Thin-section Images Research Articles

AAV-Mediated, Optogenetic Ablation of Müller Glia Leads to Structural and Functional Changes in the Mouse Retina

Müller glia, the primary glial cell in the retina, provide structural and metabolic support for neurons and are essential for retinal integrity. Müller cells are closely involved in many retinal degenerative diseases, including macular telangiectasia type 2, in which impairment of central vision may be linked to a primary defect in Müller glia. Here, we used an engineered, Müller-specific variant of AAV, called ShH10, to deliver a photo-inducibly toxic protein, KillerRed, to Müller cells in the mouse retina. We characterized the results of specific ablation of these cells on visual function and retinal structure. ShH10-KillerRed expression was obtained following intravitreal injection and eyes were then irradiated with green light to induce toxicity. Induction of KillerRed led to loss of Müller cells and a concomitant decrease of Müller cell markers glutamine synthetase and cellular retinaldehyde-binding protein, reduction of rhodopsin and cone opsin, and upregulation of glial fibrillary acidic protein. Loss of Müller cells also resulted in retinal disorganization, including thinning of the outer nuclear layer and the photoreceptor inner and outer segments. High resolution imaging of thin sections revealed displacement of photoreceptors from the ONL, formation of rosette-like structures and the presence of phagocytic cells. Furthermore, Müller cell ablation resulted in increased area and volume of retinal blood vessels, as well as the formation of tortuous blood vessels and vascular leakage. Electrophysiologic measures demonstrated reduced retinal function, evident in decreased photopic and scotopic electroretinogram amplitudes. These results show that loss of Müller cells can cause progressive retinal degenerative disease, and suggest that AAV delivery of an inducibly toxic protein in Müller cells may be useful to create large animal models of retinal dystrophies.

Timing Aegean extension: Evidence from in situ U–Pb geochronology and cathodoluminescence imaging of granitoids from NW Turkey

The Biga Peninsula of NW Turkey hosts granitoid plutons that record the timing of extension in the Aegean region. Here we focus on three plutons, the Kozak, Eybek, and Kestanbol and apply new methods to obtain a detailed tectonic history of their generation and exhumation. In situ (in thin section) ion microprobe zircon geochronology and color cathodoluminescence (CL) imaging of zircon grains and whole thin sections show these granites experienced magma mixing, brittle deformation, and significant fluid-rock interactions. Zircon ages range from the Late Eocene to Late Miocene with two ages from a single grain that are Permian. The Late Eocene–Early Oligocene ages record the end stages of subduction during the closure of a branch of the Neo-Tethyan Ocean, whereas Late Oligocene–Late Miocene ages record the plutons' extension and exhumation. We present a model in which Kozak, Eybek, and Kestanbol magmas were initially generated by fluid-flux melting from dehydration of the subducting Anatolide–Tauride block, as evidenced by the Late Eocene to Early Oligocene ages. Late Oligocene ages document the initiation of extension in the Biga Peninsula region and correlate to ages timing exhumation of the Kazdağ Massif. Early Miocene ages indicate continued Aegean extension in the southern Biga Peninsula region at this time.

2D and 3D imaging resolution trade-offs in quantifying pore throats for prediction of permeability

Although the impact of subsurface geochemical reactions on porosity is relatively well understood, changes in permeability remain difficult to estimate. In this work, pore-network modeling was used to predict permeability based on pore- and pore-throat size distributions determined from analysis of 2D scanning electron microscopy (SEM) images of thin sections and 3D X-ray computed microtomography (CMT) data. The analyzed specimens were a Viking sandstone sample from the Alberta sedimentary basin and an experimental column of reacted Hanford sediments. For the column, a decrease in permeability due to mineral precipitation was estimated, but the permeability estimates were dependent on imaging technique and resolution. X-ray CT imaging has the advantage of reconstructing a 3D pore network while 2D SEM imaging can easily analyze sub-grain and intragranular variations in mineralogy. Pore network models informed by analyses of 2D and 3D images at comparable resolutions produced permeability estimates with relatively good agreement. Large discrepancies in predicted permeabilities resulted from small variations in image resolution. Images with resolutions 0.4 to 4μm predicted permeabilities differing by orders of magnitude. While lower-resolution scans can analyze larger specimens, small pore throats may be missed due to resolution limitations, which in turn overestimates permeability in a pore-network model in which pore-to-pore conductances are statistically assigned. Conversely, high-resolution scans are capable of capturing small pore throats, but if they are not actually flow-conducting predicted permeabilities will be below expected values. In addition, permeability is underestimated due to misinterpreting surface-roughness features as small pore throats. Comparison of permeability predictions with expected and measured permeability values showed that the largest discrepancies resulted from the highest resolution images and the best predictions of permeability will result from images between 2 and 4μm resolution. To reduce permeability underestimation from analyses of high-resolution images, a resolution threshold between 3 and 15μm was found to be effective, but it is not known whether this range is applicable beyond the samples studied here.

Evolution of the pore structure of constructed Technosols during early pedogenesis quantified by image analysis

Despite Technosols being widely present in environments, their pedogenesis has been studied to a much lesser extent than “natural” soils. As the initial characteristics of constructed Technosols are controlled and well-known, they represent unique experimental models for studying the early stages of soil formation. Focusing on those processes involved in soil structuration, our study proposes an image analysis protocol for the quantification of porosity and the study of pore system architecture evolution. The implications that the architecture of soil pore system evolution could have on the capacity of these constructed soils as well as “natural” soils to carry out their basic functions are also discussed. Soils with porosities of >50μm and 0.5–50μm were directly quantified by analyzing thin section images prepared from undisturbed soil samples, collected in situ in Kubiena boxes in 2008 and 2010. Pores were classified according to their diameter (five classes: diameter>2000μm, 500–2000μm; 50–500μm; 25–50μm; and 0.5–25μm). The >50μm porosity decreased significantly between 2008 (20.60%±6.10) and 2010 (14.36%±5.35). Only the number and surface of large pores (packing pores) with equivalent diameters exceeding 2000μm decreased. The surface of 0.5–50μm porosity increased between 2008 (10.56±2.64) and 2010 (13.63±2.55). This means that the soil is compacting. The consequence of this is a reduction of water holding capacity, which has a bearing on the filtering/buffering function of soil. After statistical analysis, the number of pores (N), surface area (A), index of connectivity (Ic) and shape factor (Sf) are proposed as indicators to be monitored in the study of Technosol porosity evolution.

Transferable wavelet method for grain‐size distribution from images of sediment surfaces and thin sections, and other natural granular patterns

AbstractIn images of sedimentary or granular material, or simulations of binary (two‐phase) granular media, in which the individual grains are resolved, the complete size distribution of apparent grain axes is well‐approximated by the global power spectral density function derived using a Morlet wavelet. This approach overcomes many limitations of previous automated methods for estimating the grain‐size distribution from images, all of which rely on either: identification and segmentation of individual grains; calibration and/or relatively large sample sizes. The new method presented here is tested using: (i) various types of simulations of two‐phase media with a size distribution, with and without preferred orientation; (ii) 300 sample images drawn from 46 populations of sands and gravels from around the world, displaying a wide variability in origin (biogenic and mineralogical), size, surface texture and shape; (iii) petrographic thin section samples from nine populations of sedimentary rock; (iv) high‐resolution scans of marine sediment cores; and (v) non‐sedimentary natural granular patterns including sea ice and patterned ground. The grain‐size distribution obtained is equivalent to the distribution of apparent intermediate grain diameters, grid by number style. For images containing sufficient well‐resolved grains, root mean square errors are within tens of percent for percentiles across the entire grain‐size distribution. As such, this method is the first of its type which is completely transferable, unmodified, without calibration, for both consolidated and unconsolidated sediment, isotropic and anisotropic two‐phase media, and even non‐sedimentary granular patterns. The success of the wavelet approach is due, in part, to it quantifying both spectral and spatial information from the sediment image simultaneously, something which no previously developed technique is able to do.

Segmentation of sandstone thin section images with separation of touching grains using optimum path forest operators

The segmentation of detrical sedimentary rock images is still a challenge for characterization of grain morphology in sedimentary petrography. We propose a fast and effective approach that first segments the grains from pore in sandstone thin section images and separates the touching grains automatically, and second lets the user to correct the misclassified grains with minimum interaction. The method is mostly based on the image foresting transform (IFT)—a tool for the design of image processing operators using optimum connectivity. The IFT interprets an image as a graph, whose nodes are the image pixels, the arcs are defined by an adjacency relation between pixels, and the paths are valued by a connectivity function. The IFT algorithm transforms the image graph into an optimum-path forest and distinct operators are designed by suitable choice of the IFT parameters and post-processing of the attributes of that forest. The solution involves a sequence of three IFT-based image operators for automatic segmentation and the interactive segmentation combines region- and boundary-based object delineation using two IFT operators. Tests with thin section images of two different sandstone samples have shown very satisfactory results, yielding r2 and accuracy parameters of 0.8712 and 94.8% on average, respectively. Biases were the presence of the matrix and rock fragments.

3D microstructural architecture of muscle attachments in extant and fossil vertebrates revealed by synchrotron microtomography.

BackgroundFirm attachments binding muscles to skeleton are crucial mechanical components of the vertebrate body. These attachments (entheses) are complex three-dimensional structures, containing distinctive arrangements of cells and fibre systems embedded in the bone, which can be modified during ontogeny. Until recently it has only been possible to obtain 2D surface and thin section images of entheses, leaving their 3D histology largely unstudied except by extrapolation from 2D data. Entheses are frequently preserved in fossil bones, but sectioning is inappropriate for rare or unique fossil material.Methodology/Principal FindingsHere we present the first non-destructive 3D investigation, by propagation phase contrast synchrotron microtomography (PPC-SRµCT), of enthesis histology in extant and fossil vertebrates. We are able to identify entheses in the humerus of the salamander Desmognathus from the organization of bone-cell lacunae and extrinsic fibres. Statistical analysis of the lacunae differentiates types of attachments, and the orientation of the fibres, reflect the approximate alignment of the muscle. Similar histological structures, including ontogenetically related pattern changes, are perfectly preserved in two 380 million year old fossil vertebrates, the placoderm Compagopiscis croucheri and the sarcopterygian fish Eusthenopteron foordi.Conclusions/SignificanceWe are able to determine the position of entheses in fossil vertebrates, the approximate orientation of the attached muscles, and aspects of their ontogenetic histories, from PPC-SRµCT data. Sub-micron microtomography thus provides a powerful tool for studying the structure, development, evolution and palaeobiology of muscle attachments.

Platinum folate nanoparticles toxicity: Cancer vs. normal cells

Almost for two decades metallic nanoparticles are successfully used for cancer detection, imaging and treatment. Due to their high electron density they can be easily observed by electron microscopy and used in laser and radiofrequency therapy as energy releasing agents. However, the limitation for this practice is an inability to generate tumor-specific heating in a minimally invasive manner to the healthy tissue. To overcome this restraint we proposed to use folic acid coated metallic nanoparticles and determine whether they preferentially penetrate cancer cells.We developed technique for synthesizing platinum nanoparticles using folic acid as stabilizing agent which produced particles of relatively narrow size distribution, having d=2.3±0.5nm. High resolution TEM and zeta potential analysis indicated that the particles produced by this method had a high degree of crystalline order with no amorphous outer shell and a high degree of colloidal stability. The keratinocytes and mammary breast cells (cancer and normal) were incubated with platinum folate nanoparticles, and the results showed that the IC50 was significantly higher for the normal cells than the cancer cells in both cases, indicating that these nanoparticles preferentially target the cancer cells. TEM images of thin sections taken from the two types of cells indicated that the number of vacuoles and morphology changes after incubation with nanoparticles was also larger for the cancer cells in both types of tissue studied. No preferential toxicity was observed when folic acid receptors were saturated with free folic acid prior to exposure to nanoparticles. These results confirm our hypothesis regarding the preferential penetration of folic acid coated nanoparticles to cancer cells due to receptor mediated endocytosis.

Imaging of pancreatic ductal adenocarcinoma: State of the art

Significant advances in imaging technology have changed the management of pancreatic cancer. In computed tomography (CT), this has included development of multidetector row, rapid, thin-section imaging that has also facilitated the advent of advanced reconstructions, which in turn has offered new perspectives from which to evaluate this disease. In magnetic resonance imaging, advances including higher field strengths, thin-section volumetric acquisitions, diffusion weighted imaging, and liver specific contrast agents have also resulted in new tools for diagnosis and staging. Endoscopic ultrasound has resulted in the ability to provide high-resolution imaging rivaling intraoperative ultrasound, along with the ability to biopsy via real time imaging suspected pancreatic lesions. Positron emission tomography with CT, while still evolving in its role, provides whole body staging as well as the unique imaging characteristic of metabolic activity to aid disease management. This article will review these modalities in the diagnosis and staging of pancreatic cancer.

Seeing space: visualization and quantification of plant leaf structure using X-ray micro-computed tomography

A mechanistic understanding of plant physiological processes occurring in the above-ground organs, such as photosynthesis in leaves, requires knowledge of the structural properties of the tissues, including leaf thickness (Hanba et al., 1999; Zhu et al., 2010; Niinemets et al., 2011), cell size, and stomatal distribution influencing gas exchange (Sage and Sage, 2009; Gong et al., 2011; Terashima et al., 2011). However, previous work has been unable to determine precisely how the three dimensional (3D) complexity of leaf structure impacts upon photosynthetic activity, partly due to a lack of appropriate methods for undisturbed visualization and quantification of inner structures at an appropriate high resolution (i.e. 5–10 μm). Although there is a wide range of traditional, optical-based techniques for visualization and quantification of plant morphology and anatomy, ranging from imaging of thin sections to confocal microscopy of intact specimens, their use is usually limited by the type and size of sample material. Furthermore, analysis is often time consuming, destructive, and constrained to two dimensions (2D) (classical histology) or limited in optical depth (confocal microscopy).

Isotope ratio mapping by means of laser ablation-single collector-ICP-mass spectrometry: Zn tracer studies in thin sections of Daphnia magna

In this paper, the possibilities of LA-single collector-ICP-mass spectrometry for obtaining isotope ratio images of thin sections of Daphnia magna specimens exposed to isotopically enriched Zn tracers were evaluated. Zn was selected considering its importance in ecotoxicological studies. All aspects of the analytical methodology deployed were carefully studied and optimized for obtaining the best isotope ratio precision and accuracy. The development of this methodological approach consisted of: (i) evaluation of the performance of two different medium mass resolution exit slits, a conventional one providing a mass resolution of m/Δm ≈ 4000 and triangular shaped peaks, and another (wider) one, offering a lower mass resolution (m/Δm ≈ 2000), but providing enhanced ion transmission and flat-topped peaks; (ii) the use of a wet plasma for improving plasma robustness; (iii) thorough optimization of the ablation conditions (such as laser spot size, repetition rate, scan speed and laser fluence) and data acquisition parameters (such as scan mode, the number of nuclides monitored, mass window, the number of samples per peak and dwell times); and (iv) adequate data treatment including the use of the moving average of 5 individual values. With the methodology developed, isotope ratio images with 30 micrometer spatial resolution scale were obtained for exposed and unexposed Daphnia magna individuals. The typical overall uncertainty of the measurements was approximately 5% RSD for the 66Zn/64Zn and 68Zn/64Zn ratios, which can be considered as satisfactory taking into account that the amount of Zn present per 30 μm × 30 μm pixel only reached a few picograms in the most favourable cases (giving rise to 10 000–20 000 counts per s for 64Zn). These results open the possibility for tracer studies with stable isotopes to be carried out using single collector instrumentation, a much more widespread analytical technique than multi-collector ICP-MS.

Resin secretory structures of Boswellia papyrifera and implications for frankincense yield

Frankincense, a gum-resin, has been tapped from Boswellia papyrifera trees for centuries. Despite the intensive tapping and economic interest of B. papyrifera, information on the resin secretory structures, which are responsible for synthesis, storage and transport of frankincense, is virtually absent. This study describes the type, architecture and distribution of resin secretory structures of B. papyrifera and its relevance for the ecophysiology and economic use of the tree. The type and architecture of resin secretory structures present in bark and wood was investigated from transversal, tangential and radial sections of bark and wood samples. The diameter and density (number of resin canals mm(-2)) of axial resin canals were determined from digital images of thin sections across the different zones of inner bark. Resin canals form a three-dimensional network within the inner bark. Yet, the intact resin-conducting and producing network is on average limited to the inner 6·6 mm of the inner bark. Within the inner bark, the density of non-lignified axial resin canals decreases and the density of lignified resin canals increases from the vascular cambium towards the outer bark. In the wood, only radial resin canals were encountered. Frankincense tapping techniques can be improved based on knowledge of bark anatomy and distribution and architecture of resin secretory structures. The suggested new techniques will contribute to a more sustainable frankincense production that enhances the contribution of frankincense to rural livelihoods and the national economy.

Detection and localization of the endophyteUndifilum oxytropisin locoweed tissues

Poisoning of livestock owing to grazing on locoweeds results in significant economic losses in the western United States. Some Oxytropis spp. locoweeds contain a seed-transmitted endophytic fungus, Undifilum oxytropis, which produces the toxic alkaloid swainsonine. We sought to localize and characterize growth patterns of the fungus within leaves and petioles of Oxytropis lambertii Pursh and Oxytropis sericea Nutt. to help define the types of interactions between the fungus and its hosts. Vegetative hyphae were observed within locoweed tissues using integrated imaging. Topographical images from scanning electron microscopy revealed the presence of the endophyte in the pith tissue of petioles. The fungus was identified between plant cells but did not appear to penetrate host cells. Transmission electron microscopy images of thin sections revealed that hyphae were closely associated with host cell walls. Oxytropis sericea was innoculated with green fluorescent protein-transformed U. oxytropis and observed by confocal microscopy, confirming the presence of the endophyte hyphae in leaves and petioles. The fungus was identified only in the pith of petioles using fluorescence and in the vascular bundle throughout extracellular spaces in leaves. These results revealed no signs of a pathogenic interaction between plant and fungus and support the hypothesis of a mutualistic or commensal relationship.

The three-dimensional reconstruction of penile suspensory ligament and adjacent structures based on the MRI image

To establish a three-dimensional image of the penile suspensory ligament, and explore a stereoscopic and multi angle observation method of patient' s penile suspensory ligament. This study selected the patients with small penis from our hospital as subjects. The participants were conducted on magnetic resonance imaging (MRI) examination before operation. Afterwards, the results of MRI were imported into 3D reconstruction software (MIMICS 10.0), and the suspensory ligament of penis, the pubic symphysis and other related structures were reconstructed for observation. The pubic symphysis, penis and corpus spongiosum can be quite clearly displayed in the thin-section MRI images. In addition, penile suspensory with patchy distribution can be visible between lower part of ligament pubic symphysis and corpus cavernosum. Finally, we can reconstruct the three-dimensional structures through MIMICS 10.0, and then precisely describe the suspensory ligament's start-stop point, the angle with cavernous body of penis and the attached area in the corpus cavernosum penis. Based on the MRI 3D reconstruction of deep penile suspensory ligament and adjacent structures, we can carry out dynamic, three-dimensional multi angle observation of patients deep penile suspensory ligament, and can use the reconstructed image to provide certain theory basis for the judgement of the corpus cavernosum penis extension length and penile suspensory ligament depth before penis extension operation.

Characterizing moldic and vuggy pore space in karst aquifers using borehole-wall, slabbed-core and thin-section images

Abstract Carbonate aquifers are prolific and important sources of potable water in many parts of the world owing to enlarged dissolution features that enhance porosity and interconnectivity. To better understand the variations of pore space in different karst aquifers, image and geospatial analyses are used to analyze pore attributes (i.e., pore area and perimeter) in images of vuggy aquifers. Pore geometry and 2D porosity derived from images of the moldic Castle Hayne and vuggy Biscayne aquifers are analyzed at three scales of observation: borehole televiewer, core and thin-section. The Castle Hayne and Biscayne aquifers are the foci of this study because the pore spaces that control the hydrologic properties in each of these aquifers are markedly different even though both of these carbonate reservoirs are prolific aquifers. Assessments of pore area, perimeter and shape index (a measure of shape complexity) indicate that pore geometries and pore complexities vary as a function pore type and scale of observation. For each aquifer type, the areas, perimeters and complexities of pores are higher at the larger scale of observation (e.g., borehole) than the smaller scale of observation (e.g., thin section). When the complexity of the moldic pores is compared to the complexity of vuggy pores, the results indicate that moldic pores are generally more complex than vuggy pores at the same scale of observation. Whereas estimates of 2D porosity from the borehole televiewer image of the vuggy aquifer are higher than those derived from the moldic aquifer, the range of 2D porosities is larger in core and thin section images for the vuggy aquifer than the moldic aquifer. A model for the development of pores is presented that suggests that the coalescence of small pores with simple shapes leads to the growth of larger pores with more complex shapes. The model suggests that the younger Biscayne aquifer is a more mature karst than the Castle Hayne aquifer.

Reconstruction of three-dimensional porous media using a single thin section

The purpose of any reconstruction method is to generate realizations of two- or multiphase disordered media that honor limited data for them, with the hope that the realizations provide accurate predictions for those properties of the media for which there are no data available, or their measurement is difficult. An important example of such stochastic systems is porous media for which the reconstruction technique must accurately represent their morphology--the connectivity and geometry--as well as their flow and transport properties. Many of the current reconstruction methods are based on low-order statistical descriptors that fail to provide accurate information on the properties of heterogeneous porous media. On the other hand, due to the availability of high resolution two-dimensional (2D) images of thin sections of a porous medium, and at the same time, the high cost, computational difficulties, and even unavailability of complete 3D images, the problem of reconstructing porous media from 2D thin sections remains an outstanding unsolved problem. We present a method based on multiple-point statistics in which a single 2D thin section of a porous medium, represented by a digitized image, is used to reconstruct the 3D porous medium to which the thin section belongs. The method utilizes a 1D raster path for inspecting the digitized image, and combines it with a cross-correlation function, a grid splitting technique for deciding the resolution of the computational grid used in the reconstruction, and the Shannon entropy as a measure of the heterogeneity of the porous sample, in order to reconstruct the 3D medium. It also utilizes an adaptive technique for identifying the locations and optimal number of hard (quantitative) data points that one can use in the reconstruction process. The method is tested on high resolution images for Berea sandstone and a carbonate rock sample, and the results are compared with the data. To make the comparison quantitative, two sets of statistical tests consisting of the autocorrelation function, histogram matching of the local coordination numbers, the pore and throat size distributions, multiple-points connectivity, and single- and two-phase flow permeabilities are used. The comparison indicates that the proposed method reproduces the long-range connectivity of the porous media, with the computed properties being in good agreement with the data for both porous samples. The computational efficiency of the method is also demonstrated.

An Algorithm for 3D Pore Space Reconstruction from a 2D Image Using Sequential Simulation and Gradual Deformation with the Probability Perturbation Sampler

The construction of a faithful 3D pore space model of a porous medium that could reproduce the macroscopic behavior of that medium is of great interest in various fields including medicine, material science, hydrology and petroleum engineering. A computationally efficient algorithm is developed that uses the probability perturbation method and sequential multiple-point statistics simulations to generate 3D stochastic and equiprobable representations of random porous media when only a 2D thin section image is available. By employing the probability perturbation method as a gradual deformation technique, the pore patterns of a single 2D image are deformed to generate a series of 2D stochastically simulated images. The 3D pore structure is then generated by simply stacking the 2D-simulated images. The quality of the 3D reconstruction is critically dependent on the rate of deformation and a simple general procedure for choosing this parameter is presented. Various criteria such as porosity, two-point auto-correlation function, multiple-point connectivity function, local percolation probability, absolute permeability obtained by lattice-Boltzmann method (LBM), formation factor and two-phase relative permeability calculations are used to validate the results. The method is tested on two random porous solids; Berea Sandstone and synthetic Silica, for which directly measured 3D micro-CT images are available. The stochastically reconstructed 3D pore space preserves the low- and high-order spatial statistics, the macroscopic flow properties and the microstructure of the 3D micro-CT images.

In-air broad beam ionoluminescence microscopy as a tool for rocks and stone artworks characterisation

Broad beam ionoluminescence (IL) microscopy is a promising technique for the non-destructive characterisation of rocks and stone objects. Luminescence imaging by means of broad ion beams has been sporadically used by other authors but, to our knowledge, its potential has not yet been fully investigated, neither in geological science nor in other fields. The in-air broad beam IL microscope was developed and installed at the INFN-LABEC external microbeam in Florence. Similar to the cathodoluminescence (CL) microscope, the apparatus exploits a CCD colour camera collecting images (few square millimetres wide, with ~10-μm spatial resolution) of the luminescence emitted by the sample hit by a defocused megaelectron volt (MeV) proton beam. The main differences with the well-established and widespread CL are the possibility of working in air (no sampling or conductive coatings required) and the possibility of combining the analysis with microbeam analysis, such as, for example, μ-IL and μ-PIXE (particle-induced X-ray emission). To show the potential of the technique, IL images of thin sections of lapis lazuli are compared with those obtained by means of an in-vacuum cold CL. An application to the study of stone artworks is also reported. This technique and apparatus will provide a valuable help for interdisciplinary applications, e.g. in geological sciences and in the cultural heritage field.

Semi-automated porosity identification from thin section images using image analysis and intelligent discriminant classifiers

Identification of different types of porosity within a reservoir rock is a functional parameter for reservoir characterization since various pore types play different roles in fluid transport and also, the pore spaces determine the fluid storage capacity of the reservoir. The present paper introduces a model for semi-automatic identification of porosity types within thin section images. To get this goal, a pattern recognition algorithm is followed. Firstly, six geometrical shape parameters of sixteen largest pores of each image are extracted using image analysis techniques. The extracted parameters and their corresponding pore types of 294 pores are used for training two intelligent discriminant classifiers, namely linear and quadratic discriminant analysis. The trained classifiers take the geometrical features of the pores to identify the type and percentage of five types of porosity, including interparticle, intraparticle, oomoldic, biomoldic, and vuggy in each image. The accuracy of classifiers is determined from two standpoints. Firstly, the predicted and measured percentages of each type of porosity are compared with each other. The results indicate reliable performance for predicting percentage of each type of porosity. In the second step, the precisions of classifiers for categorizing the pore spaces are analyzed. The classifiers also took a high acceptance score when used for individual recognition of pore spaces. The proposed methodology is a further promising application for petroleum geologists allowing statistical study of pore types in a rapid and accurate way.

Effect of slice thickness on detectability in breast CT using a prewhitened matched filter and simulated mass lesions

Dedicated breast CT (bCT) is an emerging technology with the potential to improve the detection of breast cancer in screening and diagnostic capacities. Typically, the 3D volume reconstructed from the scanner is displayed as sectional images. The purpose of this study was to evaluate the effect of section thickness on the detectability of simulated masses using a prewhitened matched filter (PWMF) as a model observer. A breast CT scanner has been designed and fabricated in the authors' laboratory with more than 200 women imaged in IRB-approved phase I and phase II trials to date. Of these, 151 bilateral data sets were selected on the basis of low artifact content, sufficient breast coverage, and excluding cases with breast implants. BIRADS breast density ratings were available for 144 of these patients. Spherical mass lesions of diameter 1, 2, 3, 5, 11, and 15 mm were mathematically generated and embedded at random locations within the parenchymal region of each bCT volume. Microcalcifications were not simulated in this study. For each viewing plane (sagittal, axial, and coronal) and section thickness (ranging from 0.3 to 44 mm), section images of the breast parenchyma containing the lesion were generated from the reconstructed bCT data sets by averaging voxels over the length of the section. Using signal known exactly (SKE) model observer methodology, receiver operating characteristic (ROC) curve analysis was performed on each generated projected image using a PWMF based model observer. ROC curves were generated for each breast data set, and the area under the ROC curve (AUC) was evaluated as well as the sensitivity at 95% specificity. For all lesion sizes, performance rises modestly to a peak before falling off substantially as section thickness increases over the range of the study. We find that the optimal section thickness tracks the size of the lesion to be detected linearly with a small positive offset and slopes ranging from 0.27 to 0.44. No significant differences were observed between left and right breasts. Performance measures are negatively correlated with measures of breast density, with an average correlation coefficient of -0.48 for the BIRADS breast density score and -0.81 for the proportion of glandular tissue in the breast interior. This study shows quantitatively how PWMF detection performance of a known lesion size is influenced by section thickness in dedicated breast CT. While the optimal section thickness is tuned to the size of the lesion being detected, overall performance is more robust for thin section images compared to thicker images.