Non-invasive mapping of connections between human thalamus and cortex using diffusion imaging.

Evidence concerning anatomical connectivities in the human brain is sparse and based largely on limited post-mortem observations. Diffusion tensor imaging has previously been used to define large white-matter tracts in the living human brain, but this technique has had limited success in tracing pathways into gray matter. Here we identified specific connections between human thalamus and cortex using a novel probabilistic tractography algorithm with diffusion imaging data. Classification of thalamic gray matter based on cortical connectivity patterns revealed distinct subregions whose locations correspond to nuclei described previously in histological studies. The connections that we found between thalamus and cortex were similar to those reported for non-human primates and were reproducible between individuals. Our results provide the first quantitative demonstration of reliable inference of anatomical connectivity between human gray matter structures using diffusion data and the first connectivity-based segmentation of gray matter.

Digital mammography: a world without film?

OBJECTIVES: eDiaMoND is a next generation Internet ("Grid") multidisciplinary research project funded by the UK e-Science Programme with the following objectives; the development of a next generation Internet enabled prototype to demonstrate the potential benefits of a national infrastructure to support digital mammography; the exploration of potential benefits for digital mammography systems, with particular emphasis being placed on selected applications, namely, screening, training, computer-aided detection and appropriate support for epidemiological studies. METHODS: EDiaMoND has worked in conjunction with selected clinical partners to enable the collection of valuable mammography information and the design of applications based upon extensive requirements gathering exercises. The clinical partners validated both the immediate needs and assisted with defining future needs of such an architecture to support the UK Health Service. RESULTS: The project has succeeded in invoking the interest of clinical partners and representatives of the UK NHS Breast Screening Programme in our vision of a world without film, albeit a long way off. The project has also succeeded in identifying the barriers to adopting this approach with the current limitations within the NHS, and has developed a blueprint for working towards this strategy. CONCLUSIONS: A UK national digital mammography archive has the potential to provide major benefits for the UK. For example, such an archive could: ensure that previous mammograms are always available, and could link up seamlessly the screening, assessment and symptomatic clinics; it could provide a huge teaching and training resource; it could be a huge resource for epidemiological studies.

Scanning electron microscopy of teeth in dominant osteogenesis imperfecta: support for genetic heterogeneity.

Scanning electron microscopic studies were performed on 25 deciduous and permanent teeth from members of 7 kindreds with dominant nonlethal osteogenesis imperfects (OI). Two families had normal teeth on clinical and radiological examination; five families had blue or brown opalescent teeth with specific radiologic findings. Enamel surfaces and prism organization were normal on all teeth. On fractured surfaces, the dentin tubules of normal teeth from patients with OI were evenly distributed and coursed regularly to the dentin-enamel junction. Opalescent teeth had few tubules and those present were short, narrow, and tortuous. Dentin calcification fronts of normal teeth were composed of many nodules with regularly spaced openings on their surfaces. Calcification fronts of opalescent teeth were composed of irregularly spaced, small nodules, which varied greatly in size and the nodules lacked tubule openings on their surfaces. The results of this study support the concept that at least two dominant forms of OI exist--one in which all individuals with IO have normal teeth, and the other in which all with OI have blue or brown opalescent teeth with characteristic changes on SEM.

Osteogenesis imperfecta lethal in infancy: case report and scanning electron microscopic studies of the deciduous teeth.

Radiologic evaluation of the skeleton and scanning electron microscopic studies of the teeth were performed on an infant boy with a lethal osteogenesis imperfecta (OI) syndrome who died at 10 mo of pneumonia. The skeletal findings included ribs that were focally expanded by fracture calluses, flat vertebral bodies, and wide limb bones. On fractured tooth surfaces, the enamel and dentin were normal as was the dentin calcification front. Although microscopic abnormalities have been noted in teeth from previously reported infants with lethal OI, a few studies also report infants with normal teeth. These differences in dental findings may indicate heterogeneity in OI lethal in infancy. Results of our study indicate that, until the primary biochemical defects in the OI syndromes are elucidated, examination of teeth from other infants with lethal OI and detailed evaluation of other clinical and skeletal features will aid in delineating heterogeneity and variation in expression in lethal OI.

The electron microscopy of bacteriophage-like particles in dental plaque.

The morphology of bacteriophage-like particles contained in samples of dental plaque is described. The phage-like particles were observed within fusiform-shaped bacteria and in clumps between bacteria. The particles were hexagonal in cross section, approximately 1,100 nm in diameter and contained an electron-dense core. In areas of cell lysis tail forms were observed both free and in association with the particles. Occasional particles were attached to bacterial cell walls by means of shortened tailpieces.

Localization of bacteria on the rat tongue with scanning and transmission electron microscopy.

Scanning microscopy of rat tongue showed that bacterial habitation of the tongue was almost completely localized to the middle third of the anterior surface of the filiform papillae. Transmission microscopy showed coccal forms attached to the surface of the epithelium by means of fibrillar strands and present up to four cell layers deep within the epithelium.

Computing the scatter component of mammographic images.

The authors build upon a technical report (Tech. Report OUEL 2009/93, Engng. Sci., Oxford Uni., Oxford, UK, 1993) in which they proposed a model of the mammographic imaging process for which scattered radiation is a key degrading factor. Here, the authors propose a way of estimating the scatter component of the signal at any pixel within a mammographic image, and they use this estimate for model-based image enhancement. The first step is to extend the authors' previous model to divide breast tissue into "interesting" (fibrous/glandular/cancerous) tissue and fat. The scatter model is then based on the idea that the amount of scattered radiation reaching a point is related to the energy imparted to the surrounding neighbourhood. This complex relationship is approximated using published empirical data, and it varies with the size of the breast being imaged. The approximation is further complicated by needing to take account of extra-focal radiation and breast edge effects. The approximation takes the form of a weighting mask which is convolved with the total signal (primary and scatter) to give a value which is input to a "scatter function", approximated using three reference cases, and which returns a scatter estimate. Given a scatter estimate, the more important primary component can be calculated and used to create an image recognizable by a radiologist. The images resulting from this process are clearly enhanced, and model verification tests based on an estimate of the thickness of interesting tissue present proved to be very successful. A good scatter model opens the was for further processing to remove the effects of other degrading factors, such as beam hardening.

Detecting the brain surface in sparse MRI using boundary models.

We introduce a framework for the detection of the brain boundary (arachnoid) within sparse MRI. We use the term sparse to describe volumetric images in which the sampling resolution within the imaging plane is far higher than that of the perpendicular direction. Generic boundary detection schemes do not provide good results for such data. In the scheme we propose, the boundary is extracted using a constrained mesh surface which iteratively approximates a 3D point set consisting of detected boundary points. Boundary detection is based on a database of piecewise constant models, which represent the idealised MR intensity profile of the underlying boundary anatomy. A non-linear matching scheme is introduced to estimate the location of the boundary points using only the intensity data within each image plane. Results are shown for a number of images and are discussed in detail.

Estimation of compressed breast thickness during mammography.

To estimate radiation dose during mammography the breast thickness must be known. We present a new method for estimating the thickness of a compressed breast using only the breast image as projected onto a mammogram, calibration data such as the mAs value and image processing techniques. The method proves to be of high accuracy (+/- 0.2 cm for craniocaudal mammograms) and has the advantage over other methods of allowing retrospective estimation of thickness.

Fusion of contrast-enhanced breast MR and mammographic imaging data.

Increasing use is being made of Gd-DTPA contrast-enhanced MRI (CE-MRI) for breast cancer assessment since it provides three-dimensional (3D) functional information via pharmacokinetic interaction between contrast agent and tumour vascularity, and because it is applicable to women of all ages as well as patients with post-operative scarring. CE-MRI is complementary to conventional X-ray mammography, since it is a relatively low-resolution functional counterpart of a comparatively high-resolution 2D structural representation. However, despite the additional information provided by MRI, mammography is still an extremely important diagnostic imaging modality, particularly for several common conditions such as ductal carcinoma in situ (DCIS) where it has been shown that there is a strong correlation between microcalcification clusters and malignancy. Pathological indicators such as calcifications and fine spiculations are not visible in CE-MRI and therefore there is clinical and diagnostic value in fusing the high-resolution structural information available from mammography with the functional data acquired from MRI. This article is a clinical overview of the results of a technique to transform the coordinates of regions of interest (ROIs) from the 2D mammograms to the spatial reference frame of the contrast-enhanced MRI volume. An evaluation of the fusion framework is demonstrated with a series of clinical cases and a total of 14 patient examples.

Mammographic image analysis.

We describe our recent progress aimed at computer analysis of mammograms. The overall aim is to provide the clinician with reliable quantitative information. We summarise a representation we have developed of the 'interesting' (non-adipose) tissue in a breast, then put the representation to work in three ways: (i) to propose a new quantitative measure to aid in diagnosing masses; (ii) to explore the possibility of reducing by half the radiation dose required for a mammogram; and (iii) recalling some of the results that can be provided by differential compression mammography, in which mammograms are taken at two slightly different compressions.

Periodontosis: a case report with scanning electron microscopic observations.

A tooth and associated periodontal tissues from a patient with the diagnosis of periodontosis was subjected to scanning electron microscopic evaluation after reflection of the soft tissue portion of the lingual defect. The cemental surface of the apical portion of the lesion was found to be populated by markedly similar rod-shaped organisms. The microorganisms were observed to be continuously present in a coronal-apical direction as the transition from cementum to the attached soft tissues at the base of the defect were examined. These findings provide additional evidence that the lesion of periodontosis is characterized by a rather distinct microbial population of rod-shaped organisms located predominately at the base of the defect.

The effects of two ultrasonic instruments on root surfaces.

The Orbison ultrasonic instrument and the Cavitron ultrasonic dental unit were compared for the smoothness of the root surfaces they produced. Twenty teeth were analyzed with the scanning electron microscope and classified as to rough or smooth. Both instruments produced similar degrees of smoothness on the root surfaces with minimal scarring. Application of these instruments to the root surface apical to the epithelial attachment produced residual smearing of some of the collagenous fibrils.

Scanning electron microscope study of scalers.

Scanning electron microscopy was used to examine factory-sharpened, dulled, and resharpened scalers. The following observations were made: 1. The factory sharpened scalers exhibited metallic extensions from the lateral surface (wire edges). 2. The machine-resharpened instruments resulted in nonfunctional wire edges from the facial surface. Honing produced an exact meeting of facial and lateral surfaces. 3. Hand sharpening, using an Arkansas stone (grit 500) against the lateral surface away from the cutting edge, effected an exact meeting of the facial and lateral surfaces and no evidence of wire edges. 4. From this study an optimum cutting edge for a scaler is characterized as having a smooth, contiguous meeting of the facial and lateral surfaces free of wire edges. If a wire edge is present, it should be functional.

Corrosion of endodontic silver cones in humans: a scanning electron microscope and X-ray microprobe study.

Analyses with the scanning electron microscope and the X-ray microprobe were performed on 13 silver cones removed from 12 patients. The cones showed changes that ranged from surface dulling to black corrosion and pitting. Sulfur and chlorine were detected at the apical end of the cones and in the biopsy specimens of periapical tissues.

Postdebridement retention of endodontic reagents: a quantitative measurement with radioactive isotope.

Forty freshly extracted human teeth were biomechanically prepared for endodontic obturation using a radioisotopically labeled EDTA-urea peroxide-Carbowax compound. The amount of radiolabeled mixture remaining in the canals after through cleansing was about 3.8% of that originally applied. The amount of residue did not decrease with reinstrumentation and irrigation.

Corrosion of silver cones in bone: a scanning electron microscope and microprobe analysis.

Sections of silver cones were implanted in tibial bone wounds in 36 Sprague-Dawley rats. Groups of six rats each were killed at monthly intervals, and the specimens were examined by scanning electron microscopy and by X-ray microanalysis. The silver cones had corroded rapidly, but they were well tolerated by the tissues. Elements of silver, chlorine, and sulfur were found in the tissues adjacent to the implants.

Scanning microscopy of cervical erosion.

The dentitions of 900 dentists were examined for the presence of cervical erosion. Of these, 48 individuals of 5.3% had obserable erosion. Silicone impressions were made of the eroded labial surfaces in a typical quadrant, and epoxy resin models were constructed. These were examined in the scanning electron microscope. Cross sections of the replicas were examined in the light microscopy. Of the 48 replicas (24 of the maxilla and 24 of the mandible), the most severe erosion was found on the first premolars in 62% of the individuals, on second premolars in 19% on cuspids in 12%, and on first molars in 6%. The margin of the defect toward the gingiva was level with or just below and parallel to the gingival crest. The erosion pattern was distinguished by two shapes--an angular lesion with a flattened floor associated with deep lesions (68%), and a rounded, smaller defect with no sharp interior angles and less tooth damage (32%). It is postulated that cervical erosion may result from two different mechanisms--a more common, destructive process, angular and deep; and a less severe, shallow process with rounded form.

Findings in 1,724 buccal smears from dentists.

No changes were found in the epithelial cells from the buccal mucosa of dentists with the use of the light microscope, electron microscope, or electron probe that could be correlated with mercury exposure under the conditions of this test. In a normal population it can be expected that at least 0.01% of the population will show class 2 atypical smears. Patients with class 2 smears have fewer highly matured epithelial cells (tendency toward keratinization) of the buccal mucosa and hence a thinner epithelium.

Detecting approximal dental caries with transillumination: a clinical evaluation.

Independent examinations of 300 patients were conducted to evaluate fiber optic transillumination's performance in caries detection. FOTI was used as an adjunct to clinical and radiographic examinations for caries, restoration or secondary caries of approximal surfaces in maxillary anterior permanent teeth. Clinical and radiographic examinations were significantly more effective.