, maintain design documentation, and provide ready-made framework for later coding.

  15. Withanolide artifacts formed in methanol.

    PubMed

    Cao, Cong-Mei; Zhang, Huaping; Gallagher, Robert J; Timmermann, Barbara N

    2013-11-22

    Methanol solutions of the main withanolides (6-8) naturally present in Physalis longifolia yielded five artificial withanolides (1-5), including three new compounds (1-3). Withanolides 1 and 2 were identified as intramolecular Michael addition derivatives, while withanolides 3-5 were the result of intermolecular Michael addition. A comprehensive literature investigation was conducted to identify potential withanolide Michael addition artifacts isolated from Solanaceous species to date.

  16. Dental OCT

    NASA Astrophysics Data System (ADS)

    Colston, Bill W.; Sathyam, Ujwal S.; Dasilva, Luiz B.; Everett, Matthew J.; Stroeve, Pieter; Otis, L. L.

    1998-09-01

    We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.

  17. Reduction of truncation artifacts in CT images via a discriminative dictionary representation method

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Li, Ke; Li, Yinsheng; Hsieh, Jiang; Chen, Guang-Hong

    2016-04-01

    When the scan field of view (SFOV) of a CT system is not large enough to enclose the entire cross-section of a patient, or the patient needs to be intentionally positioned partially outside the SFOV for certain clinical CT scans, truncation artifacts are often observed in the reconstructed CT images. Conventional wisdom to reduce truncation artifacts is to complete the truncated projection data via data extrapolation with different a priori assumptions. This paper presents a novel truncation artifact reduction method that directly works in the CT image domain. Specifically, a discriminative dictionary that includes a sub-dictionary of truncation artifacts and a sub-dictionary of non-artifact image information was used to separate a truncation artifact-contaminated image into two sub-images, one with reduced truncation artifacts, and the other one containing only the truncation artifacts. Both experimental phantom and retrospective human subject studies have been performed to characterize the performance of the proposed truncation artifact reduction method.

  18. Artifacts in three-dimensional transesophageal echocardiography.

    PubMed

    Faletra, Francesco Fulvio; Ramamurthi, Alamelu; Dequarti, Maria Cristina; Leo, Laura Anna; Moccetti, Tiziano; Pandian, Natesa

    2014-05-01

    Three-dimensional (3D) transesophageal echocardiography (TEE) is subject to the same types of artifacts encountered on two-dimensional TEE. However, when displayed in a 3D format, some of the artifacts appear more "realistic," whereas others are unique to image acquisition and postprocessing. Three-dimensional TEE is increasingly used in the setting of percutaneous catheter-based interventions and ablation procedures, and 3D artifacts caused by the metallic components of catheters and devices are particularly frequent. Knowledge of these artifacts is of paramount relevance to avoid misinterpretation of 3D images. Although artifacts and pitfalls on two-dimensional echocardiography are well described and classified, a systematic description of artifacts in 3D transesophageal echocardiographic images and how they affect 3D imaging is still absent. The aim of this review is to describe the most relevant artifacts on 3D TEE, with particular emphasis on those occurring during percutaneous interventions for structural heart disease and ablation procedures.

  19. Image Degradation in Microscopic Images: Avoidance, Artifacts, and Solutions.

    PubMed

    Roels, Joris; Aelterman, Jan; De Vylder, Jonas; Lippens, Saskia; Luong, Hiêp Q; Guérin, Christopher J; Philips, Wilfried

    2016-01-01

    The goal of modern microscopy is to acquire high-quality image based data sets. A typical microscopy workflow is set up in order to address a specific biological question and involves different steps. The first step is to precisely define the biological question, in order to properly come to an experimental design for sample preparation and image acquisition. A better object representation allows biological users to draw more reliable scientific conclusions. Image restoration can manipulate the acquired data in an effort to reduce the impact of artifacts (spurious results) due to physical and technical limitations, resulting in a better representation of the object of interest. However, precise usage of these algorithms is necessary so as to avoid further artifacts that might influence the data analysis and bias the conclusions. It is essential to understand image acquisition, and how it introduces artifacts and degradations in the acquired data, so that their effects on subsequent analysis can be minimized. This paper provides an overview of the fundamental artifacts and degradations that affect many micrographs. We describe why artifacts appear, in what sense they impact overall image quality, and how to mitigate them by first improving the acquisition parameters and then applying proper image restoration techniques.

  20. Image Degradation in Microscopic Images: Avoidance, Artifacts, and Solutions.

    PubMed

    Roels, Joris; Aelterman, Jan; De Vylder, Jonas; Lippens, Saskia; Luong, Hiêp Q; Guérin, Christopher J; Philips, Wilfried

    2016-01-01

    The goal of modern microscopy is to acquire high-quality image based data sets. A typical microscopy workflow is set up in order to address a specific biological question and involves different steps. The first step is to precisely define the biological question, in order to properly come to an experimental design for sample preparation and image acquisition. A better object representation allows biological users to draw more reliable scientific conclusions. Image restoration can manipulate the acquired data in an effort to reduce the impact of artifacts (spurious results) due to physical and technical limitations, resulting in a better representation of the object of interest. However, precise usage of these algorithms is necessary so as to avoid further artifacts that might influence the data analysis and bias the conclusions. It is essential to understand image acquisition, and how it introduces artifacts and degradations in the acquired data, so that their effects on subsequent analysis can be minimized. This paper provides an overview of the fundamental artifacts and degradations that affect many micrographs. We describe why artifacts appear, in what sense they impact overall image quality, and how to mitigate them by first improving the acquisition parameters and then applying proper image restoration techniques. PMID:27207362

  1. A patient-specific scatter artifacts correction method

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Brunner, Stephen; Niu, Kai; Schafer, Sebastian; Royalty, Kevin; Chen, Guang-Hong

    2014-03-01

    This paper provides a fast and patient-specific scatter artifact correction method for cone-beam computed tomography (CBCT) used in image-guided interventional procedures. Due to increased irradiated volume of interest in CBCT imaging, scatter radiation has increased dramatically compared to 2D imaging, leading to a degradation of image quality. In this study, we propose a scatter artifact correction strategy using an analytical convolution-based model whose free parameters are estimated using a rough estimation of scatter profiles from the acquired cone-beam projections. It was evaluated using Monte Carlo simulations with both monochromatic and polychromatic X-ray sources. The results demonstrated that the proposed method significantly reduced the scatter-induced shading artifacts and recovered CT numbers.

  2. Cochlear implant artifact attenuation in late auditory evoked potentials: a single channel approach.

    PubMed

    Mc Laughlin, Myles; Lopez Valdes, Alejandro; Reilly, Richard B; Zeng, Fan-Gang

    2013-08-01

    Recent evidence suggests that late auditory evoked potentials (LAEP) provide a useful objective metric of performance in cochlear implant (CI) subjects. However, the CI produces a large electrical artifact that contaminates LAEP recordings and confounds their interpretation. Independent component analysis (ICA) has been used in combination with multi-channel recordings to effectively remove the artifact. The applicability of the ICA approach is limited when only single channel data are needed or available, as is often the case in both clinical and research settings. Here we developed a single-channel, high sample rate (125 kHz), and high bandwidth (0-100 kHz) acquisition system to reduce the CI stimulation artifact. We identified two different artifacts in the recording: 1) a high frequency artifact reflecting the stimulation pulse rate, and 2) a direct current (DC, or pedestal) artifact that showed a non-linear time varying relationship to pulse amplitude. This relationship was well described by a bivariate polynomial. The high frequency artifact was completely attenuated by a 35 Hz low-pass filter for all subjects (n = 22). The DC artifact could be caused by an impedance mismatch. For 27% of subjects tested, no DC artifact was observed when electrode impedances were balanced to within 1 kΩ. For the remaining 73% of subjects, the pulse amplitude was used to estimate and then attenuate the DC artifact. Where measurements of pulse amplitude were not available (as with standard low sample rate systems), the DC artifact could be estimated from the stimulus envelope. The present artifact removal approach allows accurate measurement of LAEPs from CI subjects from single channel recordings, increasing their feasibility and utility as an accessible objective measure of CI function.

  3. Dental Implants

    MedlinePlus

    ... Procedures Dental Implants Dentures Direct Bonding Implants versus Bridges Orthodontics and Aligners Periodontal Plastic Surgery Porcelain Crowns Porcelain Fixed Bridges Porcelain Veneers Repairing Chipped Teeth Teeth Whitening Tooth- ...

  4. Metal artifact reduction in CT by identifying missing data hidden in metals.

    PubMed

    Park, Hyoung Suk; Choi, Jae Kyu; Park, Kyung-Ran; Kim, Kyung Sang; Lee, Sang-Hwy; Ye, Jong Chul; Seo, Jin Keun

    2013-01-01

    There is increasing demand in the field of dental and medical radiography for effective metal artifact reduction (MAR) in computed tomography (CT) because artifact caused by metallic objects causes serious image degradation that obscures information regarding the teeth and/or other biological structures. This paper presents a new MAR method that uses the Laplacian operator to reveal background projection data hidden in regions containing data from metal. In the proposed method, we attempted to decompose the projection data into two parts: data from metal only (metal data), and background data in the absence of metal. Removing metal data from the projections enables us to perform sparsity-driven reconstruction of the metal component and subsequent removal of the metal artifact. The results of clinical experiments demonstrated that the proposed MAR algorithm improves image quality and increases the standard of 3D reconstruction images of the teeth and mandible. PMID:24004866

  5. Dental injuries during general anaesthesia.

    PubMed

    Chadwick, R G; Lindsay, S M

    1996-04-01

    Although most anaesthetic textbooks cite dental injury as a complication of endotracheal intubation few studies have examined the extent and nature of the problem. Such damage however, formed the basis for one-third of all confirmed or potential anaesthetic claims notified to the Medical Protection Society between 1977 and 1986. This article seeks to explore the extent of the problem, outline predisposing factors, summarise current prophylactic measures and make recommendations to reduce the overall incidence. Increased awareness of the problem, by both anaesthetists and dental surgeons, coupled with appropriate prophylactic measures may result in a reduced incidence of dental injury arising from general anaesthesia. Given the high incidence of dental damage we recommend that all patients undergoing a surgical operation under endotracheal intubation should have a pre-operative dental check wherever possible. Clearly, the first dental examination would be conducted by an anaesthetist familiar with the predisposing factors. Where he/she considers there to be a higher than average risk of dental damage occurring during intubation a more specialised examination should be conducted by a dental surgeon. It may, where appropriate, be possible for remedial dental treatment to be carried out and customised mouth guards to be constructed prior to the operation. Obviously such recommendations have certain financial implications and would have to be subject to controlled cost-benefit analysis before their widespread application. PMID:8935289

  6. Artifacts in digital coincidence timing

    SciTech Connect

    Moses, W. W.; Peng, Q.

    2014-10-16

    Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into a time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.

  7. Dental Hygienist.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of dental hygienist, lists technical competencies and competency builders for 13 units pertinent to the health technologies cluster in general and 9 units specific to the occupation of dental hygienist. The following skill areas are covered in…

  8. Dental Implants.

    PubMed

    Zohrabian, Vahe M; Sonick, Michael; Hwang, Debby; Abrahams, James J

    2015-10-01

    Dental implants restore function to near normal in partially or completely edentulous patients. A root-form implant is the most frequently used type of dental implant today. The basis for dental implants is osseointegration, in which osteoblasts grow and directly integrate with the surface of titanium posts surgically embedded into the jaw. Radiologic assessment is critical in the preoperative evaluation of the dental implant patient, as the exact height, width, and contour of the alveolar ridge must be determined. Moreover, the precise locations of the maxillary sinuses and mandibular canals, as well as their relationships to the site of implant surgery must be ascertained. As such, radiologists must be familiar with implant design and surgical placement, as well as augmentation procedures utilized in those patients with insufficient bone in the maxilla and mandible to support dental implants.

  9. Psycho-physiological effects of visual artifacts by stereoscopic display systems

    NASA Astrophysics Data System (ADS)

    Kim, Sanghyun; Yoshitake, Junki; Morikawa, Hiroyuki; Kawai, Takashi; Yamada, Osamu; Iguchi, Akihiko

    2011-03-01

    The methods available for delivering stereoscopic (3D) display using glasses can be classified as time-multiplexing and spatial-multiplexing. With both methods, intrinsic visual artifacts result from the generation of the 3D image pair on a flat panel display device. In the case of the time-multiplexing method, an observer perceives three artifacts: flicker, the Mach-Dvorak effect, and a phantom array. These only occur under certain conditions, with flicker appearing in any conditions, the Mach-Dvorak effect during smooth pursuit eye movements (SPM), and a phantom array during saccadic eye movements (saccade). With spatial-multiplexing, the artifacts are temporal-parallax (due to the interlaced video signal), binocular rivalry, and reduced spatial resolution. These artifacts are considered one of the major impediments to the safety and comfort of 3D display users. In this study, the implications of the artifacts for the safety and comfort are evaluated by examining the psychological changes they cause through subjective symptoms of fatigue and the depth sensation. Physiological changes are also measured as objective responses based on analysis of heart and brain activation by visual artifacts. Further, to understand the characteristics of each artifact and the combined effects of the artifacts, four experimental conditions are developed and tested. The results show that perception of artifacts differs according to the visual environment and the display method. Furthermore visual fatigue and the depth sensation are influenced by the individual characteristics of each artifact. Similarly, heart rate variability and regional cerebral oxygenation changes by perception of artifacts in conditions.

  10. Artifacts in digital coincidence timing

    DOE PAGESBeta

    Moses, W. W.; Peng, Q.

    2014-10-16

    Digital methods are becoming increasingly popular for measuring time differences, and are the de facto standard in PET cameras. These methods usually include a master system clock and a (digital) arrival time estimate for each detector that is obtained by comparing the detector output signal to some reference portion of this clock (such as the rising edge). Time differences between detector signals are then obtained by subtracting the digitized estimates from a detector pair. A number of different methods can be used to generate the digitized arrival time of the detector output, such as sending a discriminator output into amore » time to digital converter (TDC) or digitizing the waveform and applying a more sophisticated algorithm to extract a timing estimator.All measurement methods are subject to error, and one generally wants to minimize these errors and so optimize the timing resolution. A common method for optimizing timing methods is to measure the coincidence timing resolution between two timing signals whose time difference should be constant (such as detecting gammas from positron annihilation) and selecting the method that minimizes the width of the distribution (i.e. the timing resolution). Unfortunately, a common form of error (a nonlinear transfer function) leads to artifacts that artificially narrow this resolution, which can lead to erroneous selection of the 'optimal' method. In conclusion, the purpose of this note is to demonstrate the origin of this artifact and suggest that caution should be used when optimizing time digitization systems solely on timing resolution minimization.« less

  11. Coinsurance effects on dental prices.

    PubMed

    Grembowski, D; Conrad, D A

    1986-01-01

    For many Americans the cost of dental services represents a barrier to receiving regular dental care and maintaining proper oral health. The recent growth of the dental insurance industry, however, may partly offset this price barrier among insureds. Our purpose is to examine the relationship between coinsurance and dental prices for 16 dental services among a sample of Pennsylvania Blue Shield (PBS) adult insureds. The dependent price measure is the annual average gross price paid for 16 specific preventive, restorative, periodontic, endodontic, prosthodontic, and surgical dental services. Independent variables in the price model include the insured's age, education, coinsurance rates, time costs, market area, non-wage income, oral health status, area dentist-population ratio and usual source of care. Data sources are 1980 PBS claims and coinsurance rate data and a mail survey of sampled insureds. OLS regression analysis reveals that the model's independent variables explain little dental price variation. No variable is consistently significant across services, but market area, coinsurance rates, and time costs alternately dominate across equations. These results suggest that, among adult insureds, coinsurance and time costs influence dental fees in a minority of dental services. Insurance reduces the patient's sensitivity to money price, and non-price factors correspondingly seem to become more important in patient search.

  12. Range Condition and ML-EM Checkerboard Artifacts

    PubMed Central

    You, Jiangsheng; Wang, Jing; Liang, Zhengrong

    2007-01-01

    The expectation maximization (EM) algorithm for the maximum likelihood (ML) image reconstruction criterion generates severe checkerboard artifacts in the presence of noise. A classical remedy is to impose an a priori constraint for a penalized ML or maximum a posteriori probability solution. The penalty reduces the checkerboard artifacts and also introduces uncertainty because a priori information is usually unknown in clinic. Recent theoretical investigation reveals that the noise can be divided into two components: one is called null-space noise and the other is range-space noise. The null-space noise can be numerically estimated using filtered backprojection (FBP) algorithm. By the FBP algorithm, the null-space noise annihilates in the reconstruction while the range-space noise propagates into the reconstructed image. The aim of this work is to investigate the relation between the null-space noise and the checkerboard artifacts in the ML-EM reconstruction from noisy projection data. Our study suggests that removing the null-space noise from the projection data could improve the signal-to-noise ratio of the projection data and, therefore, reduce the checkerboard artifacts in the ML-EM reconstructed images. This study reveals an in-depth understanding of the different noise propagations in analytical and iterative image reconstructions, which may be useful to single photon emission computed tomography, where the noise has been a major factor for image degradation. The reduction of the ML-EM checkerboard artifacts by removing the null-space noise avoids the uncertainty of using a priori penalty. PMID:18449363

  13. Young Children's Rapid Learning about Artifacts

    ERIC Educational Resources Information Center

    Casler, Krista; Kelemen, Deborah

    2005-01-01

    Tool use is central to interdisciplinary debates about the evolution and distinctiveness of human intelligence, yet little is actually known about how human conceptions of artifacts develop. Results across these two studies show that even 2-year-olds approach artifacts in ways distinct from captive tool-using monkeys. Contrary to adult intuition,…

  14. A motion artifact generation and assessment system for the rapid testing of surface biopotential electrodes.

    PubMed

    Cömert, Alper; Hyttinen, Jari

    2015-01-01

    Dry electrodes can reduce cost while increasing the usability and comfort of wearable monitoring systems. They are, however, susceptible to motion artifacts. The present electrode testing methods lack reliability and do not separate the factors that affect the motion artifact. In this paper, we introduce a first generation motion artifact generation and assessment system that generates the speed, amplitude, and pattern-wise programmable movement of the electrode. The system simultaneously measures electrode-skin impedance, the motion artifact, and one channel of an electrocardiogram that contains the motion artifact and monitors the mounting force applied to the electrode. We demonstrate the system by comparing the applied movement and the measured signals for electrode movements up to 6 mm and movement frequencies from 0.4 Hz to 4 Hz. Results show that the impedance change and surface potential are visually clearly related to the applied motion, with average correlations of 0.89 and 0.64, respectively. The applied force, electrode location, and electrode structure all affect the motion artifact. The setup enables the motion of the electrode to be accurately controlled. The system can be used as a precursor to the testing of integrated systems because it enables thorough, repeatable, and robust motion artifact studies. The system allows a deeper insight into motion artifacts and the interplay of the various factors that affect them.

  15. Effect of pressure and padding on motion artifact of textile electrodes

    PubMed Central

    2013-01-01

    Background With the aging population and rising healthcare costs, wearable monitoring is gaining importance. The motion artifact affecting dry electrodes is one of the main challenges preventing the widespread use of wearable monitoring systems. In this paper we investigate the motion artifact and ways of making a textile electrode more resilient against motion artifact. Our aim is to study the effects of the pressure exerted onto the electrode, and the effects of inserting padding between the applied pressure and the electrode. Method We measure real time electrode-skin interface impedance, ECG from two channels, the motion artifact related surface potential, and exerted pressure during controlled motion by a measurement setup designed to estimate the relation of motion artifact to the signals. We use different foam padding materials with various mechanical properties and apply electrode pressures between 5 and 25 mmHg to understand their effect. A QRS and noise detection algorithm based on a modified Pan-Tompkins QRS detection algorithm estimates the electrode behaviour in respect to the motion artifact from two channels; one dominated by the motion artifact and one containing both the motion artifact and the ECG. This procedure enables us to quantify a given setup’s susceptibility to the motion artifact. Results Pressure is found to strongly affect signal quality as is the use of padding. In general, the paddings reduce the motion artifact. However the shape and frequency components of the motion artifact vary for different paddings, and their material and physical properties. Electrode impedance at 100 kHz correlates in some cases with the motion artifact but it is not a good predictor of the motion artifact. Conclusion From the results of this study, guidelines for improving electrode design regarding padding and pressure can be formulated as paddings are a necessary part of the system for reducing the motion artifact, and further, their effect maximises

  16. Silicon bulk micromachined hybrid dimensional artifact.

    SciTech Connect

    Claudet, Andre A.; Tran, Hy D.; Bauer, Todd Marks; Shilling, Katherine Meghan; Oliver, Andrew David

    2010-03-01

    A mesoscale dimensional artifact based on silicon bulk micromachining fabrication has been developed and manufactured with the intention of evaluating the artifact both on a high precision coordinate measuring machine (CMM) and video-probe based measuring systems. This hybrid artifact has features that can be located by both a touch probe and a video probe system with a k=2 uncertainty of 0.4 {micro}m, more than twice as good as a glass reference artifact. We also present evidence that this uncertainty could be lowered to as little as 50 nm (k=2). While video-probe based systems are commonly used to inspect mesoscale mechanical components, a video-probe system's certified accuracy is generally much worse than its repeatability. To solve this problem, an artifact has been developed which can be calibrated using a commercially available high-accuracy tactile system and then be used to calibrate typical production vision-based measurement systems. This allows for error mapping to a higher degree of accuracy than is possible with a glass reference artifact. Details of the designed features and manufacturing process of the hybrid dimensional artifact are given and a comparison of the designed features to the measured features of the manufactured artifact is presented and discussed. Measurement results from vision and touch probe systems are compared and evaluated to determine the capability of the manufactured artifact to serve as a calibration tool for video-probe systems. An uncertainty analysis for calibration of the artifact using a CMM is presented.

  17. Dental OCT

    NASA Astrophysics Data System (ADS)

    Wilder-Smith, Petra; Otis, Linda; Zhang, Jun; Chen, Zhongping

    This chapter describes the applications of OCT for imaging in vivo dental and oral tissue. The oral cavity is a diverse environment that includes oral mucosa, gingival tissues, teeth and their supporting structures. Because OCT can image both hard and soft tissues of the oral cavity at high resolution, it offers the unique capacity to identity dental disease before destructive changes have progressed. OCT images depict clinically important anatomical features such as the location of soft tissue attachments, morphological changes in gingival tissue, tooth decay, enamel thickness and decay, as well as the structural integrity of dental restorations. OCT imaging allows for earlier intervention than is possible with current diagnostic modalities.

  18. Dosimetric consideration for patients with dental filling materials undergoing irradiation of oral cavity using RapidArc: challenges and solution

    NASA Astrophysics Data System (ADS)

    Mail, Noor; Albarakati, Y.; Khan, M. Ahmad; Saeedi, F.; Safadi, N.; Al-Ghamdi, S.; Saoudi, A.

    2012-03-01

    In this study, we investigate the effect of dental filling materials (DFM) on RapidArcTM treatment plans and delivery in a patient undergoing radiotherapy treatment. The presence of DFM creates uncertainties in CT number and causes long streaking artifacts in the reconstructed images which greatly affect the dose distribution inside the oral cavity. The influence of extensive dental filling artifacts on dose distribution was performed using a geometrically well defined head and neck IMRT verification phantom (PTW, Freiburg, Germany) together with inserts from DFM (Amalgam, 11.3 g/cm3). The phantom was scanned using Siemens SOMATOM Sensation CT simulator (Siemens AG, Germany) under standard head and neck imaging protocol (120 kV, 120 mAs, voxel size 1×1×2 mm3). Three RapidArcTM plans were created in the Varian Eclipse treatment planning System (TPS) to treat oral cavity using the same CT dataset including; 1) raw CT image, 2) streaking artifacts replaced with a mask of 10 HU and 3) 2 cm thick 6000 HU virtual filter (a volume around the teeth in TPS to mimic extra attenuation). The virtual filter thickness optimization was purely based on measured PDD data acquired with DFM and the calculation in Eclipse Planning System using direct beam. The dose delivery and distribution for the three plans was verified using Gafchromic EBT2 (International Specialty Product, Wayne, NJ, USA) film measurements. The artifact mask and virtual filter around the teeth in the planning was found very useful to reduce the discrepancies between the dose plan and delivery. From clinical point of view, these results can be helpful to understand the increase of mucositis in patient having DFM, and further investigation is underway for clinical solution.

  19. Dental Fluorosis

    MedlinePlus

    ... when children regularly consume fluoride during the teeth-forming years, age 8 and younger. Most dental fluorosis ... over a long period when the teeth are forming under the gums. Only children aged 8 years ...

  20. Rotational artifacts in on-board cone beam computed tomography

    NASA Astrophysics Data System (ADS)

    Ali, E. S. M.; Webb, R.; Nyiri, B. J.

    2015-02-01

    Rotational artifacts in image guidance systems lead to registration errors that affect non-isocentric treatments and dose to off-axis organs-at-risk. This study investigates a rotational artifact in the images acquired with the on-board cone beam computed tomography system XVI (Elekta, Stockholm, Sweden). The goals of the study are to identify the cause of the artifact, to characterize its dependence on other quantities, and to investigate possible solutions. A 30 cm diameter cylindrical phantom is used to acquire clockwise and counterclockwise scans at five speeds (120 to 360 deg min-1) on six Elekta linear accelerators from three generations (MLCi, MLCi2 and Agility). Additional scans are acquired with different pulse widths and focal spot sizes for the same mAs. Image quality is evaluated using a common phantom with an in-house three dimensional contrast transfer function attachment. A robust, operator-independent analysis is developed which quantifies rotational artifacts with 0.02° accuracy and imaging system delays with 3 ms accuracy. Results show that the artifact is caused by mislabelling of the projections with a lagging angle due to various imaging system delays. For the most clinically used scan speed (360 deg min-1), the artifact is ˜0.5°, which corresponds to ˜0.25° error per scan direction with the standard Elekta procedure for angle calibration. This leads to a 0.5 mm registration error at 11 cm off-center. The artifact increases linearly with scan speed, indicating that the system delay is independent of scan speed. For the most commonly used pulse width of 40 ms, this delay is 34 ± 1 ms, part of which is half the pulse width. Results are consistent among the three linac generations. A software solution that corrects the angles of individual projections is shown to eliminate the rotational error for all scan speeds and directions. Until such a solution is available from the manufacturer, three clinical solutions are presented, which reduce the

  1. A Wavelet-Based Artifact Reduction From Scalp EEG for Epileptic Seizure Detection.

    PubMed

    Islam, Md Kafiul; Rastegarnia, Amir; Yang, Zhi

    2016-09-01

    This paper presents a method to reduce artifacts from scalp EEG recordings to facilitate seizure diagnosis/detection for epilepsy patients. The proposed method is primarily based on stationary wavelet transform and takes the spectral band of seizure activities (i.e., 0.5-29 Hz) into account to separate artifacts from seizures. Different artifact templates have been simulated to mimic the most commonly appeared artifacts in real EEG recordings. The algorithm is applied on three sets of synthesized data including fully simulated, semi-simulated, and real data to evaluate both the artifact removal performance and seizure detection performance. The EEG features responsible for the detection of seizures from nonseizure epochs have been found to be easily distinguishable after artifacts are removed, and consequently, the false alarms in seizure detection are reduced. Results from an extensive experiment with these datasets prove the efficacy of the proposed algorithm, which makes it possible to use it for artifact removal in epilepsy diagnosis as well as other applications regarding neuroscience studies.

  2. High-throughput ocular artifact reduction in multichannel electroencephalography (EEG) using component subspace projection.

    PubMed

    Ma, Junshui; Bayram, Sevinç; Tao, Peining; Svetnik, Vladimir

    2011-03-15

    After a review of the ocular artifact reduction literature, a high-throughput method designed to reduce the ocular artifacts in multichannel continuous EEG recordings acquired at clinical EEG laboratories worldwide is proposed. The proposed method belongs to the category of component-based methods, and does not rely on any electrooculography (EOG) signals. Based on a concept that all ocular artifact components exist in a signal component subspace, the method can uniformly handle all types of ocular artifacts, including eye-blinks, saccades, and other eye movements, by automatically identifying ocular components from decomposed signal components. This study also proposes an improved strategy to objectively and quantitatively evaluate artifact reduction methods. The evaluation strategy uses real EEG signals to synthesize realistic simulated datasets with different amounts of ocular artifacts. The simulated datasets enable us to objectively demonstrate that the proposed method outperforms some existing methods when no high-quality EOG signals are available. Moreover, the results of the simulated datasets improve our understanding of the involved signal decomposition algorithms, and provide us with insights into the inconsistency regarding the performance of different methods in the literature. The proposed method was also applied to two independent clinical EEG datasets involving 28 volunteers and over 1000 EEG recordings. This effort further confirms that the proposed method can effectively reduce ocular artifacts in large clinical EEG datasets in a high-throughput fashion.

  3. Artifact properties of carbon nanotube yarn electrode in magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Jiang, C. Q.; Hao, H. W.; Li, L. M.

    2013-04-01

    Objective. Deep brain stimulating (DBS) is a rapidly developing therapy that can treat many refractory neurological diseases. However, the traditional DBS electrodes which are made of Pt-Ir alloy may induce severe field distortions in magnetic resonance imaging (MRI) which leads to artifacts that will lower the local image quality and cause inconvenience or interference. A novel DBS electrode made from carbon nanotube yarns (CNTYs) is brought up to reduce the artifacts. This study is therefore to evaluate the artifact properties of the novel electrode. Approach. We compared its MR artifact characteristics with the Pt-Ir electrode in water phantom, including its artifact behaviors at different orientations as well as at various off-center positions, using both spin echo (SE) and gradient echo (GE) sequences, and confirmed its performance in vivo. Main results. The results in phantom showed that the CNTY electrode artifacts reduced as much as 62% and 74% on GE and SE images, respectively, compared to the Pt-Ir one. And consistent behaviors were confirmed in vivo. The susceptibility difference was identified as the dominant cause in producing artifacts. Significance. Employing the CNTY electrode may generate much less field distortion in the vicinity, improve local MR image quality and possibly be beneficial in various aspects.

  4. WE-D-18C-01: Art of Imaging: Diagnostic Ultrasound Image Artifacts

    SciTech Connect

    Zagzebski, J; Lu, Z

    2014-06-15

    Assumptions followed during construction of B-mode and color flow images are that the pulse-echo transit time can be converted to reflector depth through uniform tissue models, echoes originate only from locations along the transmit-receive axes of pulse propagation, and first order correction schemes adequately account for acoustic wave attenuation and absorption. The latter allows the display brightness to encode tissue echogenicity. This course will challenge participants to identify imaging artifacts whose origins stem from the more complex and realistic propagating and scattering conditions common in clinical ultrasound. Speckle, a very common artifact but a clinically employed feature, originates from simultaneous echoes from diffuse scatterers and is a result of coherent detection of signals. One of the most bothersome artifacts are those due to reverberations especially that originating from superficial tissue interfaces. Methods to overcome these will be discussed. This presentation also will describe and illustrate speed of sound, refraction, enhancement, shadowing, mirroring, beam width, beam-forming, and slice thickness artifacts. All are useful examples of limitations introduced by acoustic waves propagating through complex tissue paths. New formats for physician board certification exams are demanding the inclusion of image-based examples of ultrasound physics. Instructors' knowledge of, and access to examples of ultrasound artifacts are important in this effort. The presentation will incorporate an audience response system to challenge participants in correct identification of some of these artifacts. Learning Objectives: Review basic mechanisms for producing ultrasound images. Identify the etiology of speckle, reverberation noise, beam width and slice thickness artifacts, and artifacts associated with pulse propagation. Discuss methods that reduce the impact of artifacts OR employ artifacts effectively to facilitate clinical diagnosis.

  5. Artifact reduction in industrial computed tomography via data fusion

    SciTech Connect

    Schrapp, Michael; Goldammer, Matthias; Stephan, Jürgen

    2014-02-18

    As the most stressed part of a gas turbine the first row of turbine blades is not only a challenge for the materials used. Also the testing of these parts have to meet the highest standards. Computed tomography (CT) as the technique which could reveal the most details also provides the biggest challenges [1]: A full penetration of large sized turbine blades is often only possible at high X-ray voltages causing disproportional high costs. A reduction of the X-ray voltage is able to reduce these arising costs but yields non penetration artifacts in the reconstructed CT image. In most instances, these artifacts manifests itself as blurred and smeared regions at concave edges due to a reduced signal to noise ratio. In order to complement the missing information and to increase the overall image quality of our reconstruction, we use further imaging modalities such as a 3-D Scanner and ultrasonic imaging. A 3-D scanner is easy and cost effective to implement and is able to acquire all relevant data simultaneously with the CT projections. If, however, the interior structure is of supplemental interest, an ultrasonic imaging method is additionally used. We consider this data as a priori knowledge to employ them in an iterative reconstruction. To do so, standard iterative reconstruction methods are modified to incorporate the a priori data in a regularization approach in combination with minimizing the total variation of our image. Applying this procedure on turbine blades, we are able to reduce the apparent artifacts almost completely.

  6. Reweighted L1 regularization for restraining artifacts in FMT reconstruction images with limited measurements.

    PubMed

    Xie, Wenhao; Deng, Yong; Wang, Kan; Yang, Xiaoquan; Luo, Qingming

    2014-07-15

    In fluorescence molecular tomography (FMT), many artifacts exist in the reconstructed images because of the inherently ill-posed nature of the FMT inverse problem, especially with limited measurements. A new method based on iterative reweighted L1 (IRL1) regularization is proposed for reducing artifacts with limited measurements. Phantom experiments demonstrate that the reconstructed images have fewer artifacts even with very limited measurements. This indicates that FMT based on IRL1 can obtain high-quality images and thus has the potential to observe dynamic changes in fluorescence-targeted molecules.

  7. Automatic Identification of Artifact-Related Independent Components for Artifact Removal in EEG Recordings.

    PubMed

    Zou, Yuan; Nathan, Viswam; Jafari, Roozbeh

    2016-01-01

    Electroencephalography (EEG) is the recording of electrical activity produced by the firing of neurons within the brain. These activities can be decoded by signal processing techniques. However, EEG recordings are always contaminated with artifacts which hinder the decoding process. Therefore, identifying and removing artifacts is an important step. Researchers often clean EEG recordings with assistance from independent component analysis (ICA), since it can decompose EEG recordings into a number of artifact-related and event-related potential (ERP)-related independent components. However, existing ICA-based artifact identification strategies mostly restrict themselves to a subset of artifacts, e.g., identifying eye movement artifacts only, and have not been shown to reliably identify artifacts caused by nonbiological origins like high-impedance electrodes. In this paper, we propose an automatic algorithm for the identification of general artifacts. The proposed algorithm consists of two parts: 1) an event-related feature-based clustering algorithm used to identify artifacts which have physiological origins; and 2) the electrode-scalp impedance information employed for identifying nonbiological artifacts. The results on EEG data collected from ten subjects show that our algorithm can effectively detect, separate, and remove both physiological and nonbiological artifacts. Qualitative evaluation of the reconstructed EEG signals demonstrates that our proposed method can effectively enhance the signal quality, especially the quality of ERPs, even for those that barely display ERPs in the raw EEG. The performance results also show that our proposed method can effectively identify artifacts and subsequently enhance the classification accuracies compared to four commonly used automatic artifact removal methods.

  8. An energy minimization method for the correction of cupping artifacts in cone-beam CT.

    PubMed

    Xie, Shipeng; Zhuang, Wenqin; Li, Haibo

    2016-01-01

    The purpose of this study was to reduce cupping artifacts and improve quantitative accuracy of the images in cone-beam CT (CBCT). An energy minimization method (EMM) is proposed to reduce cupping artifacts in reconstructed image of the CBCT. The cupping artifacts are iteratively optimized by using efficient matrix computations, which are verified to be numerically stable by matrix analysis. Moreover, the energy in our formulation is convex in each of its variables, which brings the robustness of the proposed energy minimization algorithm. The cupping artifacts are estimated as a result of minimizing this energy. The results indicate that proposed algorithm is effective for reducing the cupping artifacts and preserving the quality of the reconstructed image. The proposed method focuses on the reconstructed image without requiring any additional physical equipment; it is easily implemented and provides cupping correction using a single scan acquisition. The experimental results demonstrate that this method can successfully reduce the magnitude of cupping artifacts. The correction algorithm reported here may improve the uniformity of the reconstructed images, thus assisting the development of perfect volume visualization and threshold-based visualization techniques for reconstructed images. PMID:27455478

  9. Characterization of Scattered X-Ray Photons in Dental Cone-Beam Computed Tomography

    PubMed Central

    Yang, Ching-Ching

    2016-01-01

    Purpose Scatter is a very important artifact causing factor in dental cone-beam CT (CBCT), which has a major influence on the detectability of details within images. This work aimed to improve the image quality of dental CBCT through scatter correction. Methods Scatter was estimated in the projection domain from the low frequency component of the difference between the raw CBCT projection and the projection obtained by extrapolating the model fitted to the raw projections acquired with 2 different sizes of axial field-of-view (FOV). The function for curve fitting was optimized by using Monte Carlo simulation. To validate the proposed method, an anthropomorphic phantom and a water-filled cylindrical phantom with rod inserts simulating different tissue materials were scanned using 120 kVp, 5 mA and 9-second scanning time covering an axial FOV of 4 cm and 13 cm. The detectability of the CT image was evaluated by calculating the contrast-to-noise ratio (CNR). Results Beam hardening and cupping artifacts were observed in CBCT images without scatter correction, especially in those acquired with 13 cm FOV. These artifacts were reduced in CBCT images corrected by the proposed method, demonstrating its efficacy on scatter correction. After scatter correction, the image quality of CBCT was improved in terms of target detectability which was quantified as the CNR for rod inserts in the cylindrical phantom. Conclusions Hopefully the calculations performed in this work can provide a route to reach a high level of diagnostic image quality for CBCT imaging used in oral and maxillofacial structures whilst ensuring patient dose as low as reasonably achievable, which may ultimately make CBCT scan a reliable and safe tool in clinical practice. PMID:26950435

  10. AFM and pulsed laser ablation methods for Cultural Heritage: application to archeometric analysis of stone artifacts

    NASA Astrophysics Data System (ADS)

    Barberio, M.; Veltri, S.; Stranges, F.; Bonanno, A.; Xu, F.; Antici, P.

    2015-09-01

    In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface's roughness is evaluated from very small artifact's fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

  11. The use of dental services for children: implications of the 2010 dental reform in Israel.

    PubMed

    Shahrabani, Shosh; Benzion, Uri; Machnes, Yaffa; Gal, Assaf

    2015-02-01

    Routine dental examinations for children are important for early diagnosis and treatment of dental problems. The level of dental morbidity among Israeli children is higher than the global average. A July 2010 reform of Israel's National Health Insurance Law gradually offers free dental services for children up to age 12. The study examines the use of dental services for children and the factors affecting mothers' decision to take their children for routine checkups. In addition, the study examines the impact of the reform on dental checkups for children in various populations groups. A national representative sample comprising 618 mothers of children aged 5-18 was surveyed by telephone. The survey integrated the principles of the health beliefs model and socio-demographic characteristics. The results show that mothers' decision to take their children for dental checkups is affected by their socio-demographic status and by their health beliefs with respect to dental health. After the reform, the frequency of children's dental checkups significantly increased among vulnerable populations. Therefore, the reform has helped reduce gaps in Israeli society regarding children's dental health. Raising families' awareness of the reform and of the importance of dental health care together with expanding national distribution of approved dental clinics can increase the frequency of dental checkups among children in Israel.

  12. Developments of metal artifact reduction methods of cone-beam computed tomography

    NASA Astrophysics Data System (ADS)

    Shih, Kun-Long; Jin, Shih-Chun D.; Chen, Jyh-Cheng

    2014-09-01

    While clinical applications of cone-beam computed tomography (CBCT) have expanded, current CBCT technology has limitations due to the streak artifacts caused by metallic objects. The aim of this work was to develop an efficient and accurate metal data interpolation in sinogram domain to achieve artifact suppression and to improve CT image quality. In this study, we propose three interpolation methods for the metal projection data. Metal objects are segmented in raw data and replacement of the segmented regions by new values is done using three interpolation schemes, (1) replacing the raw data by the simple threshold value (thresholding method), (2) reducing the raw data to half of the value which is over threshold value (modification method), (3) using the inpainting interpolation (inpainting method). Our references are the CBCT images of the phantoms without the metal implants. The performance was evaluated by comparing the differences of root mean square error (RMSE) before and after metal artifact reduction (MAR). All the metal artifacts were reduced effectively. Metal artifacts reduction using method (1) performs the best, which improve the differences of RMSE more than 60%. This study indicates that metal artifacts can be reduced effectively by manipulating metal projection data.

  13. Dental Calculus Arrest of Dental Caries

    PubMed Central

    Keyes, Paul H.; Rams, Thomas E.

    2016-01-01

    Background An inverse relationship between dental calculus mineralization and dental caries demineralization on teeth has been noted in some studies. Dental calculus may even form superficial layers over existing dental caries and arrest their progression, but this phenomenon has been only rarely documented and infrequently considered in the field of Cariology. To further assess the occurrence of dental calculus arrest of dental caries, this study evaluated a large number of extracted human teeth for the presence and location of dental caries, dental calculus, and dental plaque biofilms. Materials and methods A total of 1,200 teeth were preserved in 10% buffered formal saline, and viewed while moist by a single experienced examiner using a research stereomicroscope at 15-25× magnification. Representative teeth were sectioned and photographed, and their dental plaque biofilms subjected to gram-stain examination with light microscopy at 100× magnification. Results Dental calculus was observed on 1,140 (95%) of the extracted human teeth, and no dental carious lesions were found underlying dental calculus-covered surfaces on 1,139 of these teeth. However, dental calculus arrest of dental caries was found on one (0.54%) of 187 evaluated teeth that presented with unrestored proximal enamel caries. On the distal surface of a maxillary premolar tooth, dental calculus mineralization filled the outer surface cavitation of an incipient dental caries lesion. The dental calculus-covered carious lesion extended only slightly into enamel, and exhibited a brown pigmentation characteristic of inactive or arrested dental caries. In contrast, the tooth's mesial surface, without a superficial layer of dental calculus, had a large carious lesion going through enamel and deep into dentin. Conclusions These observations further document the potential protective effects of dental calculus mineralization against dental caries. PMID:27446993

  14. [Dental prostheses and dental impressions from a hygienic viewpoint].

    PubMed

    Engelhardt, J P

    1986-12-01

    Dentures, dental impressions, removable orthodontic appliances and all dental technical devices, which are part of any dental treatment are parts as well of a potential crosscontamination chain in dental treatment. Most of those items do not tolerate heat as a sure sterilization medium. For disinfection, chemical disinfectant solutions may be used as far as they work properly and as they are tolerated by the materials in question. Though, one can report some progress in disinfection of dentures and impressions, there are still questions open depending on safety and/or compatibility of the particular materials. For disinfection of removable dentures chlorine-yielding preparations such as Maranon can be recommended. Peracid preparations, such as Sekusept, Sekusept steril and Dentavon may be useful for disinfection of dental impressions. To do the possible means to reduce the infection risk for all persons involved in the dental treatment, patient, dentist, dental technician and all auxiliary persons. This includes both, active hygiene provisions as sterilization and disinfection, as well as possible passive self protection.

  15. Demand artifact: objectively detecting biased participants in advertising research.

    PubMed

    Miller, Felicia; Schertzer, Susan

    2014-12-01

    Detecting and reducing the effect of biased participants continues to be an important task for researchers. However, the lack of objective measures to assess demand artifact has made it difficult to effectively address this issue. This paper reports two experiments that apply a theory-based post-experimental inquiry that can systematically identify biased participants in consumer research. The results demonstrate how easily and effectively researchers can incorporate this tool into experimental studies of all types and reduce the likelihood of systematic error.

  16. Demand artifact: objectively detecting biased participants in advertising research.

    PubMed

    Miller, Felicia; Schertzer, Susan

    2014-12-01

    Detecting and reducing the effect of biased participants continues to be an important task for researchers. However, the lack of objective measures to assess demand artifact has made it difficult to effectively address this issue. This paper reports two experiments that apply a theory-based post-experimental inquiry that can systematically identify biased participants in consumer research. The results demonstrate how easily and effectively researchers can incorporate this tool into experimental studies of all types and reduce the likelihood of systematic error. PMID:25486509

  17. Wavelet approach to artifact noise removal from Capacitive coupled Electrocardiograph.

    PubMed

    Lee, Seung Min; Kim, Ko Keun; Park, Kwang Suk

    2008-01-01

    Capacitive coupled Electrocardiography (ECG) is introduced as non-invasive measurement technology for ubiquitous health care and appliance are spread out widely. Although it has many merits, however, capacitive coupled ECG is very weak for motion artifacts for its non-skin-contact property. There are many studies for artifact problems which treats all artifact signals below 0.8Hz. In our capacitive coupled ECG measurement system, artifacts exist not only below 0.8Hz but also over than 10Hz. Therefore, artifact noise removal algorithm using wavelet method is tested to reject artifact-wandered signal from measured signals. It is observed that using power calculation each decimation step, artifact-wandered signal is removed as low frequency artifacts as high frequency artifacts. Although some original ECG signal is removed with artifact signal, we could level the signal quality for long term measure which shows the best quality ECG signals as we can get. PMID:19163323

  18. Wavelet approach to artifact noise removal from Capacitive coupled Electrocardiograph.

    PubMed

    Lee, Seung Min; Kim, Ko Keun; Park, Kwang Suk

    2008-01-01

    Capacitive coupled Electrocardiography (ECG) is introduced as non-invasive measurement technology for ubiquitous health care and appliance are spread out widely. Although it has many merits, however, capacitive coupled ECG is very weak for motion artifacts for its non-skin-contact property. There are many studies for artifact problems which treats all artifact signals below 0.8Hz. In our capacitive coupled ECG measurement system, artifacts exist not only below 0.8Hz but also over than 10Hz. Therefore, artifact noise removal algorithm using wavelet method is tested to reject artifact-wandered signal from measured signals. It is observed that using power calculation each decimation step, artifact-wandered signal is removed as low frequency artifacts as high frequency artifacts. Although some original ECG signal is removed with artifact signal, we could level the signal quality for long term measure which shows the best quality ECG signals as we can get.

  19. Metal artifacts reduction in x-ray CT based on segmentation and forward-projection.

    PubMed

    Nawaz, Shoukat; Fu, Jian; Fan, Dekai

    2014-01-01

    X-ray computed tomography (CT) is a powerful clinical diagnosis tool and has been used widely in many clinical and biological settings. Metal artifacts, caused by high density implants, are commonly encountered in clinical CT applications, thereby affecting the detection of abnormal structures and undermining CT's diagnostic value. In this paper, we developed a metal artifact reduction approach based on image segmentation and forward-projection. We further demonstrate the usefulness of our approach by using a biomedical specimen consisting of muscles, bones and metals. Our aim is to remove the inaccurate metal artifact pixels in the original CT slices and exactly reconstruct the soft-tissue using the forward projections with no metal information. During the reconstruction, artifacts are reduced by replacing the metal projection using the forward projection. The presented work is of interest for CT biomedical applications.

  20. High-frequency brain activity and muscle artifacts in MEG/EEG: a review and recommendations

    PubMed Central

    Muthukumaraswamy, Suresh D.

    2013-01-01

    In recent years high-frequency brain activity in the gamma-frequency band (30–80 Hz) and above has become the focus of a growing body of work in MEG/EEG research. Unfortunately, high-frequency neural activity overlaps entirely with the spectral bandwidth of muscle activity (~20–300 Hz). It is becoming appreciated that artifacts of muscle activity may contaminate a number of non-invasive reports of high-frequency activity. In this review, the spectral, spatial, and temporal characteristics of muscle artifacts are compared with those described (so far) for high-frequency neural activity. In addition, several of the techniques that are being developed to help suppress muscle artifacts in MEG/EEG are reviewed. Suggestions are made for the collection, analysis, and presentation of experimental data with the aim of reducing the number of publications in the future that may contain muscle artifacts. PMID:23596409

  1. Demystifying Kepler Data: A Primer for Systematic Artifact Mitigation

    NASA Technical Reports Server (NTRS)

    Kinemuchi, K.; Barclay, T.; Fanelli, M.; Pepper, J.; Still, M.; Howell, B.

    2012-01-01

    The Kepler spacecraft has collected data of high photometric precision and cadence almost continuously since operations began on 2009 May 2. Primarily designed to detect planetary transits and asteroseismological signals from solar-like stars, Kepler has provided high quality data for many areas of investigation. Unconditioned simple aperture time-series photometry are however affected by systematic structure. Examples of these systematics are differential velocity aberration, thermal gradients across the spacecraft, and pointing variations. While exhibiting some impact on Kepler's primary science, these systematics can critically handicap potentially ground-breaking scientific gains in other astrophysical areas, especially over long timescales greater than 10 days. As the data archive grows to provide light curves for 10(exp 5) stars of many years in length, Kepler will only fulfill its broad potential for stellar astrophysics if these systematics are understood and mitigated. Post-launch developments in the Kepler archive, data reduction pipeline and open source data analysis software have occurred to remove or reduce systematic artifacts. This paper provides a conceptual primer for users of the Kepler data archive to understand and recognize systematic artifacts within light curves and some methods for their removal. Specific examples of artifact mitigation are provided using data available within the archive. Through the methods defined here, the Kepler community will find a road map to maximizing the quality and employment of the Kepler legacy archive.

  2. Demystifying Kepler Data: A Primer for Systematic Artifact Mitigation

    NASA Astrophysics Data System (ADS)

    Kinemuchi, K.; Barclay, T.; Fanelli, M.; Pepper, J.; Still, M.; Howell, Steve B.

    2012-09-01

    The Kepler spacecraft has collected data of high photometric precision and cadence almost continuously since operations began on 2009 May 2. Primarily designed to detect planetary transits and asteroseismological signals from solar-like stars, Kepler has provided high-quality data for many areas of investigation. Unconditioned simple aperture time-series photometry is, however, affected by systematic structure. Examples of these systematics include differential velocity aberration, thermal gradients across the spacecraft, and pointing variations. While exhibiting some impact on Kepler's primary science, these systematics can critically handicap potentially ground-breaking scientific gains in other astrophysical areas, especially over long timescales greater than 10 days. As the data archive grows to provide light curves for 105 stars of many years in length, Kepler will only fulfill its broad potential for stellar astrophysics if these systematics are understood and mitigated. Post-launch developments in the Kepler archive, data reduction pipeline and open source data analysis software have helped to remove or reduce systematic artifacts. This paper provides a conceptual primer to help users of the Kepler data archive understand and recognize systematic artifacts within light curves and some methods for their removal. Specific examples of artifact mitigation are provided using data available within the archive. Through the methods defined here, the Kepler community will find a road map to maximizing the quality and employment of the Kepler legacy archive.

  3. Motion artifact reduction in breast dynamic infrared imaging.

    PubMed

    Agostini, Valentina; Knaflitz, Marco; Molinari, Filippo

    2009-03-01

    Dynamic infrared imaging is a promising technique in breast oncology. In this paper, a quantum well infrared photodetector infrared camera is used to acquire a sequence of consecutive thermal images of the patient's breast for 10 s. Information on the local blood perfusion is obtained from the spectral analysis of the time series at each image pixel. Due to respiratory and motion artifacts, the direct comparison of the temperature values that a pixel assumes along the sequence becomes difficult. In fact, the small temperature changes due to blood perfusion, of the order of 10-50 mK, which constitute the signal of interest in the time domain, are superimposed onto large temperature fluctuations due to the subject's motion, which represent noise. To improve the time series S/N, and as a consequence, enhance the specificity and sensitivity of the dynamic infrared examination, it is important to realign the thermal images of the acquisition sequence, thus reducing motion artifacts. In a previous study, we demonstrated that a registration algorithm based on fiducial points is suitable to both clinical applications and research, when associated with a proper set of skin markers. In this paper, we quantitatively evaluate the performance of different marker sets by means of a model that allows for estimating the S/N increment due to registration, and we conclude that a 12-marker set is a good compromise between motion artifact reduction and the time required to prepare the patient.

  4. Effects of sampling artifacts on occupational samples of diesel particulate matter.

    PubMed

    Noll, James; Birch, M Eileen

    2008-07-15

    Total carbon (TC) is sometimes used to measure or characterize diesel particulate matter (DPM) in occupational settings such as underground mines. DPM samples are collected on quartz fiber filters. When using quartz fiber filters, adsorption of gas phase organic carbon (OC) has been reported, causing a positive bias in the particulate TC results (adsorption artifact). Most of the data on the sampling artifacts and corrections applyto environmental air sampling, where samples are collected at a much higher filter face velocity and the OC concentrations are generally much lower relative to occupational sampling. In this study, we investigated the effects of adsorption artifact on samples from occupational settings. Samples were collected with and without denuders to determine the amount of gas phase OC collected and the accuracy of certain corrections. In underground stone mines, the adsorption artifact was found to positively bias the particulate TC by greater than 20% for filter loadings below 25 microg/cm2 TC (8-h time weighted average = 262 microg/m3). The tandem filter correction reduced the effect of the artifact, as high as 60% of the TC value, to less than 11% for laboratory data. It also significantly reduced the effect of the artifact obtained for field samples.

  5. Removal of the ballistocardiographic artifact from EEG-fMRI data: a canonical correlation approach

    NASA Astrophysics Data System (ADS)

    Assecondi, Sara; Hallez, Hans; Staelens, Steven; Bianchi, Anna M; Huiskamp, Geertjan M; Lemahieu, Ignace

    2009-03-01

    The simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) can give new insights into how the brain functions. However, the strong electromagnetic field of the MR scanner generates artifacts that obscure the EEG and diminish its readability. Among them, the ballistocardiographic artifact (BCGa) that appears on the EEG is believed to be related to blood flow in scalp arteries leading to electrode movements. Average artifact subtraction (AAS) techniques, used to remove the BCGa, assume a deterministic nature of the artifact. This assumption may be too strong, considering the blood flow related nature of the phenomenon. In this work we propose a new method, based on canonical correlation analysis (CCA) and blind source separation (BSS) techniques, to reduce the BCGa from simultaneously recorded EEG-fMRI. We optimized the method to reduce the user's interaction to a minimum. When tested on six subjects, recorded in 1.5 T or 3 T, the average artifact extracted with BSS-CCA and AAS did not show significant differences, proving the absence of systematic errors. On the other hand, when compared on the basis of intra-subject variability, we found significant differences and better performance of the proposed method with respect to AAS. We demonstrated that our method deals with the intrinsic subject variability specific to the artifact that may cause averaging techniques to fail.

  6. Automatic probe artifact detection in MRI-guided cryoablation

    NASA Astrophysics Data System (ADS)

    Liu, Xinyang; Tuncali, Kemal; Wells, William M.; Zientara, Gary P.

    2013-03-01

    Probe or needle artifact detection in 3D scans gives an approximate location for the tools inserted, and is thus crucial in assisting many image-guided procedures. Conventional needle localization algorithms often start with cropped images, where unwanted parts of raw scans are cropped either manually or by applying pre-defined masks. In cryoablation, however, the number of probes used, the placement and direction of probe insertion, and the portions of abdomen scanned differs significantly from case to case, and probes are often constantly being adjusted during the Probe Placement Phase. These features greatly reduce the practicality of approaches based on image cropping. In this work, we present a fully Automatic Probe Artifact Detection method, APAD, that works directly on uncropped raw MRI images, taken during the Probe Placement Phase in 3Tesla MRI-guided cryoablation. The key idea of our method is to first locate an initial 2D line strip within a slice of the MR image which approximates the position and direction of the 3D probes bundle, noting that cryoprobes or biopsy needles create a signal void (black) artifact in MRI with a bright cylindrical border. With the initial 2D line, standard approaches to detect line structures such as the 3D Hough Transform can be applied to quickly detect each probe's axis. By comparing with manually labeled probes, the analysis of 5 patient treatment cases of kidney cryoablation with varying probe placements demonstrates that our algorithm combined with standard 3D line detection is an accurate and robust method to detect probe artifacts.

  7. Dental Assistant.

    ERIC Educational Resources Information Center

    Michigan State Univ., East Lansing. Coll. of Agriculture and Natural Resources Education Inst.

    This curriculum guide, developed for use in dental assistant education programs in Michigan, describes a task-based curriculum that can help a teacher to develop a classroom management system where students learn by doing. It is based on task analysis and reflects the skills, knowledge, and attitudes that employers expect entry-level dental…

  8. Mediating Artifact in Teacher Professional Development

    NASA Astrophysics Data System (ADS)

    Svendsen, Bodil

    2015-07-01

    This article focuses on teacher professional development (TPD) in natural science through the 5E model as mediating artifact. The study was conducted in an upper secondary school, grounded in a school-based intervention research project. My contribution to the field of research on TPD is founded on the hypothesis that teachers would be best facilitated to make their practice more inquiry based if they are provided with a mediating artifact. In this study the artifact is a model 5E, which is a conceptual way of thinking, to help teachers reflect on their practice. The aim is to encourage teachers to make changes themselves, by applying extended use of inquiry into their practice. This mediated artifact could thus be used across different national contexts. The main research question is; how can the 5E model as a mediating artifact enhance TPD? The article addresses the processes of the use of the 5E model and its influence on teachers' perception of the model. This is in order for teachers to conceptualize their goals related to inquiry and scientific thinking, and to solve the problems involved in achieving those goals in their own contexts. The study concludes that, after the intervention, the teachers' approaches and strategies demonstrate greater emphasis on learning.

  9. MRI-Based Computed Tomography Metal Artifact Correction Method for Improving Proton Range Calculation Accuracy

    SciTech Connect

    Park, Peter C.; Schreibmann, Eduard; Roper, Justin; Elder, Eric; Crocker, Ian; Fox, Tim; Zhu, X. Ronald; Dong, Lei; Dhabaan, Anees

    2015-03-15

    Purpose: Computed tomography (CT) artifacts can severely degrade dose calculation accuracy in proton therapy. Prompted by the recently increased popularity of magnetic resonance imaging (MRI) in the radiation therapy clinic, we developed an MRI-based CT artifact correction method for improving the accuracy of proton range calculations. Methods and Materials: The proposed method replaces corrupted CT data by mapping CT Hounsfield units (HU number) from a nearby artifact-free slice, using a coregistered MRI. MRI and CT volumetric images were registered with use of 3-dimensional (3D) deformable image registration (DIR). The registration was fine-tuned on a slice-by-slice basis by using 2D DIR. Based on the intensity of paired MRI pixel values and HU from an artifact-free slice, we performed a comprehensive analysis to predict the correct HU for the corrupted region. For a proof-of-concept validation, metal artifacts were simulated on a reference data set. Proton range was calculated using reference, artifactual, and corrected images to quantify the reduction in proton range error. The correction method was applied to 4 unique clinical cases. Results: The correction method resulted in substantial artifact reduction, both quantitatively and qualitatively. On respective simulated brain and head and neck CT images, the mean error was reduced from 495 and 370 HU to 108 and 92 HU after correction. Correspondingly, the absolute mean proton range errors of 2.4 cm and 1.7 cm were reduced to less than 2 mm in both cases. Conclusions: Our MRI-based CT artifact correction method can improve CT image quality and proton range calculation accuracy for patients with severe CT artifacts.

  10. U.S. Dental School Deans’ Perceptions of the Rising Cost of Dental Education and Borrowing Pressures on Dental Students: Report of Survey Results.

    PubMed

    McAllister, Dora Elías; Garrison, Gwen E; Feldman, Cecile A; Anderson, Eugene L; Cook, Bryan J; Valachovic, Richard W

    2015-06-01

    This report presents findings from a survey of U.S. dental school deans designed to capture their perceptions regarding the rising cost of dental education and its impact on borrowing by dental students to finance their education. The survey included questions about factors influencing the cost of dental education, concerns about dental student borrowing, and financial awareness resources for students. The survey was distributed to the deans of all 63 U.S. dental schools in January 2013; 42 deans responded, for a 67% response rate. The results indicate that, according to the responding deans, new clinical technologies, technology costs, and central university taxes are the main factors that contribute to the increasing cost of dental education. Coupled with reduced state appropriations at public dental schools and declines in private giving at all dental schools, dental school deans face a perplexing set of financial management challenges. Tuition and fees are a primary source of revenue for all dental schools; however, many deans do not have total control over the cost of attending their schools since tuition and fees are often tied to mandates and policies from the parent university and the state legislature. The findings of this study indicate that U.S. dental school deans are aware of and concerned about the impact of increases in tuition and fees on dental student debt and that they are using a variety of strategies to address the growth in dental student borrowing.

  11. Dental Training Films.

    ERIC Educational Resources Information Center

    Veterans Administration Medical Center, Washington, DC.

    This dental training films catalog is organized into two sections. Section I is a category listing of the films by number and title, indexed according to generalized headings; categories are as follow: anatomy, articulator systems, complete dentures, dental assisting, dental laboratory technology, dental materials, dental office emergencies,…

  12. Artifacts Reduction in VIR/DAWN data

    NASA Astrophysics Data System (ADS)

    Carrozzo, Filippo Giacomo

    2016-07-01

    Imaging spectrometers often suffer from the common problems of different types of systematic errors. The quality of the calibration to surface reflectance is important for accurately identifying surface materials. An inappropriate calibration could distort an absorption feature, causing a misidentification. Artifact might be interpreted as representing a material that does not really exist at that location. Also VIR (Visible and Infrared Spectrometer, De Sanctis et al., 2011) imaging spectrometer is affected by systematic and non-systematic errors, such as artifacts, vertical stripes and spikes. In VIR data, they are caused by imperfect radiometric and spectral calibration, by a peculiar readout noise in the detector (Schlapfer and Richter, 2011). In this work we apply a spectral polishing technique in order to remove artifacts, and spikes from VIR data and we show how the resulting spectra of Vesta and Ceres are affected by corrections.

  13. Dental practice in Paris.

    PubMed

    Baron, Pierre

    2003-01-01

    This describes dental practice and the availability of dental patent remedies in Paris. Accounts of legal disputes, from original sources, illustrate the status and social history of some of the most wealthy dental practitioners in Paris during the Revolution.

  14. American Dental Association

    MedlinePlus

    ... Public Prevention Summit ADA Find-a-Dentist Health Literacy in Dentistry Volunteer Efforts Dental Benefit Plan Information ... on Sleep Bruxism Rethinking Dental Insurance Oral Health Literacy's Role in Missed Appointments Dental Implant Failure Rate ...

  15. Artifact reduction in long-term monitoring of cerebral hemodynamics using near-infrared spectroscopy

    PubMed Central

    Vinette, Sarah A.; Dunn, Jeff F.; Slone, Edward; Federico, Paolo

    2015-01-01

    Abstract. Near-infrared spectroscopy (NIRS) is a noninvasive neuroimaging technique used to assess cerebral hemodynamics. Its portability, ease of use, and relatively low operational cost lend itself well to the long-term monitoring of hemodynamic changes, such as those in epilepsy, where events are unpredictable. Long-term monitoring is associated with challenges including alterations in behaviors and motion that can result in artifacts. Five patients with epilepsy were assessed for interictal hemodynamic changes and alterations in behavior or motion. Based on this work, visual inspection was used to identify NIRS artifacts during a period of interest, specifically prior to seizures, in four patients. A motion artifact reduction algorithm (MARA, also known as the spline interpolation method) was tested on these data. Alterations in the NIRS measurements often occurred simultaneously with changes in motion and behavior. Occasionally, sharp shift artifacts were observed in the data. When artifacts appeared as sustained baseline shifts in the data, MARA reduced the standard deviation of the data and the appearance improved. We discussed motion and artifacts as challenges associated with long-term monitoring of cerebral hemodynamics in patients with epilepsy and our group’s approach to circumvent these challenges and improve the quality of the data collected. PMID:26158008

  16. Flexible Capacitive Electrodes for Minimizing Motion Artifacts in Ambulatory Electrocardiograms

    PubMed Central

    Lee, Jeong Su; Heo, Jeong; Lee, Won Kyu; Lim, Yong Gyu; Kim, Youn Ho; Park, Kwang Suk

    2014-01-01

    This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring. PMID:25120162

  17. The impact of head movements on EEG and contact impedance: an adaptive filtering solution for motion artifact reduction.

    PubMed

    Mihajlovic, Vojkan; Patki, Shrishail; Grundlehner, Bernard

    2014-01-01

    Designing and developing a comfortable and convenient EEG system for daily usage that can provide reliable and robust EEG signal, encompasses a number of challenges. Among them, the most ambitious is the reduction of artifacts due to body movements. This paper studies the effect of head movement artifacts on the EEG signal and on the dry electrode-tissue impedance (ETI), monitored continuously using the imec's wireless EEG headset. We have shown that motion artifacts have huge impact on the EEG spectral content in the frequency range lower than 20 Hz. Coherence and spectral analysis revealed that ETI is not capable of describing disturbances at very low frequencies (below 2 Hz). Therefore, we devised a motion artifact reduction (MAR) method that uses a combination of a band-pass filtering and multi-channel adaptive filtering (AF), suitable for real-time MAR. This method was capable of substantially reducing artifacts produced by head movements.

  18. A robust adaptive denoising framework for real-time artifact removal in scalp EEG measurements

    NASA Astrophysics Data System (ADS)

    Kilicarslan, Atilla; Grossman, Robert G.; Contreras-Vidal, Jose Luis

    2016-04-01

    , totaling 19 sessions, with and without {H}∞ filtering of the raw data. Significance. The proposed method allows real-time adaptive artifact removal for EEG-based closed-loop BMI applications and mobile EEG studies in general, thereby increasing the range of tasks that can be studied in action and context while reducing the need for discarding data due to artifacts. Significant increase in decoding performances also justify the effectiveness of the method to be used in real-time closed-loop BMI applications.

  19. Two-stage approach for detection and reduction of motion artifacts in photoplethysmographic data.

    PubMed

    Krishnan, Rajet; Natarajan, Balasubramaniam Bala; Warren, Steve

    2010-08-01

    that is effective even in the presence of severe subject movement. The approach involves an enhanced preprocessing unit consisting of a motion detection unit (MDU, developed in this paper), period estimation unit, and Fourier series reconstruction unit. The MDU identifies clean data frames versus those corrupted with motion artifacts. The period estimation unit determines the fundamental frequency of a corrupt frame. The Fourier series reconstruction unit reconstructs the final preprocessed signal by utilizing the spectrum variability of the pulse waveform. Preprocessed data are then fed to a magnitude-based FD independent component analysis unit. This helps reduce motion artifacts present at the frequencies of the reconstruction components. Experimental results are presented to demonstrate the efficacy of the overall motion artifact reduction method.

  20. Two-stage approach for detection and reduction of motion artifacts in photoplethysmographic data.

    PubMed

    Krishnan, Rajet; Natarajan, Balasubramaniam Bala; Warren, Steve

    2010-08-01

    that is effective even in the presence of severe subject movement. The approach involves an enhanced preprocessing unit consisting of a motion detection unit (MDU, developed in this paper), period estimation unit, and Fourier series reconstruction unit. The MDU identifies clean data frames versus those corrupted with motion artifacts. The period estimation unit determines the fundamental frequency of a corrupt frame. The Fourier series reconstruction unit reconstructs the final preprocessed signal by utilizing the spectrum variability of the pulse waveform. Preprocessed data are then fed to a magnitude-based FD independent component analysis unit. This helps reduce motion artifacts present at the frequencies of the reconstruction components. Experimental results are presented to demonstrate the efficacy of the overall motion artifact reduction method. PMID:20172800

  1. Dental problems in athletes.

    PubMed

    Inouye, Jill; McGrew, Chris

    2015-01-01

    Orofacial injuries and diseases occur in athletes, and they may not always have access to dentists. Therefore team physicians should be aware of the common injuries and initial management. Treatment of dental injuries will depend on whether the teeth are primary or permanent. The most common type of fracture is crown fracture, but there are other dental injuries that can lead to future complications if not treated promptly and monitored closely. Tooth avulsions need to be handled properly, and athletes should see a dentist as soon as possible. Despite the urgency of some injuries, other orofacial injuries or diseases, such as lacerations and caries, should not be overlooked. Proper education and use of mouth guards can assist athletes in reducing their risk of orofacial injuries. PMID:25574879

  2. Effect of Perceived Stress on Student Performance in Dental School.

    ERIC Educational Resources Information Center

    Sanders, Anne E.; Lushington, Kurt

    2002-01-01

    Examined the relationship between perceived stress and academic performance in 202 dental students at an Australian dental school. Found little support for an association between increased factor stress scores on the Dental Environmental Stress (DES) questionnaire and reduced academic performance. (EV)

  3. Method to control artifacts of microstructural fabrication

    DOEpatents

    Shul, Randy J.; Willison, Christi G.; Schubert, W. Kent; Manginell, Ronald P.; Mitchell, Mary-Anne; Galambos, Paul C.

    2006-09-12

    New methods for fabrication of silicon microstructures have been developed. In these methods, an etching delay layer is deposited and patterned so as to provide differential control on the depth of features being etched into a substrate material. Compensation for etching-related structural artifacts can be accomplished by proper use of such an etching delay layer.

  4. Law addresses question of space artifact ownership

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2012-10-01

    U.S. astronauts who participated in many of NASA's early space missions will receive full ownership rights to artifacts from those missions through legislation that President Barack Obama signed into law on 25 September. The legislation, which received broad bipartisan support, provides artifact ownership rights to any of NASA's Mercury, Gemini, or Apollo space programs through the completion of the Apollo-Soyuz Test Project, whose flight occurred in July 1975. The law defines artifacts as expendable, disposable, or personal use items—including personal logs and flight hardware salvaged from jettisoned lunar modules—used by astronauts that were not required to be returned to NASA; lunar rocks and other lunar material are not defined as artifacts. Bill cosponsor Rep. Ralph Hall (R-Tex.), chair of the House of Representatives' Committee on Science, Space, and Technology, said on 19 September, “A majority of these items have been in the personal possession of the astronauts for 40 years or more. Over the last decade, NASA has begun to challenge the astronauts' ownership of these mementos. This issue was first brought to my attention late last year. I was surprised to learn that NASA had, on an irregular basis, intervened several times to claim ownership.”

  5. Operativity and the Superordinate Categorization of Artifacts.

    ERIC Educational Resources Information Center

    Ricco, Robert B.; Beilin, Harry

    1992-01-01

    The relative consistency in categorization by age-equivalent groups of preoperational and concrete-operational first graders was assessed across two categorization tasks employing color drawings of exemplars of superordinate artifact categories. Results are discussed in terms of the utilization and acquisition of knowledge about superordinate…

  6. Information Design for Visualizing History Museum Artifacts

    ERIC Educational Resources Information Center

    Chen, Yulin; Lai, Tingsheng; Yasuda, Takami; Yokoi, Shigeki

    2011-01-01

    In the past few years, museum visualization systems have become a hot topic that attracts many researchers' interests. Several systems provide Web services for browsing museum collections through the Web. In this paper, we proposed an intelligent museum system for history museum artifacts, and described a study in which we enable access to China…

  7. "Things" that Work: The Artifacts of Industrialization.

    ERIC Educational Resources Information Center

    Geenfield, Briann; Malone, Patrick

    2000-01-01

    Focuses on teaching industrialization through the use of industrial artifacts, such as tools and products. Suggests field trips to museums and historic sites, building models of waterwheels or bridges, visiting an operating factory, and studying landscapes shaped by industrialization. Includes a bibliography. (CMK)

  8. Intelligent artifact classification for ambulatory physiological signals.

    PubMed

    Sweeney, Kevin T; Leamy, Darren J; Ward, Tomas E; McLoone, Sean

    2010-01-01

    Connected health represents an increasingly important model for health-care delivery. The concept is heavily reliant on technology and in particular remote physiological monitoring. One of the principal challenges is the maintenance of high quality data streams which must be collected with minimally intrusive, inexpensive sensor systems operating in difficult conditions. Ambulatory monitoring represents one of the most challenging signal acquisition challenges of all in that data is collected as the patient engages in normal activities of everyday living. Data thus collected suffers from considerable corruption as a result of artifact, much of it induced by motion and this has a bearing on its utility for diagnostic purposes. We propose a model for ambulatory signal recording in which the data collected is accompanied by labeling indicating the quality of the collected signal. As motion is such an important source of artifact we demonstrate the concept in this case with a quality of signal measure derived from motion sensing technology viz. accelerometers. We further demonstrate how different types of artifact might be tagged to inform artifact reduction signal processing elements during subsequent signal analysis. This is demonstrated through the use of multiple accelerometers which allow the algorithm to distinguish between disturbance of the sensor relative to the underlying tissue and movement of this tissue. A brain monitoring experiment utilizing EEG and fNIRS is used to illustrate the concept.

  9. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion).

    PubMed

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-08-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging. PMID:27570690

  10. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion)

    PubMed Central

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-01-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging. PMID:27570690

  11. In vivo demonstration of reflection artifact reduction in photoacoustic imaging using synthetic aperture photoacoustic-guided focused ultrasound (PAFUSion).

    PubMed

    Singh, Mithun Kuniyil Ajith; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-08-01

    Reflection artifacts caused by acoustic inhomogeneities are a critical problem in epi-mode biomedical photoacoustic imaging. High light fluence beneath the probe results in photoacoustic transients, which propagate into the tissue and reflect back from echogenic structures. These reflection artifacts cause problems in image interpretation and significantly impact the contrast and imaging depth. We recently proposed a method called PAFUSion (Photoacoustic-guided focused ultrasound) to identify such reflection artifacts in photoacoustic imaging. In its initial version, PAFUSion mimics the inward-travelling wavefield from small blood vessel-like PA sources by applying ultrasound pulses focused towards these sources, and thus provides a way to identify the resulting reflection artifacts. In this work, we demonstrate reduction of reflection artifacts in phantoms and in vivo measurements on human volunteers. In view of the spatially distributed PA sources that are found in clinical applications, we implemented an improved version of PAFUSion where photoacoustic signals are backpropagated to imitate the inward travelling wavefield and thus the reflection artifacts. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can strongly reduce these artifacts to improve deep-tissue photoacoustic imaging.

  12. Model of Image Artifacts from Dust Particles

    NASA Technical Reports Server (NTRS)

    Willson, Reg

    2008-01-01

    A mathematical model of image artifacts produced by dust particles on lenses has been derived. Machine-vision systems often have to work with camera lenses that become dusty during use. Dust particles on the front surface of a lens produce image artifacts that can potentially affect the performance of a machine-vision algorithm. The present model satisfies a need for a means of synthesizing dust image artifacts for testing machine-vision algorithms for robustness (or the lack thereof) in the presence of dust on lenses. A dust particle can absorb light or scatter light out of some pixels, thereby giving rise to a dark dust artifact. It can also scatter light into other pixels, thereby giving rise to a bright dust artifact. For the sake of simplicity, this model deals only with dark dust artifacts. The model effectively represents dark dust artifacts as an attenuation image consisting of an array of diffuse darkened spots centered at image locations corresponding to the locations of dust particles. The dust artifacts are computationally incorporated into a given test image by simply multiplying the brightness value of each pixel by a transmission factor that incorporates the factor of attenuation, by dust particles, of the light incident on that pixel. With respect to computation of the attenuation and transmission factors, the model is based on a first-order geometric (ray)-optics treatment of the shadows cast by dust particles on the image detector. In this model, the light collected by a pixel is deemed to be confined to a pair of cones defined by the location of the pixel s image in object space, the entrance pupil of the lens, and the location of the pixel in the image plane (see Figure 1). For simplicity, it is assumed that the size of a dust particle is somewhat less than the diameter, at the front surface of the lens, of any collection cone containing all or part of that dust particle. Under this assumption, the shape of any individual dust particle artifact

  13. Dental students--dental advocates.

    PubMed

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future.

  14. Dental students--dental advocates.

    PubMed

    Bensch, Brittany

    2010-01-01

    Student advocacy and involvement in the political process is built into the structure of the American Student Dental Association (ASDA), especially in its Legislative Grassroots Network and an internal communication network among students to ensure political awareness. Students are concerned with such issues as a universally accepted, non-patient-based licensure process, mid-level providers, loan availability and tax deductibility, financial support for schools, and service early in one's professional career (giving forward rather than giving back). Through collaboration with the American Dental Education Association and with many state associations, students participate in lobbying, awareness campaigns, and behind the scenes as legislative aids. Although students share the same love for the profession that animates established practitioners, they are perceived by legislators as being different. Students are involved in the legislative process because it represents their future. PMID:21314046

  15. Artifacts for Calibration of Submicron Width Measurements

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank; Grunthaner, Paula; Bryson, Charles, III

    2003-01-01

    Artifacts that are fabricated with the help of molecular-beam epitaxy (MBE) are undergoing development for use as dimensional calibration standards with submicron widths. Such standards are needed for calibrating instruments (principally, scanning electron microscopes and scanning probe microscopes) for measuring the widths of features in advanced integrated circuits. Dimensional calibration standards fabricated by an older process that involves lithography and etching of trenches in (110) surfaces of single-crystal silicon are generally reproducible to within dimensional tolerances of about 15 nm. It is anticipated that when the artifacts of the present type are fully developed, their critical dimensions will be reproducible to within 1 nm. These artifacts are expected to find increasing use in the semiconductor-device and integrated- circuit industries as the width tolerances on semiconductor devices shrink to a few nanometers during the next few years. Unlike in the older process, one does not rely on lithography and etching to define the critical dimensions. Instead, one relies on the inherent smoothness and flatness of MBE layers deposited under controlled conditions and defines the critical dimensions as the thicknesses of such layers. An artifact of the present type is fabricated in two stages (see figure): In the first stage, a multilayer epitaxial wafer is grown on a very flat substrate. In the second stage, the wafer is cleaved to expose the layers, then the exposed layers are differentially etched (taking advantage of large differences between the etch rates of the different epitaxial layer materials). The resulting structure includes narrow and well-defined trenches and a shelf with thicknesses determined by the thicknesses of the epitaxial layers from which they were etched. Eventually, it should be possible to add a third fabrication stage in which durable, electronically inert artifacts could be replicated in diamondlike carbon from a master made by

  16. Reduction of blooming artifacts in cardiac CT images by blind deconvolution and anisotropic diffusion filtering

    NASA Astrophysics Data System (ADS)

    Castillo-Amor, Angélica M.; Navarro-Navia, Cristian A.; Cadena-Bonfanti, Alberto J.; Contreras-Ortiz, Sonia H.

    2015-12-01

    Even though CT is an imaging technique that offers high quality images, limitations on its spatial resolution cause blurring in small objects with high contrast. This phenomenon is known as blooming artifact and affects cardiac images with small calcifications and stents. This paper describes an approach to reduce the blooming artifact and improve resolution in cardiac images using blind deconvolution and anisotropic diffusion filtering. Deconvolution increases resolution but reduces signal-to-noise ratio, and the anisotropic diffusion filter counteracts this effect without affecting the edges in the image.

  17. Mammographic artifacts on full-field digital mammography.

    PubMed

    Choi, Jae Jeong; Kim, Sung Hun; Kang, Bong Joo; Choi, Byung Gil; Song, ByungJoo; Jung, Haijo

    2014-04-01

    This study investigates the incidence of full-field digital mammographic (FFDM) artifacts with three systems at two institutions and compares the artifacts between two detector types and two grid types. A total of 4,440 direct and 4,142 indirect FFDM images were reviewed by two radiologists, and artifacts were classified as patient related, hardware related, and software processing. The overall incidence of FFDM artifacts was 3.4% (292/8,582). Patient related artifacts (motion artifacts and skin line artifacts) were the most commonly detected types (1.7%). Underexposure among hardware related artifacts and high-density artifacts among software processing artifacts also were common (0.7 and 0.5%, respectively). These artifacts, specific to digital mammography, were more common with the direct detector type and the crossed air grid type than with the indirect type and linear grid type (p < 0.05). The most common mammographic artifacts on FFDM were patient related, which might be controlled by the instruction of a patient and technologist. Underexposure and high-density artifacts were more common with direct detector and crossed air type of grid.

  18. An Audit and Feedback Intervention for Reducing Antibiotic Prescribing in General Dental Practice: The RAPiD Cluster Randomised Controlled Trial

    PubMed Central

    Elouafkaoui, Paula; Young, Linda; Newlands, Rumana; Duncan, Eilidh M.; Elders, Andrew; Ramsay, Craig R.

    2016-01-01

    Background Dentists prescribe approximately 10% of antibiotics dispensed in UK community pharmacies. Despite clear clinical guidance, dentists often prescribe antibiotics inappropriately. This cluster-randomised controlled trial used routinely collected National Health Service (NHS) dental prescribing and treatment claim data to compare the impact of individualised audit and feedback (A&F) interventions on dentists’ antibiotic prescribing rates. Methods and Findings All 795 antibiotic prescribing NHS general dental practices in Scotland were included. Practices were randomised to the control (practices = 163; dentists = 567) or A&F intervention group (practices = 632; dentists = 1,999). A&F intervention practices were allocated to one of two A&F groups: (1) individualised graphical A&F comprising a line graph plotting an individual dentist’s monthly antibiotic prescribing rate (practices = 316; dentists = 1,001); or (2) individualised graphical A&F plus a written behaviour change message synthesising and reiterating national guidance recommendations for dental antibiotic prescribing (practices = 316; dentists = 998). Intervention practices were also simultaneously randomised to receive A&F: (i) with or without a health board comparator comprising the addition of a line to the graphical A&F plotting the monthly antibiotic prescribing rate of all dentists in the health board; and (ii) delivered at 0 and 6 mo or at 0, 6, and 9 mo, giving a total of eight intervention groups. The primary outcome, measured by the trial statistician who was blinded to allocation, was the total number of antibiotic items dispensed per 100 NHS treatment claims over the 12 mo post-delivery of the baseline A&F. Primary outcome data was available for 152 control practices (dentists = 438) and 609 intervention practices (dentists = 1,550). At baseline, the number of antibiotic items prescribed per 100 NHS treatment claims was 8.3 in the control group and 8.5 in the intervention group. At

  19. Artifacts and pitfalls of high-resolution CT scans.

    PubMed

    Hahn, F J; Chu, W K; Anderson, J C; Dobry, C A

    1985-01-01

    Artifacts on CT images have been observed since the introduction of CT scanners. Some artifacts have been corrected with the improvement of technology and better understanding of the image formation and reconstruction algorithms. Some artifacts, however, are still observable in state-of-the-art high-resolution scans. Many investigations on CT artifacts have been reported. Some artifacts are obvious and some are similar to patterns commonly associated with pathological conditions. The present report summarizes some of the causes of artifacts and presents some artifacts that mimic pathology on clinical scans of the head and spine. It is the intention of this report to bring these artifacts and potential pitfalls to the attention of the radiologists so that misinterpretation can be avoided.

  20. Streaking artifact reduction for quantitative susceptibility mapping of sources with large dynamic range.

    PubMed

    Wei, Hongjiang; Dibb, Russell; Zhou, Yan; Sun, Yawen; Xu, Jianrong; Wang, Nian; Liu, Chunlei

    2015-10-01

    Quantitative susceptibility mapping (QSM) is a novel MRI technique for the measurement of tissue magnetic susceptibility in three dimensions. Although numerous algorithms have been developed to solve this ill-posed inverse problem, the estimation of susceptibility maps with a wide range of values is still problematic. In cases such as large veins, contrast agent uptake and intracranial hemorrhages, extreme susceptibility values in focal areas cause severe streaking artifacts. To enable the reduction of these artifacts, whilst preserving subtle susceptibility contrast, a two-level QSM reconstruction algorithm (streaking artifact reduction for QSM, STAR-QSM) was developed in this study by tuning a regularization parameter to automatically reconstruct both large and small susceptibility values. Compared with current state-of-the-art QSM methods, such as the improved sparse linear equation and least-squares (iLSQR) algorithm, STAR-QSM significantly reduced the streaking artifacts, whilst preserving the sharp boundaries for blood vessels of mouse brains in vivo and fine anatomical details of high-resolution mouse brains ex vivo. Brain image data from patients with cerebral hematoma and multiple sclerosis further illustrated the superiority of this method in reducing streaking artifacts caused by large susceptibility sources, whilst maintaining sharp anatomical details. STAR-QSM is implemented in STI Suite, a comprehensive shareware for susceptibility imaging and quantification.

  1. A new method for pulse oximetry possessing inherent insensitivity to artifact.

    PubMed

    Hayes, M J; Smith, P R

    2001-04-01

    A new method for pulse oximetry is presented that possesses an inherent insensitivity to corruption by motion artifact, a primary limitation in the practical accuracy and clinical applicability of current technology. Artifact corruption of the underlying photoplethysmographic signals is reduced in real time, using an electronic processing methodology that is based upon inversion of a physical artifact model. This fundamental approach has the potential to provide uninterrupted output and superior accuracy under conditions of sustained subject motion, therefore, widening the clinical scope of this useful measurement. A new calibration technique for oxygen saturation is developed for use with these processed signals, which is shown to be a generalization of the classical interpretation. The detailed theoretical and practical issues of implementation are then explored, highlighting important engineering simplifications implicit in this new approach. A quantitative investigation of the degree of insensitivity to artifact is also undertaken, with the aid of a custom electronic system and commercial pulse oximeter probes, which is compared and contrasted with the performance of a conventional implementation. It is demonstrated that this new methodology results in a reduced sensitivity to common classes of motion artifact, while retaining the generality to be combined with conventional signal processing techniques.

  2. Analysis of vector models in quantification of artifacts produced by standard prosthetic inlays in Cone-Beam Computed Tomography (CBCT)--a preliminary study.

    PubMed

    Różyło-Kalinowska, Ingrid; Miechowicz, Sławomir; Sarna-Boś, Katarzyna; Borowicz, Janusz; Kalinowski, Paweł

    2014-11-17

    Cone-beam computed tomography (CBCT) is a relatively new, but highly efficient imaging method applied first in dentistry in 1998. However, the quality of the obtained slices depends among other things on artifacts generated by dental restorations as well as orthodontic and prosthetic appliances. The aim of the study was to quantify the artifacts produced by standard prosthetic inlays in CBCT images. The material consisted of 17 standard prosthetic inlays mounted in dental roots embedded in resin. The samples were examined by means of a large field of view CBCT unit, Galileos (Sirona, Germany), at 85 kV and 14 mAs. The analysis was performed using Able 3DDoctor software for data in the CT raster space as well as by means of Materialise Magics software for generated vector models (STL). The masks generated in the raster space included the area of the inlays together with image artifacts. The region of interest (ROI) of the raster space is a set of voxels from a selected range of Hounsfield units (109-3071). Ceramic inlay with zirconium dioxide (Cera Post) as well as epoxy resin inlay including silica fibers enriched with zirconium (Easy Post) produced the most intense artifacts. The smallest image distortions were created by titanium inlays, both passive (Harald Nordin) and active (Flexi Flange). Inlays containing zirconium generated the strongest artifacts, thus leading to the greatest distortions in the CBCT images. Carbon fiber inlay did not considerably affect the image quality.

  3. Analysis of vector models in quantification of artifacts produced by standard prosthetic inlays in Cone-Beam Computed Tomography (CBCT)--a preliminary study.

    PubMed

    Różyło-Kalinowska, Ingrid; Miechowicz, Sławomir; Sarna-Boś, Katarzyna; Borowicz, Janusz; Kalinowski, Paweł

    2014-01-01

    Cone-beam computed tomography (CBCT) is a relatively new, but highly efficient imaging method applied first in dentistry in 1998. However, the quality of the obtained slices depends among other things on artifacts generated by dental restorations as well as orthodontic and prosthetic appliances. The aim of the study was to quantify the artifacts produced by standard prosthetic inlays in CBCT images. The material consisted of 17 standard prosthetic inlays mounted in dental roots embedded in resin. The samples were examined by means of a large field of view CBCT unit, Galileos (Sirona, Germany), at 85 kV and 14 mAs. The analysis was performed using Able 3DDoctor software for data in the CT raster space as well as by means of Materialise Magics software for generated vector models (STL). The masks generated in the raster space included the area of the inlays together with image artifacts. The region of interest (ROI) of the raster space is a set of voxels from a selected range of Hounsfield units (109-3071). Ceramic inlay with zirconium dioxide (Cera Post) as well as epoxy resin inlay including silica fibers enriched with zirconium (Easy Post) produced the most intense artifacts. The smallest image distortions were created by titanium inlays, both passive (Harald Nordin) and active (Flexi Flange). Inlays containing zirconium generated the strongest artifacts, thus leading to the greatest distortions in the CBCT images. Carbon fiber inlay did not considerably affect the image quality. PMID:25404623

  4. Teaching and Learning the Nature of Technical Artifacts

    ERIC Educational Resources Information Center

    Frederik, Ineke; Sonneveld, Wim; de Vries, Marc J.

    2011-01-01

    Artifacts are probably our most obvious everyday encounter with technology. Therefore, a good understanding of the nature of technical artifacts is a relevant part of technological literacy. In this article we draw from the philosophy of technology to develop a conceptualization of technical artifacts that can be used for educational purposes.…

  5. Connecting Student and Subject Matter: The Cultural Artifact Discussion Assignment

    ERIC Educational Resources Information Center

    Smith-Sanders, Alane K.

    2008-01-01

    This article presents a class activity where students work in dyads to select an artifact related to a course topic and, using this artifact, develop discussion questions to engage their classmates. This cultural artifact assignment is intended to, in part, answer John Dewey's call to cultivate connections between subject matter and life…

  6. Weaker dental enamel explains dental decay.

    PubMed

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

  7. Humans perceive flicker artifacts at 500 Hz

    NASA Astrophysics Data System (ADS)

    Davis, James; Hsieh, Yi-Hsuan; Lee, Hung-Chi

    2015-02-01

    Humans perceive a stable average intensity image without flicker artifacts when a television or monitor updates at a sufficiently fast rate. This rate, known as the critical flicker fusion rate, has been studied for both spatially uniform lights, and spatio-temporal displays. These studies have included both stabilized and unstablized retinal images, and report the maximum observable rate as 50-90 Hz. A separate line of research has reported that fast eye movements known as saccades allow simple modulated LEDs to be observed at very high rates. Here we show that humans perceive visual flicker artifacts at rates over 500 Hz when a display includes high frequency spatial edges. This rate is many times higher than previously reported. As a result, modern display designs which use complex spatio-temporal coding need to update much faster than conventional TVs, which traditionally presented a simple sequence of natural images.

  8. Supporting Knowledge Transfer through Decomposable Reasoning Artifacts

    SciTech Connect

    Pike, William A.; May, Richard A.; Turner, Alan E.

    2007-01-03

    Technology to support knowledge transfer and cooperative inquiry must offer its users the ability to effectively interpret knowledge structures produced by collaborators. Communicating the reasoning processes that underlie a finding is one method for enhancing interpretation, and can result in more effective evaluation and application of shared knowledge. In knowledge management tools, interpretation is aided by creating knowledge artifacts that can expose their provenance to scrutiny and that can be transformed into diverse representations that suit their consumers’ perspectives and preferences. We outline the information management needs of inquiring communities characterized by hypothesis generation tasks, and propose a model for communication, based in theories of hermeneutics, semiotics, and abduction, in which knowledge structures can be decomposed into the lower-level reasoning artifacts that produced them. We then present a proof-of-concept implementation for an environment to support the capture and communication of analytic products, with emphasis on the domain of intelligence analysis.

  9. Dental education in Colombia

    PubMed Central

    Jaramillo, Jorge A.; Pulido, Jairo H. Ternera; Núñez, Jaime A. Castro; Bird, William F.; Komabayashi, Takashi

    2014-01-01

    This article describes Colombia's development of formal dentistry, its dental school system, curriculum, and dental licensure, and current issues in oral health care. In 1969, there were only 4 dental schools in Colombia; at this writing there are 21. Five dental schools are public and the other 16 are private. Nearly all classes are conducted in Spanish. Undergraduate pre-dental coursework is not a prerequisite for dental school in Colombia. To obtain licensure, Colombian dental students must complete 5 years of study in dental school, earn a diploma, and work for the government for 1 year. There are approximately 41,400 dentists in Colombia, and the number is increasing quickly. However, the unemployment rate among dentists is very high, even though graduation from dental school is extremely difficult. Although the 1,100:1 ratio of citizens to dentists is considered satisfactory, access to dental care is limited due to the high rate of poverty. PMID:20339245

  10. Artifacts Of Spectral Analysis Of Instrument Readings

    NASA Technical Reports Server (NTRS)

    Wise, James H.

    1995-01-01

    Report presents experimental and theoretical study of some of artifacts introduced by processing outputs of two nominally identical low-frequency-reading instruments; high-sensitivity servo-accelerometers mounted together and operating, in conjunction with signal-conditioning circuits, as seismometers. Processing involved analog-to-digital conversion with anti-aliasing filtering, followed by digital processing including frequency weighting and computation of different measures of power spectral density (PSD).

  11. Hepatic MR imaging techniques, optimization, and artifacts.

    PubMed

    Guglielmo, Flavius F; Mitchell, Donald G; Roth, Christopher G; Deshmukh, Sandeep

    2014-08-01

    This article describes a basic 1.5-T hepatic magnetic resonance (MR) imaging protocol, strategies for optimizing pulse sequences while managing artifacts, the proper timing of postgadolinium 3-dimensional gradient echo sequences, and an effective order of performing pulse sequences with the goal of creating an efficient and high-quality hepatic MR imaging examination. The authors have implemented this general approach on General Electric, Philips, and Siemens clinical scanners.

  12. Correction of motion artifacts in OCT-AFI data collected in airways (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Abouei, Elham; Lane, Pierre M.; Pahlevaninezhad, Hamid; Lee, Anthony; Lam, Stephen; MacAulay, Calum E.

    2016-03-01

    Abstract: Optical coherence tomography (OCT) provides in vivo imaging with near-histologic resolution of tissue morphology. OCT has been successfully employed in clinical practice in non-pulmonary fields of medicine such as ophthalmology and cardiology. Studies suggest that OCT has the potential to be a powerful tool for the detection and localization of malignant and non-malignant pulmonary diseases. The combination of OCT with autofluorescence imaging (AFI) provides valuable information about the structural and metabolic state of tissues. Successful application of OCT or OCT-AFI to the field of pulmonary medicine requires overcoming several challenges. This work address those associated with motion: cardiac cycle, breathing and non-uniform rotation distortion (NURD) artifacts. Mechanically rotated endoscopic probes often suffer from image degradation due to NURD. In addition cardiac and breathing motion artifacts may be present in-vivo that are not seen ex-vivo. These motion artifacts can be problematic in OCT-AFI systems with slower acquisition rates and have been observed to generate identifiable prominent artifacts which make confident interpretation of observed structures (blood vessels, etc) difficult. Understanding and correcting motion artifact could improve the image quality and interpretation. In this work, the motion artifacts in pulmonary OCT-AFI data sets are estimated in both AFI and OCT images using a locally adaptive registration algorithm that can be used to correct/reduce such artifacts. Performance of the algorithm is evaluated on images of a NURD phantom and on in-vivo OCT-AFI datasets of peripheral lung airways.

  13. The effects of transducer geometry on artifacts common to diagnostic bone imaging with conventional medical ultrasound.

    PubMed

    Mauldin, F William; Owen, Kevin; Tiouririne, Mohamed; Hossack, John A

    2012-06-01

    The portability, low cost, and non-ionizing radiation associated with medical ultrasound suggest that it has potential as a superior alternative to X-ray for bone imaging. However, when conventional ultrasound imaging systems are used for bone imaging, clinical acceptance is frequently limited by artifacts derived from reflections occurring away from the main axis of the acoustic beam. In this paper, the physical source of off-axis artifacts and the effect of transducer geometry on these artifacts are investigated in simulation and experimental studies. In agreement with diffraction theory, the sampled linear-array geometry possessed increased off-axis energy compared with single-element piston geometry, and therefore, exhibited greater levels of artifact signal. Simulation and experimental results demonstrated that the linear-array geometry exhibited increased artifact signal when the center frequency increased, when energy off-axis to the main acoustic beam (i.e., grating lobes) was perpendicularly incident upon off-axis surfaces, and when off-axis surfaces were specular rather than diffusive. The simulation model used to simulate specular reflections was validated experimentally and a correlation coefficient of 0.97 between experimental and simulated peak reflection contrast was observed. In ex vivo experiments, the piston geometry yielded 4 and 6.2 dB average contrast improvement compared with the linear array when imaging the spinous process and interlaminar space of an animal spine, respectively. This work indicates that off-axis reflections are a major source of ultrasound image artifacts, particularly in environments comprising specular reflecting (i.e., bone or bone-like) objects. Transducer geometries with reduced sensitivity to off-axis surface reflections, such as a piston transducer geometry, yield significant reductions in image artifact.

  14. Separating drought effects from roof artifacts on ecosystem processes in a grassland drought experiment.

    PubMed

    Vogel, Anja; Fester, Thomas; Eisenhauer, Nico; Scherer-Lorenzen, Michael; Schmid, Bernhard; Weisser, Wolfgang W; Weigelt, Alexandra

    2013-01-01

    1: Given the predictions of increased drought probabilities under various climate change scenarios, there have been numerous experimental field studies simulating drought using transparent roofs in different ecosystems and regions. Such roofs may, however, have unknown side effects, called artifacts, on the measured variables potentially confounding the experimental results. A roofed control allows the quantification of potential artifacts, which is lacking in most experiments. 2: We conducted a drought experiment in experimental grasslands to study artifacts of transparent roofs and the resulting effects of artifacts on ecosystems relative to drought on three response variables (aboveground biomass, litter decomposition and plant metabolite profiles). We established three drought treatments, using (1) transparent roofs to exclude rainfall, (2) an unroofed control treatment receiving natural rainfall and (3) a roofed control, nested in the drought treatment but with rain water reapplied according to ambient conditions. 3: Roofs had a slight impact on air (+0.14°C during night) and soil temperatures (-0.45°C on warm days, +0.25°C on cold nights), while photosynthetically active radiation was decreased significantly (-16%). Aboveground plant community biomass was reduced in the drought treatment (-41%), but there was no significant difference between the roofed and unroofed control, i.e., there were no measurable roof artifact effects. 4: Compared to the unroofed control, litter decomposition was decreased significantly both in the drought treatment (-26%) and in the roofed control treatment (-18%), suggesting artifact effects of the transparent roofs. Moreover, aboveground metabolite profiles in the model plant species Medicago x varia were different from the unroofed control in both the drought and roofed control treatments, and roof artifact effects were of comparable magnitude as drought effects. 5: Our results stress the need for roofed control treatments

  15. Separating Drought Effects from Roof Artifacts on Ecosystem Processes in a Grassland Drought Experiment

    PubMed Central

    Vogel, Anja; Fester, Thomas; Eisenhauer, Nico; Scherer-Lorenzen, Michael; Schmid, Bernhard; Weisser, Wolfgang W.; Weigelt, Alexandra

    2013-01-01

    1 Given the predictions of increased drought probabilities under various climate change scenarios, there have been numerous experimental field studies simulating drought using transparent roofs in different ecosystems and regions. Such roofs may, however, have unknown side effects, called artifacts, on the measured variables potentially confounding the experimental results. A roofed control allows the quantification of potential artifacts, which is lacking in most experiments. 2 We conducted a drought experiment in experimental grasslands to study artifacts of transparent roofs and the resulting effects of artifacts on ecosystems relative to drought on three response variables (aboveground biomass, litter decomposition and plant metabolite profiles). We established three drought treatments, using (1) transparent roofs to exclude rainfall, (2) an unroofed control treatment receiving natural rainfall and (3) a roofed control, nested in the drought treatment but with rain water reapplied according to ambient conditions. 3 Roofs had a slight impact on air (+0.14°C during night) and soil temperatures (−0.45°C on warm days, +0.25°C on cold nights), while photosynthetically active radiation was decreased significantly (−16%). Aboveground plant community biomass was reduced in the drought treatment (−41%), but there was no significant difference between the roofed and unroofed control, i.e., there were no measurable roof artifact effects. 4 Compared to the unroofed control, litter decomposition was decreased significantly both in the drought treatment (−26%) and in the roofed control treatment (−18%), suggesting artifact effects of the transparent roofs. Moreover, aboveground metabolite profiles in the model plant species Medicago x varia were different from the unroofed control in both the drought and roofed control treatments, and roof artifact effects were of comparable magnitude as drought effects. 5 Our results stress the need for roofed control

  16. Reduction of display artifacts by random sampling

    NASA Technical Reports Server (NTRS)

    Ahumada, A. J., Jr.; Nagel, D. C.; Watson, A. B.; Yellott, J. I., Jr.

    1983-01-01

    The application of random-sampling techniques to remove visible artifacts (such as flicker, moire patterns, and paradoxical motion) introduced in TV-type displays by discrete sequential scanning is discussed and demonstrated. Sequential-scanning artifacts are described; the window of visibility defined in spatiotemporal frequency space by Watson and Ahumada (1982 and 1983) and Watson et al. (1983) is explained; the basic principles of random sampling are reviewed and illustrated by the case of the human retina; and it is proposed that the sampling artifacts can be replaced by random noise, which can then be shifted to frequency-space regions outside the window of visibility. Vertical sequential, single-random-sequence, and continuously renewed random-sequence plotting displays generating 128 points at update rates up to 130 Hz are applied to images of stationary and moving lines, and best results are obtained with the single random sequence for the stationary lines and with the renewed random sequence for the moving lines.

  17. Sampling Artifacts from Conductive Silicone Tubing

    SciTech Connect

    Timko, Michael T.; Yu, Zhenhong; Kroll, Jesse; Jayne, John T.; Worsnop, Douglas R.; Miake-Lye, Richard C.; Onasch, Timothy B.; Liscinsky, David; Kirchstetter, Thomas W.; Destaillats, Hugo; Holder, Amara L.; Smith, Jared D.; Wilson, Kevin R.

    2009-05-15

    We report evidence that carbon impregnated conductive silicone tubing used in aerosol sampling systems can introduce two types of experimental artifacts: 1) silicon tubing dynamically absorbs carbon dioxide gas, requiring greater than 5 minutes to reach equilibrium and 2) silicone tubing emits organic contaminants containing siloxane that adsorb onto particles traveling through it and onto downstream quartz fiber filters. The consequence can be substantial for engine exhaust measurements as both artifacts directly impact calculations of particulate mass-based emission indices. The emission of contaminants from the silicone tubing can result in overestimation of organic particle mass concentrations based on real-time aerosol mass spectrometry and the off-line thermal analysis of quartz filters. The adsorption of siloxane contaminants can affect the surface properties of aerosol particles; we observed a marked reduction in the water-affinity of soot particles passed through conductive silicone tubing. These combined observations suggest that the silicone tubing artifacts may have wide consequence for the aerosol community and should, therefore, be used with caution. Gentle heating, physical and chemical properties of the particle carriers, exposure to solvents, and tubing age may influence siloxane uptake. The amount of contamination is expected to increase as the tubing surface area increases and as the particle surface area increases. The effect is observed at ambient temperature and enhanced by mild heating (<100 oC). Further evaluation is warranted.

  18. Atypical Forensic Dental Identifications.

    PubMed

    Cardoza, Anthony R; Wood, James D

    2015-06-01

    Forensic dental identification specialists are typically the last conventional option for postmortem identification. Forensic dental identification is most often accomplished by comparing radiographs of the decedent's teeth with the dental radiographs obtained from the dentist of the suspected victim. Unfortunately, antemortem dental radiographs are not always available. When presented with this challenge, the authors of this article have been successful in completing identifications using means other than dental radiographic comparison. PMID:26126345

  19. Atypical Forensic Dental Identifications.

    PubMed

    Cardoza, Anthony R; Wood, James D

    2015-06-01

    Forensic dental identification specialists are typically the last conventional option for postmortem identification. Forensic dental identification is most often accomplished by comparing radiographs of the decedent's teeth with the dental radiographs obtained from the dentist of the suspected victim. Unfortunately, antemortem dental radiographs are not always available. When presented with this challenge, the authors of this article have been successful in completing identifications using means other than dental radiographic comparison.

  20. Ultrasound artifacts: classification, applied physics with illustrations, and imaging appearances.

    PubMed

    Prabhu, Somnath J; Kanal, Kalpana; Bhargava, Puneet; Vaidya, Sandeep; Dighe, Manjiri K

    2014-06-01

    Ultrasound has become a widely used diagnostic imaging modality in medicine because of its safety and portability. Because of rapid advances in technology, in recent years, sonographic imaging quality has significantly increased. Despite these advances, the potential to encounter artifacts while imaging remains.This article classifies both common and uncommon gray-scale and Doppler ultrasound artifacts into those resulting from physiology and those caused by hardware. A brief applied-physics explanation for each artifact is listed along with an illustrated diagram. The imaging appearance of artifacts is presented in case examples, along with strategies to minimize the artifacts in real time or use them for clinical advantage where applicable.

  1. SUBSURFACE MOBILE PLUTONIUM SPECIATION: SAMPLING ARTIFACTS FOR GROUNDWATER COLLOIDS

    SciTech Connect

    Kaplan, D.; Buesseler, K.

    2010-06-29

    A recent review found several conflicting conclusions regarding colloid-facilitated transport of radionuclides in groundwater and noted that colloids can both facilitate and retard transport. Given these contrasting conclusions and the profound implications even trace concentrations of plutonium (Pu) have on the calculated risk posed to human health, it is important that the methodology used to sample groundwater colloids be free of artifacts. The objective of this study was: (1) to conduct a field study and measure Pu speciation, ({sup 239}Pu and {sup 240}Pu for reduced-Pu{sub aq}, oxidized-Pu{sub aq}, reduced-Pu{sub colloid}, and oxidized-Pu{sub colloid}), in a Savannah River Site (SRS) aquifer along a pH gradient in F-Area, (2) to determine the impact of pumping rate on Pu concentration, Pu speciation, and Pu isotopic ratios, (3) determine the impact of delayed sample processing (as opposed to processing directly from the well).

  2. Drug and dental impression materials.

    PubMed

    Maller, Sudhakara V; Karthik, K S; Maller, Udita S; Abraham, Mathew C; Kumar, Rachuri Narendra; Manikandan, R

    2012-08-01

    Guidelines to prevent cross contamination with infectious agents have been instituted for dental clinical and laboratory procedures. However, compliance by dental offices and clinics in disinfecting impression material has not been universal. Techniques for disinfecting impression materials are spraying or immersing impression materials. These techniques can reduce the surface detail and dimensional accuracy of impressions; most disinfectants are irritants. This study reviewed whether antimicrobial activity can be achieved by mixing certain drugs with the impression material and their effects on the disinfection are achieved through such additions.

  3. Dental hyponatraemia.

    PubMed

    Simpson, R M

    2011-08-01

    A 14-year-old girl developed dental pain and was treated for acute infected pulpitis of her right upper lateral incisor with drilling and filling. The pain continued and was helped by analgesia, sucking ice cubes and drinking cold water. Forty-eight hours later, she became confused and disoriented. She started to vomit and complained of headache. Investigations revealed hyponatraemia with normal serum potassium levels and initially normal urinary sodium excretion. Over the next 24 hours, she passed 5.45 L of urine and her serum sodium rose from 125 to 143 mmol/L. Self-induced water intoxication has been described during drinking games and initiation ceremonies, but this would appear to an unusual cause. Conservative management proved successful in allowing this girl to recover without sequelae. PMID:21873727

  4. A simple technique to reduce epistaxis and nasopharyngeal trauma during nasotracheal intubation in a child with factor IX deficiency having dental restoration.

    PubMed

    Delgado, Anita V; Sanders, John C

    2004-10-01

    Epistaxis and airway trauma are often associated with nasotracheal intubation. We describe a patient with Factor IX deficiency who required nasotracheal intubation. An inexpensive, nonproprietary, rapid technique was used to reduce the trauma of intubation.

  5. Neural networks improve brain cancer detection with Raman spectroscopy in the presence of light artifacts

    NASA Astrophysics Data System (ADS)

    Jermyn, Michael; Desroches, Joannie; Mercier, Jeanne; St-Arnaud, Karl; Guiot, Marie-Christine; Petrecca, Kevin; Leblond, Frederic

    2016-03-01

    It is often difficult to identify cancer tissue during brain cancer (glioma) surgery. Gliomas invade into areas of normal brain, and this cancer invasion is frequently not detected using standard preoperative magnetic resonance imaging (MRI). This results in enduring invasive cancer following surgery and leads to recurrence. A hand-held Raman spectroscopy is able to rapidly detect cancer invasion in patients with grade 2-4 gliomas. However, ambient light sources can produce spectral artifacts which inhibit the ability to distinguish between cancer and normal tissue using the spectral information available. To address this issue, we have demonstrated that artificial neural networks (ANN) can accurately classify invasive cancer versus normal brain tissue, even when including measurements with significant spectral artifacts from external light sources. The non-parametric and adaptive model used by ANN makes it suitable for detecting complex non-linear spectral characteristics associated with different tissues and the confounding presence of light artifacts. The use of ANN for brain cancer detection with Raman spectroscopy, in the presence of light artifacts, improves the robustness and clinical translation potential for intraoperative use. Integration with the neurosurgical workflow is facilitated by accounting for the effect of light artifacts which may occur, due to operating room lights, neuronavigation systems, windows, or other light sources. The ability to rapidly detect invasive brain cancer under these conditions may reduce residual cancer remaining after surgery, and thereby improve patient survival.

  6. Artifact reduction in moving-table acquisitions using parallel imaging and multiple averages.

    PubMed

    Fautz, H P; Honal, M; Saueressig, U; Schäfer, O; Kannengiesser, S A R

    2007-01-01

    Two-dimensional (2D) axial continuously-moving-table imaging has to deal with artifacts due to gradient nonlinearity and breathing motion, and has to provide the highest scan efficiency. Parallel imaging techniques (e.g., generalized autocalibrating partially parallel acquisition GRAPPA)) are used to reduce such artifacts and avoid ghosting artifacts. The latter occur in T(2)-weighted multi-spin-echo (SE) acquisitions that omit an additional excitation prior to imaging scans for presaturation purposes. Multiple images are reconstructed from subdivisions of a fully sampled k-space data set, each of which is acquired in a single SE train. These images are then averaged. GRAPPA coil weights are estimated without additional measurements. Compared to conventional image reconstruction, inconsistencies between different subsets of k-space induce less artifacts when each k-space part is reconstructed separately and the multiple images are averaged afterwards. These inconsistencies may lead to inaccurate GRAPPA coil weights using the proposed intrinsic GRAPPA calibration. It is shown that aliasing artifacts in single images are canceled out after averaging. Phantom and in vivo studies demonstrate the benefit of the proposed reconstruction scheme for free-breathing axial continuously-moving-table imaging using fast multi-SE sequences.

  7. Metal artifact reduction in x-ray computed tomography (CT) by constrained optimization

    SciTech Connect

    Zhang Xiaomeng; Wang Jing; Xing Lei

    2011-02-15

    Purpose: The streak artifacts caused by metal implants have long been recognized as a problem that limits various applications of CT imaging. In this work, the authors propose an iterative metal artifact reduction algorithm based on constrained optimization. Methods: After the shape and location of metal objects in the image domain is determined automatically by the binary metal identification algorithm and the segmentation of ''metal shadows'' in projection domain is done, constrained optimization is used for image reconstruction. It minimizes a predefined function that reflects a priori knowledge of the image, subject to the constraint that the estimated projection data are within a specified tolerance of the available metal-shadow-excluded projection data, with image non-negativity enforced. The minimization problem is solved through the alternation of projection-onto-convex-sets and the steepest gradient descent of the objective function. The constrained optimization algorithm is evaluated with a penalized smoothness objective. Results: The study shows that the proposed method is capable of significantly reducing metal artifacts, suppressing noise, and improving soft-tissue visibility. It outperforms the FBP-type methods and ART and EM methods and yields artifacts-free images. Conclusions: Constrained optimization is an effective way to deal with CT reconstruction with embedded metal objects. Although the method is presented in the context of metal artifacts, it is applicable to general ''missing data'' image reconstruction problems.

  8. Multidistance probe arrangement to eliminate artifacts in functional near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamada, Toru; Umeyama, Shinji; Matsuda, Keiji

    2009-11-01

    Functional near-infrared spectroscopy has the potential to easily detect cerebral functional hemodynamics. However, in practical fNIRS measurements, a subject's physical or systemic physiological activities often cause undesirable artifacts. Such activities can be evoked even by task execution. In this case, observed artifacts may correlate strongly with the task sequence, and it is difficult to eliminate them by conventional signal filtering techniques. We present a theoretical analysis and Monte Carlo simulations of layered media in which both scattering and absorption changes occur, and show that a multidistance probe arrangement is effective in removing artifacts and extracting functional hemodynamics. The probe arrangement is determined based on simulation results. Artifacts induced by nonfunctional tasks (body tilting, head nodding, and breath holding) are clearly observed when a conventional method is used; such artifacts are appreciably reduced by the proposed method. Signals evoked by single-sided finger movements are observed at both hemispheres when we use a conventional method. On the other hand, localized signals at the primary motor area are observed by the proposed method. A statistically significant increase in oxygenated hemoglobin and decrease in deoxygenated hemoglobin are simultaneously observed at the contralateral primary motor area.

  9. Artifact reduction in moving-table acquisitions using parallel imaging and multiple averages.

    PubMed

    Fautz, H P; Honal, M; Saueressig, U; Schäfer, O; Kannengiesser, S A R

    2007-01-01

    Two-dimensional (2D) axial continuously-moving-table imaging has to deal with artifacts due to gradient nonlinearity and breathing motion, and has to provide the highest scan efficiency. Parallel imaging techniques (e.g., generalized autocalibrating partially parallel acquisition GRAPPA)) are used to reduce such artifacts and avoid ghosting artifacts. The latter occur in T(2)-weighted multi-spin-echo (SE) acquisitions that omit an additional excitation prior to imaging scans for presaturation purposes. Multiple images are reconstructed from subdivisions of a fully sampled k-space data set, each of which is acquired in a single SE train. These images are then averaged. GRAPPA coil weights are estimated without additional measurements. Compared to conventional image reconstruction, inconsistencies between different subsets of k-space induce less artifacts when each k-space part is reconstructed separately and the multiple images are averaged afterwards. These inconsistencies may lead to inaccurate GRAPPA coil weights using the proposed intrinsic GRAPPA calibration. It is shown that aliasing artifacts in single images are canceled out after averaging. Phantom and in vivo studies demonstrate the benefit of the proposed reconstruction scheme for free-breathing axial continuously-moving-table imaging using fast multi-SE sequences. PMID:17191244

  10. A model for filtered backprojection reconstruction artifacts due to time-varying attenuation values in perfusion C-arm CT.

    PubMed

    Fieselmann, Andreas; Dennerlein, Frank; Deuerling-Zheng, Yu; Boese, Jan; Fahrig, Rebecca; Hornegger, Joachim

    2011-06-21

    Filtered backprojection is the basis for many CT reconstruction tasks. It assumes constant attenuation values of the object during the acquisition of the projection data. Reconstruction artifacts can arise if this assumption is violated. For example, contrast flow in perfusion imaging with C-arm CT systems, which have acquisition times of several seconds per C-arm rotation, can cause this violation. In this paper, we derived and validated a novel spatio-temporal model to describe these kinds of artifacts. The model separates the temporal dynamics due to contrast flow from the scan and reconstruction parameters. We introduced derivative-weighted point spread functions to describe the spatial spread of the artifacts. The model allows prediction of reconstruction artifacts for given temporal dynamics of the attenuation values. Furthermore, it can be used to systematically investigate the influence of different reconstruction parameters on the artifacts. We have shown that with optimized redundancy weighting function parameters the spatial spread of the artifacts around a typical arterial vessel can be reduced by about 70%. Finally, an inversion of our model could be used as the basis for novel dynamic reconstruction algorithms that further minimize these artifacts.

  11. A model for filtered backprojection reconstruction artifacts due to time-varying attenuation values in perfusion C-arm CT

    NASA Astrophysics Data System (ADS)

    Fieselmann, Andreas; Dennerlein, Frank; Deuerling-Zheng, Yu; Boese, Jan; Fahrig, Rebecca; Hornegger, Joachim

    2011-06-01

    Filtered backprojection is the basis for many CT reconstruction tasks. It assumes constant attenuation values of the object during the acquisition of the projection data. Reconstruction artifacts can arise if this assumption is violated. For example, contrast flow in perfusion imaging with C-arm CT systems, which have acquisition times of several seconds per C-arm rotation, can cause this violation. In this paper, we derived and validated a novel spatio-temporal model to describe these kinds of artifacts. The model separates the temporal dynamics due to contrast flow from the scan and reconstruction parameters. We introduced derivative-weighted point spread functions to describe the spatial spread of the artifacts. The model allows prediction of reconstruction artifacts for given temporal dynamics of the attenuation values. Furthermore, it can be used to systematically investigate the influence of different reconstruction parameters on the artifacts. We have shown that with optimized redundancy weighting function parameters the spatial spread of the artifacts around a typical arterial vessel can be reduced by about 70%. Finally, an inversion of our model could be used as the basis for novel dynamic reconstruction algorithms that further minimize these artifacts.

  12. Streaking artifacts reduction in four-dimensional cone-beam computed tomography.

    PubMed

    Leng, Shuai; Zambelli, Joseph; Tolakanahalli, Ranjini; Nett, Brian; Munro, Peter; Star-Lack, Joshua; Paliwal, Bhudatt; Chen, Guang-Hong

    2008-10-01

    Cone-beam computed tomography (CBCT) using an "on-board" x-ray imaging device integrated into a radiation therapy system has recently been made available for patient positioning, target localization, and adaptive treatment planning. One of the challenges for gantry mounted image-guided radiation therapy (IGRT) systems is the slow acquisition of projections for cone-beam CT (CBCT), which makes them sensitive to any patient motion during the scans. Aiming at motion artifact reduction, four-dimensional CBCT (4D CBCT) techniques have been introduced, where a surrogate for the target's motion profile is utilized to sort the cone-beam data by respiratory phase. However, due to the limited gantry rotation speed and limited readout speed of the on-board imager, fewer than 100 projections are available for the image reconstruction at each respiratory phase. Thus, severe undersampling streaking artifacts plague 4D CBCT images. In this paper, the authors propose a simple scheme to significantly reduce the streaking artifacts. In this method, a prior image is first reconstructed using all available projections without gating, in which static structures are well reconstructed while moving objects are blurred. The undersampling streaking artifacts from static structures are estimated from this prior image volume and then can be removed from the phase images using gated reconstruction. The proposed method was validated using numerical simulations, experimental phantom data, and patient data. The fidelity of stationary and moving objects is maintained, while large gains in streak artifact reduction are observed. Using this technique one can reconstruct 4D CBCT datasets using no more projections than are acquired in a 60 s scan. At the same time, a temporal gating window as narrow as 100 ms was utilized. Compared to the conventional 4D CBCT reconstruction, streaking artifacts were reduced by 60% to 70%.

  13. [Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - Part 1: B-mode artifacts].

    PubMed

    Tuma, J; Jenssen, C; Möller, K; Cui, X W; Kinkel, H; Uebel, S; Dietrich, C F

    2016-05-01

    Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues and with foreign bodies. On the one hand, they may be distracting and may lead to misdiagnosis. On the other hand, they may be diagnostically helpful. Ultrasound imaging suffers from artifacts, because in reality, parameters assumed to be constant values, such as sound speed, sound rectilinear propagation, attenuation, etc., are often different from the actual parameters. Moreover, inadequate device settings may cause artifacts. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review comments on the physics of artifacts and describes the most important B-mode artifacts. Pitfalls, as well as diagnostic chances resulting from B-mode artifacts, are discussed.

  14. [Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - Part 1: B-mode artifacts].

    PubMed

    Tuma, J; Jenssen, C; Möller, K; Cui, X W; Kinkel, H; Uebel, S; Dietrich, C F

    2016-05-01

    Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues and with foreign bodies. On the one hand, they may be distracting and may lead to misdiagnosis. On the other hand, they may be diagnostically helpful. Ultrasound imaging suffers from artifacts, because in reality, parameters assumed to be constant values, such as sound speed, sound rectilinear propagation, attenuation, etc., are often different from the actual parameters. Moreover, inadequate device settings may cause artifacts. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review comments on the physics of artifacts and describes the most important B-mode artifacts. Pitfalls, as well as diagnostic chances resulting from B-mode artifacts, are discussed. PMID:27171335

  15. Metallic artifact mitigation and organ-constrained tissue assignment for Monte Carlo calculations of permanent implant lung brachytherapy

    SciTech Connect

    Sutherland, J. G. H.; Miksys, N.; Thomson, R. M.; Furutani, K. M.

    2014-01-15

    Purpose: To investigate methods of generating accurate patient-specific computational phantoms for the Monte Carlo calculation of lung brachytherapy patient dose distributions. Methods: Four metallic artifact mitigation methods are applied to six lung brachytherapy patient computed tomography (CT) images: simple threshold replacement (STR) identifies high CT values in the vicinity of the seeds and replaces them with estimated true values; fan beam virtual sinogram replaces artifact-affected values in a virtual sinogram and performs a filtered back-projection to generate a corrected image; 3D median filter replaces voxel values that differ from the median value in a region of interest surrounding the voxel and then applies a second filter to reduce noise; and a combination of fan beam virtual sinogram and STR. Computational phantoms are generated from artifact-corrected and uncorrected images using several tissue assignment schemes: both lung-contour constrained and unconstrained global schemes are considered. Voxel mass densities are assigned based on voxel CT number or using the nominal tissue mass densities. Dose distributions are calculated using the EGSnrc user-code BrachyDose for{sup 125}I, {sup 103}Pd, and {sup 131}Cs seeds and are compared directly as well as through dose volume histograms and dose metrics for target volumes surrounding surgical sutures. Results: Metallic artifact mitigation techniques vary in ability to reduce artifacts while preserving tissue detail. Notably, images corrected with the fan beam virtual sinogram have reduced artifacts but residual artifacts near sources remain requiring additional use of STR; the 3D median filter removes artifacts but simultaneously removes detail in lung and bone. Doses vary considerably between computational phantoms with the largest differences arising from artifact-affected voxels assigned to bone in the vicinity of the seeds. Consequently, when metallic artifact reduction and constrained tissue

  16. Artifacts in cone-beam computed tomography of a post and core restoration: a case report.

    PubMed

    Parirokh, Masoud; Ardjomand, Karim; Manochehrifar, Hamed

    2012-01-01

    Cone-beam computed tomography (CBCT) has been accepted as a useful tool for diagnosis and treatment in endodontics. Despite a growing trend toward using CBCT in endodontic practice the CBCT images should be interpreted carefully. This case report presents a case that showed radiolucency inside and around a tooth which was free of pathologic changes under a dental operative microscope and conventional radiographs. A male patient was referred to an endodontic office for evaluation of radiolucency inside and around tooth #21 in his CBCT images. The post and crown over the tooth was removed and the tooth was observed under a dental operative microscope. Clinical examination as well as direct observation under a dental operative microscope showed no pathological lesions inside and around the tooth. The misdiagnosis was based on an artifact on CBCT. Despite the advantages of CBCT images as a great radiographic aid in endodontic practice, in the presence of metallic structures such as post and core the images should be interpreted with caution.

  17. Reimbursing Dentists for Smoking Cessation Treatment: Views From Dental Insurers

    PubMed Central

    Wright, Shana; McNeely, Jennifer; Rotrosen, John; Winitzer, Rebecca F.; Pollack, Harold; Abel, Stephen; Metsch, Lisa

    2012-01-01

    Introduction: Screening and delivery of evidence-based interventions by dentists is an effective way to reduce tobacco use. However, dental visits remain an underutilized opportunity for the treatment of tobacco dependence. This is, in part, because the current reimbursement structure does not support expansion of dental providers’ role in this arena. The purpose of this study was to interview dental insurers to assess attitudes toward tobacco use treatment in dental practice, pros and cons of offering dental provider reimbursement, and barriers to instituting a tobacco use treatment-related payment policy for dental providers. Methods: Semi-structured interviews were conducted with 11 dental insurance company executives. Participants were identified using a targeted sampling method and represented viewpoints from a significant share of companies within the dental insurance industry. Results: All insurers believed that screening and intervention for tobacco use was an appropriate part of routine care during a dental visit. Several indicated a need for more evidence of clinical and cost-effectiveness before reimbursement for these services could be actualized. Lack of purchaser demand, questionable returns on investment, and segregation of the medical and dental insurance markets were cited as additional barriers to coverage. Conclusions: Dissemination of findings on efficacy and additional research on financial returns could help to promote uptake of coverage by insurers. Wider issues of integration between dental and medical care and payment systems must be addressed in order to expand opportunities for preventive services in dental care settings. PMID:22387994

  18. Motion artifacts in functional near-infrared spectroscopy: a comparison of motion correction techniques applied to real cognitive data.

    PubMed

    Brigadoi, Sabrina; Ceccherini, Lisa; Cutini, Simone; Scarpa, Fabio; Scatturin, Pietro; Selb, Juliette; Gagnon, Louis; Boas, David A; Cooper, Robert J

    2014-01-15

    Motion artifacts are a significant source of noise in many functional near-infrared spectroscopy (fNIRS) experiments. Despite this, there is no well-established method for their removal. Instead, functional trials of fNIRS data containing a motion artifact are often rejected completely. However, in most experimental circumstances the number of trials is limited, and multiple motion artifacts are common, particularly in challenging populations. Many methods have been proposed recently to correct for motion artifacts, including principle component analysis, spline interpolation, Kalman filtering, wavelet filtering and correlation-based signal improvement. The performance of different techniques has been often compared in simulations, but only rarely has it been assessed on real functional data. Here, we compare the performance of these motion correction techniques on real functional data acquired during a cognitive task, which required the participant to speak aloud, leading to a low-frequency, low-amplitude motion artifact that is correlated with the hemodynamic response. To compare the efficacy of these methods, objective metrics related to the physiology of the hemodynamic response have been derived. Our results show that it is always better to correct for motion artifacts than reject trials, and that wavelet filtering is the most effective approach to correcting this type of artifact, reducing the area under the curve where the artifact is present in 93% of the cases. Our results therefore support previous studies that have shown wavelet filtering to be the most promising and powerful technique for the correction of motion artifacts in fNIRS data. The analyses performed here can serve as a guide for others to objectively test the impact of different motion correction algorithms and therefore select the most appropriate for the analysis of their own fNIRS experiment.

  19. Virtual monochromatic spectral imaging with fast kilovoltage switching: reduction of metal artifacts at CT.

    PubMed

    Pessis, Eric; Campagna, Raphaël; Sverzut, Jean-Michel; Bach, Fabienne; Rodallec, Mathieu; Guerini, Henri; Feydy, Antoine; Drapé, Jean-Luc

    2013-01-01

    With arthroplasty being increasingly used to relieve joint pain, imaging of patients with metal implants can represent a significant part of the clinical work load in the radiologist's daily practice. Computed tomography (CT) plays an important role in the postoperative evaluation of patients who are suspected of having metal prosthesis-related problems such as aseptic loosening, bone resorption or osteolysis, infection, dislocation, metal hardware failure, or periprosthetic bone fracture. Despite advances in detector technology and computer software, artifacts from metal implants can seriously degrade the quality of CT images, sometimes to the point of making them diagnostically unusable. Several factors may help reduce the number and severity of artifacts at multidetector CT, including decreasing the detector collimation and pitch, increasing the kilovolt peak and tube charge, and using appropriate reconstruction algorithms and section thickness. More recently, dual-energy CT has been proposed as a means of reducing beam-hardening artifacts. The use of dual-energy CT scanners allows the synthesis of virtual monochromatic spectral (VMS) images. Monochromatic images depict how the imaged object would look if the x-ray source produced x-ray photons at only a single energy level. For this reason, VMS imaging is expected to provide improved image quality by reducing beam-hardening artifacts.

  20. Metal artifact reduction in cone beam computed tomography using forward projected reconstruction information.

    PubMed

    Meilinger, Manuel; Schmidgunst, Christian; Schütz, Oliver; Lang, Elmar W

    2011-09-01

    In this work we present a new method to reduce artifacts, produced by high-density objects, especially metal implants, in X-ray cone beam computed tomography (CBCT). These artifacts influence clinical diagnostics and treatments using CT data, if metal objects are located in the field of view (FOV). Our novel method reduces metal artifacts by virtually replacing the metal objects with tissue objects of the same shape. First, the considered objects must be segmented in the original 2D projection data as well as in a reconstructed 3D volume. The attenuation coefficients of the segmented voxels are replaced with adequate attenuation coefficients of tissue (or water), then the required parts of the volume are projected onto the segmented 2D pixels, to replace the original information. This corrected 2D data can then be reconstructed with reduced artifacts, i. e. all metal objects virtually vanished. After the reconstruction, the segmented 3D metal objects were re-inserted into the corrected 3D volume. Our method was developed for mobile C-arm CBCTs; as it is necessary that they are of low weight, the C-arm results in unpredictable distortion. This misalignment between the original 2D data and the forward projection of the reconstructed 3D volume must be adjusted before the correction of the segmented 2D pixels. We applied this technique to clinical data and will now present the results.

  1. Complementary contrast media for metal artifact reduction in dual-energy computed tomography

    PubMed Central

    Lambert, Jack W.; Edic, Peter M.; FitzGerald, Paul F.; Torres, Andrew S.; Yeh, Benjamin M.

    2015-01-01

    Abstract. Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration. PMID:26839905

  2. Complementary contrast media for metal artifact reduction in dual-energy computed tomography.

    PubMed

    Lambert, Jack W; Edic, Peter M; FitzGerald, Paul F; Torres, Andrew S; Yeh, Benjamin M

    2015-07-01

    Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration. PMID:26839905

  3. Sugars and dental caries.

    PubMed

    Touger-Decker, Riva; van Loveren, Cor

    2003-10-01

    A dynamic relation exists between sugars and oral health. Diet affects the integrity of the teeth; quantity, pH, and composition of the saliva; and plaque pH. Sugars and other fermentable carbohydrates, after being hydrolyzed by salivary amylase, provide substrate for the actions of oral bacteria, which in turn lower plaque and salivary pH. The resultant action is the beginning of tooth demineralization. Consumed sugars are naturally occurring or are added. Many factors in addition to sugars affect the caries process, including the form of food or fluid, the duration of exposure, nutrient composition, sequence of eating, salivary flow, presence of buffers, and oral hygiene. Studies have confirmed the direct relation between intake of dietary sugars and dental caries across the life span. Since the introduction of fluoride, the incidence of caries worldwide has decreased, despite increases in sugars consumption. Other dietary factors (eg, the presence of buffers in dairy products; the use of sugarless chewing gum, particularly gum containing xylitol; and the consumption of sugars as part of meals rather than between meals) may reduce the risk of caries. The primary public health measures for reducing caries risk, from a nutrition perspective, are the consumption of a balanced diet and adherence to dietary guidelines and the dietary reference intakes; from a dental perspective, the primary public health measures are the use of topical fluorides and consumption of fluoridated water.

  4. A comparative quantitative analysis of magnetic susceptibility artifacts in echo planar and PROPELLER diffusion-weighted images

    NASA Astrophysics Data System (ADS)

    Cho, Jae-Hwan; Lee, Hae-Kag; Yang, Han-Joon; Lee, Gui-Won; Park, Yong-Soon; Chung, Woon-Kwan

    2013-01-01

    In this study, the authors investigated whether periodically-rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted imaging (DWI) can remove magnetic susceptibility artifacts and compared apparent diffusion coefficient (ADC) values for PROPELLER DWI and the common echo planar (EP) DWI. Twenty patients that underwent brain MRI with a metal dental implant were selected. A 3.0T MR scanner was then used to obtain EP DWI, PROPELLER DWI, and corresponding apparent diffusion coefficient (ADC) maps for a b-value of 0 and 1,000 s/mm2. The frequencies of magnetic susceptibility artifacts in four parts of the brain (bilateral temporal lobes, pons, and orbit) were selected. In the ADC maps, we measured the ADC values of both sides of the temporal lobe and the pons. According to the study results, the frequency of magnetic susceptibility artifacts in PROPELLER DW images was lower than it was in EP DW images. In ADC maps, the ADC values of the bilateral temporal lobes and the pons were all higher in PROPELLER ADC maps than in EP ADC maps. Our findings show that when a high-field MRI machine is used, magnetic susceptibility artifacts can distort anatomical structures and produce high-intensity signals. Furthermore, our findings suggest that in many cases, PROPELLER DWI would be helpful in terms of achieving a correct diagnosis.

  5. Quantification and elimination of windmill artifacts in multi slice CT

    NASA Astrophysics Data System (ADS)

    Utrup, Steven J.; Brown, Kevin M.

    2008-03-01

    In multi-slice cone beam CT imaging, there are artifacts known as windmill artifacts. These artifacts are due to not satisfying the Nyquist criteria in the patient longitudinal direction. This paper quantifies and compares these artifacts as a function of the number of rows, pitch, collimation, and image thickness of the CT scanner. Scanners with rows of 16, 64 and 128 are measured and compared with simulated data, using both Helical and Axial scanning modes. In addition three focal spot switching modes are compared: the traditional within image plane mode; diagonal mode; and quad mode. All images are compared via four criteria: artifacts, MTF, SSP and noise. Results show that the frequency of the artifact, or number of blades on the windmill and magnitude of each blade, is dependent on the rate at which the rows are crossed for an image. For example, for a given pitch, doubling the rows doubles the frequency of the artifact, with each artifact approximately the magnitude. A similar result can be obtained by keeping the number of rows constant and varying the pitch. The artifact disappears as the Nyquist criteria is satisfied by either increasing the slice thickness or incorporating one of the focal spot switching modes that switch in the patient longitudinal direction. For a given MTF and SSP, the diagonal focal spot switching mode has slightly more noise while the other two are approximately equal. The artifact varies with the quad mode being the best and traditional mode being the worse.

  6. Software Artifacts Extraction for Program Comprehension

    NASA Astrophysics Data System (ADS)

    Rasool, Ghulam; Philippow, Ilka

    The maintenance of legacy software applications is a complex, expensive, quiet challenging, time consuming and daunting task due to program comprehension difficulties. The first step for software maintenance is to understand the existing software and to extract the high level abstractions from the source code. A number of methods, techniques and tools are applied to understand the legacy code. Each technique supports the particular legacy applications with automated/semi-automated tool support keeping in view the requirements of the maintainer. Most of the techniques support the modern languages but lacks support for older technologies. This paper presents a lightweight methodology for extraction of different artifacts from legacy COBOL and other applications

  7. Coordinate Measuring Machine Pit Artifact Inspection Procedure

    SciTech Connect

    Montano, Joshua D.

    2012-07-31

    The goal of this document is to outline a procedure for dimensional measurement of Los Alamos National Laboratory's CMM Pit Artifact. This procedure will be used by the Manufacturing Practice's Inspection Technology Subgroup of the Interagency Manufacturing Operations Group and Joint Operations Weapon Operations Group (IMOG/JOWOG 39) round robin participants. The intent is to assess the state of industry within the Nuclear Weapons Complex for measurements made on this type of part and find which current measurement strategies and techniques produce the best results.

  8. Dental Auxiliary Occupations. Interim Report.

    ERIC Educational Resources Information Center

    Kingston, Richard D.

    As part of a dental auxiliaries project, a Dental Auxiliary National Technical Advisory Committee was established, and its major undertaking was to assist in the development of a functional inventory for each of the three dental auxiliary occupations (dental assisting, dental hygiene, and dental laboratory technology). The analysis consisted of…

  9. The utilization of dental hygiene students in school-based dental sealant programs.

    PubMed

    Miller, Faith Y

    2005-01-01

    Early detection of childhood caries is important to childrens' overall health. Untreated childhood caries can lead to pain, as in abscesses from prolonged neglect; altered dietary intake; and delays in the development of the permanent teeth if the primary teeth are prematurely lost. In the summer of 2000, funds were provided to various oral health care provider organizations by the Illinois Department of Public Health, Division of Oral Health, to purchase portable equipment to deliver preventive services (i.e., exams, sealants, and oral hygiene education) to second-grade and sixth-grade children who qualified for Medicaid and/or free and reduced-cost lunch programs. The Dental Sealant Grant Program at Southern Illinois University in Carbondale was a unique program that utilized dental hygiene students as the primary human resource. Within the state, the Dental Sealant Grant Program was, at the time of this report, the only grantee sponsored by a stand-alone dental hygiene program (not affiliated with a dental school). Other positive aspects of the dental hygiene-sponsored sealant program were that the supervising dentist was the primary Medicaid provider and a member of the dental hygiene faculty; dental hygiene faculty participated actively as site coordinators and clinicians; and dental hygiene students were given the opportunity to volunteer for the program as a service-learning option. PMID:16297312

  10. Artifacts to avoid while taking advantage of top-down mass spectrometry based detection of protein S-thiolation.

    PubMed

    Auclair, Jared R; Salisbury, Joseph P; Johnson, Joshua L; Petsko, Gregory A; Ringe, Dagmar; Bosco, Daryl A; Agar, Nathalie Y R; Santagata, Sandro; Durham, Heather D; Agar, Jeffrey N

    2014-05-01

    Bottom-up MS studies typically employ a reduction and alkylation step that eliminates a class of PTM, S-thiolation. Given that molecular oxygen can mediate S-thiolation from reduced thiols, which are abundant in the reducing intracellular milieu, we investigated the possibility that some S-thiolation modifications are artifacts of protein preparation. Cu/Zn-superoxide dismutase (SOD1) was chosen for this case study as it has a reactive surface cysteine residue, which is readily cysteinylated in vitro. The ability of oxygen to generate S-thiolation artifacts was tested by comparing purification of SOD1 from postmortem human cerebral cortex under aerobic and anaerobic conditions. S-thiolation was ∼50% higher in aerobically processed preparations, consistent with oxygen-dependent artifactual S-thiolation. The ability of endogenous small molecule disulfides (e.g. cystine) to participate in artifactual S-thiolation was tested by blocking reactive protein cysteine residues during anaerobic homogenization. A 50-fold reduction in S-thiolation occurred indicating that the majority of S-thiolation observed aerobically was artifact. Tissue-specific artifacts were explored by comparing brain- and blood-derived protein, with remarkably more artifacts observed in brain-derived SOD1. Given the potential for such artifacts, rules of thumb for sample preparation are provided. This study demonstrates that without taking extraordinary precaution, artifactual S-thiolation of highly reactive, surface-exposed, cysteine residues can result.

  11. Detection of artifacts from high energy bursts in neonatal EEG.

    PubMed

    Bhattacharyya, Sourya; Biswas, Arunava; Mukherjee, Jayanta; Majumdar, Arun Kumar; Majumdar, Bandana; Mukherjee, Suchandra; Singh, Arun Kumar

    2013-11-01

    Detection of non-cerebral activities or artifacts, intermixed within the background EEG, is essential to discard them from subsequent pattern analysis. The problem is much harder in neonatal EEG, where the background EEG contains spikes, waves, and rapid fluctuations in amplitude and frequency. Existing artifact detection methods are mostly limited to detect only a subset of artifacts such as ocular, muscle or power line artifacts. Few methods integrate different modules, each for detection of one specific category of artifact. Furthermore, most of the reference approaches are implemented and tested on adult EEG recordings. Direct application of those methods on neonatal EEG causes performance deterioration, due to greater pattern variation and inherent complexity. A method for detection of a wide range of artifact categories in neonatal EEG is thus required. At the same time, the method should be specific enough to preserve the background EEG information. The current study describes a feature based classification approach to detect both repetitive (generated from ECG, EMG, pulse, respiration, etc.) and transient (generated from eye blinking, eye movement, patient movement, etc.) artifacts. It focuses on artifact detection within high energy burst patterns, instead of detecting artifacts within the complete background EEG with wide pattern variation. The objective is to find true burst patterns, which can later be used to identify the Burst-Suppression (BS) pattern, which is commonly observed during newborn seizure. Such selective artifact detection is proven to be more sensitive to artifacts and specific to bursts, compared to the existing artifact detection approaches applied on the complete background EEG. Several time domain, frequency domain, statistical features, and features generated by wavelet decomposition are analyzed to model the proposed bi-classification between burst and artifact segments. A feature selection method is also applied to select the

  12. Nanotechnology for dental implants.

    PubMed

    Tomsia, Antoni P; Lee, Janice S; Wegst, Ulrike G K; Saiz, Eduardo

    2013-01-01

    With the advent of nanotechnology, an opportunity exists for the engineering of new dental implant materials. Metallic dental implants have been successfully used for decades, but they have shortcomings related to osseointegration and mechanical properties that do not match those of bone. Absent the development of an entirely new class of materials, faster osseointegration of currently available dental implants can be accomplished by various surface modifications. To date, there is no consensus regarding the preferred method(s) of implant surface modification, and further development will be required before the ideal implant surface can be created, let alone become available for clinical use. Current approaches can generally be categorized into three areas: ceramic coatings, surface functionalization, and patterning on the micro- to nanoscale. The distinctions among these are imprecise, as some or all of these approaches can be combined to improve in vivo implant performance. These surface improvements have resulted in durable implants with a high percentage of success and long-term function. Nanotechnology has provided another set of opportunities for the manipulation of implant surfaces in its capacity to mimic the surface topography formed by extracellular matrix components of natural tissue. The possibilities introduced by nanotechnology now permit the tailoring of implant chemistry and structure with an unprecedented degree of control. For the first time, tools are available that can be used to manipulate the physicochemical environment and monitor key cellular events at the molecular level. These new tools and capabilities will result in faster bone formation, reduced healing time, and rapid recovery to function.

  13. American Dental Education Association

    MedlinePlus

    ... Diversity and Inclusion ADEA Commission on Change and Innovation in Dental Education What is ADEA CCI? ADEA ... Education, 2016–2017 Beyond the Crossroads: Change and Innovation in Dental Education ADEA Guidelines for Ethical Academic ...

  14. Dental x-rays

    MedlinePlus

    X-ray - teeth; Radiograph - dental; Bitewings; Periapical film; Panoramic film; Digital image ... dentist's office. There are many types of dental x-rays. Some of them are: Bitewing. Shows the crown ...

  15. Reduction of ring artifacts in CBCT: Detection and correction of pixel gain variations in flat panel detectors

    SciTech Connect

    Altunbas, Cem; Lai, Chao-Jen; Zhong, Yuncheng; Shaw, Chris C.

    2014-09-15

    Purpose: In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accounted by conventional flat field correction methods. In this work, the authors presented a method to identify isolated pixel clusters that exhibit gain variations and proposed a pixel gain correction (PGC) method to suppress both beam hardening and exposure level dependent gain variations. Methods: To modulate both beam spectrum and entrance exposure, flood field FPD projections were acquired using beam filters with varying thicknesses. “Ideal” pixel values were estimated by performing polynomial fits in both raw and flat field corrected projections. Residuals were calculated by taking the difference between measured and ideal pixel values to identify clustered image and FPD artifacts in flat field corrected and raw images, respectively. To correct clustered image artifacts, the ratio of ideal to measured pixel values in filtered images were utilized as pixel-specific gain correction factors, referred as PGC method, and they were tabulated as a function of pixel value in a look-up table. Results: 0.035% of detector pixels lead to clustered image artifacts in flat field corrected projections, where 80% of these pixels were traced back and linked to artifacts in the FPD. The performance of PGC method was tested in variety of imaging conditions and phantoms. The PGC method reduced clustered image artifacts and fixed pattern noise in projections, and ring artifacts in CBCT images. Conclusions: Clustered projection image artifacts that lead to ring artifacts in CBCT can be better identified with our artifact detection approach. When compared to the conventional flat field correction method, the proposed PGC method enables characterization of nonlinear

  16. Distinction of bloodstain patterns from fly artifacts.

    PubMed

    Benecke, Mark; Barksdale, Larry

    2003-11-26

    Forensic scientists may encounter blood spatter at a scene which may be pure or a mixture of fly artifacts and human bloodstains. It is important to be able to make an informed identification, or at least advanced documentation of such stains since the mechanics of production of fly artifacts are not determinable to the crime scene reconstructionist from regular police forces. We describe three cases in which experiments and crime scene reconstruction led to additional information. Case 1: Above the position of a victim, numerous blood stains of the low-high-velocity type were found. Exclusion of these stains being caused by force (but instead caused by the activity of adult blow flies) by use of the following observations that were confirmed in experiments: (a) sperm-/tadpole-like structure with length > width, (b) random directionality, and (c) mixture of round symmetrical and teardrop shaped stains. Case 2: A reddish spatter field was found on a fan chain two rooms away from the place where a dead woman was found. Localization of the spatter on the bottom end of the surface hinted strongly towards fly activity. Case 3: Double homicide; submillimeter stains were found on a lamp between the two corpses. Activity of flies was less likely compared to alternative scenario of moving lampshade and violent stabbing. PMID:14609651

  17. Single authentication: exposing weighted splining artifacts

    NASA Astrophysics Data System (ADS)

    Ciptasari, Rimba W.

    2016-05-01

    A common form of manipulation is to combine parts of the image fragment into another different image either to remove or blend the objects. Inspired by this situation, we propose a single authentication technique for detecting traces of weighted average splining technique. In this paper, we assume that image composite could be created by joining two images so that the edge between them is imperceptible. The weighted average technique is constructed from overlapped images so that it is possible to compute the gray level value of points within a transition zone. This approach works on the assumption that although splining process leaves the transition zone smoothly. They may, nevertheless, alter the underlying statistics of an image. In other words, it introduces specific correlation into the image. The proposed idea dealing with identifying these correlations is to generate an original model of both weighting function, left and right functions, as references to their synthetic models. The overall process of the authentication is divided into two main stages, which are pixel predictive coding and weighting function estimation. In the former stage, the set of intensity pairs {Il,Ir} is computed by exploiting pixel extrapolation technique. The least-squares estimation method is then employed to yield the weighted coefficients. We show the efficacy of the proposed scheme on revealing the splining artifacts. We believe that this is the first work that exposes the image splining artifact as evidence of digital tampering.

  18. Recognizing Scientific Artifacts in Biomedical Literature

    PubMed Central

    Groza, Tudor; Hassanzadeh, Hamed; Hunter, Jane

    2013-01-01

    Today’s search engines and digital libraries offer little or no support for discovering those scientific artifacts (hypotheses, supporting/contradicting statements, or findings) that form the core of scientific written communication. Consequently, we currently have no means of identifying central themes within a domain or to detect gaps between accepted knowledge and newly emerging knowledge as a means for tracking the evolution of hypotheses from incipient phases to maturity or decline. We present a hybrid Machine Learning approach using an ensemble of four classifiers, for recognizing scientific artifacts (ie, hypotheses, background, motivation, objectives, and findings) within biomedical research publications, as a precursory step to the general goal of automatically creating argumentative discourse networks that span across multiple publications. The performance achieved by the classifiers ranges from 15.30% to 78.39%, subject to the target class. The set of features used for classification has led to promising results. Furthermore, their use strictly in a local, publication scope, ie, without aggregating corpus-wide statistics, increases the versatility of the ensemble of classifiers and enables its direct applicability without the necessity of re-training. PMID:23645987

  19. Artifacts with uneven sampling of red noise.

    PubMed

    Milotti, Edoardo

    2007-01-01

    The vast majority of sampling systems operate in a standard way: at each tick of a fixed-frequency master clock a digitizer reads out a voltage that corresponds to the value of some physical quantity and translates it into a bit pattern that is either transmitted, stored, or processed right away. Thus signal sampling at evenly spaced time intervals is the rule: however, this is not always the case, and uneven sampling is sometimes unavoidable. While periodic or quasiperiodic uneven sampling of a deterministic signal can reasonably be expected to produce artifacts, it is much less obvious that the same happens with noise: here I show that this is indeed the case only for long-memory noise processes, i.e., power-law noises 1f;{alpha} with alpha>2 . The resulting artifacts are usually a nuisance although they can be eliminated with a proper processing of the signal samples, but they could also be turned to advantage and used to encode information.

  20. Ontological System for Context Artifacts and Resources

    NASA Astrophysics Data System (ADS)

    Huang, T.; Chung, N. T.; Mukherjee, R. M.

    2012-12-01

    The Adaptive Vehicle Make (AVM) program is a portfolio of programs, managed by the Defense Advanced Research Projects Agency (DARPA). It was established to revolutionize how DoD designs, verifies, and manufactures complex defense systems and vehicles. The Component, Context, and Manufacturing Model Library (C2M2L; pronounced "camel") seeks to develop domain-specific models needed to enable design, verification, and fabrication of the Fast Adaptable Next-Generation (FANG) infantry fighting vehicle using in its overall infrastructure. Terrain models are being developed to represent the surface/fluid that an amphibious infantry fighting vehicle would traverse, ranging from paved road surfaces to rocky, mountainous terrain, slope, discrete obstacles, mud, sand snow, and water fording. Context models are being developed to provide additional data for environmental factors, such as: humidity, wind speed, particulate presence and character, solar radiation, cloud cover, precipitation, and more. The Ontological System for Context Artifacts and Resources (OSCAR) designed and developed at the Jet Propulsion Laboratory is semantic web data system that enables context artifacts to be registered and searched according to their meaning, rather than indexed according to their syntactic structure alone (as in the case for traditional search engines). The system leverages heavily on the Semantic Web for Earth and Environmental Terminology (SWEET) ontologies to model physical terrain environment and context model characteristics. In this talk, we focus on the application of the SWEET ontologies and the design of the OSCAR system architecture.

  1. Reference geometry-based detection of (4D-)CT motion artifacts: a feasibility study

    NASA Astrophysics Data System (ADS)

    Werner, René; Gauer, Tobias

    2015-03-01

    Respiration-correlated computed tomography (4D or 3D+t CT) can be considered as standard of care in radiation therapy treatment planning for lung and liver lesions. The decision about an application of motion management devices and the estimation of patient-specific motion effects on the dose distribution relies on precise motion assessment in the planning 4D CT data { which is impeded in case of CT motion artifacts. The development of image-based/post-processing approaches to reduce motion artifacts would benefit from precise detection and localization of the artifacts. Simple slice-by-slice comparison of intensity values and threshold-based analysis of related metrics suffer from- depending on the threshold- high false-positive or -negative rates. In this work, we propose exploiting prior knowledge about `ideal' (= artifact free) reference geometries to stabilize metric-based artifact detection by transferring (multi-)atlas-based concepts to this specific task. Two variants are introduced and evaluated: (S1) analysis and comparison of warped atlas data obtained by repeated non-linear atlas-to-patient registration with different levels of regularization; (S2) direct analysis of vector field properties (divergence, curl magnitude) of the atlas-to-patient transformation. Feasibility of approaches (S1) and (S2) is evaluated by motion-phantom data and intra-subject experiments (four patients) as well as - adopting a multi-atlas strategy- inter-subject investigations (twelve patients involved). It is demonstrated that especially sorting/double structure artifacts can be precisely detected and localized by (S1). In contrast, (S2) suffers from high false positive rates.

  2. WE-G-18A-03: Cone Artifacts Correction in Iterative Cone Beam CT Reconstruction

    SciTech Connect

    Yan, H; Folkerts, M; Jiang, S; Jia, X; Wang, X; Bai, T; Lu, W

    2014-06-15

    Purpose: For iterative reconstruction (IR) in cone-beam CT (CBCT) imaging, data truncation along the superior-inferior (SI) direction causes severe cone artifacts in the reconstructed CBCT volume images. Not only does it reduce the effective SI coverage of the reconstructed volume, it also hinders the IR algorithm convergence. This is particular a problem for regularization based IR, where smoothing type regularization operations tend to propagate the artifacts to a large area. It is our purpose to develop a practical cone artifacts correction solution. Methods: We found it is the missing data residing in the truncated cone area that leads to inconsistency between the calculated forward projections and measured projections. We overcome this problem by using FDK type reconstruction to estimate the missing data and design weighting factors to compensate the inconsistency caused by the missing data. We validate the proposed methods in our multi-GPU low-dose CBCT reconstruction system on multiple patients' datasets. Results: Compared to the FDK reconstruction with full datasets, while IR is able to reconstruct CBCT images using a subset of projection data, the severe cone artifacts degrade overall image quality. For head-neck case under a full-fan mode, 13 out of 80 slices are contaminated. It is even more severe in pelvis case under half-fan mode, where 36 out of 80 slices are affected, leading to inferior soft-tissue delineation. By applying the proposed method, the cone artifacts are effectively corrected, with a mean intensity difference decreased from ∼497 HU to ∼39HU for those contaminated slices. Conclusion: A practical and effective solution for cone artifacts correction is proposed and validated in CBCT IR algorithm. This study is supported in part by NIH (1R01CA154747-01)

  3. Sterilization of dental instruments and devices: an update.

    PubMed

    Goodman, H S; Carpenter, R D; Cox, M R

    1994-04-01

    Dental sterilization techniques have become a focus of attention as a result of disclosure of occupational HIV transmission from an infected dentist to a cluster of patients. Although there has never been a confirmed report of a patient acquiring an infectious blood-borne disease from a dental instrument or device, recommendations for universal sterilization of dental handpieces and other devices have recently been implemented. Because of the higher rate of hepatitis B virus transmissability in the dental health care environment, an upgrade in sterilization protocols may be warranted. Stringent sterilization standards are especially necessary in higher-risk institutional dental care settings. However, a high rate of dental sterilization errors has been reported and traced to operator error. Recent institutional dental sterilization policy changes have been developed to reduce the chance of sterilization error, further diminishing the risk of cross contamination. PMID:8060010

  4. Financial impact of community-based dental education.

    PubMed

    Bailit, Howard L

    2010-10-01

    The financial impact of community-based dental education on dental school and community clinic budgets is a major issue. The evidence suggests that community experiences for dental students of fifty or more days, if effectively managed, can increase school net revenues due to the following factors: 1) the community rotations increase student productivity, approximating the loss of dental school clinical income; 2) the reallocation of unused clinical resources at the dental school reduces student clinic deficits; 3) schools and federally qualified health centers (FQHCs) that share surplus student patient revenues generate additional net income; and 4) enrollment of more students without additional new facilities and faculty increases total school tuition revenues. For FQHC dental clinics, student rotations increase the number of patients treated and may generate surplus revenues. Community-based dental education also provides schools and clinics important non-financial advantages. PMID:20930225

  5. Dental laser technology.

    PubMed

    Fasbinder, Dennis J

    2008-10-01

    Dental technology is rapidly affecting the treatment options available to patients. Dental lasers are an innovative technology for both hard- and soft-tissue treatment applications. The ability to recontour soft tissues efficiently and predictably with immediate hemostatsis and minimal postoperative sequelae is of value to both the dentist and the patient. This article reviews the principles of dental lasers, criteria to consider when selecting a dental laser, and some of their clinical applications.

  6. Artifact reduction in short-scan CBCT by use of optimization-based reconstruction

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Han, Xiao; Pearson, Erik; Pelizzari, Charles; Sidky, Emil Y.; Pan, Xiaochuan

    2016-05-01

    Increasing interest in optimization-based reconstruction in research on, and applications of, cone-beam computed tomography (CBCT) exists because it has been shown to have to potential to reduce artifacts observed in reconstructions obtained with the Feldkamp–Davis–Kress (FDK) algorithm (or its variants), which is used extensively for image reconstruction in current CBCT applications. In this work, we carried out a study on optimization-based reconstruction for possible reduction of artifacts in FDK reconstruction specifically from short-scan CBCT data. The investigation includes a set of optimization programs such as the image-total-variation (TV)-constrained data-divergency minimization, data-weighting matrices such as the Parker weighting matrix, and objects of practical interest for demonstrating and assessing the degree of artifact reduction. Results of investigative work reveal that appropriately designed optimization-based reconstruction, including the image-TV-constrained reconstruction, can reduce significant artifacts observed in FDK reconstruction in CBCT with a short-scan configuration.

  7. Focal volume optics and experimental artifacts in confocal fluorescence correlation spectroscopy.

    PubMed Central

    Hess, Samuel T; Webb, Watt W

    2002-01-01

    Fluorescence correlation spectroscopy (FCS) can provide a wealth of information about biological and chemical systems on a broad range of time scales (<1 micros to >1 s). Numerical modeling of the FCS observation volume combined with measurements has revealed, however, that the standard assumption of a three-dimensional Gaussian FCS observation volume is not a valid approximation under many common measurement conditions. As a result, the FCS autocorrelation will contain significant, systematic artifacts that are most severe with confocal optics when using a large detector aperture and aperture-limited illumination. These optical artifacts manifest themselves in the fluorescence correlation as an apparent additional exponential component or diffusing species with significant (>30%) amplitude that can imply extraneous kinetics, shift the measured diffusion time by as much as approximately 80%, and cause the axial ratio to diverge. Artifacts can be minimized or virtually eliminated by using a small confocal detector aperture, underfilled objective back-aperture, or two-photon excitation. However, using a detector aperture that is smaller or larger than the optimal value (approximately 4.5 optical units) greatly reduces both the count rate per molecule and the signal-to-noise ratio. Thus, there is a tradeoff between optimizing signal-to-noise and reducing experimental artifacts in one-photon FCS. PMID:12324447

  8. Artifact reduction in short-scan CBCT by use of optimization-based reconstruction

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng; Han, Xiao; Pearson, Erik; Pelizzari, Charles; Sidky, Emil Y.; Pan, Xiaochuan

    2016-05-01

    Increasing interest in optimization-based reconstruction in research on, and applications of, cone-beam computed tomography (CBCT) exists because it has been shown to have to potential to reduce artifacts observed in reconstructions obtained with the Feldkamp-Davis-Kress (FDK) algorithm (or its variants), which is used extensively for image reconstruction in current CBCT applications. In this work, we carried out a study on optimization-based reconstruction for possible reduction of artifacts in FDK reconstruction specifically from short-scan CBCT data. The investigation includes a set of optimization programs such as the image-total-variation (TV)-constrained data-divergency minimization, data-weighting matrices such as the Parker weighting matrix, and objects of practical interest for demonstrating and assessing the degree of artifact reduction. Results of investigative work reveal that appropriately designed optimization-based reconstruction, including the image-TV-constrained reconstruction, can reduce significant artifacts observed in FDK reconstruction in CBCT with a short-scan configuration.

  9. Hybrid ICA—Regression: Automatic Identification and Removal of Ocular Artifacts from Electroencephalographic Signals

    PubMed Central

    Mannan, Malik M. Naeem; Jeong, Myung Y.; Kamran, Muhammad A.

    2016-01-01

    Electroencephalography (EEG) is a portable brain-imaging technique with the advantage of high-temporal resolution that can be used to record electrical activity of the brain. However, it is difficult to analyze EEG signals due to the contamination of ocular artifacts, and which potentially results in misleading conclusions. Also, it is a proven fact that the contamination of ocular artifacts cause to reduce the classification accuracy of a brain-computer interface (BCI). It is therefore very important to remove/reduce these artifacts before the analysis of EEG signals for applications like BCI. In this paper, a hybrid framework that combines independent component analysis (ICA), regression and high-order statistics has been proposed to identify and eliminate artifactual activities from EEG data. We used simulated, experimental and standard EEG signals to evaluate and analyze the effectiveness of the proposed method. Results demonstrate that the proposed method can effectively remove ocular artifacts as well as it can preserve the neuronal signals present in EEG data. A comparison with four methods from literature namely ICA, regression analysis, wavelet-ICA (wICA), and regression-ICA (REGICA) confirms the significantly enhanced performance and effectiveness of the proposed method for removal of ocular activities from EEG, in terms of lower mean square error and mean absolute error values and higher mutual information between reconstructed and original EEG. PMID:27199714

  10. SU-E-J-58: Dosimetric Verification of Metal Artifact Effects: Comparison of Dose Distributions Affected by Patient Teeth and Implants

    SciTech Connect

    Lee, M; Kang, S; Lee, S; Suh, T; Lee, J; Park, J; Park, H; Lee, B

    2014-06-01

    Purpose: Implant-supported dentures seem particularly appropriate for the predicament of becoming edentulous and cancer patients are no exceptions. As the number of people having dental implants increased in different ages, critical dosimetric verification of metal artifact effects are required for the more accurate head and neck radiation therapy. The purpose of this study is to verify the theoretical analysis of the metal(streak and dark) artifact, and to evaluate dosimetric effect which cause by dental implants in CT images of patients with the patient teeth and implants inserted humanoid phantom. Methods: The phantom comprises cylinder which is shaped to simulate the anatomical structures of a human head and neck. Through applying various clinical cases, made phantom which is closely allied to human. Developed phantom can verify two classes: (i)closed mouth (ii)opened mouth. RapidArc plans of 4 cases were created in the Eclipse planning system. Total dose of 2000 cGy in 10 fractions is prescribed to the whole planning target volume (PTV) using 6MV photon beams. Acuros XB (AXB) advanced dose calculation algorithm, Analytical Anisotropic Algorithm (AAA) and progressive resolution optimizer were used in dose optimization and calculation. Results: In closed and opened mouth phantom, because dark artifacts formed extensively around the metal implants, dose variation was relatively higher than that of streak artifacts. As the PTV was delineated on the dark regions or large streak artifact regions, maximum 7.8% dose error and average 3.2% difference was observed. The averaged minimum dose to the PTV predicted by AAA was about 5.6% higher and OARs doses are also 5.2% higher compared to AXB. Conclusion: The results of this study showed that AXB dose calculation involving high-density materials is more accurate than AAA calculation, and AXB was superior to AAA in dose predictions beyond dark artifact/air cavity portion when compared against the measurements.

  11. Accreditation in Dental Hygiene.

    ERIC Educational Resources Information Center

    National Commission on Accrediting, Washington, DC.

    The Council on Dental Education cooperates with the American Dental Hygienists' Association in developing educational requirements for schools of dental hygiene. To be eligible for accreditation, schools must operate on a non-profit basis. A school applying for accreditation completes a previsitation questionnaire concerning its program. The…

  12. Dental records: An overview

    PubMed Central

    Charangowda, B K

    2010-01-01

    Dental records consist of documents related to the history of present illness, clinical examination, diagnosis, treatment done, and the prognosis. A thorough knowledge of dental records is essential for the practicing dentist, as it not only has a forensic application, but also a legal implication with respect to insurance and consumerism. This article reviews the importance of dental records in forensics. PMID:21189983

  13. Dental Manpower Fact Book.

    ERIC Educational Resources Information Center

    Ake, James N.; Johnson, Donald W.

    Statistical data on many aspects of dental and allied dental personnel supply, distribution, characteristics, and education and on certain other aspects of dental services are presented and discussed. The data on dentist supply show the national trend in the supply of active dentists since 1950 and the concurrent changes in dentist-to-population…

  14. Dental Laboratory Technology.

    ERIC Educational Resources Information Center

    Department of the Air Force, Washington, DC.

    The Air Force dental laboratory technology manual is designed as a basic training text as well as a reference source for dental laboratory technicians, a specialty occupation concerned with the design, fabrication, and repair of dental prostheses. Numerous instructive diagrams and photographs are included throughout the manual. The comprehensive…

  15. DENTAL SCHOOL PLANNING.

    ERIC Educational Resources Information Center

    GALAGAN, DONALD J.

    THIS DISCUSSION PRESENTS A COMPLETE PICTURE OF THE CURRENT STATE OF DENTAL EDUCATION WITH SUGGESTIONS FOR MEETING THE DEMANDS FOR DENTAL STAFF AND FACILITIES. THE AREAS INVESTIGATED ARE (1) OBJECTIVES IN DENTAL EDUCATION--COURSES, TEACHING MODES, INNOVATIONS IN CURRICULUM, COORDINATION OF BASIC AND CLINICAL INSTRUCTION, (2) FACILITY…

  16. Computerized Tool to Manage Dental Anxiety: A Randomized Clinical Trial.

    PubMed

    Tellez, M; Potter, C M; Kinner, D G; Jensen, D; Waldron, E; Heimberg, R G; Myers Virtue, S; Zhao, H; Ismail, A I

    2015-09-01

    Anxiety regarding dental and physical health is a common and potentially distressing problem, for both patients and health care providers. Anxiety has been identified as a barrier to regular dental visits and as an important target for enhancement of oral health-related quality of life. The study aimed to develop and evaluate a computerized cognitive-behavioral therapy dental anxiety intervention that could be easily implemented in dental health care settings. A cognitive-behavioral protocol based on psychoeducation, exposure to feared dental procedures, and cognitive restructuring was developed. A randomized controlled trial was conducted (N = 151) to test its efficacy. Consenting adult dental patients who met inclusion criteria (e.g., high dental anxiety) were randomized to 1 of 2 groups: immediate treatment (n = 74) or a wait-list control (n = 77). Analyses of covariance based on intention-to-treat analyses were used to compare the 2 groups on dental anxiety, fear, avoidance, and overall severity of dental phobia. Baseline scores on these outcomes were entered into the analyses as covariates. Groups were equivalent at baseline but differed at 1-mo follow-up. Both groups showed improvement in outcomes, but analyses of covariance demonstrated significant differences in dental anxiety, fear, avoidance, and overall severity of dental phobia in favor of immediate treatment at the follow-up assessment. Of the patients who met diagnostic criteria for phobia at baseline, fewer patients in the immediate treatment group continued to meet criteria for dental phobia at follow-up as compared with the wait-list group. A new computer-based tool seems to be efficacious in reducing dental anxiety and fear/avoidance of dental procedures. Examination of its effectiveness when administered in dental offices under less controlled conditions is warranted (ClinicalTrials.gov NCT02081365). PMID:26202996

  17. The dosimetric impact of dental implants on head-and-neck volumetric modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Lin, Mu-Han; Li, Jinsheng; Price, Robert A., Jr.; Wang, Lu; Lee, Chung-Chi; Ma, C.-M.

    2013-02-01

    This work aims to investigate the dosimetric impact of dental implants on volumetric modulated arc therapy (VMAT) for head-and-neck patients and to evaluate the effectiveness of using the material's electron-density ratio for the correction. An in-house Monte Carlo (MC) code was utilized for the dose calculation to account for the scattering and attenuation caused by the high-Z implant material. Three different dental implant materials were studied in this work: titanium, Degubond®4 and gold. The dose perturbations caused by the dental implant materials were first investigated in a water phantom with a 1 cm3 insert. The per cent depth dose distributions of a 3 × 3 cm2 photon field were compared with the insert material as water and the three selected dental implant materials. To evaluate the impact of the dental implant on VMAT patient dose calculation, four head-and-neck cases were selected. For each case, the VMAT plan was designed based on the artifact-corrected patient geometry using a treatment planning system (TPS) that was typically utilized for routine patient treatment. The plans were re-calculated using the MC code for five situations: uncorrected geometry, artifact-corrected geometry and artifact-corrected geometry with one of the three different implant materials. The isodose distributions and the dose-volume histograms were cross-compared with each other. To evaluate the effectiveness of using the material's electron-density ratio for dental implant correction, the implant region was set as water with the material's electron-density ratio and the calculated dose was compared with the MC simulation with the real material. The main effect of the dental implant was the severe attenuation in the downstream. The 1 cm3 dental implant can lower the downstream dose by 10% (Ti) to 51% (Au) for a 3 × 3 cm2 field. The TPS failed to account for the dose perturbation if the dental implant material was not precisely defined. For the VMAT patient dose calculation

  18. CT metal artifact reduction by soft inequality constraints

    NASA Astrophysics Data System (ADS)

    Chukalina, Marina; Nikolaev, Dmitry; Sokolov, Valerii; Ingacheva, Anastasiya; Buzmakov, Alexey; Prun, Victor

    2015-12-01

    The artifacts (known as metal-like artifacts) arising from incorrect reconstruction may obscure or simulate pathology in medical applications, hide or mimic cracks and cavities in the scanned objects in industrial tomographic scans. One of the main reasons caused such artifacts is photon starvation on the rays which go through highly absorbing regions. We indroduce a way to suppress such artifacts in the reconstructions using soft penalty mimicing linear inequalities on the photon starved rays. An efficient algorithm to use such information is provided and the effect of those inequalities on the reconstruction quality is studied.

  19. Wavelet-based motion artifact removal for electrodermal activity.

    PubMed

    Chen, Weixuan; Jaques, Natasha; Taylor, Sara; Sano, Akane; Fedor, Szymon; Picard, Rosalind W

    2015-01-01

    Electrodermal activity (EDA) recording is a powerful, widely used tool for monitoring psychological or physiological arousal. However, analysis of EDA is hampered by its sensitivity to motion artifacts. We propose a method for removing motion artifacts from EDA, measured as skin conductance (SC), using a stationary wavelet transform (SWT). We modeled the wavelet coefficients as a Gaussian mixture distribution corresponding to the underlying skin conductance level (SCL) and skin conductance responses (SCRs). The goodness-of-fit of the model was validated on ambulatory SC data. We evaluated the proposed method in comparison with three previous approaches. Our method achieved a greater reduction of artifacts while retaining motion-artifact-free data.

  20. [Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - part 2: color and spectral Doppler artifacts].

    PubMed

    Jenssen, C; Tuma, J; Möller, K; Cui, X W; Kinkel, H; Uebel, S; Dietrich, C F

    2016-06-01

    Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues of the body and with foreign materials. On the one hand, they may be diagnostically helpful. On the other hand, they may be distracting and may lead to misdiagnosis. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review commented on the physics of artifacts and described the most important B-mode artifacts. Part 2 focuses on the clinically relevant artifacts in Doppler and color-coded duplex sonography. Problems and pitfalls of interpretation arising from artifacts, as well as the diagnostic use of Doppler and colour-coded duplex sonography, are discussed.

  1. [Ultrasound artifacts and their diagnostic significance in internal medicine and gastroenterology - part 2: color and spectral Doppler artifacts].

    PubMed

    Jenssen, C; Tuma, J; Möller, K; Cui, X W; Kinkel, H; Uebel, S; Dietrich, C F

    2016-06-01

    Artifacts in ultrasonographic diagnostics are a result of the physical properties of the ultrasound waves and are caused by interaction of the ultrasound waves with biological structures and tissues of the body and with foreign materials. On the one hand, they may be diagnostically helpful. On the other hand, they may be distracting and may lead to misdiagnosis. Profound knowledge of the causes, avoidance, and interpretation of artifacts is a necessary precondition for correct clinical appraisal of ultrasound images. Part 1 of this review commented on the physics of artifacts and described the most important B-mode artifacts. Part 2 focuses on the clinically relevant artifacts in Doppler and color-coded duplex sonography. Problems and pitfalls of interpretation arising from artifacts, as well as the diagnostic use of Doppler and colour-coded duplex sonography, are discussed. PMID:27284933

  2. Navigating career pathways--dental therapists in the workforce: a report of the career path subcommittee.

    PubMed

    Yoder, Karen; DePaola, Dominick

    2011-01-01

    Creating career pathways to facilitate current dental and other healthcare providers becoming dental therapists can be an efficient means to expand the dental workforce and reduce barriers to access to oral health services. Career pathways are proposed to facilitate dental providers building on previously learned skills to broaden their scope of practice and become even more versatile and productive providers of oral health services. Creation of a unified and integrated curriculum will enable research to document the effectiveness of this new dental provider who will work as part of dental teams and with supervision by dentists. The goal of augmenting the current dental team and reducing barriers to access to dental services for underserved populations can be enhanced by offering alternative pathways to achieve the competencies required of dental therapists.

  3. Weaker dental enamel explains dental decay.

    PubMed

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution. PMID:25885796

  4. Weaker Dental Enamel Explains Dental Decay

    PubMed Central

    Vieira, Alexandre R.; Gibson, Carolyn W.; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is “weaker” while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution. PMID:25885796

  5. Facial and Dental Injuries Facial and Dental Injuries in Karate.

    PubMed

    Vidovic-Stesevic, Vesna; Verna, Carlalberta; Krastl, Gabriel; Kuhl, Sebastian; Filippi, Andreas

    2015-01-01

    Karate is a martial art that carries a high trauma risk. Trauma-related Swiss and European karate data are currently unavailable. This survey seeks to increase knowledge of the incidence of traumatic facial and dental injuries, their emergency management, awareness of tooth rescue boxes, the use of mouthguards and their modifications. Interviews were conducted with 420 karate fighters from 43 European countries using a standardized questionnaire. All the participants were semi-professionals. The data were evaluated with respect to gender, kumite level (where a karate practitioner trains against an adversary), and country. Of the 420 fighters interviewed, 213 had experienced facial trauma and 44 had already had dental trauma. A total of 192 athletes had hurt their opponent by inflicting a facial or dental injury, and 290 knew about the possibility of tooth replantation following an avulsion. Only 50 interviewees knew about tooth rescue boxes. Nearly all the individuals interviewed wore a mouthguard (n = 412), and 178 of them had made their own modifications to the guard. The results of the present survey suggest that more information and education in wearing protective gear are required to reduce the incidence of dental injuries in karate.

  6. The pregnant dental patient.

    PubMed

    Singh, Medha

    2012-01-01

    When dealing with a pregnant patient, the dental practitioner should keep in mind the various physiological changes that occur in the pregnant female and the potential effects on the fetus in using various types of local anesthesia. This article reviews the current considerations in the use of local anesthesia in the pregnant dental patient, and the safety of local anesthetics, their dosage, and any adverse effect on mother and fetus. It also discusses various dental procedures and the trimester during which they can be performed. Lastly, this article talks about the complications that can occur with a pregnant dental patient in the dental chair.

  7. Artifacts in single-molecule localization microscopy.

    PubMed

    Burgert, Anne; Letschert, Sebastian; Doose, Sören; Sauer, Markus

    2015-08-01

    Single-molecule localization microscopy provides subdiffraction resolution images with virtually molecular resolution. Through the availability of commercial instruments and open-source reconstruction software, achieving super resolution is now public domain. However, despite its conceptual simplicity, localization microscopy remains prone to user errors. Using direct stochastic optical reconstruction microscopy, we investigate the impact of irradiation intensity, label density and photoswitching behavior on the distribution of membrane proteins in reconstructed super-resolution images. We demonstrate that high emitter densities in combination with inappropriate photoswitching rates give rise to the appearance of artificial membrane clusters. Especially, two-dimensional imaging of intrinsically three-dimensional membrane structures like microvilli, filopodia, overlapping membranes and vesicles with high local emitter densities is prone to generate artifacts. To judge the quality and reliability of super-resolution images, the single-molecule movies recorded to reconstruct the images have to be carefully investigated especially when investigating membrane organization and cluster analysis.

  8. An extension to artifact-free projection overlaps

    SciTech Connect

    Lin, Jianyu

    2015-05-15

    Purpose: In multipinhole single photon emission computed tomography, the overlapping of projections has been used to increase sensitivity. Avoiding artifacts in the reconstructed image associated with projection overlaps (multiplexing) is a critical issue. In our previous report, two types of artifact-free projection overlaps, i.e., projection overlaps that do not lead to artifacts in the reconstructed image, were formally defined and proved, and were validated via simulations. In this work, a new proposition is introduced to extend the previously defined type-II artifact-free projection overlaps so that a broader range of artifact-free overlaps is accommodated. One practical purpose of the new extension is to design a baffle window multipinhole system with artifact-free projection overlaps. Methods: First, the extended type-II artifact-free overlap was theoretically defined and proved. The new proposition accommodates the situation where the extended type-II artifact-free projection overlaps can be produced with incorrectly reconstructed portions in the reconstructed image. Next, to validate the theory, the extended-type-II artifact-free overlaps were employed in designing the multiplexing multipinhole spiral orbit imaging systems with a baffle window. Numerical validations were performed via simulations, where the corresponding 1-pinhole nonmultiplexing reconstruction results were used as the benchmark for artifact-free reconstructions. The mean square error (MSE) was the metric used for comparisons of noise-free reconstructed images. Noisy reconstructions were also performed as part of the validations. Results: Simulation results show that for noise-free reconstructions, the MSEs of the reconstructed images of the artifact-free multiplexing systems are very similar to those of the corresponding 1-pinhole systems. No artifacts were observed in the reconstructed images. Therefore, the testing results for artifact-free multiplexing systems designed using the

  9. Bacterial aerosols in the dental clinic: a review.

    PubMed

    Leggat, P A; Kedjarune, U

    2001-02-01

    A number of sources of bacterial aerosols exist within and outside the dental clinic. The concentration of bacterial aerosols and splatters appears to be highest during dental procedures, especially those generated by some procedures such as ultrasonic scaling, or using a high speed drill. Several infectious diseases could be transmitted to staff and patients by airborne bacterial and other contaminants in the dental clinic. Air-conditioning and ventilation systems should be regularly maintained to reduce environmental contaminants and to prevent recirculation of bacterial aerosols. Pre-procedural rinsing by patients with mouthwashes as well as vacuum and electrostatic extraction of aerosols during dental procedures could also be employed. Dental staff should also consider appropriate immunizations and continue to use personal protective measures, which reduce contact with bacterial aerosols and splatters in the dental clinic.

  10. Correction of Non-Linear Propagation Artifact in Contrast-Enhanced Ultrasound Imaging of Carotid Arteries: Methods and in Vitro Evaluation.

    PubMed

    Yildiz, Yesna O; Eckersley, Robert J; Senior, Roxy; Lim, Adrian K P; Cosgrove, David; Tang, Meng-Xing

    2015-07-01

    Non-linear propagation of ultrasound creates artifacts in contrast-enhanced ultrasound images that significantly affect both qualitative and quantitative assessments of tissue perfusion. This article describes the development and evaluation of a new algorithm to correct for this artifact. The correction is a post-processing method that estimates and removes non-linear artifact in the contrast-specific image using the simultaneously acquired B-mode image data. The method is evaluated on carotid artery flow phantoms with large and small vessels containing microbubbles of various concentrations at different acoustic pressures. The algorithm significantly reduces non-linear artifacts while maintaining the contrast signal from bubbles to increase the contrast-to-tissue ratio by up to 11 dB. Contrast signal from a small vessel 600 μm in diameter buried in tissue artifacts before correction was recovered after the correction.

  11. Description and Documentation of the Dental School Dental Delivery System.

    ERIC Educational Resources Information Center

    Chase, Rosen and Wallace, Inc., Alexandria, VA.

    A study was undertaken to describe and document the dental school dental delivery system using an integrated systems approach. In late 1976 and early 1977, a team of systems analysts and dental consultants visited three dental schools to observe the delivery of dental services and patient flow and to interview administrative staff and faculty.…

  12. Efficient correction for CT image artifacts caused by objects extending outside the scan field of view.

    PubMed

    Ohnesorge, B; Flohr, T; Schwarz, K; Heiken, J P; Bae, K T

    2000-01-01

    The purpose of this paper is to develop a method of eliminating CT image artifacts generated by objects extending outside the scan field of view, such as obese or inadequately positioned patients. CT projection data are measured only within the scan field of view and thus are abruptly discontinuous at the projection boundaries if the scanned object extends outside the scan field of view. This data discontinuity causes an artifact that consists of a bright peripheral band that obscures objects near the boundary of the scan field of view. An adaptive mathematical extrapolation scheme with low computational expense was applied to reduce the data discontinuity prior to convolution in a filtered backprojection reconstruction. Despite extended projection length, the convolution length was not increased and thus the reconstruction time was not affected. Raw projection data from ten patients whose bodies extended beyond the scan field of view were reconstructed using a conventional method and our extended reconstruction method. Limitations of the algorithm are investigated and extensions for further improvement are discussed. The images reconstructed by conventional filtered backprojection demonstrated peripheral bright-band artifacts near the boundary of the scan field of view. Images reconstructed with our technique were free of such artifacts and clearly showed the anatomy at the periphery of the scan field of view with correct attenuation values. We conclude that bright-band artifacts generated by obese patients whose bodies extend beyond the scan field of view were eliminated with our reconstruction method, which reduces boundary data discontinuity. The algorithm can be generalized to objects with inhomogeneous peripheral density and to true "Region of Interest Reconstruction" from truncated projections.

  13. 77 FR 40914 - Arts and Artifacts Indemnity Panel Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-11

    ... ARTS AND THE HUMANITIES Arts and Artifacts Indemnity Panel Advisory Committee AGENCY: Federal Council... Arts and the Humanities will hold a meeting of the Arts and Artifacts Domestic Indemnity Panel. The..., and because it is important to keep the values of objects to be indemnified, and the methods...

  14. 76 FR 25378 - Arts and Artifacts Indemnity Panel Advisory; Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-04

    ... THE ARTS AND THE HUMANITIES Federal Council on the Arts and the Humanities Arts and Artifacts...) notice is hereby given that a meeting of the Arts and Artifacts Indemnity Panel of the Federal Council on... data and because it is important to keep values of objects, methods of transportation and...

  15. Magnetic resonance imaging susceptibility artifacts due to metallic foreign bodies.

    PubMed

    Hecht, Silke; Adams, William H; Narak, Jill; Thomas, William B

    2011-01-01

    Susceptibility artifacts due to metallic foreign bodies may interfere with interpretation of magnetic resonance (MR) imaging studies. Additionally, migration of metallic objects may pose a risk to patients undergoing MR imaging. Our purpose was to investigate prevalence, underlying cause, and diagnostic implications of susceptibility artifacts in small animal MR imaging and report associated adverse effects. MR imaging studies performed in dogs and cats between April 2008 and March 2010 were evaluated retrospectively for the presence of susceptibility artifacts associated with metallic foreign bodies. Studies were performed using a 1.0 T scanner. Severity of artifacts was graded as 0 (no interference with area of interest), 1 (extension of artifact to area of interest without impairment of diagnostic quality), 2 (impairment of diagnostic quality but diagnosis still possible), or 3 (severe involvement of area of interest resulting in nondiagnostic study). Medical records were evaluated retrospectively to identify adverse effects. Susceptibility artifacts were present in 99/754 (13.1%) of MR imaging studies and were most common in examinations of the brachial plexus, thorax, and cervical spine. Artifacts were caused by identification microchips, ballistic fragments, skin staples/suture material, hemoclips, an ameroid constrictor, and surgical hardware. Three studies were nondiagnostic due to the susceptibility artifact. Adverse effects were not documented.

  16. Detection and removal of artifacts in astronomical images

    NASA Astrophysics Data System (ADS)

    Desai, S.; Mohr, J. J.; Bertin, E.; Kümmel, M.; Wetzstein, M.

    2016-07-01

    Astronomical images from optical photometric surveys are typically contaminated with transient artifacts such as cosmic rays, satellite trails and scattered light. We have developed and tested an algorithm that removes these artifacts using a deep, artifact free, static sky coadd image built up through the median combination of point spread function (PSF) homogenized, overlapping single epoch images. Transient artifacts are detected and masked in each single epoch image through comparison with an artifact free, PSF-matched simulated image that is constructed using the PSF-corrected, model fitting catalog from the artifact free coadd image together with the position variable PSF model of the single epoch image. This approach works well not only for cleaning single epoch images with worse seeing than the PSF homogenized coadd, but also the traditionally much more challenging problem of cleaning single epoch images with better seeing. In addition to masking transient artifacts, we have developed an interpolation approach that uses the local PSF and performs well in removing artifacts whose widths are smaller than the PSF full width at half maximum, including cosmic rays, the peaks of saturated stars and bleed trails. We have tested this algorithm on Dark Energy Survey Science Verification data and present performance metrics. More generally, our algorithm can be applied to any survey which images the same part of the sky multiple times.

  17. 77 FR 64146 - Arts and Artifacts Indemnity Panel Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-18

    ... ARTS AND THE HUMANITIES Arts and Artifacts Indemnity Panel Advisory Committee AGENCY: Federal Council... Artifacts International Indemnity Panel. The purpose of the meeting is for panel review, discussion... important to keep the values of objects to be indemnified and the methods of transportation and...

  18. 78 FR 4878 - Arts and Artifacts Indemnity Panel Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-23

    ... ARTS AND THE HUMANITIES Arts and Artifacts Indemnity Panel Advisory Committee AGENCY: Federal Council... Artifacts Domestic Indemnity Panel. The purpose of the meeting is for panel review, discussion, evaluation... important to keep the values of objects to be indemnified and the methods of transportation and...

  19. Kindergarten Children's Perceptions of "Anthropomorphic Artifacts" with Adaptive Behavior

    ERIC Educational Resources Information Center

    Kuperman, Asi; Mioduser, David

    2012-01-01

    In recent years, children from a kindergarten in central Israel have been exposed to learning experiences in technology as part of the implementation of a curriculum based on technological thinking, including topics related to behaving-adaptive-artifacts (e.g., robots). This study aims to unveil children's stance towards behaving artifacts:…

  20. Naturalistic Experience and the Early Use of Symbolic Artifacts

    ERIC Educational Resources Information Center

    Troseth, Georgene L.; Casey, Amy M.; Lawver, Kelly A.; Walker, Joan M. T.; Cole, David A.

    2007-01-01

    Experience with a variety of symbolic artifacts has been proposed as a mechanism underlying symbolic development. In this study, the parents of 120 2-year-old children who participated in symbolic object retrieval tasks completed a questionnaire regarding their children's naturalistic experience with symbolic artifacts and activities. In separate…

  1. Developmental Changes within the Core of Artifact Concepts.

    ERIC Educational Resources Information Center

    Matan, Adee; Carey, Susan

    2001-01-01

    Three experiments examined the relative importance of original function and current function in artifact categorization for young children and adults. It was concluded that 6-year-olds have begun to organize their understanding of artifacts around the notion of original function, whereas 4-year-olds have not. Data were examined in terms of how…

  2. An approach to artifact identification: application to heart period data.

    PubMed

    Berntson, G G; Quigley, K S; Jang, J F; Boysen, S T

    1990-09-01

    A rational strategy for the automated detection of artifacts in heart period data is outlined and evaluated. The specific implementation of this approach for heart period data is based on the distribution characteristics of successive heart period differences. Because beat-to-beat differences generated by artifacts are large, relative to normal heart period variability, extreme differences between successive heart periods serve to identify potential artifacts. Critical to this approach are: 1) the derivation of the artifact criterion from the distribution of beat differences of the individual subject, and 2) the use of percentile-based distribution indexes, which are less sensitive to corruption by the presence of artifactual values than are least-squares estimates. The artifact algorithms were able to effectively identify artifactual beats embedded in heart period records, flagging each of the 1494 simulated and actual artifacts in data sets derived from both humans and chimpanzees. At the same time, the artifact algorithms yielded a false alarm rate of less than 0.3%. Although the present implementation was restricted to heart period data, the outlined approach to artifact detection may also be applicable to other biological signals.

  3. Implementing a Smart Method to Eliminate Artifacts of Vital Signals

    PubMed Central

    Javadpour, A.; Mohammadi, A.

    2015-01-01

    Background Electroencephalography (EEG) has vital and significant applications in different medical fields and is used for the primary evaluation of neurological disorders. Hence, having easy access to suitable and useful signal is very important. Artifacts are undesirable confusions which are generally originated from inevitable human activities such as heartbeat, blinking of eyes and facial muscle activities while receiving EEG signal. It can bring about deformation in these waves though. Objective The objective of this study was to find a suitable solution to eliminate the artifacts of Vital Signals. Methods In this study, wavelet transform technique was used. This method is compared with threshold level. The threshold intensity is efficiently crucial because it should not remove the original signal instead of artifacts, and does not hold artifact signal instead of original ones. In this project, we seek to find and implement the algorithm with the ability to automatically remove the artifacts in EEG signals. For this purpose, the use of adaptive filtering methods such as wavelet analysis is appropriate. Finally, we observed that Functional Link Neural Network (FLN) performance is better than ANFIS and RBFN to remove such artifacts. Results We offer an intelligent method for removing artifacts from vital signals in neurological disorders. Conclusion The proposed method can obtain more accurate results by removing artifacts of vital signals and can be useful in the early diagnosis of neurological and cardiovascular disorders. PMID:26688799

  4. Turquoise mine and artifact correlation for snaketown site, Arizona.

    PubMed

    Sigleo, A C

    1975-08-01

    Trace element analyses on turquoise from 24 mines in the southwestern United States indicate that the turquoise artifacts from Snaketown site in south-central Arizona came from the Himalaya mine near Halloron Springs, California. The correlation of artifact and mine turquoise in the Southwest is a means of determining prehistoric exchange patterns.

  5. A constrained ICA approach for real-time cardiac artifact rejection in magnetoencephalography.

    PubMed

    Breuer, Lukas; Dammers, Jürgen; Roberts, Timothy P L; Shah, N Jon

    2014-02-01

    Recently, magnetoencephalography (MEG)-based real-time brain computing interfaces (BCI) have been developed to enable novel and promising methods of neuroscience research and therapy. Artifact rejection prior to source localization largely enhances the localization accuracy. However, many BCI approaches neglect real-time artifact removal due to its time consuming processing. With cardiac artifact rejection for real-time analysis (CARTA), we introduce a novel algorithm capable of real-time cardiac artifact (CA) rejection. The method is based on constrained independent component analysis (ICA), where a priori information of the underlying source signal is used to optimize and accelerate signal decomposition. In CARTA, this is performed by estimating the subject's individual density distribution of the cardiac activity, which leads to a subject-specific signal decomposition algorithm. We show that the new method is capable of effectively reducing CAs within one iteration and a time delay of 1 ms. In contrast, Infomax and Extended Infomax ICA converged not until seven iterations, while FastICA needs at least ten iterations. CARTA was tested and applied to data from three different but most common MEG systems (4-D-Neuroimaging, VSM MedTech Inc., and Elekta Neuromag). Therefore, the new method contributes to reliable signal analysis utilizing BCI approaches.

  6. Robust and accurate anomaly detection in ECG artifacts using time series motif discovery.

    PubMed

    Sivaraks, Haemwaan; Ratanamahatana, Chotirat Ann

    2015-01-01

    Electrocardiogram (ECG) anomaly detection is an important technique for detecting dissimilar heartbeats which helps identify abnormal ECGs before the diagnosis process. Currently available ECG anomaly detection methods, ranging from academic research to commercial ECG machines, still suffer from a high false alarm rate because these methods are not able to differentiate ECG artifacts from real ECG signal, especially, in ECG artifacts that are similar to ECG signals in terms of shape and/or frequency. The problem leads to high vigilance for physicians and misinterpretation risk for nonspecialists. Therefore, this work proposes a novel anomaly detection technique that is highly robust and accurate in the presence of ECG artifacts which can effectively reduce the false alarm rate. Expert knowledge from cardiologists and motif discovery technique is utilized in our design. In addition, every step of the algorithm conforms to the interpretation of cardiologists. Our method can be utilized to both single-lead ECGs and multilead ECGs. Our experiment results on real ECG datasets are interpreted and evaluated by cardiologists. Our proposed algorithm can mostly achieve 100% of accuracy on detection (AoD), sensitivity, specificity, and positive predictive value with 0% false alarm rate. The results demonstrate that our proposed method is highly accurate and robust to artifacts, compared with competitive anomaly detection methods.

  7. Kinect-Based Correction of Overexposure Artifacts in Knee Imaging with C-Arm CT Systems

    PubMed Central

    Choi, Jang-Hwan; Hinshaw, Waldo; Haase, Sven; Wasza, Jakob; Hornegger, Joachim

    2016-01-01

    Objective. To demonstrate a novel approach of compensating overexposure artifacts in CT scans of the knees without attaching any supporting appliances to the patient. C-Arm CT systems offer the opportunity to perform weight-bearing knee scans on standing patients to diagnose diseases like osteoarthritis. However, one serious issue is overexposure of the detector in regions close to the patella, which can not be tackled with common techniques. Methods. A Kinect camera is used to algorithmically remove overexposure artifacts close to the knee surface. Overexposed near-surface knee regions are corrected by extrapolating the absorption values from more reliable projection data. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates. Results. Artifacts at both knee phantoms are reduced significantly in the reconstructed data and a major part of the truncated regions is restored. Conclusion. The results emphasize the feasibility of the proposed approach. The accuracy of the cross-calibration procedure can be increased to further improve correction results. Significance. The correction method can be extended to a multi-Kinect setup for use in real-world scenarios. Using depth cameras does not require prior scans and offers the possibility of a temporally synchronized correction of overexposure artifacts. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates. PMID:27516772

  8. Investigation of the potential causes of partial scan artifacts in dynamic CT myocardial perfusion imaging

    NASA Astrophysics Data System (ADS)

    Tao, Yinghua; Speidel, Michael; Szczykutowicz, Timothy; Chen, Guang-Hong

    2014-03-01

    In recent years, there have been several findings regarding CT number variations (partial scan artifact or PSA) across time in dynamic myocardial perfusion studies with short scan gated reconstruction. These variations are correlated with the view angle range corresponding to the short scan acquisition for a given cardiac phase, which can vary from one cardiac cycle to another due to the asynchrony between heart rate and gantry rotation speed. In this study, we investigate several potential causes of PSA, including noise, beam hardening and scatter, using numerical simulations. In addition, we investigate partial scan artifact in a single source 64-slice diagnostic CT scanner in vivo data sets, and report its effect on perfusion analysis. Results indicated that among all three factors investigated, scatter can cause obvious partial scan artifact in dynamic myocardial perfusion imaging. Further, scatter is a low frequency phenomenon and is not heavily dependent on the changing contrasts, as both the frequency method and the virtual scan method are effective in reducing partial scan artifact. However, PSA does not necessarily lead to different blood volume maps compared to the full scan, because these maps are usually generated with a curve fitting procedure.

  9. Dental Arch Wire

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Straightening teeth is an arduous process requiring months, often years, of applying corrective pressure by means of arch wires-better known as brace-which may have to be changed several times in the course of treatment. A new method has been developed by Dr. George Andreasen, orthodontist and dental scientist at the University of Iowa. The key is a new type of arch wire material, called Nitinol, with exceptional elasticity which helps reduce the required number of brace changes. An alloy of nickel and titanium, Nitinol was originally developed for aerospace applications by the Naval Ordnance Laboratory, now the Naval Surface Weapons Laboratory, White Oaks, Maryland. NASA subsequently conducted additional research on the properties of Nitinol and on procedures for processing the metal.

  10. Factors influencing the use of public dental services: An application of the Theory of Planned Behaviour

    PubMed Central

    Luzzi, Liana; Spencer, A John

    2008-01-01

    Background There is limited evidence of the influence of psychosocial factors and health beliefs on public dental patient's patterns of service use in Australia. The research aims were to examine associations between dental attitudes and beliefs of public dental service users and dental visiting intention and behaviour using the Theory of Planned Behaviour. Methods 517 randomly selected adult public dental patients completed a questionnaire assessing dental attitudes and beliefs which was matched with electronic records for past and future dental service use. A questionnaire measured intentions, attitudes, subjective norms and perceptions of behavioural control and self-efficacy in relation to visiting public dentists. A measure of dental attendance at public dental clinics was obtained retrospectively (over 3 1/2 years) and prospectively (over a one year period following the return of the questionnaire) by accessing electronic patient clinical records. Results Participants had positive attitudes, subjective norms and self-efficacy beliefs towards dental visiting but perceived a lack of control over visiting the dentist. Attitudes, subjective norms, self-efficacy and perceived control were significant predictors of intention (P < 0.05). Intentions, self-efficacy and past dental attendance were significant predictors of actual dental attendance (P < 0.05). Conclusion Public dental patients held favourable attitudes and beliefs but perceived a lack of control towards dental visiting. Reducing structural barriers may therefore improve access to public dental services. PMID:18445298

  11. Working postures of dentists and dental hygienists.

    PubMed

    Marklin, Richard W; Cherney, Kevin

    2005-02-01

    A joint study was conducted by a manufacturer of dental stools in the Midwest of the United States and Marquette University to measure the occupational postures of dentists and dental hygienists. The postures of 10 dentists and 10 dental hygienists were assessed using work sampling and video techniques. Postural data of the neck, shoulders and lower back were recorded from video and categorized into 30-degree intervals: o (neutral posture of respective joint), 30, 60 and 90 degrees. Each subject's postures were observed while they were treating patients during a four-hour period, during which 100 observations of postures were recorded at random times. Compared to standing, dentists and dental hygienists were seated 78 percent and 66 percent of the time, respectively. Dentists and dental hygienists flexed their trunk at least 30 degrees more than 50 percent of the time. They flexed their neck at least 30 degrees 85 percent of the time during the four-hour duration, and their shoulders were elevated to the side of their trunk (abducted) at least 30 degrees more half of the time. The postures of the trunk, shoulders, and neck were primarily static. This database of postures can be used by dental professionals and ergonomists to assess the risk dentists and dental hygienists are exposed to musculoskeletal disorders, such as low back pain or shoulder tenosynovitis, from deviated joint postures. They could use these data to select dental furniture or dental devices that promote good body posture, i.e., reduce the magnitude and duration of deviated joint postures, which, in theory, would decrease the risk of musculoskeletal disorders.

  12. Processing dental claims electronically.

    PubMed

    Mylan, V

    1996-01-01

    A reduction of healthcare costs is an important part of the reform our society is demanding. We cannot ignore this. Lowering administrative costs is a particularly good way to reduce health care expenditures since this decreases the cost without compromising the quality of services. Implementing an EDI structure for submitting claims and receiving claim remittance advice is one way to significantly reduce the cost of health care by lowering administrative costs. EDI allows the consumer to receive the same level of health care at a lower cost. To accomplish this goal, the industry must accept some standardization. While providers, dental software vendors, and clearinghouses request an electronic claims system that is uniform-payers (insurance companies, State-administered Medicaid programs, etc.) often insist on proprietary formats that fit their own requirements. This impedes the implementation of a successful electronic interchange of data. Under the leadership of the Canadian Dental Association, payers and dentists in Canada were able to create a superior electronic claim processing network, CDAnet. Providers and payers using CDAnet agree that the system works very well. The Canadian dentist does not pay for this service, and insurance companies benefit significantly. Dentists in the USA do not have a universal electronic claim processing network. A USA dentist who wants to send claims electronically has limited selections and often pays additional fees. Organized dentistry has the best opportunity of establishing electronic data interchange between providers and payers in the USA. The first step is creating a universal electronic claim processing system. This system must protect confidentiality by maintaining data that keeps anonymous provider and patient data. It is the dentist who produces the claim. Dentists must become involved in the decisions affecting electronic claim processing. The proper guidance from organized dentistry will enable providers, payers

  13. The Future of Dental Education.

    ERIC Educational Resources Information Center

    Simonsen, Richard J.

    1994-01-01

    The author, a representative of the American Dental Trade Association, identifies major challenges facing dental education in the areas of predoctoral dental education, postdoctoral dental education, and continuing dental education. Ten recommendations address preclinical and clinical courses, licensing examinations, mandatory continuing…

  14. Comparing the Performance of Popular MEG/EEG Artifact Correction Methods in an Evoked-Response Study.

    PubMed

    Haumann, Niels Trusbak; Parkkonen, Lauri; Kliuchko, Marina; Vuust, Peter; Brattico, Elvira

    2016-01-01

    We here compared results achieved by applying popular methods for reducing artifacts in magnetoencephalography (MEG) and electroencephalography (EEG) recordings of the auditory evoked Mismatch Negativity (MMN) responses in healthy adult subjects. We compared the Signal Space Separation (SSS) and temporal SSS (tSSS) methods for reducing noise from external and nearby sources. Our results showed that tSSS reduces the interference level more reliably than plain SSS, particularly for MEG gradiometers, also for healthy subjects not wearing strongly interfering magnetic material. Therefore, tSSS is recommended over SSS. Furthermore, we found that better artifact correction is achieved by applying Independent Component Analysis (ICA) in comparison to Signal Space Projection (SSP). Although SSP reduces the baseline noise level more than ICA, SSP also significantly reduces the signal-slightly more than it reduces the artifacts interfering with the signal. However, ICA also adds noise, or correction errors, to the waveform when the signal-to-noise ratio (SNR) in the original data is relatively low-in particular to EEG and to MEG magnetometer data. In conclusion, ICA is recommended over SSP, but one should be careful when applying ICA to reduce artifacts on neurophysiological data with relatively low SNR. PMID:27524998

  15. Comparing the Performance of Popular MEG/EEG Artifact Correction Methods in an Evoked-Response Study

    PubMed Central

    Kliuchko, Marina; Vuust, Peter

    2016-01-01

    We here compared results achieved by applying popular methods for reducing artifacts in magnetoencephalography (MEG) and electroencephalography (EEG) recordings of the auditory evoked Mismatch Negativity (MMN) responses in healthy adult subjects. We compared the Signal Space Separation (SSS) and temporal SSS (tSSS) methods for reducing noise from external and nearby sources. Our results showed that tSSS reduces the interference level more reliably than plain SSS, particularly for MEG gradiometers, also for healthy subjects not wearing strongly interfering magnetic material. Therefore, tSSS is recommended over SSS. Furthermore, we found that better artifact correction is achieved by applying Independent Component Analysis (ICA) in comparison to Signal Space Projection (SSP). Although SSP reduces the baseline noise level more than ICA, SSP also significantly reduces the signal—slightly more than it reduces the artifacts interfering with the signal. However, ICA also adds noise, or correction errors, to the waveform when the signal-to-noise ratio (SNR) in the original data is relatively low—in particular to EEG and to MEG magnetometer data. In conclusion, ICA is recommended over SSP, but one should be careful when applying ICA to reduce artifacts on neurophysiological data with relatively low SNR. PMID:27524998

  16. What is dental ecology?

    PubMed

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context.

  17. Body MR Imaging: Artifacts, k-Space, and Solutions.

    PubMed

    Huang, Susie Y; Seethamraju, Ravi T; Patel, Pritesh; Hahn, Peter F; Kirsch, John E; Guimaraes, Alexander R

    2015-01-01

    Body magnetic resonance (MR) imaging is challenging because of the complex interaction of multiple factors, including motion arising from respiration and bowel peristalsis, susceptibility effects secondary to bowel gas, and the need to cover a large field of view. The combination of these factors makes body MR imaging more prone to artifacts, compared with imaging of other anatomic regions. Understanding the basic MR physics underlying artifacts is crucial to recognizing the trade-offs involved in mitigating artifacts and improving image quality. Artifacts can be classified into three main groups: (a) artifacts related to magnetic field imperfections, including the static magnetic field, the radiofrequency (RF) field, and gradient fields; (b) artifacts related to motion; and (c) artifacts arising from methods used to sample the MR signal. Static magnetic field homogeneity is essential for many MR techniques, such as fat saturation and balanced steady-state free precession. Susceptibility effects become more pronounced at higher field strengths and can be ameliorated by using spin-echo sequences when possible, increasing the receiver bandwidth, and aligning the phase-encoding gradient with the strongest susceptibility gradients, among other strategies. Nonuniformities in the RF transmit field, including dielectric effects, can be minimized by applying dielectric pads or imaging at lower field strength. Motion artifacts can be overcome through respiratory synchronization, alternative k-space sampling schemes, and parallel imaging. Aliasing and truncation artifacts derive from limitations in digital sampling of the MR signal and can be rectified by adjusting the sampling parameters. Understanding the causes of artifacts and their possible solutions will enable practitioners of body MR imaging to meet the challenges of novel pulse sequence design, parallel imaging, and increasing field strength.

  18. Body MR Imaging: Artifacts, k-Space, and Solutions

    PubMed Central

    Seethamraju, Ravi T.; Patel, Pritesh; Hahn, Peter F.; Kirsch, John E.; Guimaraes, Alexander R.

    2015-01-01

    Body magnetic resonance (MR) imaging is challenging because of the complex interaction of multiple factors, including motion arising from respiration and bowel peristalsis, susceptibility effects secondary to bowel gas, and the need to cover a large field of view. The combination of these factors makes body MR imaging more prone to artifacts, compared with imaging of other anatomic regions. Understanding the basic MR physics underlying artifacts is crucial to recognizing the trade-offs involved in mitigating artifacts and improving image quality. Artifacts can be classified into three main groups: (a) artifacts related to magnetic field imperfections, including the static magnetic field, the radiofrequency (RF) field, and gradient fields; (b) artifacts related to motion; and (c) artifacts arising from methods used to sample the MR signal. Static magnetic field homogeneity is essential for many MR techniques, such as fat saturation and balanced steady-state free precession. Susceptibility effects become more pronounced at higher field strengths and can be ameliorated by using spin-echo sequences when possible, increasing the receiver bandwidth, and aligning the phase-encoding gradient with the strongest susceptibility gradients, among other strategies. Nonuniformities in the RF transmit field, including dielectric effects, can be minimized by applying dielectric pads or imaging at lower field strength. Motion artifacts can be overcome through respiratory synchronization, alternative k-space sampling schemes, and parallel imaging. Aliasing and truncation artifacts derive from limitations in digital sampling of the MR signal and can be rectified by adjusting the sampling parameters. Understanding the causes of artifacts and their possible solutions will enable practitioners of body MR imaging to meet the challenges of novel pulse sequence design, parallel imaging, and increasing field strength. ©RSNA, 2015 PMID:26207581

  19. Dental hygiene in Slovakia.

    PubMed

    Luciak-Donsberger, C; Krizanová, M

    2004-08-01

    This article reports on the development of the dental hygiene profession in Slovakia from a global perspective. The aim is to inform about current developments and to examine, how access to qualified dental hygiene care might be improved and how professional challenges might be met. For an international study on dental hygiene, secondary source data were obtained from members of the House of Delegates of the International Federation of Dental Hygienists (IFDH) or by fax and e-mail from experts involved in the national professional and educational organization of dental hygiene in non-IFDH member countries, such as Slovakia. Responses were followed-up by interviews, e-mail correspondence, visits to international universities, and a review of supporting studies and reference literature. Results show that the introduction of dental hygiene in Slovakia in 1992 was inspired by the delivery of preventive care in Switzerland. Initiating local dentists and dental hygienists strive to attain a high educational level, equitable to that of countries in which dental hygiene has an established tradition of high quality care. Low access to qualified dental hygiene care may be a result of insufficient funding for preventive services, social and cultural lack of awareness of the benefits of preventive care, and of limitations inherent in the legal constraints preventing unsupervised dental hygiene practice. These may be a result of gender politics affecting a female-dominated profession and of a perception that dental hygiene is auxiliary to dental care. International comparison show that of all Eastern European countries, the dental hygiene profession appears most advanced in Slovakia. This is expressed in high evidence-based academic goals, in extensive work with international consultants from the Netherlands and Switzerland, in annual congresses of high professional quality, and in the establishment of a profession, which has not been introduced in all Western EU countries

  20. Meeting Dental Health Needs Through Dental Education

    ERIC Educational Resources Information Center

    Morris, Alvin L.

    1972-01-01

    Dental health needs of the country cannot be met through education of more dentists. Rather, we must educate auxiliaries to perform many of the intraoral procedures now regarded the sole responsibility of dentists. (SB)

  1. Employment of Dental Hygienists as Dental Educators.

    ERIC Educational Resources Information Center

    Fong, Cynthia; Odrich, Johanna

    1987-01-01

    A study of the use of dental hygienists to teach periodontics, preventive dentistry, community dentistry, and public health courses looked at employment patterns and practices and the qualifications of the teachers. (MSE)

  2. [Joint correction for motion artifacts and off-resonance artifacts in multi-shot diffusion magnetic resonance imaging].

    PubMed

    Wu, Wenchuan; Fang, Sheng; Guo, Hua

    2014-06-01

    Aiming at motion artifacts and off-resonance artifacts in multi-shot diffusion magnetic resonance imaging (MRI), we proposed a joint correction method in this paper to correct the two kinds of artifacts simultaneously without additional acquisition of navigation data and field map. We utilized the proposed method using multi-shot variable density spiral sequence to acquire MRI data and used auto-focusing technique for image deblurring. We also used direct method or iterative method to correct motion induced phase errors in the process of deblurring. In vivo MRI experiments demonstrated that the proposed method could effectively suppress motion artifacts and off-resonance artifacts and achieve images with fine structures. In addition, the scan time was not increased in applying the proposed method.

  3. The demand for preventive and restorative dental services.

    PubMed

    Meyerhoefer, Chad D; Zuvekas, Samuel H; Manski, Richard

    2014-01-01

    Chronic tooth decay is the most common chronic condition in the United States among children ages 5-17 and also affects a large percentage of adults. Oral health conditions are preventable, but less than half of the US population uses dental services annually. We seek to examine the extent to which limited dental coverage and high out-of-pocket costs reduce dental service use by the nonelderly privately insured and uninsured. Using data from the 2001-2006 Medical Expenditure Panel Survey and an American Dental Association survey of dental procedure prices, we jointly estimate the probability of using preventive and both basic and major restorative services through a correlated random effects specification that controls for endogeneity. We found that dental coverage increased the probability of preventive care use by 19% and the use of restorative services 11% to 16%. Both conditional and unconditional on dental coverage, the use of dental services was not sensitive to out-of-pocket costs. We conclude that dental coverage is an important determinant of preventive dental service use, but other nonprice factors related to consumer preferences, especially education, are equal if not stronger determinants.

  4. The demand for preventive and restorative dental services.

    PubMed

    Meyerhoefer, Chad D; Zuvekas, Samuel H; Manski, Richard

    2014-01-01

    Chronic tooth decay is the most common chronic condition in the United States among children ages 5-17 and also affects a large percentage of adults. Oral health conditions are preventable, but less than half of the US population uses dental services annually. We seek to examine the extent to which limited dental coverage and high out-of-pocket costs reduce dental service use by the nonelderly privately insured and uninsured. Using data from the 2001-2006 Medical Expenditure Panel Survey and an American Dental Association survey of dental procedure prices, we jointly estimate the probability of using preventive and both basic and major restorative services through a correlated random effects specification that controls for endogeneity. We found that dental coverage increased the probability of preventive care use by 19% and the use of restorative services 11% to 16%. Both conditional and unconditional on dental coverage, the use of dental services was not sensitive to out-of-pocket costs. We conclude that dental coverage is an important determinant of preventive dental service use, but other nonprice factors related to consumer preferences, especially education, are equal if not stronger determinants. PMID:23349123

  5. Case based dental radiology.

    PubMed

    Niemiec, Brook A

    2009-02-01

    Dental radiology is quickly becoming integral to the standard of care in veterinary dentistry. This is not only because it is critical for proper patient care, but also because client expectations have increased. Furthermore, providing dental radiographs as a routine service can create significant practice income. This article details numerous conditions that are indications for dental radiographs. As you will see, dental radiographs are often critical for proper diagnosis and treatment. These conditions should not be viewed as unusual; they are present within all of our practices. When you choose not to radiograph these teeth, you leave behind painful pathology. Utilizing the knowledge gained from dental radiographs will both improve patient care and increase acceptance of treatment recommendations. Consequently, this leads to increased numbers of dental procedures performed at your practice. PMID:19410233

  6. An algorithm for efficient metal artifact reductions in permanent seed implants

    SciTech Connect

    Xu Chen; Verhaegen, Frank; Laurendeau, Denis; Enger, Shirin A.; Beaulieu, Luc

    2011-01-15

    Purpose: In permanent seed implants, 60 to more than 100 small metal capsules are inserted in the prostate, creating artifacts in x-ray computed tomography (CT) imaging. The goal of this work is to develop an automatic method for metal artifact reduction (MAR) from small objects such as brachytherapy seeds for clinical applications. Methods: The approach for MAR is based on the interpolation of missing projections by directly using raw helical CT data (sinogram). First, an initial image is reconstructed from the raw CT data. Then, the metal objects segmented from the reconstructed image are reprojected back into the sinogram space to produce a metal-only sinogram. The Steger method is used to determine precisely the position and edges of the seed traces in the raw CT data. By combining the use of Steger detection and reprojections, the missing projections are detected and replaced by interpolation of non-missing neighboring projections. Results: In both phantom experiments and patient studies, the missing projections have been detected successfully and the artifacts caused by metallic objects have been substantially reduced. The performance of the algorithm has been quantified by comparing the uniformity between the uncorrected and the corrected phantom images. The results of the artifact reduction algorithm are indistinguishable from the true background value. Conclusions: An efficient algorithm for MAR in seed brachytherapy was developed. The test results obtained using raw helical CT data for both phantom and clinical cases have demonstrated that the proposed MAR method is capable of accurately detecting and correcting artifacts caused by a large number of very small metal objects (seeds) in sinogram space. This should enable a more accurate use of advanced brachytherapy dose calculations, such as Monte Carlo simulations.

  7. SU-E-I-63: Quantitative Evaluation of the Effects of Orthopedic Metal Artifact Reduction (OMAR) Software On CT Images for Radiotherapy Simulation

    SciTech Connect

    Jani, S

    2014-06-01

    Purpose: CT simulation for patients with metal implants can often be challenging due to artifacts that obscure tumor/target delineation and normal organ definition. Our objective was to evaluate the effectiveness of Orthopedic Metal Artifact Reduction (OMAR), a commercially available software, in reducing metal-induced artifacts and its effect on computed dose during treatment planning. Methods: CT images of water surrounding metallic cylindrical rods made of aluminum, copper and iron were studied in terms of Hounsfield Units (HU) spread. Metal-induced artifacts were characterized in terms of HU/Volume Histogram (HVH) using the Pinnacle treatment planning system. Effects of OMAR on enhancing our ability to delineate organs on CT and subsequent dose computation were examined in nine (9) patients with hip implants and two (2) patients with breast tissue expanders. Results: Our study characterized water at 1000 HU with a standard deviation (SD) of about 20 HU. The HVHs allowed us to evaluate how the presence of metal changed the HU spread. For example, introducing a 2.54 cm diameter copper rod in water increased the SD in HU of the surrounding water from 20 to 209, representing an increase in artifacts. Subsequent use of OMAR brought the SD down to 78. Aluminum produced least artifacts whereas Iron showed largest amount of artifacts. In general, an increase in kVp and mA during CT scanning showed better effectiveness of OMAR in reducing artifacts. Our dose analysis showed that some isodose contours shifted by several mm with OMAR but infrequently and were nonsignificant in planning process. Computed volumes of various dose levels showed <2% change. Conclusions: In our experience, OMAR software greatly reduced the metal-induced CT artifacts for the majority of patients with implants, thereby improving our ability to delineate tumor and surrounding organs. OMAR had a clinically negligible effect on computed dose within tissues. Partially funded by unrestricted

  8. [Determination of dental age].

    PubMed

    Willems, Guy

    2005-01-01

    A review of the most commonly used dental age estimating techniques is generated. The most important issue for the forensic odontologist involved in dental age estimation is to employ as many of these methods as possible by performing repetitive measurements and calculations of different age-related parameters. That is the only way in order to try and establish reliable dental age estimations. In particular, a special chapter is attributed to the complex problem of determining the age of majority. PMID:16370435

  9. GUV Preparation and Imaging: Minimizing artifacts

    PubMed Central

    Morales-Penningston, Nelson F.; Wu, Jing; Farkas, Elaine R.; Goh, Shih Lin; Konyakhina, Tatyana M.; Zheng, Judy Y.; Webb, Watt W.; Feigenson, Gerald W.

    2010-01-01

    The components of biological membranes are present in a physical mixture. The nonrandom ways that the molecules of lipids and proteins mix together can strongly influence the association of proteins with each other, and the chemical reactions that occur in the membrane, or that are mediated by the membrane. A particular type of nonrandom mixing is the separation of compositionally distinct phases. Any such phase separation would result in preferential partition of some proteins and lipids between the coexisting phases, and thus would influence which proteins could be in contact, and whether a protein could find its target. Phase separation in a plasma membrane would also influence the binding of molecules from outside the cell to the membrane, including recognition proteins on viruses, bacteria, and other cells. The concept of these and other events associated with membrane phase separation are sometimes grouped together as the “raft model” of biological membranes. Several types of experiments are aimed at detecting and characterizing membrane phase separation. Visualizing phase separation has special value, both because the immiscibility is so decisively determined, and also because the type of phase can often be identified. The fluorescence microscope has proven uniquely useful for yielding images of separated phases, both in certain cell preparations, and especially in models of cell membranes. Here we discuss ways to prepare useful model membranes for image studies, and how to avoid some of the artifacts that can plague these studies. PMID:20302841

  10. Searching for alien artifacts on the moon

    NASA Astrophysics Data System (ADS)

    Davies, P. C. W.; Wagner, R. V.

    2013-08-01

    The Search for Extraterrestrial Intelligence (SETI) has a low probability of success, but it would have a high impact if successful. Therefore it makes sense to widen the search as much as possible within the confines of the modest budget and limited resources currently available. To date, SETI has been dominated by the paradigm of seeking deliberately beamed radio messages. However, indirect evidence for extraterrestrial intelligence could come from any incontrovertible signatures of non-human technology. Existing searchable databases from astronomy, biology, earth and planetary sciences all offer low-cost opportunities to seek a footprint of extraterrestrial technology. In this paper we take as a case study one particular new and rapidly-expanding database: the photographic mapping of the Moon's surface by the Lunar Reconnaissance Orbiter (LRO) to 0.5 m resolution. Although there is only a tiny probability that alien technology would have left traces on the moon in the form of an artifact or surface modification of lunar features, this location has the virtue of being close, and of preserving traces for an immense duration. Systematic scrutiny of the LRO photographic images is being routinely conducted anyway for planetary science purposes, and this program could readily be expanded and outsourced at little extra cost to accommodate SETI goals, after the fashion of the SETI@home and Galaxy Zoo projects.

  11. Method for eliminating artifacts in CCD imagers

    DOEpatents

    Turko, B.T.; Yates, G.J.

    1992-06-09

    An electronic method for eliminating artifacts in a video camera employing a charge coupled device (CCD) as an image sensor is disclosed. The method comprises the step of initializing the camera prior to normal read out and includes a first dump cycle period for transferring radiation generated charge into the horizontal register while the decaying image on the phosphor being imaged is being integrated in the photosites, and a second dump cycle period, occurring after the phosphor image has decayed, for rapidly dumping unwanted smear charge which has been generated in the vertical registers. Image charge is then transferred from the photosites and to the vertical registers and read out in conventional fashion. The inventive method allows the video camera to be used in environments having high ionizing radiation content, and to capture images of events of very short duration and occurring either within or outside the normal visual wavelength spectrum. Resultant images are free from ghost, smear and smear phenomena caused by insufficient opacity of the registers and, and are also free from random damage caused by ionization charges which exceed the charge limit capacity of the photosites. 3 figs.

  12. Method for eliminating artifacts in CCD imagers

    DOEpatents

    Turko, Bojan T.; Yates, George J.

    1992-01-01

    An electronic method for eliminating artifacts in a video camera (10) employing a charge coupled device (CCD) (12) as an image sensor. The method comprises the step of initializing the camera (10) prior to normal read out and includes a first dump cycle period (76) for transferring radiation generated charge into the horizontal register (28) while the decaying image on the phosphor (39) being imaged is being integrated in the photosites, and a second dump cycle period (78), occurring after the phosphor (39) image has decayed, for rapidly dumping unwanted smear charge which has been generated in the vertical registers (32). Image charge is then transferred from the photosites (36) and (38) to the vertical registers (32) and read out in conventional fashion. The inventive method allows the video camera (10) to be used in environments having high ionizing radiation content, and to capture images of events of very short duration and occurring either within or outside the normal visual wavelength spectrum. Resultant images are free from ghost, smear and smear phenomena caused by insufficient opacity of the registers (28) and (32), and are also free from random damage caused by ionization charges which exceed the charge limit capacity of the photosites (36) and (37).

  13. Automating Traceability for Generated Software Artifacts

    NASA Technical Reports Server (NTRS)

    Richardson, Julian; Green, Jeffrey

    2004-01-01

    Program synthesis automatically derives programs from specifications of their behavior. One advantage of program synthesis, as opposed to manual coding, is that there is a direct link between the specification and the derived program. This link is, however, not very fine-grained: it can be best characterized as Program is-derived- from Specification. When the generated program needs to be understood or modified, more $ne-grained linking is useful. In this paper, we present a novel technique for automatically deriving traceability relations between parts of a specification and parts of the synthesized program. The technique is very lightweight and works -- with varying degrees of success - for any process in which one artifact is automatically derived from another. We illustrate the generality of the technique by applying it to two kinds of automatic generation: synthesis of Kalman Filter programs from speci3cations using the Aut- oFilter program synthesis system, and generation of assembly language programs from C source code using the GCC C compilel: We evaluate the effectiveness of the technique in the latter application.

  14. A preventive dental care programme at the workplace.

    PubMed

    Westerman, B

    1993-06-01

    Employees from an industrial group in Brisbane were examined at the workplace and found to have generally low levels of dental disease. At the same time, the Australian Bureau of Statistics suggests that less than 45 per cent of Australians attend a dentist annually. This low attendance for regular dental care reduces the effectiveness of any preventive dental service. A pilot scheme of preventive dental care was provided for employees at the workplace in Brisbane. The aim of the programme was to provide regular health counselling and reinforcement of oral health activities, general dental information, regular prophylaxis, scaling and cleaning, and referrals for restorative care. The preventive programme was appropriate given the disease levels. The services were effective in improving the periodontal status and restorative care which resulted from referrals. As well, the preventive dental care programme proved to be readily acceptable to both employees and management.

  15. Dental Implant Systems

    PubMed Central

    Oshida, Yoshiki; Tuna, Elif B.; Aktören, Oya; Gençay, Koray

    2010-01-01

    Among various dental materials and their successful applications, a dental implant is a good example of the integrated system of science and technology involved in multiple disciplines including surface chemistry and physics, biomechanics, from macro-scale to nano-scale manufacturing technologies and surface engineering. As many other dental materials and devices, there are crucial requirements taken upon on dental implants systems, since surface of dental implants is directly in contact with vital hard/soft tissue and is subjected to chemical as well as mechanical bio-environments. Such requirements should, at least, include biological compatibility, mechanical compatibility, and morphological compatibility to surrounding vital tissues. In this review, based on carefully selected about 500 published articles, these requirements plus MRI compatibility are firstly reviewed, followed by surface texturing methods in details. Normally dental implants are placed to lost tooth/teeth location(s) in adult patients whose skeleton and bony growth have already completed. However, there are some controversial issues for placing dental implants in growing patients. This point has been, in most of dental articles, overlooked. This review, therefore, throws a deliberate sight on this point. Concluding this review, we are proposing a novel implant system that integrates materials science and up-dated surface technology to improve dental implant systems exhibiting bio- and mechano-functionalities. PMID:20480036

  16. Loss of Alloy in Cast Restorations Fabricated by Dental Students.

    ERIC Educational Resources Information Center

    Soh, George

    1991-01-01

    A study investigated the quantity of alloy lost in the fabrication of three types of cast restoration by dental students, and identified the proportion of loss at each of the four principal stages of the fabrication process. Suggestions for reducing metal loss and related costs in dental schools are offered. (MSE)

  17. [Dental implants in tooth grinders].

    PubMed

    Lobbezoo, F; Brouwers, J E; Cune, M S; Naeije, M

    2004-03-01

    Bruxism (tooth grinding and clenching) is generally considered a contraindication for dental implants, although the evidence is usually based on clinical experience only. So far, studies to the possible cause-and-effect relationship between bruxism and implant failure do not yield consistent and specific outcomes. This is partly due to the large variation in the technical and the biological aspects of the investigations. Although there is still no proof that bruxism causes overload of dental implants and their suprastructures, a careful approach is recommended. Practical advices as to minimize the chance of implant failure are given. Besides the recommendation to reduce or eliminate bruxism itself, these advices concern the number and dimensions of the implants, the design of the occlusion and articulation patterns, and the use of a hard nightguard. PMID:15058243

  18. Artifacts interfering with interpretation of cone beam computed tomography images.

    PubMed

    Makins, Scott R

    2014-07-01

    Artifacts in radiographic imaging are discrepancies between the reconstructed visual image and the content of the subject. In radiographic imaging, this means the grayscale values in the image do not accurately reflect the attenuation values of the subject. Structures may also appear that do not exist in the subject. Whatever the source or appearance of image artifacts, their presence degrades the accuracy of the image in relation to the true characteristics of the subject. One should therefore be aware of the presence of artifacts and be familiar with their characteristic appearances in order to enhance the extraction of diagnostic information.

  19. Reduction of phase artifacts in differential phase contrast computed tomography.

    PubMed

    Jerjen, Iwan; Revol, Vincent; Schuetz, Philipp; Kottler, Christian; Kaufmann, Rolf; Luethi, Thomas; Jefimovs, Konstantins; Urban, Claus; Sennhauser, Urs

    2011-07-01

    X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer setup allows visualizing the three-dimensional distribution of the refractive index by measuring the shifts of an interference pattern due to phase variations of the X-ray beam. Unfortunately, severe reconstruction artifacts appear in the presence of differential phase wrapping and clipping. In this paper, we propose to use the attenuation contrast, which is obtained from the same measurement, for correcting the DPC signal. Using the example of a DPC CT measurement with pronounced phase artifacts, we will discuss the efficiency of our phase artifact correction method. PMID:21747516

  20. Computed Tomography Imaging Artifact Simulating Type A Aortic Dissection

    PubMed Central

    Chou, Alan S.; Ziganshin, Bulat A.; Elefteriades, John A.

    2016-01-01

    Contrast-enhanced computed tomography (CT) is an effective tool for assessment of thoracic aortic disease in the modern era. Here, we describe a case of Type A aortic dissection incidentally detected by CT in a 63-year old man. Upon more precise imaging with electrocardiography (ECG)-gated CT, the dissection vanished, revealing it to be an aortic motion artifact. This report highlights the importance of motion artifacts mimicking a dissection flap. CT imaging gated with ECG can distinguish a dissection flap from an artifact.

  1. Gagging and Associations with Dental Care-Related Fear, Fear of Pain, and Beliefs about Treatment

    PubMed Central

    Randall, Cameron L.; Shulman, Grant P.; Crout, Richard J.; McNeil, Daniel W.

    2014-01-01

    Background Gagging is a behavioral response that interferes with oral health care and has been suggested to relate to dental care-related fear. Little is known, however, about the epidemiology of gagging during dental treatment. Methods To explore this phenomenon, 478 participants were recruited from the waiting area of an oral diagnosis clinic. Participants completed the Dental Fear Survey, the Short Form-Fear of Pain Questionnaire, Dental Beliefs Scale, and a demographics questionnaire that included items about problems with gagging. Results Over half of the participants reported gagging on at least one occasion during dental visits, with 7.5% almost always, or always gagging. With higher frequency of problems with gagging, patients were more likely to have greater levels of dental care-related fear, fear of pain, and more negative beliefs of dental professionals and dental treatment. Further, participants who gagged more readily had greater dental care-related fear than other gaggers. Conclusion Gagging in the dental clinic is a prevalent problem, and dental care-related fear and fear of pain are associated with more frequent gagging. Clinical Implications Given the prevalence of patients reporting problem gagging, it may be helpful for providers to assess for this barrier to treatment. By targeting dental care-related fear, fear of pain, and negative beliefs about dental care in patients who often gag in the clinic, gagging may be reduced in frequency or intensity, potentially making treatment more comfortable for patients and easier for dental care providers. PMID:24789238

  2. Craniofacial and Dental Findings in Cystinosis

    PubMed Central

    Bassim, CW; Gautam, P; Domingo, DL; Balog, JZ; Guadagnini, JP; Gahl, WA; Hart, TC

    2009-01-01

    Objectives Cystinosis is a rare autosomal recessive lysosomal storage disorder with developmental and mineralization anomalies as part of its clinical presentation. The objective of this study was to provide the first systematic assessment of the craniofacial and dental characteristics associated with cystinosis. Study Design Oral and radiographic evaluations were performed on 73 patients with cystinosis. Analyses of cephalometry (n=20), taurodontism (n=47), caries (n=47), enamel defects (n=48), soft tissue anomalies (n=48), and dental age (n=41) were performed on the cystinosis group, and compared with age- and sex- comparable controls or standards. Results Cystinosis patients manifested relative mandibular deficiency, an increased facial height, and a reduced airway space. Taurodontism and enamel defects were significantly more prevalent in cystinosis patients compared with controls (p<0.0001 and p=0.027, respectively). Children (aged < 15 years) with cystinosis also demonstrated a significant delay, of almost 9 months, of their dental development (p<0.001). Conclusion Novel craniofacial and dental features are associated with cystinosis. Craniofacial deficiencies may influence the swallowing and respiratory complications seen in cystinosis. Renal pathology and associated mineral imbalance may explain the dental root and enamel anomalies found in cystinosis patients; the developmental delays in cystinosis include delayed dental formation. PMID:20233313

  3. Development of a new metal artifact reduction algorithm by using an edge preserving method for CBCT imaging

    NASA Astrophysics Data System (ADS)

    Kim, Juhye; Nam, Haewon; Lee, Rena

    2015-07-01

    CT (computed tomography) images, metal materials such as tooth supplements or surgical clips can cause metal artifact and degrade image quality. In severe cases, this may lead to misdiagnosis. In this research, we developed a new MAR (metal artifact reduction) algorithm by using an edge preserving filter and the MATLAB program (Mathworks, version R2012a). The proposed algorithm consists of 6 steps: image reconstruction from projection data, metal segmentation, forward projection, interpolation, applied edge preserving smoothing filter, and new image reconstruction. For an evaluation of the proposed algorithm, we obtained both numerical simulation data and data for a Rando phantom. In the numerical simulation data, four metal regions were added into the Shepp Logan phantom for metal artifacts. The projection data of the metal-inserted Rando phantom were obtained by using a prototype CBCT scanner manufactured by medical engineering and medical physics (MEMP) laboratory research group in medical science at Ewha Womans University. After these had been adopted the proposed algorithm was performed, and the result were compared with the original image (with metal artifact without correction) and with a corrected image based on linear interpolation. Both visual and quantitative evaluations were done. Compared with the original image with metal artifacts and with the image corrected by using linear interpolation, both the numerical and the experimental phantom data demonstrated that the proposed algorithm reduced the metal artifact. In conclusion, the evaluation in this research showed that the proposed algorithm outperformed the interpolation based MAR algorithm. If an optimization and a stability evaluation of the proposed algorithm can be performed, the developed algorithm is expected to be an effective tool for eliminating metal artifacts even in commercial CT systems.

  4. Statistical characteristics of streak artifacts on CT images: relationship between streak artifacts and mA s values.

    PubMed

    Imai, Kuniahru; Ikeda, Mitsuru; Enchi, Yukihiro; Niimi, Takanaga

    2009-02-01

    The purpose of this study is to investigate how streak artifacts on computed tomography (CT) images vary with reduction in radiation doses by assessing the quantitative relationship between the streak artifacts and milliampere-time product (mA s) values. A commercially available chest phantom was used to measure the streak artifacts on the CT images obtained using a 4- and 16-multidetector-row helical CT scanners with various mA s values at a constant tube voltage of 120 kVp. The cardiac slice image was employed as a target image for evaluating the streak artifacts on the CT image. Eighty parallel line segments with a length of 20 pixels were placed perpendicular to numerous streak artifacts on the cardiac slice image, and the largest difference between adjacent CT values in each of the 80 CT-value profiles of these line segments was employed as a feature variable of streak artifacts; these feature variables have been analyzed by the extreme value theory. The largest difference between adjacent CT values in each CT-value profile can be statistically modeled by a Gumbel distribution. Further, the maximum level of streak artifacts on CT images that will be tolerated for clinical use and low-dose CT screening examination was expected to be estimated using the location parameter in the Gumbel distribution.

  5. Education About Dental Hygienists' Roles in Public Dental Prevention Programs: Dental and Dental Hygiene Students' and Faculty Members' and Dental Hygienists' Perspectives.

    PubMed

    Pervez, Anushey; Kinney, Janet S; Gwozdek, Anne; Farrell, Christine M; Inglehart, Marita R

    2016-09-01

    In 2005, Public Act No. 161 (PA 161) was passed in Michigan, allowing dental hygienists to practice in approved public dental prevention programs to provide services for underserved populations while utilizing a collaborative agreement with a supervising dentist. The aims of this study were to assess how well dental and dental hygiene students and faculty members and practicing dental hygienists have been educated about PA 161, what attitudes and knowledge about the act they have, and how interested they are in additional education about it. University of Michigan dental and dental hygiene students and faculty members, students in other Michigan dental hygiene programs, and dental hygienists in the state were surveyed. Respondents (response rate) were 160 dental students (50%), 63 dental hygiene students (82%), 30 dental faculty members (26%), and 12 dental hygiene faculty members (52%) at the University of Michigan; 143 dental hygiene students in other programs (20%); and 95 members of the Michigan Dental Hygienists' Association (10%). The results showed that the dental students were less educated about PA 161 than the dental hygiene students, and the dental faculty members were less informed than the dental hygiene faculty members and dental hygienists. Responding dental hygiene faculty members and dental hygienists had more positive attitudes about PA 161 than did the students and dental faculty members. Most of the dental hygiene faculty members and dental hygienists knew a person providing services in a PA 161 program. Most dental hygiene students, faculty members, and dental hygienists wanted more education about PA 161. Overall, the better educated about the program the respondents were, the more positive their attitudes, and the more interested they were in learning more. PMID:27587574

  6. [Reduction of accompanied deployment failure artifacts using a thick slice sensitivity map to assist with array spatial sensitivity encoding technique imaging].

    PubMed

    Fujita, Takushi; Watanabe, Takayuki; Kihara, Shou

    2014-08-01

    The array spatial sensitivity encoding technique (ASSET) is a form of parallel imaging (PI). Another scan, called a reference scan (Ref) is required before acquiring the ASSET image. However, artifacts tend to interfere with recognition of the object due to differences between the ASSET scan and Ref. scan. This is because the liver is in contact with the diaphragm, making it susceptible to respiratory motion. Further, since the liver upper edge is surrounded by the lung field, there is a risk of susceptibility artifacts. The purpose of this study was to reduce the accompanied deployment failure artifact using a thick slice sensitivity map. Our data showed it was possible to reduce accompanied deployment failure artifacts, as well as to suppress noise, by increasing the slice thickness of the Ref scan.

  7. Investigating the effect of modifying the EEG cap lead configuration on the gradient artifact in simultaneous EEG-fMRI.

    PubMed

    Mullinger, Karen J; Chowdhury, Muhammad E H; Bowtell, Richard

    2014-01-01

    EEG data recorded during simultaneous fMRI are contaminated by large voltages generated by time-varying magnetic field gradients. Correction of the resulting gradient artifact (GA) generally involves low-pass filtering to attenuate the high-frequency voltage fluctuations of the GA, followed by subtraction of a GA template produced by averaging over repeats of the artifact waveforms. This average artifact subtraction (AAS) process relies on the EEG amplifier having a large enough dynamic range to characterize the artifact voltages and on invariance of the artifact waveform over repeated image acquisitions. Saturation of the amplifiers and changes in subject position can leave unwanted residual GA after AAS. Previous modeling work suggested that modifying the lead layout and the exit position of the cable bundle on the EEG cap could reduce the GA amplitude. Here, we used simulations and experiments to evaluate the effect of modifying the lead paths on the magnitude of the GA and on the residual artifact after AAS. The modeling work showed that for wire paths following great circles, the smallest overall GA occurs when the leads converge at electrode Cz. The performance of this new cap design was compared with a standard cap in experiments on a spherical agar phantom and human subjects. Using gradient pulses applied separately along the three Cartesian axes, we found that the GA due to the foot-head gradient was most significantly reduced relative to a standard cap for the phantom, whereas the anterior-posterior GA was most attenuated for human subjects. In addition, there was an overall 37% reduction in the RMS GA amplitude produced by a standard EPI sequence when comparing the two caps on the phantom. In contrast, the subjects showed an 11% increase in the average RMS of the GA. This work shows that the optimal design reduces the GA on a spherical phantom however; these gains are not translated to human subjects, probably due to the differences in geometry. PMID

  8. Artifact Diamond Its Allure And Significance

    NASA Astrophysics Data System (ADS)

    Yoder, Max N.

    1989-01-01

    While the preponderance of the mechanical, optical, and electronic properties of natural diamond have been known for over a decade, only recently has artifact diamond in technologically useful form factors become an exciting possibility. The advent of sacrificial, lattice matched crystalline substrates provides the basis not only for semiconducting applications of diamond, but for optical mirrors, lenses, and windows as well. As a semiconductor, diamond has the highest resistivity, the highest saturated electron velocity, the highest thermal conductivity, the lowest dielectric constant, the highest dielectric strength, the greatest hardness, the largest bandgap and the smallest lattice constant of any material. It also has electron and hole mobilities greater than those of silicon. Its figure of merit as a microwave power amplifier is unexcelled and exceeds that of silicon by a multiplier of 8200. For integrated circuit potential, its thermal conductivity, saturated velocity, and dielectric constant also place it in the premier position (32 times that of silicon, 46 times that of GaAs). Although not verified, its radiation hardness should also be unmatched. Aside from its brilliant sparkle as a gemstone, there has been little use of diamond in the field of optics. Processing of the diamond surface now appears to be as simple as that of any other material --albeit with different techniques. In fact, it may be possible to etch diamond far more controllably (at economically viable rates) than any other material as the product of the etch is gaseous and the etched trough is self-cleaning. Other properties of diamond make it an ideal optical material. Among them are its unmatched thermal conductivity, its extremely low absorption loss above 228 nanometers, and unmatched Young's modulus, Poisson's ratio, tensile strength, hardness, thermal shock, and modulus of elasticity. If the recently-found mechanisms by which erbium impurities in III-V junctions can be made to "lase

  9. Analytic solutions of an unclassified artifact /

    SciTech Connect

    Trent, Bruce C.

    2012-03-01

    This report provides the technical detail for analytic solutions for the inner and outer profiles of the unclassified CMM Test Artifact (LANL Part Number 157Y-700373, 5/03/2001) in terms of radius and polar angle. Furthermore, analytic solutions are derived for the legacy Sheffield measurement hardware, also in terms of radius and polar angle, using part coordinates, i.e., relative to the analytic profile solutions obtained. The purpose of this work is to determine the exact solution for the “cosine correction” term inherent to measurement with the Sheffield hardware. The cosine correction is required in order to interpret the actual measurements taken by the hardware in terms of an actual part definition, or “knot-point spline definition,” that typically accompanies a component drawing. Specifically, there are two portions of the problem: first an analytic solution must be obtained for any point on the part, e.g., given the radii and the straight lines that define the part, it is required to find an exact solution for the inner and outer profile for any arbitrary polar angle. Next, the problem of the inspection of this part must be solved, i.e., given an arbitrary sphere (representing the inspection hardware) that comes in contact with the part (inner and outer profiles) at any arbitrary polar angle, it is required to determine the exact location of that intersection. This is trivial for the case of concentric circles. In the present case, however, the spherical portion of the profiles is offset from the defined center of the part, making the analysis nontrivial. Here, a simultaneous solution of the part profiles and the sphere was obtained.

  10. Dental Pulp Defence and Repair Mechanisms in Dental Caries.

    PubMed

    Farges, Jean-Christophe; Alliot-Licht, Brigitte; Renard, Emmanuelle; Ducret, Maxime; Gaudin, Alexis; Smith, Anthony J; Cooper, Paul R

    2015-01-01

    Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

  11. Dental Pulp Defence and Repair Mechanisms in Dental Caries

    PubMed Central

    Farges, Jean-Christophe; Alliot-Licht, Brigitte; Renard, Emmanuelle; Ducret, Maxime; Gaudin, Alexis; Smith, Anthony J.; Cooper, Paul R.

    2015-01-01

    Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo. PMID:26538821

  12. Pulse transducer with artifact signal attenuator. [heart rate sensors

    NASA Technical Reports Server (NTRS)

    Cash, W. H., Jr.; Polhemus, J. T. (Inventor)

    1980-01-01

    An artifact signal attenuator for a pulse rate sensor is described. The circuit for attenuating background noise signals is connected with a pulse rate transducer which has a light source and a detector for light reflected from blood vessels of a living body. The heart signal provided consists of a modulated dc signal voltage indicative of pulse rate. The artifact signal resulting from light reflected from the skin of the body comprises both a constant dc signal voltage and a modulated dc signal voltage. The amplitude of the artifact signal is greater and the frequency less than that of the heart signal. The signal attenuator circuit includes an operational amplifier for canceling the artifact signal from the output signal of the transducer and has the capability of meeting packaging requirements for wrist-watch-size packages.

  13. Miscellaneous artifacts relating to experiments with talking motion pictures about ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Miscellaneous artifacts relating to experiments with talking motion pictures about 1912 and to loudspeaking phonographs in the 1920s, third floor. - Thomas A. Edison Laboratories, Building No. 5, Main Street & Lakeside Avenue, West Orange, Essex County, NJ

  14. Optical interference artifacts in contact atomic force microscopy images.

    PubMed

    Méndez-Vilas, A; González-Martin, M L; Nuevo, M J

    2002-08-01

    Atomic force microscopy images are usually affected by different kinds of artifacts due to either the microscope design and operation mode or external environmental factors. Optical interferences between the laser light reflected off the top of the cantilever and the light scattered by the surface in the same direction is one of the most frequent sources of height artifact in contact (and occasionally non-contact) images. They are present when imaging highly reflective surfaces, or even when imaging non-reflective materials deposited onto reflective ones. In this study interference patterns have been obtained with a highly polished stainless steel planchet. The influence of these artifacts in surface roughness measurements is discussed, and a semi-quantitative method based on the fast Fourier transform technique is proposed to remove the artifacts from the images. This method improves the results obtained by applying the usual flattening routines.

  15. Dental Assisting Program Guide.

    ERIC Educational Resources Information Center

    Georgia Univ., Athens. Dept. of Vocational Education.

    This program guide contains the standard dental assisting curriculum for technical institutes in Georgia. The curriculum encompasses the minimum competencies required for entry-level dental assistants, and includes job skills in the technical areas of preventive dentistry; four-handed dentistry; chairside assisting with emphasis in diagnostics,…

  16. Dental Charting. Student's Manual.

    ERIC Educational Resources Information Center

    Weaver, Trudy Karlene; Apfel, Maura

    This manual is part of a series dealing with skills and information needed by students in dental assisting. The individualized student materials are suitable for classroom, laboratory, or cooperative training programs. This student manual contains four units covering the following topics: dental anatomical terminology; tooth numbering systems;…

  17. Dental Laboratory Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document, which is designed for use in developing a tech prep competency profile for the occupation of dental laboratory technician, lists technical competencies and competency builders for 13 units pertinent to the health technologies cluster in general and 8 units to the occupation of dental laboratory technician. The following skill areas…

  18. Optimization-based reconstruction for reduction of CBCT artifact in IGRT

    NASA Astrophysics Data System (ADS)

    Xia, Dan; Zhang, Zheng; Paysan, Pascal; Seghers, Dieter; Brehm, Marcus; Munro, Peter; Sidky, Emil Y.; Pelizzari, Charles; Pan, Xiaochuan

    2016-04-01

    Kilo-voltage cone-beam computed tomography (CBCT) plays an important role in image guided radiation therapy (IGRT) by providing 3D spatial information of tumor potentially useful for optimizing treatment planning. In current IGRT CBCT system, reconstructed images obtained with analytic algorithms, such as FDK algorithm and its variants, may contain artifacts. In an attempt to compensate for the artifacts, we investigate optimization-based reconstruction algorithms such as the ASD-POCS algorithm for potentially reducing arti- facts in IGRT CBCT images. In this study, using data acquired with a physical phantom and a patient subject, we demonstrate that the ASD-POCS reconstruction can significantly reduce artifacts observed in clinical re- constructions. Moreover, patient images reconstructed by use of the ASD-POCS algorithm indicate a contrast level of soft-tissue improved over that of the clinical reconstruction. We have also performed reconstructions from sparse-view data, and observe that, for current clinical imaging conditions, ASD-POCS reconstructions from data collected at one half of the current clinical projection views appear to show image quality, in terms of spatial and soft-tissue-contrast resolution, higher than that of the corresponding clinical reconstructions.

  19. Removing movement artifacts from equine ECG recordings acquired with textile electrodes.

    PubMed

    Lanata, Antonio; Guidi, Andrea; Baragli, Paolo; Paradiso, Rita; Valenza, Gaetano; Scilingo, Enzo Pasquale

    2015-08-01

    This study reports on the implementation of a novel system to detect and reduce movement artifact (MA) contribution in electrocardiogram (ECG) recordings acquired from horses in free movement conditions. The system comprises both integrated textile electrodes for ECG acquisition and one triaxial accelerometer for movement monitoring. Here, ECG and physical activity are continuously acquired from seven horses through the wearable system and a model that integrates cardiovascular and movement information to estimate the MA contribution is implemented. Moreover, in this study we propose a new algorithm where the Stationary Wavelet Transform (SWT) decomposition algorithm is employed to identify and remove movement artifacts from ECG recodigns. Achieved results showed a reduction of MA percentage greater than 40% between before- and after- the application of the proposed algorithm to seven hours of recordings. PMID:26736667

  20. [An adaptive scaling hybrid algorithm for reduction of CT artifacts caused by metal objects].

    PubMed

    Chen, Yu; Luo, Hai; Zhou, He-qin

    2009-03-01

    A new adaptively hybrid filtering algorithm is proposed to reduce the artifacts caused by metal in CT image. Firstly, the method is used to preprocess the projection data of metal region and is reconstruct by filtered back projection (FBP) method. Then the expectation maximization algorithm (EM) is performed on the iterative original metal project data. Finally, a compensating procedure is applied to the reconstructed metal region. The simulation result has demonstrated that the proposed algorithm can remove the metal artifacts and keep the structure information of metal object effectively. It ensures that the tissues around the metal will not be distorted. The method is also computational efficient and effective for the CT images which contains several metal objects.

  1. Use of multiscale entropy to facilitate artifact detection in electroencephalographic signals.

    PubMed

    Mariani, Sara; Borges, Ana F T; Henriques, Teresa; Goldberger, Ary L; Costa, Madalena D

    2015-01-01

    Electroencephalographic (EEG) signals present a myriad of challenges to analysis, beginning with the detection of artifacts. Prior approaches to noise detection have utilized multiple techniques, including visual methods, independent component analysis and wavelets. However, no single method is broadly accepted, inviting alternative ways to address this problem. Here, we introduce a novel approach based on a statistical physics method, multiscale entropy (MSE) analysis, which quantifies the complexity of a signal. We postulate that noise corrupted EEG signals have lower information content, and, therefore, reduced complexity compared with their noise free counterparts. We test the new method on an open-access database of EEG signals with and without added artifacts due to electrode motion. PMID:26738116

  2. Two-level optical coherence tomography scheme for suppressing spectral saturation artifacts.

    PubMed

    Wu, Chiung-Ting; Tsai, Meng-Tsan; Lee, Cheng-Kuang

    2014-01-01

    We demonstrate a novel method for reducing saturation artifacts in spectral-domain optical coherence tomography (SD-OCT) systems. This method is based on a two-level SD-OCT system with a dual-line charge-coupled device (CCD) camera. We compensate the saturated signal detected by the first line using the unsaturated signal detected by the second line. The Fourier transform of the compensated spectrum shows effective suppression of saturation artifacts. This method was also successfully performed on phantom material and skin on a human finger. Our method causes neither back-scattering power loss nor signal-to-noise ratio (SNR) degradation. The only difference between the traditional system and our two-level system is our utilization of the dual-line CCD camera; no additional devices or complex designs are needed. PMID:25068864

  3. Removing movement artifacts from equine ECG recordings acquired with textile electrodes.

    PubMed

    Lanata, Antonio; Guidi, Andrea; Baragli, Paolo; Paradiso, Rita; Valenza, Gaetano; Scilingo, Enzo Pasquale

    2015-01-01

    This study reports on the implementation of a novel system to detect and reduce movement artifact (MA) contribution in electrocardiogram (ECG) recordings acquired from horses in free movement conditions. The system comprises both integrated textile electrodes for ECG acquisition and one triaxial accelerometer for movement monitoring. Here, ECG and physical activity are continuously acquired from seven horses through the wearable system and a model that integrates cardiovascular and movement information to estimate the MA contribution is implemented. Moreover, in this study we propose a new algorithm where the Stationary Wavelet Transform (SWT) decomposition algorithm is employed to identify and remove movement artifacts from ECG recodigns. Achieved results showed a reduction of MA percentage greater than 40% between before- and after- the application of the proposed algorithm to seven hours of recordings.

  4. Reduction of motion artifacts during in vivo two-photon imaging of brain through heartbeat triggered scanning.

    PubMed

    Paukert, Martin; Bergles, Dwight E

    2012-07-01

    Two-photon imaging of fluorescence in brain enables analysis of the structure and dynamic activity of neurons and glial cells in living animals. However, vital functions such as beating of the heart cause pulsations in brain tissue, leading to image distortion and loss of resolution. We find that synchronizing imaging scans to the cardiac cycle reduces motion artifacts, significantly improving the resolution of cellular structures. By interlacing multiple heartbeat triggered imaging scans, it was possible to image large brain volumes with negligible distortion. This approach can be readily incorporated into conventional microscopes to achieve substantial reductions in motion artifacts during two-photon imaging.

  5. Accuracy and artifact: reexamining the intensity bias in affective forecasting.

    PubMed

    Levine, Linda J; Lench, Heather C; Kaplan, Robin L; Safer, Martin A

    2012-10-01

    Research on affective forecasting shows that people have a robust tendency to overestimate the intensity of future emotion. We hypothesized that (a) people can accurately predict the intensity of their feelings about events and (b) a procedural artifact contributes to people's tendency to overestimate the intensity of their feelings in general. People may misinterpret the forecasting question as asking how they will feel about a focal event, but they are later asked to report their feelings in general without reference to that event. In the current investigation, participants predicted and reported both their feelings in general and their feelings about an election outcome (Study 1) and an exam grade (Study 3). We also assessed how participants interpreted forecasting questions (Studies 2 and 4) and conducted a meta-analysis of affective forecasting research (Study 5). The results showed that participants accurately predicted the intensity of their feelings about events. They overestimated only when asked to predict how they would feel in general and later report their feelings without reference to the focal event. Most participants, however, misinterpreted requests to predict their feelings in general as asking how they would feel when they were thinking about the focal event. Clarifying the meaning of the forecasting question significantly reduced overestimation. These findings reveal that people have more sophisticated self-knowledge than is commonly portrayed in the affective forecasting literature. Overestimation of future emotion is partly due to a procedure in which people predict one thing but are later asked to report another.

  6. The future dental workforce?

    PubMed

    Gallagher, J E; Wilson, N H F

    2009-02-28

    The Editor-in-Chief of the BDJ has previously raised important questions about dental workforce planning and the implications for dental graduates of recent changes and pressures. It is now time to revisit this issue. Much has changed since the last workforce review in England and Wales, and the rate of change is in all probability set to increase. First, at the time of writing this paper the momentous step of including dental care professionals (DCPs) on General Dental Council (GDC) registers in the United Kingdom has recently been completed. Second, the Scope of Practice of all dental professionals has been under consultation by the General Dental Council, and research evidence suggests that greater use should be made of skill-mix in the dental team. Third, within England, Lord Darzi has just published the 'Final Report of the NHS Next Stage Review', which emphasises 'quality care' and 'team-working' as key features of healthcare; this report was accompanied by an important document entitled 'A High Quality Workforce', in which plans for local workforce planning within the NHS are outlined, placing responsibilities at national, local and regional levels. Fourth, policy makers across the UK are wrestling with addressing oral health needs, promoting health and facilitating access to dental care, all of which have implications for the nature and shape of the dental workforce. Fifth, with the impact of globalisation and European policies we are net gainers of dentists as well as having more in training. Sixth, although there have been reviews and policy initiatives by regulatory, professional and other bodies in support of shaping the dental workforce, there has been little serious consideration of skill-mix and funding mechanisms to encourage team-working. Together, these events demand that we enter a fresh debate on the future dental workforce which should extend beyond professional and national boundaries and inform workforce planning. This debate is of great

  7. The future dental workforce?

    PubMed

    Gallagher, J E; Wilson, N H F

    2009-02-28

    The Editor-in-Chief of the BDJ has previously raised important questions about dental workforce planning and the implications for dental graduates of recent changes and pressures. It is now time to revisit this issue. Much has changed since the last workforce review in England and Wales, and the rate of change is in all probability set to increase. First, at the time of writing this paper the momentous step of including dental care professionals (DCPs) on General Dental Council (GDC) registers in the United Kingdom has recently been completed. Second, the Scope of Practice of all dental professionals has been under consultation by the General Dental Council, and research evidence suggests that greater use should be made of skill-mix in the dental team. Third, within England, Lord Darzi has just published the 'Final Report of the NHS Next Stage Review', which emphasises 'quality care' and 'team-working' as key features of healthcare; this report was accompanied by an important document entitled 'A High Quality Workforce', in which plans for local workforce planning within the NHS are outlined, placing responsibilities at national, local and regional levels. Fourth, policy makers across the UK are wrestling with addressing oral health needs, promoting health and facilitating access to dental care, all of which have implications for the nature and shape of the dental workforce. Fifth, with the impact of globalisation and European policies we are net gainers of dentists as well as having more in training. Sixth, although there have been reviews and policy initiatives by regulatory, professional and other bodies in support of shaping the dental workforce, there has been little serious consideration of skill-mix and funding mechanisms to encourage team-working. Together, these events demand that we enter a fresh debate on the future dental workforce which should extend beyond professional and national boundaries and inform workforce planning. This debate is of great

  8. Interactions between magnetic resonance imaging and dental material

    PubMed Central

    Mathew, Chalakuzhiyl Abraham; Maller, Sudhakara; Maheshwaran

    2013-01-01

    Magnetic resonance imaging (MRI) has become a common and important life-saving diagnostic tool in recent times, for diseases of the head and neck region. Dentists should be aware of the interactions of various restorative dental materials and different technical factors put to use by an MRI scanning machine. Specific knowledge about these impacts, at the dentist level and at the level of the personnel at the MRI centers can save valuable time for the patient and prevent errors in MRI images. Artifacts from metal restorations are a major hindrance at such times, as they result in disappearance or distortion of the image and loss of important information. PMID:23946562

  9. Detection of eye blink artifacts from single prefrontal channel electroencephalogram.

    PubMed

    Chang, Won-Du; Cha, Ho-Seung; Kim, Kiwoong; Im, Chang-Hwan

    2016-02-01

    Eye blinks are one of the most influential artifact sources in electroencephalogram (EEG) recorded from frontal channels, and thereby detecting and rejecting eye blink artifacts is regarded as an essential procedure for improving the quality of EEG data. In this paper, a novel method to detect eye blink artifacts from a single-channel frontal EEG signal was proposed by combining digital filters with a rule-based decision system, and its performance was validated using an EEG dataset recorded from 24 healthy participants. The proposed method has two main advantages over the conventional methods. First, it uses single-channel EEG data without the need for electrooculogram references. Therefore, this method could be particularly useful in brain-computer interface applications using headband-type wearable EEG devices with a few frontal EEG channels. Second, this method could estimate the ranges of eye blink artifacts accurately. Our experimental results demonstrated that the artifact range estimated using our method was more accurate than that from the conventional methods, and thus, the overall accuracy of detecting epochs contaminated by eye blink artifacts was markedly increased as compared to conventional methods. The MATLAB package of our library source codes and sample data, named Eyeblink Master, is open for free download.

  10. Sampling artifact in volume weighted velocity measurement. I. Theoretical modeling

    NASA Astrophysics Data System (ADS)

    Zhang, Pengjie; Zheng, Yi; Jing, Yipeng

    2015-02-01

    Cosmology based on large scale peculiar velocity prefers volume weighted velocity statistics. However, measuring the volume weighted velocity statistics from inhomogeneously distributed galaxies (simulation particles/halos) suffers from an inevitable and significant sampling artifact. We study this sampling artifact in the velocity power spectrum measured by the nearest particle velocity assignment method by Zheng et al., [Phys. Rev. D 88, 103510 (2013).]. We derive the analytical expression of leading and higher order terms. We find that the sampling artifact suppresses the z =0 E -mode velocity power spectrum by ˜10 % at k =0.1 h /Mpc , for samples with number density 10-3 (Mpc /h )-3 . This suppression becomes larger for larger k and for sparser samples. We argue that this source of systematic errors in peculiar velocity cosmology, albeit severe, can be self-calibrated in the framework of our theoretical modelling. We also work out the sampling artifact in the density-velocity cross power spectrum measurement. A more robust evaluation of related statistics through simulations will be presented in a companion paper by Zheng et al., [Sampling artifact in volume weighted velocity measurement. II. Detection in simulations and comparison with theoretical modelling, arXiv:1409.6809.]. We also argue that similar sampling artifact exists in other velocity assignment methods and hence must be carefully corrected to avoid systematic bias in peculiar velocity cosmology.

  11. Inference and coherence in causal-based artifact categorization.

    PubMed

    Puebla, Guillermo; Chaigneau, Sergio E

    2014-01-01

    In four experiments, we tested conditions under which artifact concepts support inference and coherence in causal categorization. In all four experiments, participants categorized scenarios in which we systematically varied information about artifacts' associated design history, physical structure, user intention, user action and functional outcome, and where each property could be specified as intact, compromised or not observed. Consistently across experiments, when participants received complete information (i.e., when all properties were observed), they categorized based on individual properties and did not show evidence of using coherence to categorize. In contrast, when the state of some property was not observed, participants gave evidence of using available information to infer the state of the unobserved property, which increased the value of the available information for categorization. Our data offers answers to longstanding questions regarding artifact categorization, such as whether there are underlying causal models for artifacts, which properties are part of them, whether design history is an artifact's causal essence, and whether physical appearance or functional outcome is the most central artifact property.

  12. Recognizing and avoiding artifacts in atomic force microscopy imaging.

    PubMed

    Canale, Claudio; Torre, Bruno; Ricci, Davide; Braga, Pier Carlo

    2011-01-01

    Atomic force microscopy (AFM) measurements could be affected by different kinds of artifacts; some of them derive from the improper use of the instrument and can be avoided by setting the correct experimental parameters and conditions. In other cases, distortions of the images acquired by AFM are intrinsically related to the operating principle of the instrument itself and to the kind of interactions taken into account for the reconstruction of the sample topography. A perfect knowledge of all the artifacts that can perturb AFM measurements is fundamental to avoid misleading interpretations of the results. In this chapter, all the most common sources of artifact are presented, and strategies to avoid them are proposed.Subheading 1 is a brief introduction to the chapter. In Subheading 2, the artifacts due to the interactions between the sample and the AFM tip are presented. Subheading 3 is focused on the deformations due to the AFM scanner nonlinear movements. The interaction with the environment surrounding the instrument can affect the quality of the AFM results and the environmental instability are discussed in Subheading 4. Subheading 5 shows the effects of an incorrect setting of the feedback gains or other parameters. Subheading 6 aims on the artifacts that can be produced by the improper use of the image processing software. Subheading 7 is a short guide on the test that can be done to easily recognize some of the artifacts previously described.

  13. Artifact-Based Transformation of IBM Global Financing

    NASA Astrophysics Data System (ADS)

    Chao, Tian; Cohn, David; Flatgard, Adrian; Hahn, Sandy; Linehan, Mark; Nandi, Prabir; Nigam, Anil; Pinel, Florian; Vergo, John; Wu, Frederick Y.

    IBM Global Financing (IGF) is transforming its business using the Business Artifact Method, an innovative business process modeling technique that identifies key business artifacts and traces their life cycles as they are processed by the business. IGF is a complex, global business operation with many business design challenges. The Business Artifact Method is a fundamental shift in how to conceptualize, design and implement business operations. The Business Artifact Method was extended to solve the problem of designing a global standard for a complex, end-to-end process while supporting local geographic variations. Prior to employing the Business Artifact method, process decomposition, Lean and Six Sigma methods were each employed on different parts of the financing operation. Although they provided critical input to the final operational model, they proved insufficient for designing a complete, integrated, standard operation. The artifact method resulted in a business operations model that was at the right level of granularity for the problem at hand. A fully functional rapid prototype was created early in the engagement, which facilitated an improved understanding of the redesigned operations model. The resulting business operations model is being used as the basis for all aspects of business transformation in IBM Global Financing.

  14. Dental amalgam--environmental aspects

    SciTech Connect

    Arenholt-Bindslev, D. )

    1992-09-01

    Increasing knowledge about the risk of toxic effects caused by anthropogenic mercury accumulation in ecosystems has resulted in a growing pressure for reduction of the discharge of mercury waste. Consequently, the mercury waste problems of dental clinics have been given increased attention, and restrictions on handling and discharge of contaminated waste have been established in several countries. Major amalgam particles from trituration surplus of those produced during the carving and burnishing of new amalgam restorations are generally collected in coarse filters and sold for refinement. Minor amalgam particles released by production of new fillings or by removal of old restorations partly sediment in tubes and drains. The remaining particles are carried with the waste water stream to the local purifying plant. In Scandinavia, the industrial discharge of mercury-contaminated waste water has been reduced to a minimum. According to recent investigations, dental clinics appear to be responsible for the major amount of mercury collected in the sludge generated in purifying plants. If threshold values for heavy metal content, including mercury, are exceeded, the sludge is not allowed to be recycled as fertilizer. Installation of an approved amalgam-separating apparatus in dental clinics is now mandatory in several countries--for example, Switzerland, Germany, Sweden, and Denmark. Approval of amalgam separators is based on national testing programs, including clinical or laboratory tests demanding 95-99% separating efficiency. 18 refs.

  15. What is dental ecology?

    PubMed

    Cuozzo, Frank P; Sauther, Michelle L

    2012-06-01

    Teeth have long been used as indicators of primate ecology. Early work focused on the links between dental morphology, diet, and behavior, with more recent years emphasizing dental wear, microstructure, development, and biogeochemistry, to understand primate ecology. Our study of Lemur catta at the Beza Mahafaly Special Reserve, Madagascar, has revealed an unusual pattern of severe tooth wear and frequent tooth loss, primarily the result of consuming a fallback food for which these primates are not dentally adapted. Interpreting these data was only possible by combining our areas of expertise (dental anatomy [FC] and primate ecology [MS]). By integrating theoretical, methodological, and applied aspects of both areas of research, we adopted the term "dental ecology"-defined as the broad study of how teeth respond to the environment. Specifically, we view dental ecology as an interpretive framework using teeth as a vehicle for understanding an organism's ecology, which builds upon earlier work, but creates a new synthesis of anatomy and ecology that is only possible with detailed knowledge of living primates. This framework includes (1) identifying patterns of dental pathology and tooth use-wear, within the context of feeding ecology, behavior, habitat variation, and anthropogenic change, (2) assessing ways in which dental development and biogeochemical signals can reflect habitat, environmental change and/or stress, and (3) how dental microstructure and macro-morphology are adapted to, and reflect feeding ecology. Here we define dental ecology, provide a short summary of the development of this perspective, and place our new work into this context. PMID:22610892

  16. A diffusion-based truncated projection artifact reduction method for iterative digital breast tomosynthesis reconstruction

    NASA Astrophysics Data System (ADS)

    Lu, Yao; Chan, Heang-Ping; Wei, Jun; Hadjiiski, Lubomir M.

    2013-02-01

    Digital breast tomosynthesis (DBT) has strong promise to improve sensitivity for detecting breast cancer. DBT reconstruction estimates the breast tissue attenuation using projection views (PVs) acquired in a limited angular range. Because of the limited field of view (FOV) of the detector, the PVs may not completely cover the breast in the x-ray source motion direction at large projection angles. The voxels in the imaged volume cannot be updated when they are outside the FOV, thus causing a discontinuity in intensity across the FOV boundaries in the reconstructed slices, which we refer to as the truncated projection artifact (TPA). Most existing TPA reduction methods were developed for the filtered backprojection method in the context of computed tomography. In this study, we developed a new diffusion-based method to reduce TPAs during DBT reconstruction using the simultaneous algebraic reconstruction technique (SART). Our TPA reduction method compensates for the discontinuity in background intensity outside the FOV of the current PV after each PV updating in SART. The difference in voxel values across the FOV boundary is smoothly diffused to the region beyond the FOV of the current PV. Diffusion-based background intensity estimation is performed iteratively to avoid structured artifacts. The method is applicable to TPA in both the forward and backward directions of the PVs and for any number of iterations during reconstruction. The effectiveness of the new method was evaluated by comparing the visual quality of the reconstructed slices and the measured discontinuities across the TPA with and without artifact correction at various iterations. The results demonstrated that the diffusion-based intensity compensation method reduced the TPA while preserving the detailed tissue structures. The visibility of breast lesions obscured by the TPA was improved after artifact reduction.

  17. Health Instruction Packages: Permanent Teeth, Dental Deposits, and Dental Instruments. Dientes Permanentes, Depositos Dentales y Instrumentos Dentales.

    ERIC Educational Resources Information Center

    Lind, Patricia; Germano, Catherine

    These five learning modules use text interspersed with illustrations and reinforcement exercises to instruct dental aide and dental hygiene students about jaw bones and gums, dental deposits, and dental instruments. The first four modules were prepared by Patricia Lind in both Spanish and English. "The Gum and Bone of Permanent Teeth" ("La Encia y…

  18. Dental journals: yesterday and today.

    PubMed

    Woodmansey, Karl

    2012-10-01

    Today's dentists may subscribe to, or receive complimentarily, a number of periodical publications containing technical professional information. Dental journals are the prime example: providing timely, reliable and useful information. The development of dental journals is a component of the evolution of scientific communication. This article reviews the origins and evolution of dental journals, including the Texas Dental Journal. PMID:23311024

  19. Functionalized bio-artifact fabricated via selective slurry extrusion. Part 1: Preparation of slurry containing tourmaline superfine powders.

    PubMed

    Zhu, Dongbin; Xu, Anping; Qu, Yunxia; Liu, Yushan

    2011-12-01

    The far infrared dental porcelain slurry for fabricating artificial tooth via selective slurry extrusion (SSE) of solid freeform fabrication (also known as rapid prototyping) techniques was prepared by using tourmaline as additive and employing ball-milling approach. After characterization by transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry, it was found that the far infrared emission properties of the dental porcelain were apparently improved in the ranges of 2000-1201 cm(-1) and 881-600 cm(-1). This is due to the increase of the number of infrared active bonds that are from the tourmaline superfine powders. Moreover, it was also found that the tourmaline superfine powders can improve the pseudo-plastic properties of dental porcelain slurries, which results from the increase of the absolute value of zeta potential of the suspensions. Slurries with pseudo-plastic behavior are highly desirable in controlling the shape of the extrudate during solid freeform fabrication. With the functionalized material, a variety of bio-artifacts beneficial to body health can be built by using selective slurry extrusion machine. PMID:22409019

  20. Functionalized bio-artifact fabricated via selective slurry extrusion. Part 1: Preparation of slurry containing tourmaline superfine powders.

    PubMed

    Zhu, Dongbin; Xu, Anping; Qu, Yunxia; Liu, Yushan

    2011-12-01

    The far infrared dental porcelain slurry for fabricating artificial tooth via selective slurry extrusion (SSE) of solid freeform fabrication (also known as rapid prototyping) techniques was prepared by using tourmaline as additive and employing ball-milling approach. After characterization by transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry, it was found that the far infrared emission properties of the dental porcelain were apparently improved in the ranges of 2000-1201 cm(-1) and 881-600 cm(-1). This is due to the increase of the number of infrared active bonds that are from the tourmaline superfine powders. Moreover, it was also found that the tourmaline superfine powders can improve the pseudo-plastic properties of dental porcelain slurries, which results from the increase of the absolute value of zeta potential of the suspensions. Slurries with pseudo-plastic behavior are highly desirable in controlling the shape of the extrudate during solid freeform fabrication. With the functionalized material, a variety of bio-artifacts beneficial to body health can be built by using selective slurry extrusion machine.

  1. Can midlevel dental providers be a benefit to the American public?

    PubMed

    Rodriguez, Tobias E; Galka, Audrey L; Lacy, Ernestine S; Pellegrini, August D; Sweier, Domenica G; Romito, Laura M

    2013-05-01

    The use of midlevel dental providers (MLDPs) is being debated as a means of reducing oral health disparities and increasing access to care among underserved populations. Midlevel dental providers include the advanced dental hygiene practitioner, community dental health coordinator, dental health aide therapist, and dental therapist. While midlevel providers are new to the U.S. dental profession, medicine has utilized these positions for years. Medical literature has shown mixed results as to whether midlevel providers improve access to care and increased practice efficiency, however, it has demonstrated clearly that the quality of care outcomes of these providers have been comparable to those of physicians. Studies of MLDPs suggest potential practice and public health benefits. With appropriate training, licensure, supervision, and deployment to geographical areas of significant need, we believe MLDPs could increase access to care to underserved populations and help in the prevention of deaths attributable to untreated dental disease.

  2. Mediators between education and dental pain: a cross-sectional study to assess the role of dental services utilization.

    PubMed

    Constante, Helena M; Peres, Marco A; Schroeder, Fernanda C; Bastos, João L

    2016-02-01

    This study tested whether the pattern of dental services utilization and the reason for the last dental visit mediate the association between educational attainment and dental pain. This is a cross-sectional analysis (n = 1099) based on data from a prospective cohort study in adults, southern Brazil. The mediating effects were assessed by including interaction terms in logistic regression models and by the KHB method, which estimated the direct, mediated, and total effects of education on dental pain. The prevalence of dental pain was 17.5%. Individuals with less than 12 yr of study who visited the dentist to solve dental problems had a 20% higher odds of reporting dental pain than those with 12 or more years of study, who sought the dentist for preventive reasons. Dental services should also focus on preventive measures, especially if less-educated individuals visit the dentist only to treat problems; this may help reduce the frequency of negative oral health outcomes, including dental pain. PMID:26718615

  3. Education on and prevention of dental trauma: it's time to act!

    PubMed

    Levin, Liran; Zadik, Yehuda

    2012-02-01

    Dental trauma is, unfortunately, not uncommon and may be even more prevalent in high-risk populations. It should be emphasized and acknowledged that many cases of dental trauma are preventable. Appropriate management includes primary prevention, i.e. avoidance of pathology development, and secondary prevention, i.e. early diagnosing and treatment of the pathology before significant morbidity occurs. The aim of this article is to provide a review of the current dental trauma literature with regard to education and knowledge and with relevance to primary and secondary prevention. As the duty of providing the public with measures for the maintenance of proper oral health is of the dental profession, the responsibility of providing primary and secondary prevention of dental trauma is of dentists, dental hygienists, and dental nurses. They may, and should, educate other medical, paramedical, and non-medical professionals, taking into account that those non-dental professionals could not maintain a high level of knowledge and service regarding dental trauma without a continuous backing by the dental professionals. It should be remembered that as the prevalence of dental decay has reduced in the Western world during recent decades, dental trauma plays a significant part in causing dental morbidity and mortality (tooth loss). It seems that now is the time to act for the benefit of our community and move from 'treating' toward 'managing' risk factors and prevention.

  4. Motion artifacts of extended high frame rate imaging.

    PubMed

    Wang, Jing; Lu, Jian-yu

    2007-07-01

    Based on the high frame rate (HFR) imaging method developed in our lab, an extended high frame rate imaging method with various transmission schemes was developed recently. In this method, multiple, limited-diffraction array beams or steered plane wave transmissions are used to increase image resolution and field of view as well as to reduce sidelobes. Furthermore, the multiple, limited-diffraction array beam transmissions can be approximated with square-wave aperture weightings, allowing one or two transmitters to be used with a multielement array transducer to simplify imaging systems. By varying the number of transmissions, the extended HFR imaging method allows a continuous trade-off between image quality and frame rate. Because multiple transmissions are needed to obtain one frame of image for the method, motion could cause phase misalignment and thus produce artifacts, reducing image contrast and resolution and leading to an inaccurate clinical interpretation of images. Therefore, it is important to study how motion affects the method and provide a useful guidance of using the method properly in various applications. In this paper, computer simulations, in vitro and in vivo experiments were performed to study the effects of motion on the method in different conditions. Results show that a number of factors may affect the motion effects. However, it was found that the extended HFR imaging method is not sensitive to the motions commonly encountered in the clinical applications, as is demonstrated by an in vivo heart experiment, unless the number of transmissions is large and objects are moving at a high velocity near the surface of a transducer.

  5. Dental student debt.

    PubMed

    Mannion, H; Bedi, R

    1995-09-01

    The aim of this investigation is to provide information about the financial status of dental students enrolled on the Bachelor of Dental Surgery degree course at the University of Birmingham. All undergraduate dental students enrolled during the academic year 1993-94 were asked to participate in the study. The pre-tested questionnaire, which was given to all students, covered personal details, expenditure levels, income, loans, overdrafts, use of government schemes ('top-up loans'), and so on. The questionnaire was completed by 115 dental students (response rate 47%). The results showed that dental students' debts increased each year throughout the course. A top-up loan (range 700 Pounds-850 Pounds) had been taken out by 36% of students. The financial status of 9% of students was severe enough to warrant their eligibility for awards from access funds. Credit cards were possessed by 52% of the surveyed students, and although only half of these owed money, 22% owed between 500 Pounds and 2000 Pounds. Personal overdrafts were held by 56% of respondents. A total of 17% of students engaged in weekly part-time employment. The average debt for final year students was 1200 Pounds. Dental students' estimates of the level of debt they were likely to incur was greater than the actual debt presently experienced by final year students. In conclusion, this preliminary study showed that most dental students incur debt during their undergraduate course and that this debt increases during the course.

  6. Silver Nanoparticles in Dental Biomaterials

    PubMed Central

    Corrêa, Juliana Mattos; Mori, Matsuyoshi; Sanches, Heloísa Lajas; da Cruz, Adriana Dibo; Poiate, Isis Andréa Venturini Pola

    2015-01-01

    Silver has been used in medicine for centuries because of its antimicrobial properties. More recently, silver nanoparticles have been synthesized and incorporated into several biomaterials, since their small size provides great antimicrobial effect, at low filler level. Hence, these nanoparticles have been applied in dentistry, in order to prevent or reduce biofilm formation over dental materials surfaces. This review aims to discuss the current progress in this field, highlighting aspects regarding silver nanoparticles incorporation, such as antimicrobial potential, mechanical properties, cytotoxicity, and long-term effectiveness. We also emphasize the need for more studies to determine the optimal concentration of silver nanoparticle and its release over time. PMID:25667594

  7. Motion artifacts occurring at the lung/diaphragm interface using 4D CT attenuation correction of 4D PET scans.

    PubMed

    Killoran, Joseph H; Gerbaudo, Victor H; Mamede, Marcelo; Ionascu, Dan; Park, Sang-June; Berbeco, Ross

    2011-11-15

    For PET/CT, fast CT acquisition time can lead to errors in attenuation correction, particularly at the lung/diaphragm interface. Gated 4D PET can reduce motion artifacts, though residual artifacts may persist depending on the CT dataset used for attenuation correction. We performed phantom studies to evaluate 4D PET images of targets near a density interface using three different methods for attenuation correction: a single 3D CT (3D CTAC), an averaged 4D CT (CINE CTAC), and a fully phase matched 4D CT (4D CTAC). A phantom was designed with two density regions corresponding to diaphragm and lung. An 8 mL sphere phantom loaded with 18F-FDG was used to represent a lung tumor and background FDG included at an 8:1 ratio. Motion patterns of sin(x) and sin4(x) were used for dynamic studies. Image data was acquired using a GE Discovery DVCT-PET/CT scanner. Attenuation correction methods were compared based on normalized recovery coefficient (NRC), as well as a novel quantity "fixed activity volume" (FAV) introduced in our report. Image metrics were compared to those determined from a 3D PET scan with no motion present (3D STATIC). Values of FAV and NRC showed significant variation over the motion cycle when corrected by 3D CTAC images. 4D CTAC- and CINE CTAC-corrected PET images reduced these motion artifacts. The amount of artifact reduction is greater when the target is surrounded by lower density material and when motion was based on sin4(x). 4D CTAC reduced artifacts more than CINE CTAC for most scenarios. For a target surrounded by water equivalent material, there was no advantage to 4D CTAC over CINE CTAC when using the sin(x) motion pattern. Attenuation correction using both 4D CTAC or CINE CTAC can reduce motion artifacts in regions that include a tissue interface such as the lung/diaphragm border. 4D CTAC is more effective than CINE CTAC at reducing artifacts in some, but not all, scenarios.

  8. Optimization-based image reconstruction with artifact reduction in C-arm CBCT

    NASA Astrophysics Data System (ADS)

    Xia, Dan; Langan, David A.; Solomon, Stephen B.; Zhang, Zheng; Chen, Buxin; Lai, Hao; Sidky, Emil Y.; Pan, Xiaochuan

    2016-10-01

    We investigate an optimization-based reconstruction, with an emphasis on image-artifact reduction, from data collected in C-arm cone-beam computed tomography (CBCT) employed in image-guided interventional procedures. In the study, an image to be reconstructed is formulated as a solution to a convex optimization program in which a weighted data divergence is minimized subject to a constraint on the image total variation (TV); a data-derivative fidelity is introduced in the program specifically for effectively suppressing dominant, low-frequency data artifact caused by, e.g. data truncation; and the Chambolle–Pock (CP) algorithm is tailored to reconstruct an image through solving the program. Like any other reconstructions, the optimization-based reconstruction considered depends upon numerous parameters. We elucidate the parameters, illustrate their determination, and demonstrate their impact on the reconstruction. The optimization-based reconstruction, when applied to data collected from swine and patient subjects, yields images with visibly reduced artifacts in contrast to the reference reconstruction, and it also appears to exhibit a high degree of robustness against distinctively different anatomies of imaged subjects and scanning conditions of clinical significance. Knowledge and insights gained in the study may be exploited for aiding in the design of practical reconstructions of truly clinical-application utility.

  9. Characterization of ultrasound elevation beamwidth artifacts for prostate brachytherapy needle insertion

    SciTech Connect

    Peikari, Mohammad; Chen, Thomas Kuriran; Lasso, Anras; Heffter, Tamas; Fichtinger, Gabor; Burdette, Everette C.

    2012-01-15

    Purpose: Ultrasound elevation beamwidth leads to image artifacts and uncertainties in localizing objects (such as a surgical needle) in ultrasound images. The authors examined the clinical significance of errors caused by elevation beamwidth artifacts and imaging parameters in needle insertion procedures. Methods: Beveled prostate brachytherapy needles were inserted through all holes of a grid template under real-time transrectal ultrasound (TRUS) guidance. The needle tip position as indicated by the TRUS image was compared to their observed physical location. A new device was developed to measure the ultrasound elevation beamwidth. Results: Imaging parameters of the TRUS scanner have direct impact on the localization error ranging from 0.5 up to 4 mm. The smallest localization error was observed laterally close to the center of the grid template and axially within the beam's focal zone. Largest localization error occurs laterally around both sides of the grid template and axially within the beam's far field. The authors also found that the localization errors vary with both lateral and elevation offsets. Conclusions: The authors found properly adjusting the TRUS imaging settings to lower the ultrasound gain and power effectively minimized the appearance of elevation beamwidth artifacts and in turn reduced the localization errors of the needle tip.

  10. Towards Semi-Automatic Artifact Rejection for the Improvement of Alzheimer's Disease Screening from EEG Signals.

    PubMed

    Solé-Casals, Jordi; Vialatte, François-Benoît

    2015-01-01

    A large number of studies have analyzed measurable changes that Alzheimer's disease causes on electroencephalography (EEG). Despite being easily reproducible, those markers have limited sensitivity, which reduces the interest of EEG as a screening tool for this pathology. This is for a large part due to the poor signal-to-noise ratio of EEG signals: EEG recordings are indeed usually corrupted by spurious extra-cerebral artifacts. These artifacts are responsible for a consequent degradation of the signal quality. We investigate the possibility to automatically clean a database of EEG recordings taken from patients suffering from Alzheimer's disease and healthy age-matched controls. We present here an investigation of commonly used markers of EEG artifacts: kurtosis, sample entropy, zero-crossing rate and fractal dimension. We investigate the reliability of the markers, by comparison with human labeling of sources. Our results show significant differences with the sample entropy marker. We present a strategy for semi-automatic cleaning based on blind source separation, which may improve the specificity of Alzheimer screening using EEG signals. PMID:26213933

  11. Towards Semi-Automatic Artifact Rejection for the Improvement of Alzheimer's Disease Screening from EEG Signals.

    PubMed

    Solé-Casals, Jordi; Vialatte, François-Benoît

    2015-07-23

    A large number of studies have analyzed measurable changes that Alzheimer's disease causes on electroencephalography (EEG). Despite being easily reproducible, those markers have limited sensitivity, which reduces the interest of EEG as a screening tool for this pathology. This is for a large part due to the poor signal-to-noise ratio of EEG signals: EEG recordings are indeed usually corrupted by spurious extra-cerebral artifacts. These artifacts are responsible for a consequent degradation of the signal quality. We investigate the possibility to automatically clean a database of EEG recordings taken from patients suffering from Alzheimer's disease and healthy age-matched controls. We present here an investigation of commonly used markers of EEG artifacts: kurtosis, sample entropy, zero-crossing rate and fractal dimension. We investigate the reliability of the markers, by comparison with human labeling of sources. Our results show significant differences with the sample entropy marker. We present a strategy for semi-automatic cleaning based on blind source separation, which may improve the specificity of Alzheimer screening using EEG signals.

  12. [Elimination of electrocardiogram artifacts from electroencephalogram records by using the simultaneously recorded electrocardiograph data].

    PubMed

    Okamoto, Yasuyuki; Yuki, Michi; Imai, Ryuko; Shinki, Yoshiyuki; Yamanaka, Masami; Masutani, Takayuki

    2002-12-01

    We developed a simple method to eliminate electrocardiogram (ECG) artifacts from electroencephalogram (EEG) records by using simultaneously recorded ECG data. The raw EEG data, the real EEG data and the ECG data were regarded as multi-dimensional vectors Ea, Er and C, respectively. Also, the ECG data, with reduced amplitude whose coefficient was denoted as 'k', were assumed to be overlapped on the real EEG. These assumptions introduced the equations [Ea = Er + k.C], [Er.C = 0] and finally [k = Ea. C/C.C]. This calculation method was implemented by a Macintosh computer using data exported from digital EEG recordings (sampled at 200 Hz with 16-bit resolution). In several subjects, sampling intervals of 5 or 10 seconds for calculation succeeded in eliminating ECG artifacts. However, regardless of the sampling interval, this elimination condition was not always efficient in several other subjects, including a brain-dead patient. It was suggested that the ECG data used were insufficient for the calculation, because only one hand-to-hand reference was used for simultaneous recording, as usual. This one ECG reference was able to express only one ECG projection. Then two other hand-to-foot references of ECG were added to the recordings, and the elimination procedure was performed using all of the simultaneously recorded ECG data at the three references. Consequently, elimination was much improved in most subjects, including the brain-dead patient. Our method may be useful for eliminating ECG artifacts without changing reference electrodes.

  13. Optical coherence tomography guided dental drill

    DOEpatents

    DaSilva, Luiz B.; Colston, Jr., Bill W.; James, Dale L.

    2002-01-01

    A dental drill that has one or multiple single mode fibers that can be used to image in the vicinity of the drill tip. It is valuable to image below the surface being drilled to minimize damage to vital or normal tissue. Identifying the boundary between decayed and normal enamel (or dentine) would reduce the removal of viable tissue, and identifying the nerve before getting too close with the drill could prevent nerve damage. By surrounding a drill with several optical fibers that can be used by an optical coherence domain reflectometry (OCDR) to image several millimeters ahead of the ablation surface will lead to a new and improved dental treatment device.

  14. Economic impact of dental hygienists on solo dental practices.

    PubMed

    Lazar, Vickie F; Guay, Albert H; Beazoglou, Tryfon J

    2012-08-01

    The fact that a significant percentage of dentists employ dental hygienists raises an important question: Are dental practices that utilize a dental hygienist structurally and operationally different from practices that do not? This article explores differences among dental practices that operate with and without dental hygienists. Using data from the American Dental Association's 2003 Survey of Dental Practice, a random sample survey of U.S. dentists, descriptive statistics were used to compare selected characteristics of solo general practitioners with and without dental hygienists. Multivariate regression analysis was used to estimate the effect of dental hygienists on the gross billings and net incomes of solo general practitioners. Differences in practice characteristics--such as hours spent in the practice and hours spent treating patients, wait time for a recall visit, number of operatories, square feet of office space, net income, and gross billings--were found between solo general practitioners who had dental hygienists and those who did not. Solo general practitioners with dental hygienists had higher gross billings. Higher gross billings would be expected, as would higher expenses. However, net incomes of those with dental hygienists were also higher. In contrast, the mean waiting time for a recall visit was higher among dentists who employed dental hygienists. Depending on personal preferences, availability of qualified personnel, etc., dentists who do not employ dental hygienists but have been contemplating that path may want to further research the benefits and opportunities that may be realized.

  15. Synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON): A statistical model based iterative image reconstruction method to eliminate limited-view artifacts and to mitigate the temporal-average artifacts in time-resolved CT

    PubMed Central

    Chen, Guang-Hong; Li, Yinsheng

    2015-01-01

    Purpose: In x-ray computed tomography (CT), a violation of the Tuy data sufficiency condition leads to limited-view artifacts. In some applications, it is desirable to use data corresponding to a narrow temporal window to reconstruct images with reduced temporal-average artifacts. However, the need to reduce temporal-average artifacts in practice may result in a violation of the Tuy condition and thus undesirable limited-view artifacts. In this paper, the authors present a new iterative reconstruction method, synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON), to eliminate limited-view artifacts using data acquired within an ultranarrow temporal window that severely violates the Tuy condition. Methods: In time-resolved contrast enhanced CT acquisitions, image contrast dynamically changes during data acquisition. Each image reconstructed from data acquired in a given temporal window represents one time frame and can be denoted as an image vector. Conventionally, each individual time frame is reconstructed independently. In this paper, all image frames are grouped into a spatial–temporal image matrix and are reconstructed together. Rather than the spatial and/or temporal smoothing regularizers commonly used in iterative image reconstruction, the nuclear norm of the spatial–temporal image matrix is used in SMART-RECON to regularize the reconstruction of all image time frames. This regularizer exploits the low-dimensional structure of the spatial–temporal image matrix to mitigate limited-view artifacts when an ultranarrow temporal window is desired in some applications to reduce temporal-average artifacts. Both numerical simulations in two dimensional image slices with known ground truth and in vivo human subject data acquired in a contrast enhanced cone beam CT exam have been used to validate the proposed SMART-RECON algorithm and to demonstrate the initial performance of the algorithm. Reconstruction errors and temporal fidelity

  16. The impacts of dental filling materials on RapidArc treatment planning and dose delivery: Challenges and solution

    SciTech Connect

    Mail, Noor; Al-Ghamdi, S.; Saoudi, A.; Albarakati, Y.; Ahmad Khan, M.; Saeedi, F.; Safadi, N.

    2013-08-15

    Purpose: The presence of high-density material in the oral cavity creates dose perturbation in both downstream and upstream directions at the surfaces of dental filling materials (DFM). In this study, the authors have investigated the effect of DFM on head and neck RapidArc treatment plans and delivery. Solutions are proposed to address (1) the issue of downstream dose perturbation, which might cause target under dosage, and (2) to reduce the upstream dose from DFM which may be the primary source of mucositis. In addition, an investigation of the clinical role of a custom-made plastic dental mold/gutter (PDM) in sparing the oral mucosa and tongue reaction is outlined.Methods: The influence of the dental filling artifacts on dose distribution was investigated using a geometrically well-defined head and neck intensity modulated radiation therapy (IMRT) verification phantom (PTW, Freiberg, Germany) with DFM inserts called amalgam, which contained 50% mercury, 25% silver, 14% tin, 8% copper, and 3% other trace metals. Three RapidArc plans were generated in the Varian Eclipse System to treat the oral cavity using the same computer tomography (CT) dataset, including (1) a raw CT image, (2) a streaking artifacts region, which was replaced with a mask of 10 HU, and (3) a 2 cm-thick 6000 HU virtual filter [a volume created in treatment planning system to compensate for beam attenuation, where the thickness of this virtual filter is based on the measured percent depth dose (PDD) data and Eclipse calculation]. The dose delivery for the three plans was verified using Gafchromic-EBT2 film measurements. The custom-made PDM technique to reduce backscatter dose was clinically tested on four head and neck cancer patients (T3, N1, M0) with DFM, two patients with PDM and the other two patients without PDM. The thickness calculation of the PDM toward the mucosa and tongue was purely based on the measured upstream dose. Patients’ with oral mucosal reaction was clinically examined

  17. Optimizing cardiac MR imaging: practical remedies for artifacts.

    PubMed

    Saremi, Farhood; Grizzard, John D; Kim, Raymond J

    2008-01-01

    With ongoing technical advances in magnetic resonance (MR) imaging, the clinical demand for cardiac MR evaluations has been increasing. Cardiac MR imaging techniques have evolved from traditional spin-echo sequences to breath-hold spoiled gradient-echo and balanced steady-state free precession sequences. The most recently developed techniques allow evaluation of myocardial function, perfusion, and viability; coronary angiography; flow quantification; and standard morphologic assessments. However, even with the most sophisticated acquisition techniques, artifacts commonly occur at cardiac MR imaging. Knowledge of the origin, imaging appearance, and significance of these artifacts is essential to avoid misinterpreting them as true lesions. Some artifacts are caused by simple errors in positioning of the patient, coil, or electrocardiographic leads; radiofrequency interference from nearby electronic equipment; or metallic objects within the magnetic field. Others are directly related to a specific MR imaging sequence or technique. Accelerated imaging techniques such as parallel imaging, which are used to shorten acquisition and breath-hold times in cardiac evaluations, are particularly vulnerable to artifacts. If an artifact severely degrades image quality, the acquisition should be repeated with appropriate adjustments to decrease or eliminate the problem.

  18. Metal artifact reduction in CT via ray profile correction

    NASA Astrophysics Data System (ADS)

    Ha, Sungsoo; Mueller, Klaus

    2016-03-01

    In computed tomography (CT), metal implants increase the inconsistencies between the measured data and the linear assumption made by the analytical CT reconstruction algorithm. The inconsistencies appear in the form of dark and bright bands and streaks in the reconstructed image, collectively called metal artifacts. The standard method for metal artifact reduction (MAR) replaces the inconsistent data with the interpolated data. However, sinogram interpolation not only introduces new artifacts but it also suffers from the loss of detail near the implanted metals. With the help of a prior image that is usually estimated from the metal artifact-degraded image via computer vision techniques, improvements are feasible but still no MAR method exists that is widely accepted and utilized. We propose a technique that utilizes a prior image from a CT scan taken of the patient before implanting the metal objects. Hence there is a sufficient amount of structural similarity to cover the loss of detail around the metal implants. Using the prior scan and a segmentation or model of the metal implant our method then replaces sinogram interpolation with ray profile matching and estimation which yields much more reliable data estimates for the affected sinogram regions. As preliminary work, we built a new MAR framework on fan-beam geometry and tested it to remove simulated metal artifacts on a thorax phantom. The comparison with two representative sinogram correction based MAR methods shows very promising results.

  19. Removing speech artifacts from electroencephalographic recordings during overt picture naming.

    PubMed

    Porcaro, Camillo; Medaglia, Maria Teresa; Krott, Andrea

    2015-01-15

    A number of electroencephalography (EEG) studies have investigated the time course of brain activation during overt word production. The interpretation of their results is complicated by the fact that articulatory movements may mask the cognitive components of interest. The first aim of the present study was to investigate when speech artifacts occur during word production planning and what effects they have on the spatio-temporal neural activation pattern. The second aim was to propose a new method that strongly attenuates speech artifacts during overt picture naming and to compare it with existing methods. EEG and surface electromyograms (EMGs) of the lips were recorded while participants overtly named pictures in a picture-word interference paradigm. The comparison of the raw data with lip EMG and the comparison of source localizations of raw and corrected EEG data showed that speech artifacts occurred mainly from ~400 ms post-stimulus onset, but some earlier artifacts mean that they occur much earlier than hitherto assumed. We compared previously used methods of speech artifacts removal (SAR) with a new method, which is based on Independent Component Analysis (SAR-ICA). Our new method clearly outperformed other methods. In contrast to other methods, there was only a weak correlation between the lip EMG and the corrected data by SAR-ICA. Also, only the data corrected with our method showed activation of cerebral sources consistent with meta-analyses of word production.

  20. Real time ECG artifact removal for myoelectric prosthesis control.

    PubMed

    Zhou, Ping; Lock, Blair; Kuiken, Todd A

    2007-04-01

    The electrocardiogram (ECG) artifact is a major noise source contaminating the electromyogram (EMG) of torso muscles. This study investigates removal of ECG artifacts in real time for myoelectric prosthesis control, a clinical application that demands speed and efficiency. Three methods with simple and fast implementation were investigated. Removal of ECG artifacts by digital high-pass filtering was implemented. The effects of the cutoff frequency and filter order of high-pass filtering on the resulting EMG signal were quantified. An alternative adaptive spike-clipping approach was also developed to dynamically detect and suppress the ECG artifacts in the signal. Finally, the two methods were combined. Experimental surface EMG recordings with different ECG/EMG ratios were used as testing signals to evaluate the proposed methods. As a key parameter for clinical myoelectric prosthesis control, the average rectified amplitude of the signal was used as the performance indicator to quantitatively analyze the EMG content distortion and the ECG artifact suppression imposed by the two methods. Aiming at clinical application, the optimal parameter assignment for each method was determined on the basis of the performance using the suite of testing signals with various ECG/EMG ratios. PMID:17395995

  1. Dental care - child

    MedlinePlus

    ... Zakher B, Mitchell JP, Pappas M. Preventing dental caries in children <5 years: systematic review updating USPSTF ... chap 7. Ng MW, Chase I. Early childhood caries: risk-based disease prevention and management. Dent Clin ...

  2. Dental mesenchymal stem cells.

    PubMed

    Sharpe, Paul T

    2016-07-01

    Mammalian teeth harbour mesenchymal stem cells (MSCs), which contribute to tooth growth and repair. These dental MSCs possess many in vitro features of bone marrow-derived MSCs, including clonogenicity, expression of certain markers, and following stimulation, differentiation into cells that have the characteristics of osteoblasts, chondrocytes and adipocytes. Teeth and their support tissues provide not only an easily accessible source of MSCs but also a tractable model system to study their function and properties in vivo In addition, the accessibility of teeth together with their clinical relevance provides a valuable opportunity to test stem cell-based treatments for dental disorders. This Review outlines some recent discoveries in dental MSC function and behaviour and discusses how these and other advances are paving the way for the development of new biologically based dental therapies. PMID:27381225

  3. Glossary of Dental Terms

    MedlinePlus

    ... geta poker friv Home InfoBites Find an AGD Dentist Your Family's Oral Health About the AGD Dental ... and shape of teeth performed by a general dentist | More Edentulous having lost most or all of ...

  4. Infant dental care (image)

    MedlinePlus

    Even though newborns and infants do not have teeth, care of the mouth and gums is important. ... sugar water. As the child grows, establishing proper dental hygiene will promote healthy teeth and gums which ...

  5. Dental Care in Pregnancy

    MedlinePlus

    ... for you and your baby and contain less sugar that can damage your teeth. Water or low-fat milk hydrates you and contains little or no sugar. For More Information American Dental Association: Pregnancy http : / / ...

  6. Acute focal infections of dental origin.

    PubMed

    Olsen, Ingar; van Winkelhoff, Arie J

    2014-06-01

    This article describes the most important pus-producing acute oral infections (dental infections) that can spread extra-orally. Most of these infections are spread by bacteria entering the bloodstream. However, dental infections have a number of other pathways for dissemination. By forming abscesses or phlegmon they can reach facial spaces that communicate with each other and then spread downwards to the mediastinum or upwards to the brain. In such cases dental infections can become, if not properly treated, life-threatening. It seems that early diagnosis and treatment are imperative, and potentially infectious foci should be traced and eliminated. Dental hygiene and prophylaxis to prevent dental biofilm formation are important measures to reduce the risk of these calamities. The more compromised the host defense is, the more importance should be put on these measures. Although commensal bacteria are often involved in these infections, attention should also be paid to specific periodontal pathogens, and a proper microbial diagnosis, obtained using molecular methods plus bacterial sensitivity testing, can provide the patient with optimal care. Drainage of pus must be established where possible so that the optimal effect of antibiotics can be achieved. Penicillin is still the drug of first choice in settings where suspicion of methicillin-resistant Staphylococcus aureus is low.

  7. Assessment of dental plaque by optoelectronic methods

    NASA Astrophysics Data System (ADS)

    Negrutiu, Meda-Lavinia; Sinescu, Cosmin; Bortun, Cristina Maria; Levai, Mihaela-Codrina; Topala, Florin Ionel; Crǎciunescu, Emanuela Lidia; Cojocariu, Andreea Codruta; Duma, Virgil Florin; Podoleanu, Adrian Gh.

    2016-03-01

    The formation of dental biofilm follows specific mechanisms of initial colonization on the surface, microcolony formation, development of organized three dimensional community structures, and detachment from the surface. The structure of the plaque biofilm might restrict the penetration of antimicrobial agents, while bacteria on a surface grow slowly and display a novel phenotype; the consequence of the latter is a reduced sensitivity to inhibitors. The aim of this study was to evaluate with different optoelectronic methods the morphological characteristics of the dental biofilm. The study was performed on samples from 25 patients aged between 18 and 35 years. The methods used in this study were Spectral Domain Optical Coherence Tomography (SD-OCT) working at 870 nm for in vivo evaluations and Scanning Electron Microscopy (SEM) for validations. For each patient a sample of dental biofilm was obtained directly from the vestibular surface of the teeth's. SD-OCT produced C- and B-scans that were used to generate three dimensional (3D) reconstructions of the sample. The results were compared with SEM evaluations. The biofilm network was dramatically destroyed after the professional dental cleaning. OCT noninvasive methods can act as a valuable tool for the 3D characterization of dental biofilms.

  8. Elevated T cell subpopulations in dental students

    SciTech Connect

    Eedy, D.J.; Burrows, D.; Clifford, T.; Fay, A. )

    1990-05-01

    The absolute numbers of circulating white cells and lymphocyte subpopulations were studied in 25 final-year dental students and compared with a control group of 28 medical students. The total lymphocyte count, total T cell numbers (CD3), T helper/inducer (CD4), and T suppressor/cytotoxic (CD8) numbers were significantly elevated in the dental students as compared with the control group. There was no significant difference in the T helper/inducer to T suppressor/cytotoxic cell ratios or the circulating B cell (CD21) and natural killer cell (CD16) numbers between the study and control groups. Patch testing to mercury and mercuric compounds in both the study and control groups showed no evidence of cutaneous hypersensitivity to mercury. The reason for the observed elevations in T cell subpopulations in dental students is not clear. However, one possible explanation is the dental student's occupational exposure to mercury. Further work is underway to examine this possible relationship and it is suggested that dental personnel take adequate measures to reduce their exposure to mercury until the results of these studies are available.

  9. Acute focal infections of dental origin.

    PubMed

    Olsen, Ingar; van Winkelhoff, Arie J

    2014-06-01

    This article describes the most important pus-producing acute oral infections (dental infections) that can spread extra-orally. Most of these infections are spread by bacteria entering the bloodstream. However, dental infections have a number of other pathways for dissemination. By forming abscesses or phlegmon they can reach facial spaces that communicate with each other and then spread downwards to the mediastinum or upwards to the brain. In such cases dental infections can become, if not properly treated, life-threatening. It seems that early diagnosis and treatment are imperative, and potentially infectious foci should be traced and eliminated. Dental hygiene and prophylaxis to prevent dental biofilm formation are important measures to reduce the risk of these calamities. The more compromised the host defense is, the more importance should be put on these measures. Although commensal bacteria are often involved in these infections, attention should also be paid to specific periodontal pathogens, and a proper microbial diagnosis, obtained using molecular methods plus bacterial sensitivity testing, can provide the patient with optimal care. Drainage of pus must be established where possible so that the optimal effect of antibiotics can be achieved. Penicillin is still the drug of first choice in settings where suspicion of methicillin-resistant Staphylococcus aureus is low. PMID:24738592

  10. Dental arch asymmetry

    PubMed Central

    Al-Zubair, Nabil Muhsen

    2014-01-01

    Objective: This study was conducted to assess the dental arch asymmetry in a Yemeni sample aged (18-25) years. Materials and Methods: The investigation involved clinical examination of 1479 adults; only 253 (129 females, 124 males) out of the total sample were selected to fulfill the criteria for the study sample. Study models were constructed and evaluated to measure mandibular arch dimensions. Three linear distances were utilized on each side on the dental arch: Incisal-canine distance, canine-molar distance and incisal-molar distance, which represent the dental arch segmental measurements. Results: When applying “t-test” at P < 0.05, no significant differences were found between the right and left canine-molar, incisal-canine and incisal-molar distances in both dental arches for both sexes. The greater variation (0.30 mm) was observed between right and left canine-molar distance in the maxillary dental arch in male and the smaller (0.04 mm) in the mandibular dental arch between the right and left canine-molar distance in females. Conclusion: The findings of the present study revealed a symmetrical pattern of dental arches, since the right and left sides showed no statistically significant difference. In general, it can be observed that the measurements related to the central incisors and canines have the widest range of reading and give the impression that the location of central incisor and canines to each other and to other teeth is the strongest factor in determining the dental arch asymmetry. PMID:24966774

  11. Dental (Odontogenic) Pain

    PubMed Central

    Renton, Tara

    2011-01-01

    This article provides a simple overview of acute trigeminal pain for the non dentist. This article does not cover oral mucosal diseases (vesiculobullous disorders) that may cause acute pain. Dental pain is the most common in this group and it can present in several different ways. Of particular interest for is that dental pain can mimic both trigeminal neuralgia and other chronic trigeminal pain disorders. It is crucial to exclude these disorders whilst managing patients with chronic trigeminal pain. PMID:26527224

  12. Portable Dental System

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Portable dental system provides dental care in isolated communities. System includes a patient's chair and a dentist's stool, an X-ray machine and a power unit, all of which fold into compact packages. A large yellow "pumpkin" is a collapsible compressed air tank. Portable system has been used successfully in South America in out of the way communities with this back-packable system, and in American nursing homes. This product is no longer manufactured.

  13. Artifact Reduction in X-Ray CT Images of Al-Steel-Perspex Specimens Mimicking a Hip Prosthesis

    SciTech Connect

    Madhogarhia, Manish; Munshi, P.; Lukose, Sijo; Subramanian, M. P.; Muralidhar, C.

    2008-09-26

    X-ray Computed Tomography (CT) is a relatively new technique developed in the late 1970's, which enables the nondestructive visualization of the internal structure of objects. Beam hardening caused by the polychromatic spectrum is an important problem in X-ray computed tomography (X-CT). It leads to various artifacts in reconstruction images and reduces image quality. In the present work we are considering the Artifact Reduction in Total Hip Prosthesis CT Scan which is a problem of medical imaging. We are trying to reduce the cupping artifact induced by beam hardening as well as metal artifact as they exist in the CT scan of a human hip after the femur is replaced by a metal implant. The correction method for beam hardening used here is based on a previous work. Simulation study for the present problem includes a phantom consisting of mild steel, aluminium and perspex mimicking the photon attenuation properties of a hum hip cross section with metal implant.

  14. Artifact Reduction in X-Ray CT Images of Al-Steel-Perspex Specimens Mimicking a Hip Prosthesis

    NASA Astrophysics Data System (ADS)

    Madhogarhia, Manish; Munshi, P.; Lukose, Sijo; Subramanian, M. P.; Muralidhar, C.

    2008-09-01

    X-ray Computed Tomography (CT) is a relatively new technique developed in the late 1970's, which enables the nondestructive visualization of the internal structure of objects. Beam hardening caused by the polychromatic spectrum is an important problem in X-ray computed tomography (X-CT). It leads to various artifacts in reconstruction images and reduces image quality. In the present work we are considering the Artifact Reduction in Total Hip Prosthesis CT Scan which is a problem of medical imaging. We are trying to reduce the cupping artifact induced by beam hardening as well as metal artifact as they exist in the CT scan of a human hip after the femur is replaced by a metal implant. The correction method for beam hardening used here is based on a previous work. Simulation study for the present problem includes a phantom consisting of mild steel, aluminium and perspex mimicking the photon attenuation properties of a hum hip cross section with metal implant.

  15. The effect of fluoride impregnated dental floss on enamel fluoride uptake in vitro and streptococcus mutans colonization in vivo.

    PubMed

    Chaet, R; Wei, S H

    1977-01-01

    The conclusions reached from this investigation can be summarized as follows: Fluoride can be incorporated into unwaxed dental floss. Placement of the fluoride impregnated dental floss in acid-buffer solution results in the release of most of the fluoride in the floss. Interproximal surfaces of teeth treated in vitro with fluoride impregnated dental floss acquired significantly (approximately three fold) more enamel fluoride than those treated with plain dental floss. The number of in vivo interproximal areas harboring Streptococcus mutans was reduced significantly after treatment with fluoride impregnated dental floss. Further studies should be done to establish the biological, physiochemical, manufacturing, and practical aspects of fluoride impregnated dental floss.

  16. Saliva and dental erosion

    PubMed Central

    BUZALAF, Marília Afonso Rabelo; HANNAS, Angélicas Reis; KATO, Melissa Thiemi

    2012-01-01

    Dental erosion is a multifactorial condition. The consideration of chemical, biological and behavioral factors is fundamental for its prevention and therapy. Among the biological factors, saliva is one of the most important parameters in the protection against erosive wear. Objective This review discusses the role of salivary factors on the development of dental erosion. Material and Methods A search was undertaken on MEDLINE website for papers from 1969 to 2010. The keywords used in the research were "saliva", "acquired pellicle", "salivary flow", "salivary buffering capacity" and "dental erosion". Inclusion of studies, data extraction and quality assessment were undertaken independently and in duplicate by two members of the review team. Disagreements were solved by discussion and consensus or by a third party. Results Several characteristics and properties of saliva play an important role in dental erosion. Salivary clearance gradually eliminates the acids through swallowing and saliva presents buffering capacity causing neutralization and buffering of dietary acids. Salivary flow allows dilution of the acids. In addition, saliva is supersaturated with respect to tooth mineral, providing calcium, phosphate and fluoride necessary for remineralization after an erosive challenge. Furthermore, many proteins present in saliva and acquired pellicle play an important role in dental erosion. Conclusions Saliva is the most important biological factor affecting the progression of dental erosion. Knowledge of its components and properties involved in this protective role can drive the development of preventive measures targeting to enhance its known beneficial effects. PMID:23138733

  17. Fast Stimulus Artifact Recovery in a Multichannel Neural Recording System

    PubMed Central

    Schoenecker, Matthew C.; Bonham, Ben H.

    2010-01-01

    We describe a 32-channel recording system and software artifact blanking technique for recording neuronal responses to high-rate electrical stimulation. Each recording channel recovers from biphasic full-scale-input pulses (1.5-V) in less than 80 μs. Artifacts are blanked online in software, allowing flexibility in the choice of blanking period and the possibility of recovering neural data occurring simultaneously with non-saturating artifacts. The system has been used in-vivo to record central neuronal responses to intracochlear electrical stimulation at 2000 pulses per second. Simplicity of the hardware design makes the technique well suited to an implantable multi-channel recording system. PMID:20559458

  18. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following...

  19. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following...

  20. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following...

  1. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following...

  2. 42 CFR Appendix G to Part 75 - Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography G Appendix G to Part 75 Public Health PUBLIC HEALTH SERVICE...—Standards for Licensing Dental Hygienists and Dental Assistants in Dental Radiography The following...

  3. Cost-effectiveness of preventing dental caries and full mouth dental reconstructions among Alaska Native children in the Yukon–Kuskokwim delta region of Alaska

    PubMed Central

    Atkins, Charisma Y.; Thomas, Timothy K.; Lenaker, Dane; Day, Gretchen M.; Hennessy, Thomas W.; Meltzer, Martin I.

    2016-01-01

    Objective We conducted a cost-effectiveness analysis of five specific dental interventions to help guide resource allocation. Methods We developed a spreadsheet-based tool, from the healthcare payer perspective, to evaluate the cost effectiveness of specific dental interventions that are currently used among Alaska Native children (6-60 months). Interventions included: water fluoridation, dental sealants, fluoride varnish, tooth brushing with fluoride toothpaste, and conducting initial dental exams on children <18 months of age. We calculated the cost-effectiveness ratio of implementing the proposed interventions to reduce the number of carious teeth and full mouth dental reconstructions (FMDRs) over 10 years. Results A total of 322 children received caries treatments completed by a dental provider in the dental chair, while 161 children received FMDRs completed by a dental surgeon in an operating room. The average cost of treating dental caries in the dental chair was $1,467 (~258,000 per year); while the cost of treating FMDRs was $9,349 (~1.5 million per year). All interventions were shown to prevent caries and FMDRs; however tooth brushing prevented the greatest number of caries at minimum and maximum effectiveness with 1,433 and 1,910, respectively. Tooth brushing also prevented the greatest number of FMDRs (159 and 211) at minimum and maximum effectiveness. Conclusions All of the dental interventions evaluated were shown to produce cost savings. However, the level of that cost saving is dependent on the intervention chosen. PMID:26990678

  4. EEG artifact removal—state-of-the-art and guidelines

    NASA Astrophysics Data System (ADS)

    Urigüen, Jose Antonio; Garcia-Zapirain, Begoña

    2015-06-01

    This paper presents an extensive review on the artifact removal algorithms used to remove the main sources of interference encountered in the electroencephalogram (EEG), specifically ocular, muscular and cardiac artifacts. We first introduce background knowledge on the characteristics of EEG activity, of the artifacts and of the EEG measurement model. Then, we present algorithms commonly employed in the literature and describe their key features. Lastly, principally on the basis of the results provided by various researchers, but also supported by our own experience, we compare the state-of-the-art methods in terms of reported performance, and provide guidelines on how to choose a suitable artifact removal algorithm for a given scenario. With this review we have concluded that, without prior knowledge of the recorded EEG signal or the contaminants, the safest approach is to correct the measured EEG using independent component analysis—to be precise, an algorithm based on second-order statistics such as second-order blind identification (SOBI). Other effective alternatives include extended information maximization (InfoMax) and an adaptive mixture of independent component analyzers (AMICA), based on higher order statistics. All of these algorithms have proved particularly effective with simulations and, more importantly, with data collected in controlled recording conditions. Moreover, whenever prior knowledge is available, then a constrained form of the chosen method should be used in order to incorporate such additional information. Finally, since which algorithm is the best performing is highly dependent on the type of the EEG signal, the artifacts and the signal to contaminant ratio, we believe that the optimal method for removing artifacts from the EEG consists in combining more than one algorithm to correct the signal using multiple processing stages, even though this is an option largely unexplored by researchers in the area.

  5. EEG artifact removal-state-of-the-art and guidelines.

    PubMed

    Urigüen, Jose Antonio; Garcia-Zapirain, Begoña

    2015-06-01

    This paper presents an extensive review on the artifact removal algorithms used to remove the main sources of interference encountered in the electroencephalogram (EEG), specifically ocular, muscular and cardiac artifacts. We first introduce background knowledge on the characteristics of EEG activity, of the artifacts and of the EEG measurement model. Then, we present algorithms commonly employed in the literature and describe their key features. Lastly, principally on the basis of the results provided by various researchers, but also supported by our own experience, we compare the state-of-the-art methods in terms of reported performance, and provide guidelines on how to choose a suitable artifact removal algorithm for a given scenario. With this review we have concluded that, without prior knowledge of the recorded EEG signal or the contaminants, the safest approach is to correct the measured EEG using independent component analysis-to be precise, an algorithm based on second-order statistics such as second-order blind identification (SOBI). Other effective alternatives include extended information maximization (InfoMax) and an adaptive mixture of independent component analyzers (AMICA), based on higher order statistics. All of these algorithms have proved particularly effective with simulations and, more importantly, with data collected in controlled recording conditions. Moreover, whenever prior knowledge is available, then a constrained form of the chosen method should be used in order to incorporate such additional information. Finally, since which algorithm is the best performing is highly dependent on the type of the EEG signal, the artifacts and the signal to contaminant ratio, we believe that the optimal method for removing artifacts from the EEG consists in combining more than one algorithm to correct the signal using multiple processing stages, even though this is an option largely unexplored by researchers in the area.

  6. EEG Artifact Removal Using a Wavelet Neural Network

    NASA Technical Reports Server (NTRS)

    Nguyen, Hoang-Anh T.; Musson, John; Li, Jiang; McKenzie, Frederick; Zhang, Guangfan; Xu, Roger; Richey, Carl; Schnell, Tom

    2011-01-01

    !n this paper we developed a wavelet neural network. (WNN) algorithm for Electroencephalogram (EEG) artifact removal without electrooculographic (EOG) recordings. The algorithm combines the universal approximation characteristics of neural network and the time/frequency property of wavelet. We. compared the WNN algorithm with .the ICA technique ,and a wavelet thresholding method, which was realized by using the Stein's unbiased risk estimate (SURE) with an adaptive gradient-based optimal threshold. Experimental results on a driving test data set show that WNN can remove EEG artifacts effectively without diminishing useful EEG information even for very noisy data.

  7. "Diabetes and literacy: negotiating control through artifacts of medicalization".

    PubMed

    Martins, David S

    2009-06-01

    My experience with the California Department of Motor Vehicles offers a case to explore how bureaucratic institutions monitor, classify, and control individuals. By examining artifacts created for and used by the DMV through the lens of literacy studies, I discuss the variety of rhetorical strategies used in each document and the effects and implications of those strategies, for example on subjectivity or identity, and move beyond the language of the artifacts themselves to attend to how they are invested with power in the management and control of populations.

  8. Influence of dental materials on dental MRI

    PubMed Central

    Tymofiyeva, O; Vaegler, S; Rottner, K; Boldt, J; Hopfgartner, AJ; Proff, PC; Richter, E-J; Jakob, PM

    2013-01-01

    Objectives: To investigate the potential influence of standard dental materials on dental MRI (dMRI) by estimating the magnetic susceptibility with the help of the MRI-based geometric distortion method and to classify the materials from the standpoint of dMRI. Methods: A series of standard dental materials was studied on a 1.5 T MRI system using spin echo and gradient echo pulse sequences and their magnetic susceptibility was estimated using the geometric method. Measurements on samples of dental materials were supported by in vivo examples obtained in dedicated dMRI procedures. Results: The tested materials showed a range of distortion degrees. The following materials were classified as fully compatible materials that can be present even in the tooth of interest: the resin-based sealer AH Plus® (Dentsply, Maillefer, Germany), glass ionomer cement, gutta-percha, zirconium dioxide and composites from one of the tested manufacturers. Interestingly, composites provided by the other manufacturer caused relatively strong distortions and were therefore classified as compatible I, along with amalgam, gold alloy, gold–ceramic crowns, titanium alloy and NiTi orthodontic wires. Materials, the magnetic susceptibility of which differed from that of water by more than 200 ppm, were classified as non-compatible materials that should not be present in the patient’s mouth for any dMRI applications. They included stainless steel orthodontic appliances and CoCr. Conclusions: A classification of the materials that complies with the standard grouping of materials according to their magnetic susceptibility was proposed and adopted for the purposes of dMRI. The proposed classification can serve as a guideline in future dMRI research. PMID:23610088

  9. Improved method using a bubble-free adhesion technique for the preparation of semi-serial undecalcified histologic sections containing dental implants.

    PubMed

    Kihara, A; Morimoto, K; Suetsugu, T

    1989-01-01

    The preparation technique, with the minimum of artifacts for the semi-serial undecalcified histologic sections containing dental implants, is presented in this study. The sections enabled finer light-microscopic observations to be made. A formalin-fixed tissue block containing a dental implant was dehydrated in ethanol and acetone, and then embedded in polyester resin under 76 cm Hg reduced pressure. The embedded block was trimmed by a cutter and ground by abrasive paper. In a 1.5 Kg f/cm2 pressurized chamber, its polished surface was bonded to a methacrylate slide by means of ethylcyanoacrylate used in an adhesion loading device. This meant that no bubbles could arise in the interface between the slide and the block. The slide-block was then attached to an adsorptive specimen-holder of a hard-tissue cutting machine and cut to a thickness of approximately 50 microns, with use of a diamond blade. The slide-section was ground to 15-40 microns with wet-type abrasive paper and film on a polishing table. Etching with weak acid and surface staining with toluidine blue and methylene blue/basic fuchsin/light green were performed on the section. PMID:2701107

  10. Compressed-sensing (CS)-based 3D image reconstruction in cone-beam CT (CBCT) for low-dose, high-quality dental X-ray imaging

    NASA Astrophysics Data System (ADS)

    Lee, M. S.; Kim, H. J.; Cho, H. S.; Hong, D. K.; Je, U. K.; Oh, J. E.; Park, Y. O.; Lee, S. H.; Cho, H. M.; Choi, S. I.; Koo, Y. S.

    2013-09-01

    The most popular reconstruction algorithm for cone-beam computed tomography (CBCT) is based on the computationally-inexpensive filtered-backprojection (FBP) method. However, that method usually requires dense projections over the Nyquist samplings, which imposes severe restrictions on the imaging doses. Moreover, the algorithm tends to produce cone-beam artifacts as the cone angle is increased. Several variants of the FBP-based algorithm have been developed to overcome these difficulties, but problems with the cone-beam reconstruction still remain. In this study, we considered a compressed-sensing (CS)-based reconstruction algorithm for low-dose, high-quality dental CBCT images that exploited the sparsity of images with substantially high accuracy. We implemented the algorithm and performed systematic simulation works to investigate the imaging characteristics. CBCT images of high quality were successfully reconstructed by using the built-in CS-based algorithm, and the image qualities were evaluated quantitatively in terms of the universal-quality index (UQI) and the slice-profile quality index (SPQI).We expect the reconstruction algorithm developed in the work to be applicable to current dental CBCT systems, to reduce imaging doses, and to improve the image quality further.

  11. History of dental hygiene research.

    PubMed

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society. PMID:24046337

  12. History of dental hygiene research.

    PubMed

    Bowen, Denise M

    2013-01-01

    Dental hygiene is defined as the science and practice of the recognition, treatment and prevention of oral diseases. The history of dental hygiene research is considered in the context of the development of the discipline and an emerging infrastructure. Research-related events supporting the growth and maturation of the profession are considered from the early years to the most recent. The benefits of preventive oral health services provided by dental hygienists have been supported by research, and the practice of dental hygiene has expanded as a result of research findings since its inception 100 years ago. Dental hygienists' engagement in research, however, did not begin until the 1960s as research associates or administrators, primarily with dental researchers as primary investigators. The Journal of Dental Hygiene (JDH) has provided information for dental hygiene practice since 1927, and has been the primary venue for dissemination of dental hygiene research since 1945. Graduate education in dental hygiene at the master's degree level and the work of early dental hygiene researchers led to the first conference on dental hygiene research in 1982. Over 30 years later, dental hygiene has established a meta-paradigm and defined conceptual models, built an initial infrastructure to support research endeavors and contributed much to the development of dental hygiene as a unique discipline. A doctoral degree in the discipline, continued theory-based research, initiatives to foster collaborations between dental hygiene and other researchers and enhanced capabilities to attract funding to support large scale studies are goals that must be attained through the efforts of future researchers to address the needs for additional development in the discipline of dental hygiene. Dental hygiene research supports the growing discipline and its value to society.

  13. High-fidelity artifact correction for cone-beam CT imaging of the brain.

    PubMed

    Sisniega, A; Zbijewski, W; Xu, J; Dang, H; Stayman, J W; Yorkston, J; Aygun, N; Koliatsos, V; Siewerdsen, J H

    2015-02-21

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening.The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT.Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  14. High-fidelity artifact correction for cone-beam CT imaging of the brain

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Zbijewski, W.; Xu, J.; Dang, H.; Stayman, J. W.; Yorkston, J.; Aygun, N.; Koliatsos, V.; Siewerdsen, J. H.

    2015-02-01

    CT is the frontline imaging modality for diagnosis of acute traumatic brain injury (TBI), involving the detection of fresh blood in the brain (contrast of 30-50 HU, detail size down to 1 mm) in a non-contrast-enhanced exam. A dedicated point-of-care imaging system based on cone-beam CT (CBCT) could benefit early detection of TBI and improve direction to appropriate therapy. However, flat-panel detector (FPD) CBCT is challenged by artifacts that degrade contrast resolution and limit application in soft-tissue imaging. We present and evaluate a fairly comprehensive framework for artifact correction to enable soft-tissue brain imaging with FPD CBCT. The framework includes a fast Monte Carlo (MC)-based scatter estimation method complemented by corrections for detector lag, veiling glare, and beam hardening. The fast MC scatter estimation combines GPU acceleration, variance reduction, and simulation with a low number of photon histories and reduced number of projection angles (sparse MC) augmented by kernel de-noising to yield a runtime of ~4 min per scan. Scatter correction is combined with two-pass beam hardening correction. Detector lag correction is based on temporal deconvolution of the measured lag response function. The effects of detector veiling glare are reduced by deconvolution of the glare response function representing the long range tails of the detector point-spread function. The performance of the correction framework is quantified in experiments using a realistic head phantom on a testbench for FPD CBCT. Uncorrected reconstructions were non-diagnostic for soft-tissue imaging tasks in the brain. After processing with the artifact correction framework, image uniformity was substantially improved, and artifacts were reduced to a level that enabled visualization of ~3 mm simulated bleeds throughout the brain. Non-uniformity (cupping) was reduced by a factor of 5, and contrast of simulated bleeds was improved from ~7 to 49.7 HU, in good agreement

  15. Spatiotemporal filtering of MR-temperature artifacts arising from bowel motion during transurethral MR-HIFU

    SciTech Connect

    Schmitt, Alain; Mougenot, Charles; Chopra, Rajiv

    2014-11-01

    Purpose: Transurethral MR-HIFU is a minimally invasive image-guided treatment for localized prostate cancer that enables precise targeting of tissue within the gland. The treatment is performed within a clinical MRI to obtain real-time MR thermometry used as an active feedback to control the spatial heating pattern in the prostate and to monitor for potential damage to surrounding tissues. This requires that the MR thermometry measurements are an accurate representation of the true tissue temperature. The proton resonance frequency shift thermometry method used is sensitive to tissue motion and changes in the local magnetic susceptibility that can be caused by the motion of air bubbles in the rectum, which can impact the performance of transurethral MR-HIFU in these regions of the gland. Methods: A method is proposed for filtering of temperature artifacts based on the temporal variance of the temperature, using empirical and dynamic positional knowledge of the ultrasonic heating beam, and an estimation of the measurement noise. A two-step correction strategy is introduced which eliminates artifact-detected temperature variations while keeping the noise level low through spatial averaging. Results: The filter has been evaluated by postprocessing data from five human transurethral ultrasound treatments. The two-step correction process led to reduced final temperature standard deviation in the prostate and rectum areas where the artifact was located, without negatively affecting areas distal to the artifact. The performance of the filter was also found to be consistent across all six of the data sets evaluated. The evaluation of the detection criterion parameter M determined that a value of M = 3 achieves a conservative filter with minimal loss of spatial resolution during the process. Conclusions: The filter was able to remove most artifacts due to the presence of moving air bubbles in the rectum during transurethral MR-HIFU. A quantitative estimation of the filter

  16. True Pathologic Abnormality versus Artifact Foot Position and Magic Angle Artifact in the Peroneal Tendons with 3T Imaging.

    PubMed

    Horn, Deena B; Meyers, Steven; Astor, William

    2015-09-01

    Magnetic resonance imaging is a commonly ordered examination by many foot and ankle surgeons for ankle pain and suspected peroneal tendon pathologic abnormalities. Magic angle artifact is one of the complexities associated with this imaging modality. Magic angle refers to the increased signal on magnetic resonance images associated with the highly organized collagen fibers in tendons and ligaments when they are orientated at a 55° angle to the main magnetic field. We present several examples from a clinical practice setting using 3T imaging illustrating a substantial reduction in magic angle artifact of the peroneal tendon in the prone plantarflexed position compared with the standard neutral (right angle) position.

  17. Bulimia and Anorexia Nervosa in Dental and Dental Hygiene Curricula.

    ERIC Educational Resources Information Center

    Gross, Karen B. W.; And Others

    1990-01-01

    Dentists and dental hygienists are in a unique position to identify an eating disorder patient from observed oral manifestations and to refer the patient for psychological therapy. The inclusion of information on general and oral complications of bulimia and anorexia nervosa in dental and dental hygiene curriculum was examined. (MLW)

  18. Dental practice network of U.S. dental schools.

    PubMed

    Fisher, Monica A; Beeson, Dennis C; Hans, Mark G

    2009-12-01

    As dental schools incorporate training in evidence-based dentistry (EBD) into their curricula, students must learn how to critically evaluate systematic reviews and meta-analyses. It is important that dental education in the United States support the American Dental Association's position statement on EBD, which defines "best evidence" as data obtained from all study designs. Given that much evidence is missing when EBD is derived from Cochrane Systematic Reviews' randomized clinical trials, we propose the creation of a dental practice network of U.S. dental schools. We developed an electronic clinical dentistry research database for EBD using Epi-Info (available at www.cdc.gov/epiinfo/downloads.htm). As a free, public use software, Epi-Info provides the foundation for the development of clinical research databases that can increase the research capacity through multisite studies designed to generate outcomes data on the effectiveness of dental treatment. The creation of a dental practice network of dental schools with their large number of patients would expand the research capacity for EBD practice and advance the EBD science regarding the effectiveness of dental treatment. The next step is to link clinical dental researchers/educators at multiple dental schools through a collaborative clinical research network, so that the findings can be applied to the EBD component of problem-based learning curricula of dental education.

  19. Dental Implantology in U.S. Dental Schools.

    ERIC Educational Resources Information Center

    Bavitz, J. Bruce

    1990-01-01

    The results of a survey of 44 dental schools corroborate the belief that dental implantology is gaining widespread acceptance in U.S. dental schools. Currently, predoctoral students have limited clinical participation. Most programs have taken the position that clinical techniques are best taught within the existing specialties at a graduate…

  20. Utility of Megavoltage Fan-Beam CT for Treatment Planning in a Head-And-Neck Cancer Patient with Extensive Dental Fillings Undergoing Helical Tomotherapy

    SciTech Connect

    Yang, Claus; Liu Tianxiao; Jennelle, Richard L.; Ryu, Janice K.; Vijayakumar, Srinivasan; Purdy, James A.; Chen, Allen M.

    2010-07-01

    The purpose of this study was to demonstrate the potential utility of megavoltage fan-beam computed tomography (MV-FBCT) for treatment planning in a patient undergoing helical tomotherapy for nasopharyngeal carcinoma in the presence of extensive dental artifact. A 28-year-old female with locally advanced nasopharyngeal carcinoma presented for radiation therapy. Due to the extensiveness of the dental artifact present in the oral cavity kV-CT scan acquired at simulation, which made treatment planning impossible on tomotherapy planning system, MV-FBCT imaging was obtained using the HI-ART tomotherapy treatment machine, with the patient in the treatment position, and this information was registered with her original kV-CT scan for the purposes of structure delineation, dose calculation, and treatment planning. To validate the feasibility of the MV-FBCT-generated treatment plan, an electron density CT phantom (model 465, Gammex Inc., Middleton, WI) was scanned using MV-FBCT to obtain CT number to density table. Additionally, both a 'cheese' phantom (which came with the tomotherapy treatment machine) with 2 inserted ion chambers and a generic phantom called Quasar phantom (Modus Medical Devices Inc., London, ON, Canada) with one inserted chamber were used to confirm dosimetric accuracy. The MV-FBCT could be used to clearly visualize anatomy in the region of the dental artifact and provide sufficient soft-tissue contrast to assist in the delineation of normal tissue structures and fat planes. With the elimination of the dental artifact, the MV-FBCT images allowed more accurate dose calculation by the tomotherapy system. It was confirmed that the phantom material density was determined correctly by the tomotherapy MV-FBCT number to density table. The ion chamber measurements agreed with the calculations from the MV-FBCT generated phantom plan within 2%. MV-FBCT may be useful in radiation treatment planning for nasopharyngeal cancer patients in the setting of extensive