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Tomography Images (tomography + image)
Selected AbstractsAdjusted Scaling of FDG Positron Emission Tomography Images for Statistical Evaluation in Patients With Suspected Alzheimer's DiseaseJOURNAL OF NEUROIMAGING, Issue 4 2005Ralph Buchert PhD ABSTRACT Background and Purpose. Statistical parametric mapping (SPM) gained increasing acceptance for the voxel-based statistical evaluation of brain positron emission tomography (PET) with the glucose analog 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) in patients with suspected Alzheimer's disease (AD). To increase the sensitivity for detection of local changes, individual differences of total brain FDG uptake are usually compensated for by proportional scaling. However, in cases of extensive hypometabolic areas, proportional scaling overestimates scaled uptake. This may cause significant underestimation of the extent of hypometabolic areas by the statistical test. Methods. To detect this problem, the authors tested for hyper metabolism. In patients with no visual evidence of true focal hypermetabolism, significant clusters of hypermetabolism in the presence of extended hypometabolism were interpreted as false-positive findings, indicating relevant overestimation of scaled uptake. In this case, scaled uptake was reduced step by step until there were no more significant clusters of hypermetabolism. Results. In 22 consecutive patients with suspected AD, proportional scaling resulted in relevant overestimation of scaled uptake in 9 patients. Scaled uptake had to be reduced by 11.1%± 5.3% in these cases to eliminate the artifacts. Adjusted scaling resulted in extension of existing and appearance of new clusters of hypometabolism. Total volume of the additional voxels with significant hypometabolism depended linearly on the extent of the additional scaling and was 202 ± 118 mL on average. Conclusions. Adjusted scaling helps to identify characteristic metabolic patterns in patients with suspected AD. It is expected to increase specificity of FDGPET in this group of patients. [source] The seismic anomaly beneath Iceland extends down to the mantle transition zone and no deeperGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000G. R. Foulger A 3-D teleseismic tomography image of the upper mantle beneath Iceland of unprecedented resolution reveals a subvertical low wave speed anomaly that is cylindrical in the upper 250 km but tabular below this. Such a morphological transition is expected towards the bottom of a buoyant upwelling. Our observations thus suggest that magmatism at the Iceland hotspot is fed by flow rising from the mantle transition zone. This result contributes to the ongoing debate about whether the upper and lower mantles convect separately or as one. The image also suggests that material flows outwards from Iceland along the Reykjanes Ridge in the upper 200 km, but is blocked in the upper 150 km beneath the Tjornes Fracture Zone. This provides direct observational support for the theory that fracture zones dam lateral flow along ridges. [source] Odontogenic keratocyst in maxillary sinus with invasive behaviourJOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 4 2006Eneida Franco Vencio Odontogenic keratocyst is a cystic lesion characterized by a high rate of recurrence. This report describes a rare case of ciliated epithelium-lined odontogenic keratocyst in the maxilla of a 27-year-old female. Panoramic radiography showed a lytic lesion on the right maxilla associated with an impacted molar tooth. Computerized tomography image revealed the involvement of the lesion with the right maxillary sinus, destroying the sinus floor. Histopathologically, the typical keratinized epithelial-lined cyst of odontogenic keratocyst abruptly changed into a ciliated epithelium, suggesting the fusion of both these epithelia rather a metaplastic transformation. The biological behaviour of odontogenic keratocysts is discussed. [source] Micro-focus X-ray computed tomography images of the 3D structure of the cranium of a fetus with asymmetric double malformationCONGENITAL ANOMALIES, Issue 1 2006Takashi Shibata ABSTRACT,, Reconstructed micro computed tomography (Micro-CT, µ-CT) images have revealed the detailed three-dimensional structure of the cranium of human fetal congenital anomalies for the first time. The objects were a head and a cervix of female autosite and a parasite consisting of only a head conjoined to the scapular region of the autosite of an asymmetric double malformation (asymmetric conjoined twins, heteropagus twinning) at a gestational age of 8 months. The cranium of the autosite was normal, but that of the parasite was characterized by otocephaly (agnathia, synotia, and monorhina) and almost all the cranial bones were of an abnormal shape. It is suggested that a part of occipital bone (the basioccipital and exoccipital bones), the vomer and cribriform plate were absent and this resulted in the fusion and overlapping of bilateral temporal and craniofacial bones that should have been adjacent to them. This resulted in a reformation and relocation of most of the cranial bones. Micro-CT is a useful tool to visualize the detailed bone structure which has not been clarified by the conventional dissection methods and other imaging technologies and is a powerful instrument for studying congenital anomalies. [source] Colon segmentation and colonic polyp detection using cellular neural networks and three-dimensional template matchingEXPERT SYSTEMS, Issue 5 2009Niyazi Kilic Abstract: In this study, an automatic three-dimensional computer-aided detection system for colonic polyps was developed. Computer-aided detection for computed tomography colonography aims at facilitating the detection of colonic polyps. First, the colon regions of whole computed tomography images were carefully segmented to reduce computational burden and prevent false positive detection. In this process, the colon regions were extracted by using a cellular neural network and then the regions of interest were determined. In order to improve the segmentation performance of the study, weights in the cellular neural network were calculated by three heuristic optimization techniques, namely genetic algorithm, differential evaluation and artificial immune system. Afterwards, a three-dimensional polyp template model was constructed to detect polyps on the segmented regions of interest. At the end of the template matching process, the volumes geometrically similar to the template were emhanced. [source] Computer-aided diagnosis system for the detection of bronchiectasis in chest computed tomography imagesINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2009D. Shiloah Elizabeth Abstract A computer-aided diagnosis (CAD) system has been developed for the detection of bronchiectasis from computed tomography (CT) images of chest. A set of CT images of the chest with known diagnosis were collected and these images were first denoised using Wiener filter. The lung tissue was then segmented using optimal thresholding. The Pathology Bearing Regions (PBRs) were then extracted by applying pixel-based segmentation. For each PBR, a gray level co-occurrence matrix (GLCM) was constructed. From the GLCM texture features were extracted and feature vectors were constructed. A probabilistic neural network (PNN) was constructed and trained using this set of feature vectors. The images together with the PBRs and the corresponding feature vector and diagnosis were stored in an image database. Rules for diagnosis and for determining the severity of the disease were generated by analyzing the images known to be affected by bronchiectasis. The rules were then validated by a human expert. The validated rules were stored in the Knowledge Base. When a physician gives a CT image to the CAD system, it first transforms the image into a set of feature vectors, one for each PBR in the image. It then performs the diagnosis using two techniques: PNN and mahalanobis distance measure. The final diagnosis and the severity of the disease are determined by correlating the diagnosis determined by both the techniques in consultation with the knowledge base. The system also retrieves similar cases from the database. Thus, this system would aid the physicians in diagnosing bronchiectasis. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 290,298, 2009 [source] Validation of the murine aortic arch as a model to study human vascular diseasesJOURNAL OF ANATOMY, Issue 5 2010Christophe Casteleyn Abstract Although the murine thoracic aorta and its main branches are widely studied to gain more insight into the pathogenesis of human vascular diseases, detailed anatomical data on the murine aorta are sparse. Moreover, comparative studies between mice and men focusing on the topography and geometry of the heart and aorta are lacking. As this hampers the validation of murine vascular models, the branching pattern of the murine thoracic aorta was examined in 30 vascular corrosion casts. On six casts the intrathoracic position of the heart was compared with that of six younger and six older men of whom contrast-enhanced computer tomography images of the thorax were three-dimensionally reconstructed. In addition, the geometry of the human thoracic aorta was compared with that of the mouse by reconstructing micro-computer tomography images of six murine casts. It was found that the right brachiocephalic trunk, left common carotid artery and left subclavian artery branched subsequently from the aortic arch in both mice and men. The geometry of the branches of the murine aortic arch was quite similar to that of men. In both species the initial segment of the aorta, comprising the ascending aorta, aortic arch and cranial/superior part of the descending aorta, was sigmoidally curved on a cranial/superior view. Although some analogy between the intrathoracic position of the murine and human heart was observed, the murine heart manifestly deviated more ventrally. The major conclusion of this study is that, in both mice and men, the ascending and descending aorta do not lie in a single vertical plane (non-planar aortic geometry). This contrasts clearly with most domestic mammals in which a planar aortic pattern is present. As the vascular branching pattern of the aortic arch is also similar in mice and men, the murine model seems valuable to study human vascular diseases. [source] Trabecular Bone Tissue Strains in the Healthy and Osteoporotic Human Femur,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2003B Van Rietbergen Quantitative information about bone tissue-level loading is essential for understanding bone mechanical behavior. We made microfinite element models of a healthy and osteoporotic human femur and found that tissue-level strains in the osteoporotic femoral head were 70% higher on average and less uniformly distributed than those in the healthy one. Introduction: Bone tissue stresses and strains in healthy load-adapted trabecular architectures should be distributed rather evenly, because no bone tissue is expected to be overloaded or unused. In this study, we evaluate this paradigm with the use of microfinite element (,FE) analyses to calculate tissue-level stresses and strains for the human femur. Our objectives were to quantify the strain distribution in the healthy femur, to investigate to what extent this distribution is affected by osteoporosis, to determine if osteoporotic bone is simply bone adapted to lower load levels, and to determine the "safety factor" for trabecular bone. Materials and Methods: ,FE models of a healthy and osteoporotic proximal femur were made from microcomputed tomography images. The models consisted of over 96 and 71 million elements for the healthy and osteoporotic femur, respectively, and represented their internal and external morphology in detail. Stresses and strains were calculated for each element and their distributions were calculated for a volume of interest (VOI) of trabecular bone in the femoral head. Results: The average tissue-level principal strain magnitude in the healthy VOI was 304 ± 185 microstrains and that in the osteoporotic VOI was 520 ± 355 microstrains. Calculated safety factors were 8.6 for the healthy and 4.9 for the osteoporotic femurs. After reducing the force applied to the osteoporotic model to 59%, the average strain compared with that of the healthy femur, but the SD was larger (208 microstrains). Conclusions: Strain magnitudes in the osteoporotic bone were much higher and less uniformly distributed than those in the healthy one. After simulated joint-load reduction, strain magnitudes in the osteoporotic femur were very similar to those in the healthy one, but their distribution is still wider and thus less favorable. [source] Effect of lateral target motion on image registration accuracy in CT-guided helical tomotherapy: A phantom studyJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 3 2010J Medwig Summary Optimisation of imaging modes for kilovoltage CT (kVCT) used for treatment planning and megavoltage CT (MVCT) image guidance used in ungated helical tomotherapy was investigated for laterally moving targets. Computed tomography images of the QUASARÔ Respiratory Motion Phantom were acquired without target motion and for lateral motion of the target, with 2-cm peak-to-peak amplitude and a period of 4 s. Reference kVCT images were obtained using a 16-slice CT scanner in standard fast helical CT mode, untagged average CT mode and various post-processed 4D-CT modes (0% phase, average and maximum intensity projection). Three sets of MVCT images with different inter-slice spacings of were obtained on a Hi-Art tomotherapy system with the phantom displaced by a known offset position. Eight radiation therapists performed co-registration of MVCT obtained with 2-, 4- and 6-mm slice spacing and kVCT studies independently for all 15 CT imaging combinations. In the investigated case, the untagged average kVCT and 4-mm slice spacing for the MVCT yielded more accurate registration in the transverse plane. The average residual uncertainty of this combination of imaging procedures was 0.61 ± 0.16 mm in the longitudinal direction, 0.45 ± 0.14 mm in the anterior,posterior direction and insignificant in the lateral direction. Manual registration of MVCT,kVCT study pairs is necessary to account for a target in significant lateral motion with respect to bony structures. [source] Topical administration of simvastatin recovers alveolar bone loss in ratsJOURNAL OF PERIODONTAL RESEARCH, Issue 3 2008H. Seto Background and Objective:, Simvastatin, a cholesterol-lowering drug, has been reported to show anabolic effects on bone metabolism. We examined the effects of simvastatin in vitro using cultured rat calvaria cells and in vivo using periodontitis-induced rats. Material and Methods:, Alkaline phosphatase activity and bone nodule formation were measured in cultured rat calvaria cells. Nylon ligature was placed around the maxillary molars of Fischer male rats for 20 d to induce alveolar bone resorption. After ligature removal, simvastatin was topically injected into the buccal gingivae for 70 d and then microcomputed tomography and histological examinations were performed. Results:, Simvastatin maintained high alkaline phosphatase activity and increased bone nodule formation in rat calvaria cells in a dose-dependent manner, showing that simvastatin increased and maintained a high level of osteoblastic function. Microcomputed tomography images revealed that treatment with simvastatin recovered the ligature-induced alveolar bone resorption, showing a 46% reversal of bone height. Histological examination clarified that low-mineralized alveolar bone was formed in simvastatin-treated rats. Conclusion:, These findings demonstrate that simvastatin has the potential to stimulate osteoblastic function and that topical administration of simvastatin may be effective for the recovery of alveolar bone loss in rats. [source] Analyser-based tomography images of cartilageJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2008Ahi S. Issever Analyser-based imaging expands the performance of X-ray imaging by utilizing not only the absorption properties of X-rays but also the refraction and scatter rejection (extinction) properties. In this study, analyser-based computed tomography has been implemented on imaging an articular cartilage sample, depicting substructural variations, without overlay, at a pixel resolution of 3.6,µm. [source] Principal component analysis of landmarks from reversible imagesJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2004C. M. Theobald Summary., We consider the use of principal component analysis to summarize the variation in labelled landmark data for images which are reversible in the sense that a mirror image may be defined for each image and the original and mirror images may be regarded as equally representative of the population. We examine the effect of including the original and mirror images on a principal component analysis based on the landmark co-ordinates. The inclusion of mirror images is found to lead to a simplified interpretation in which some components measure asymmetry in the images and the remainder depend symmetrically on pairs of co-ordinates. This is illustrated on shape variation in carrots. A second application is to the segmentation of X-ray computed tomography images of sheep to locate the inner boundary of the carcass. It is found that image boundaries can be identified more accurately by modelling them with principal components, and that including mirror images can offer a further improvement in accuracy. Similar arguments apply when a population of images is thought to be invariant under a rotation and may also be relevant when a principal component analysis is applied to descriptive statistics such as Fourier sums. [source] Modeling Flow in a Compromised Pediatric Airway Breathing Air and HelioxTHE LARYNGOSCOPE, Issue 12 2008Mihai Mihaescu PhD Abstract Objectives/Hypothesis: The aim of this study was to perform computer simulations of flow within an accurate model of a pediatric airway with subglottic stenosis. It is believed that the airflow characteristics in a stenotic airway are strongly related to the sensation of dyspnea. Methodology: Computed tomography images through the respiratory tract of an infant with subglottic stenosis, were used to construct the three-dimensional geometry of the airway. By using computational fluid dynamics (CFD) modeling to capture airway flow patterns during inspiration and expiration, we obtained information pertaining to flow velocity, static airway wall pressure, pressure drop across the stenosis, and wall shear stress. These simulations were performed with both air and heliox. Results: Unlike air, heliox maintained laminar flow through the stenosis. The calculated pressure drop over stenosis was lower for the heliox flow, in contrast to the airflow case. This lead to an approximately 40% decrease in airway resistance when using heliox, and presumably causes a decrease in the level of effort required for breathing. Conclusions: CFD simulations offer a quantitative method of evaluating airway flow dynamics in patients with airway abnormalities. CFD modeling illustrated the flow features and quantified flow parameters within a pediatric airway with subglottic stenosis. Simulations with air and heliox conditions mirrored the known clinical benefits of heliox as compared with air. We anticipate that computer simulation models will ultimately allow a better understanding of changes in flow caused by specific medical and surgical interventions in patients with conditions associated with dyspnea. [source] Functional Generalized Linear Models with Images as PredictorsBIOMETRICS, Issue 1 2010Philip T. Reiss Summary Functional principal component regression (FPCR) is a promising new method for regressing scalar outcomes on functional predictors. In this article, we present a theoretical justification for the use of principal components in functional regression. FPCR is then extended in two directions: from linear to the generalized linear modeling, and from univariate signal predictors to high-resolution image predictors. We show how to implement the method efficiently by adapting generalized additive model technology to the functional regression context. A technique is proposed for estimating simultaneous confidence bands for the coefficient function; in the neuroimaging setting, this yields a novel means to identify brain regions that are associated with a clinical outcome. A new application of likelihood ratio testing is described for assessing the null hypothesis of a constant coefficient function. The performance of the methodology is illustrated via simulations and real data analyses with positron emission tomography images as predictors. [source] Histology of highly echolucent regions in optical coherence tomography images from two patients with sirolimus-eluting stent restenosis,CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 6 2010Hiroyuki Nagai MD Abstract We report on two patients with sirolimus-eluting stent (SES) restenosis lesions who showed highly echolucent regions by optical coherence tomography (OCT) and who could be assessed histologically after removal by directional coronary atherectomy (DCA). One restenosis lesion had a bilayer structure of hyperechoic outer layers and highly echolucent inner layers on OCT images and histologically exhibited myxomatous neointima tissue in the highly echolucent regions; another restenosis case showed patchy and highly echolucent regions throughout the layers and its histology revealed fibrin thrombosis. We should be aware that patterns of echolucent on OCT images may have various histology. OCT allows the visualization of fine lesions that conventional intravascular ultrasound (IVUS) cannot provide. The OCT images of drug-eluting stent restenosis lesions often show echolucent regions [Shuzoh et al., EuroInterv 2006;1:484]. However, no histological study of the lesions has been reported to date. Here we report on two patients with SES restenosis lesions that showed highly echolucent regions by OCT and that could be assessed histologically after removal by DCA. © 2009 Wiley-Liss, Inc. [source] Evaluating the effect of the new alignment algorithm for longitudinal series of Heidelberg retina tomography imagesACTA OPHTHALMOLOGICA, Issue 2 2008Ciara Bergin Abstract. Purpose:, To evaluate the impact of a new image-alignment algorithm on the repeatability of longitudinal measurements obtained from Heidelberg retina tomograph (HRT) images. Methods:, HRTI and HRTII image series from 124 patients with glaucoma or ocular hypertension were made available from previously reported studies and were reprocessed with the old and new image-alignment algorithms. Improvements afforded by the new alignment algorithm were examined by considering statistically significant improvement in repeatability of specific stereometric parameters (SP), namely rim area (RA), rim volume (RV), cup volume (CV) and cup shape measure (CSM). A further comparison was made by examining reduction in the variability of pixel-by-pixel height measures within image series. Results:, In some HRT image series, the new algorithm automatically corrected obvious misalignment events that occurred with the previous algorithm. However, average improvement in repeatability of the SP in HRTI image series was not statistically significant (P = 0.13) and there was no statistically significant reduction in pixel-by-pixel height measurement variability (P =0.73). In HRTII image series, there was evidence of improvement, on average, in the repeatability of some parameters (RA, P = 0.01; RV, P = 0.02; CSM, P = 0.05), but not in CV (P = 0.22). There was a large reduction in pixel-by-pixel variability in HRTII image series (P,<,0.001). Conclusion:, There was no evidence to show that the new algorithm improved repeatability, on average, in HRTI images. However, the application of the new algorithm to HRTII image series marginally improved repeatability in stereometric measures and yielded a significant reduction in pixel-by-pixel variability. [source] Laryngeal epithelial thickness: a comparison between optical coherence tomography and histologyCLINICAL OTOLARYNGOLOGY, Issue 5 2009M.L. Kaiser Objectives:, Optical coherence tomography, an imaging modality using near-infrared light, produces cross-sectional tissue images with a lateral pixel resolution of 10 ,m. However, normative data is first needed on epithelial thickness for lesion characterisation, and, to date, little exists. The purpose of our study is to measure normal laryngeal epithelial thickness by in vivo optical coherence tomography, and compare these values to those obtained from fixed ex-vivo laryngectomy specimens. Design and Setting:, Prospective at a single medical center in California, United States. Participants: A total of 116 patients undergoing operative endoscopy. Main outcome measures:, Optical coherence tomography images of clinically normal laryngeal subsites were selected. Calibrated measurements of epithelial thickness at various laryngeal subsites were recorded. Measurements of epithelial thickness from corresponding areas were obtained using optical micrometry on histologically normal regions of 15 total laryngectomy specimens. Descriptive statistics were performed. Results:, Mean epithelial optical coherence tomography thicknesses were: true vocal cords (81 ,m), false vocal cords (78 ,m), subglottis (61 ,m), aryepiglottic folds (111 ,m), laryngeal epiglottis (116 ,m) and lingual epiglottis (170 ,m). Epithelial thicknesses in fixed tissues were: true vocal cords (103 ,m), false vocal cords (79 ,m), aryepiglottic folds (205 ,m) subglottis (61 ,m), laryngeal epiglottis (38 ,m) and lingual epiglottis (130 ,m). Conclusions:, Optical coherence tomography does not have the artifacts associated with conventional histologic techniques. The inevitable development of office-based optical coherence tomography devices will increase the precision of laryngeal measurements and contribute to the clinical application of this technology in diagnosing laryngeal disease. [source] | |||||||||||||||||||||||||