Shadow Density Research Articles

Assessment of corneal vessels activity through the 'Barcode sign' of corneal OCT.

Anterior segment optical Coherence Tomography (AS-OCT) is used extensively in imaging the cornea in health and disease. Our objective was to analyse and monitor corneal vascularisation (CVas) through the corresponding back-shadows visible on AS-OCT. AS-OCT scans were obtained from 26 consecutive patients (eyes) with CVas of different aetiologies. AS-OCT horizontal line scans showing the back shadows cast by the vessels were analysed and correlated with findings seen on slit lamp examination. Vessels were graded clinically as active, partially regressed, and regressed. The density of back shadow in the patient samples before and after treatment was analysed using Image-J software. AS-OCT demonstrated a dense back shadow in all the 26 active vessels studied. When multiple vessels were present, the barcode sign was apparent. The back shadows absent in 22 (84.62%) at the regressed (healed) stage. The intensity of the backshadow had reduced in regressing vessels 4 (15.38%). The integrated density of the backshadow on AS-OCT in the active stage (pre-treatment) and corresponding healed (post-treatment, partially regressed or ghost vessels) scans was statistically significantly different (P < 0.0001). This study demonstrates that AS-OCT provides additional important information in patients with CVas enabling distinction between active and regressing/regressed vessels. Semiquantitative assessment can be made by measuring the integrated density of the back shadows produced by the vessels.

COMPARATIVE CHARACTERISTICS OF THE LINEAR DIMENSIONS OF VARIOUS FORMS OF THE FACIAL SKULL

For many years, radiography has traditionally been the main method for studying of the morphology of the facial skull and identifying craniofacial deformities, however, it is difficult to assess the typical variability of the linear dimensions of the facial skull on radiographs due to the many overlapping shadows of anatomical structures. Comparison of the results of craniometry of macerated skulls, radiographs and spiral computed tomography shows that multislice computed tomography in some cases can be the best alternative to conventional radiography and other methods of studying the facial skull. The purpose of the study was to conduct a comparative analysis of the linear dimensions of the facial skull with its various forms according to multislice computed tomography. Tomograms of 105 patients with different facial skull shapes were studied. Tomography was performed on a «Brilliance 64 Slice» multislice spiral X-ray computed tomography scanner at the Department of Magnetic Resonance and X-ray Computed Tomography of the Rostov State Medical University for suspected cerebrovascular pathology. The obtained images were analyzed using axial, multiplanar, and shadow density surface reconstructions in various projections. Measurements were made using a standard digital ruler of a computer tomography workstation, typical features of the linear dimensions of the facial skull were evaluated using the fan-beam method. In the studied group of individuals, the predominance of euryenes (46.7%, n=49) over mezenes (37.2%, n=35) and leptens (18.1%, n=9) was revealed. A comparative characteristic of the linear dimensions of the facial skull on spiral computed tomograms is described. According to the results of the study, the linear dimensions of the facial skull on the right dominate in leptens and euryenes, on the right in sections of the upper fan on the right, and on the left in sections of the lower and lateral fans. A left-sided asymmetry of the linear dimensions of the facial skull in sections of the lower fan, which is characteristic of mezenes, was established, while a right-sided asymmetry was found for euryenes and leptens. The data obtained as indicators of normal craniometry can be used in clinical practice by radiologists, plastic surgeons, maxillofacial surgeons, as well as in anthropology and forensic medicine.

Structural topology optimization of layout and raster angle for additive manufacturing technology with the shadow density filter

• A new shadow density filter to consider the overhang constraint. • Allowing the self-supporting structures in topology optimization. • Proving experimentally the importance of the raster angles. • Concurrently optimizing topology as well as raster angles. • Overcoming the limitation of the isotropic material. The present research contributes in the structural topology optimization with the manufacturing limitation called the overhang constraint and the optimization of the anisotropic material properties. For the optimization with self-supporting structure, the overhang-free shadow filter method is developed. To consider the anisotropic material property, the raster angles of each layer (the printing direction used to print structures) are optimized simultaneously with topology. By adding the raster angles as the design variables, it is possible to find out optimal layouts as well as optimal raster angles considering the anisotropicity. Several numerical examples of compliance minimization problem are solved to demonstrate the validity and effectiveness of the present density filter and to show the importance of the raster angle.

Investigation of Single Image Depth Prediction Under Different Lighting Conditions

This article investigates the limitations of single image depth prediction (SIDP) under different lighting conditions. Besides that, it also offers a new approach to obtain the ideal condition for SIDP. To satisfy the data requirement, we exploit a photometric stereo dataset consisting of several images of an object under different light properties. In this work, we used a dataset of ancient Roman coins captured under 54 different lighting conditions to illustrate how the approach is affected by them. This dataset emulates many lighting variances with a different state of shading and reflectance common in the natural environment. The ground truth depth data in the dataset was obtained using the stereo photometric method and used as training data. We investigated the capabilities of three different state-of-the-art methods to reconstruct ancient Roman coins with different lighting scenarios. The first investigation compares the performance of a given network using previously trained data to check cross-domains performance. Second, the model is fine-tuned from pre-trained data and trained using 70% of the ancient Roman coin dataset. Both models are tested on the remaining 30% of the data. As evaluation metrics, root mean square error and visual inspection are used. As a result, the methods show different characteristic results based on the lighting condition of the test data. Overall, they perform better at 51° and 71° angles of light, so-called ideal condition afterward. However, they perform worse at 13° and 32° because of the high density of shadows. They also cannot reach the best performance at 82° caused by the reflection that appears on the image. Based on these findings, we propose a new approach to reduce the shadows and reflections on the image using intrinsic image decomposition to achieve a synthetic ideal condition. Based on the results of synthetic images, this approach can enhance the performance of SIDP. For some state-of-the-art methods, it also achieves better results than previous original RGB images.

Adaptively Setting the Path Length for Separable Shadow Hamiltonian Hybrid Monte Carlo

Hybrid Monte Carlo (HMC) has been widely applied to numerous posterior inference problems in machine learning and statistics. HMC has two main practical issues, the first is the deterioration in acceptance rates as the system size increases and the second is its sensitivity to two user-specified parameters: the step size and trajectory length. The former issue is addressed by sampling from an integrator-dependent modified or shadow density and compensating for the induced bias via importance sampling. The latter issue is addressed by adaptively setting the HMC parameters, with the state-of-the-art method being the No-U-Turn Sampler (NUTS). We combine the benefits of NUTS with those attained by sampling from the shadow density, by adaptively setting the trajectory length and step size of Separable Shadow Hamiltonian Hybrid Monte Carlo (S2HMC). This leads to a new algorithm, adaptive S2HMC (A-S2HMC), that shows improved performance over S2HMC and NUTS across various targets and leaves the target density invariant.

The feasible region of hypergraphs

Let F be a family of r -uniform hypergraphs. The feasible region Ω ( F ) of F is the set of points ( x , y ) in the unit square such that there exists a sequence of F -free r -uniform hypergraphs whose shadow density approaches x and whose edge density approaches y . The feasible region provides a lot of combinatorial information, for example, the supremum of y over all ( x , y ) ∈ Ω ( F ) is the Turán density π ( F ) , and Ω ( ∅ ) gives the Kruskal-Katona theorem. We undertake a systematic study of Ω ( F ) , and prove that Ω ( F ) is completely determined by a left-continuous almost everywhere differentiable function; and moreover, there exists an F for which this function is not continuous. We also extend some old related theorems. For example, we generalize a result of Fisher and Ryan to hypergraphs and extend a classical result of Bollobás by almost completely determining the feasible region for cancellative triple systems.

A New Development of a Shadow Density Filter for Manufacturing Constraint and Its Applications to Multiphysics Topology Optimization

Abstract The present research develops a new shadow filter and presents its usage for structural topology optimization (TO) considering the molding manufacturability. It is important to consider manufacturing methods in designing products. Some geometrical features not allowing molded parts should be removed. In addition, it has been an important issue to efficiently impose these manufacturing constraints in TO. For this purpose, the present research emulates implementation of shadowing of products and applies the shadow images as pseudo-density variables in TO. The use of this shadow density filter ensures that the optimized layouts comply with the conditions of the manufacturing constraints. Various manufacturing conditions can be imposed depending on the direction and the position of the light. Several numerical examples of compliance minimization problem, conjugate heat transfer problem, and fluid–structure interaction problem are solved to demonstrate the validity and effectiveness of the present shadow density filters, and their performances are compared.

SPECTRAL DIFFERENCES OF TREE SPECIES BELONGING TO ATLANTIC FOREST OBTAINED FROM UAV HYPERSPECTRAL IMAGES

Abstract. The objective of this study is to evaluate the spectral difference between and within 11 tree species belonging to Brazilian Atlantic Forest located in the countryside of São Paulo State, Brazil. Tree species with different development stages may have different reflectance spectra because of the structural and phenological influence on it. Tree structure can affect the crown spectra due to the differences in geometry of view and density of shadow and sunlight pixels. Additionally, reflectance spectra can be similar between tree species belonging from different species, which affect the classification accuracy of these targets. In this sense, we evaluate the spectral difference between highly diverse Atlantic Forest using two different features extracted from individual tree crowns (ITCs). Mean reflectance spectra and mean normalized reflectance spectra of each ITC were used. They were computed from hyperspectral images acquired with sensor onboard unmanned aerial vehicle. Differences between tree species and within-species were calculated. Wilcoxon-Mann-Whitney test was applied in order to statistically evaluate whether the reflectance spectra were different. Results showed that the normalized values are more propense to increase the classification accuracies than using the mean values since it reduces the variability within-species and present a higher number of different values between-species.

Imaging manifestations and diagnostic value of chest CT of coronavirus disease 2019 (COVID-19) in the Xiaogan area

AIMTo report the epidemiological, clinical, and radiological characteristics of patients with COVID-19 in Xiaogan, Hubei, China.MATERIALS AND METHODSThe complete clinical and imaging data of 114 confirmed COVID-19 patients treated in Xiaogan Hospital were analysed retrospectively. Data were gathered regarding the presence of chest computed tomography (CT) abnormalities; the distribution, morphology, density, location, and stage of abnormal shadows on chest CT; and observing the correlation between the severity of chest infection and lymphocyte ratio and blood oxygen saturation (SPO2) in patients.RESULTSChest CT revealed abnormal lung shadows in 110 patients. Regarding lesion distribution, multi-lobe lesions in both lungs were present in most patients (80 cases; 72.7%). Lesions most frequently involved both the peripheral zone and the central zone (62 cases; 56.4%). Regarding lesion morphology, 56 cases (50.1%) demonstrated patchy shadows that were partially fused into large areas. Thirty cases showed ground-glass opacity (27.3%), 30 cases showed the consolidation change (27.3%), and the remaining 50 cases showed both types of changes (45.4%). The progressing stage was the most common stage (54 cases; 49.1%). CT results showed a negative correlation with SPO2 and lymphocyte numbers (p<0.05), with r-values of −0.446 and −0.780, respectively.CONCLUSIONSpiral CT is a sensitive examination method, which can be applied to make an early diagnosis and for evaluation of progression, with a diagnostic sensitivity and accuracy better than that of nucleic acid detection.

Clinical characteristics of connective tissue disease-related interstitial lung disease: an analysis of 186 cases

Objective To analyze the clinical characteristics of connective tissue disease related interstitial lung disease (CTD-ILD). Methods The demographic data, clinical manifestations, blood gas analysis, lung function, chest high resolution CT (HRCT), histopathology of 186 patients with CTD-ILD admitted in Jinhua Central Hospital from January 2013 to December 2017 were retrospectively analyzed. Results In 186 patients with CTD-ILD,70 were males and 116 were females, with a mean age of 56.22±12.27. Among them, 61 cases were polymyositis/dermatomyositis (DM/PM)-ILD, 44 cases were rheumatoid arthritis (RA)-ILD, 26 cases were interstitial pneumonia with autoimmune features (IPAF), 16 cases were systemic sclerosis (SSc)-ILD, 14 cases were Sjogren syndrome (SS)-ILD, 11 cases were overlap syndrome (OS)-ILD, 7 cases were systemic lupus erythematosus (SLE)-ILD, 5 cases were undifferentiated connective tissue disease (UCTD)-ILD, and 2 cases were mixed connective tissue disease (MCTD)-ILD. The incidence of respiratory symptoms was higher than that of systemic symptoms, and the incidence of systemic symptoms was higher than that of skin symptoms. Cough was the most common symptom of respiratory system, and arthralgia was the most common symptom of systemic symptoms, accounting for 54.9% (101/186) and 48.9% (91/186) respectively. Blood gas analysis showed that hypoxemia accounted for 56.5% (83/147) and type Ⅰ respiratory failure accounted for 26.5% (39/147) . The proportion of restrictive ventilation dysfunction in pulmonary function tests was 70.9% (105/148) and the diffuse dysfunction was 81.1% (120/148) . The manifestations on HRCT were reticular linear shadow (44.1%), ground-glass opacity (54.3%), consolidation (23.1%), nodules shadow (20.9%) and cystic low density shadow (9.1%) . The histopathological diagnosis mainly was non-specific interstitial pneumonia (NSIP, 43.0%) and usual interstitial pneumonia (UIP,40.0%). Conclusion The arterial blood gas analysis, lung function and chest HRCT screening, and lung histopathological examination are important for early identification and diagnosis of CTD-ILD. Key words: Connective tissue diseases; Lung diseases, interstitial; Blood gas analysis

ANALYSIS OF THE RADIOMETRIC RESPONSE OF ORANGE TREE CROWN IN HYPERSPECTRAL UAV IMAGES

Abstract. High spatial resolution remote sensing images acquired by drones are highly relevant data source in many applications. However, strong variations of radiometric values are difficult to correct in hyperspectral images. Honkavaara et al. (2013) presented a radiometric block adjustment method in which hyperspectral images taken from remotely piloted aerial systems – RPAS were processed both geometrically and radiometrically to produce a georeferenced mosaic in which the standard Reflectance Factor for the nadir is represented. The plants crowns in permanent cultivation show complex variations since the density of shadows and the irradiance of the surface vary due to the geometry of illumination and the geometry of the arrangement of branches and leaves. An evaluation of the radiometric quality of the mosaic of an orange plantation produced using images captured by a hyperspectral imager based on a tunable Fabry-Pérot interferometer and applying the radiometric block adjustment method, was performed. A high-resolution UAV based hyperspectral survey was carried out in an orange-producing farm located in Santa Cruz do Rio Pardo, state of São Paulo, Brazil. A set of 25 narrow spectral bands with 2.5 cm of GSD images were acquired. Trend analysis was applied to the values of a sample of transects extracted from plants appearing in the mosaic. The results of these trend analysis on the pixels distributed along transects on orange tree crown showed the reflectance factor presented a slightly trend, but the coefficients of the polynomials are very small, so the quality of mosaic is good enough for many applications.

Characteristics of lung function in patients with asbestosis of different stages

Objective: To investigate the characteristics of lung function in the patients with asbestosis of different stages, and analyze the correlations between the pulmonary function values and imaging score of chest X-ray. Methods: A cohort of newly diagnosed 249 asbestosis patients over a period of eight years in a single center were evaluated. Clinical data were collected from clinical charts. Radiographs were reviewed by the experts blinded to clinical data. The asbestosis patients were classified into I to III stages by chest X-ray according to the guideline. The correlations between the pulmonary function values and imaging score of chest X-ray were analyzed. Results: The prevalence of stage I to III in this asbestosis cohort was 73.5%, 19.3% and 7.2% respectively. With the stages increasing, the patients' forced vital capacity (FVC) , total lung capacity (TLC) , total carbon monoxide diffusion capacity (DLCO) predicted values were all reduced showing the restrictive ventilation impairment and/or gas exchange barrier. The obstruction of the small respiratory tracts was detected in the asbestosis of all the different stages. According to the small shadow density of each lung area, chest small shadow density score had a significant negative correlation with FVC, TLC or DLCO predicted values respectively (all P<0.01). Conclusion: The patients with asbestosis of different stages had varying degrees of gas exchange impairment, small airway dysfunction with or without ventilation dysfunction. The decreasing of DLCO was earlier than lung volume change. Chest X-ray image score paralleled the decline of lung function values, reflecting the severity of the disease.

Processing method for near-field in-line holograms (Fresnel number ≥1)

Abstract Liquid–liquid extraction is used in many industrial processes. Such processes involve liquid–liquid flows, called emulsions, which can be successfully characterized by especially suited holographic techniques. Because the droplets are millimeter size, a near-field diffraction regime is observed. This regime departs from conventional holography and requires adapted numerical solutions. Due to droplets transparency, positioning could not be achieved by usual focusing methods based on research of singularities. The only suitable method is based on calculating an indicator. To be effective a segmentation of the image into individual diffraction patterns is needed. As initial reconstruction can lead to errors, to further improve robustness, the hologram restitution is checked, and then the four parameters, radius and position, are optimized to fit the acquired hologram. If some missing droplets are found, they are identified and included. As a result about slightly less than twice as many drops are included, leading to a shadow density of 20%. Outlooks are regarding the adaptation to cylindrical geometry of industrial columns and a two channel system to improve the maximum hold-up to be measured.

Shadow Detection and Removal Based on YCbCr Color Space

Shadows in an image can reveal information about the object’s shape and orientation, and even about the light source. Thus shadow detection and removal is a very crucial and inevitable task of some computer vision algorithms for applications such as image segmentation and object detection and tracking. This paper proposes a simple framework using the luminance, chroma: blue, chroma: red (YCbCr) color space to detect and remove shadows from images. Initially, an approach based on statistics of intensity in the YCbCr color space is proposed for detecting shadows. After the shadows are identified, a shadow density model is applied. According to the shadow density model, the image is segmented into several regions that have the same density. Finally, the shadows are removed by relighting each pixel in the YCbCr color space and correcting the color of the shadowed regions in the red-green-blue (RGB) color space. The most salient feature of our proposed framework is that after removing shadows, there is no harsh transition between the shadowed parts and non-shadowed parts, and all the details in the shadowed regions remain intact. Various shadow images were used with a variety of conditions (i.e. outdoor and semi-indoor) to test the proposed framework, and results are presented to prove its effectiveness.

Injectable thermosensitive PEG–PCL–PEG hydrogel/acellular bone matrix composite for bone regeneration in cranial defects

We have certified that the injectable thermosensitive ABM/PECE composite presented promising potential in bone regeneration benefited from the incorporation of the intrinsic osteoinductive acellular bone matrix (ABM) granules into the poly(ethylene glycol)-poly(ε-capro-lactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) hydrogel. In this study, the 12 mm × 8 mm × 2 mm cranial defects of the New Zealand white rabbits were fabricated to evaluate the bone regeneration effect. The ABM/PECE composite was injected into the defect while the pure PECE as control, and the bone regeneration was evaluated at 4, 12 and 20 weeks post-surgery by X-radiological examination, micro-computed tomography examination and histological analysis. In ABM/PECE composite treated group, the new bone formed originally from both the margin and the center of the defect, and the defect region had healed up to 20 weeks. Furthermore, the shadow density of the newly formed bone eventually approximated to host cortical bone. In comparison, the control group was filled with sparing new bone with low-density only from the periphery of the defect. Meanwhile, the quantitative determination of new bone by histomorphometry confirmed the excellent bone regeneration of ABM/PECE composite. All the results suggested that the ABM/PECE composite presented enhanced bone regeneration guidance in rabbit cranial defects.

Four cases of lung abscess related to Mycoplasma pneumoniae infection

Objective To investigate the clinical characteristics of pediatric Mycoplasma pneumoniae (MP) complicated with lung abscess. Methods Data of 4 cases suffering from pulmonary abscess associated with MP from Jan.2000 to Jun.2011, including manifestations, imaging, laboratory examinations and therapies, were collected and analyzed.Related literatures were reviewed. Results Two female and 2 male cases were included in this study.The age ranged from 3 to 6 years old, and all patients had a history of acute onset, severe cough and little sputum.Three cases had remittent fever, and 3 cases had fixed small and medium-sized blisters sound in the lung.The levels of MP antibody M (MP-IgM) in the serum were higher than 1∶160 and sputum fluorescence quantitative-mycoplasma pneumonia (FQ-MP DNA) tests were positive in 4 patients.The white blood cells (WBC), polymorphonuclear leukocyte (PMN), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) in 3 cases were significantly higher than the normal level, and the FQ-MP DNA tests in the bronchoalveolar lavage fluid (BALF) were positive in 3 cases.The FQ-MP DNA in both blood and chest water were positive in 1 case.Cultures of sputum, blood, chest water, BALF and procalcitionin tests were negative, except for 1 case with positive sputum culture of Branhamellacatarrhalis.The imaging examinations on admission of 4 cases strongly suggested that the interstitial and parenchymal lung disease and subsequently appeared the different sized cystic shadow, liquid flat cystic shadow, thickened wall empty tissue image during the course of 5 to 20 days.All cases were sequentially treated with azithromycin after full erythromycin, 3 cases received intravenous glucocorticoid, 1 case received intravenous gamma globulin.The bronchial mucosal hyperemia and edema, submucosal scattered small nodules, pathological changes of bronchial sticky phlegm jam were observed in 3 cases by flexible bronchoscopy.After 3 to 5 days of admission, all patients' temperature returned to normal, the cough was reduced, and the characteristics of the lung were gradually improved.After 3 to 4 weeks, the chest radiograph showed that most pneumonia was absorbed.The 6 to 18 month follow-up indicated that absorption was good.The upper left lung limited atelectasis was found in 1 case. Conclusions Pulmonary abscess is a rare complication of MP.The major clinical manifestations are high fever, significantly higher levels of blood WBC, PMN, CRP and ESR, and high density of shadow in chest X-ray.The regular dose of erythromycin doesn't work well.However, the prognosis is good after conservative therapy with the sufficient macrolide antibiotics with glucocorticoid and immunoglobulin. Key words: Mycoplasma pneumoniae; Necrotizing pneumonia; Lung abscess; Child

Influence of recording parameters on particle field measurement by digital holographic microscopy：a numerical investigation

数字显微全息技术由于具有三维、非接触和实时测量微小空间内流场的能力, 已引起了国内外学者的广泛关注. 利用数字显微全息方法测量微通道流场时, 记录距离、颗粒尺寸、颗粒浓度、入射光波长、CCD分辨率等参数会对颗粒重建结果产生重要影响. 为了评估颗粒浓度和样本空间深度对重建结果的影响, 本文开展了数值模拟研究. 采用基于洛伦兹-米散射理论的程序产生不同浓度的颗粒全息图, 用小波变换重建算法对其进行重建. 结果表明: 在样本空间深度为24 μm 时, 颗粒浓度ns在3.44&#215;105 mm-3&#8211;13.77&#215;105 mm-3 范围内时, 颗粒重建率Ep随着颗粒浓度ns 的增大而迅速减小, 在13.77&#215;105 mm-3&#8211;55.08&#215;105 mm-3范围内时, 颗粒重建率Ep 随颗粒浓度ns增大而缓慢减少. 在颗粒浓度ns (13.77&#215;105 mm-3) 保持不变时, 颗粒重建率Ep与样本空间深度满足单调递减的线性关系. 当阴影密度不变时, 重建率的变化呈现一定的规律性:当深度L较小时, 样本空间深度对颗粒重建的影响要比颗粒浓度的影响大; 当深度L较大时, 颗粒浓度对颗粒重建的影响较大.

Numerical evaluation of the limit of concentration of colloidal samples for their study with digital lensless holographic microscopy

The number of colloidal particles per unit of volume that can be imaged correctly with digital lensless holographic microscopy (DLHM) is determined numerically. Typical in-line DLHM holograms with controlled concentration are modeled and reconstructed numerically. By quantifying the ratio of the retrieved particles from the reconstructed hologram to the number of the seeding particles in the modeled intensity, the limit of concentration of the colloidal suspensions up to which DLHM can operate successfully is found numerically. A new shadow density parameter for spherical illumination is defined. The limit of performance of DLHM is determined from a graph of the shadow density versus the efficiency of the microscope.

Lateral Ankle Radiographs: Do We Really Understand What We Are Seeing?

To evaluate the validity of using lateral intraoperative fluoroscopic imaging to assess the reduction of the tibial plafond articular surface, two hypotheses were tested: 1) the distal tibial subchondral shadow on the lateral ankle radiograph is created equally by the medial, central, and lateral portions of the distal tibia; and (2) displacement of a 5-mm width osteochondral fragment is consistently recognizable on lateral fluoroscopic imaging. Six human fresh-frozen tibial plafond cadaveric specimens were sagitally sectioned in 5-mm increments after removal of the anterior soft tissue and stabilization of the position of the ankle through external fixation. To test the first hypothesis, a perfect lateral radiograph was taken after sectioning the specimens. The sagittal sections were then removed sequentially from medial to lateral. A perfect lateral radiograph was taken after each change. The sagittal sections were then removed beginning laterally and moving medially. A perfect lateral radiograph was taken after each change. The images were then compared with specific evaluation of the change in the subchondral shadow density. To test the second hypothesis, three malreductions were created by displacing a 5-mm osteochondral segment. After each malreduction, a perfect lateral radiograph was saved. These saved fluoroscopic images were placed in random order with lateral images of normal specimens. Four experienced ankle surgeons were then asked to determine whether the radiographs revealed displacement. Inter- and intraobserver reliability was then evaluated. First, the subchondral shadow of the distal tibia appears to be created by an equal confluence of the subchondral bone of the medial, central, and lateral aspects of the tibial plafond. Second, fellowship-trained observers experienced in pilon fracture treatment correctly identified malreduction only 45% of the time. Intraclass correlation coefficient revealed very poor interobserver reliability with an alpha reliability statistic of 0.183. Intraobserver reliability across all four observers yielded an alpha statistic of 0.474, indicating inconsistencies in observers' evaluation of identical images at separate viewings. It is difficult to discern rotational or translational displacement of a 5-mm osteochondral fragment on a perfect lateral fluoroscopic view of the ankle. Even with what appears to be a perfect lateral fluoroscopic view intraoperatively, displacement may still be present. When small osteochondral fragments are present, direct visualization of the articular surface is necessary to confidently establish that an anatomic reduction has been achieved.

Digital in-line holography: influence of the shadow density on particle field

We have used a digital in-line holography system with numerical reconstruction for 3D particle field extraction. In this system the diffraction patterns (holograms) are directly recorded on a charge-coupled device (CCD) camera. The numerical reconstruction is based on the wavelet transformation method. A sample volume is reconstructed by computing the wavelet components for different scale parameters. These parameters are related to the axial distance between a particle and the CCD camera. The particle images are identified and localized by analyzing the maximum of the wavelet transform modulus and the equivalent diameter of the particle image. The general process for the 3D particle location and data processing method are presented. As in classical holography we found that the signal to noise ratio depends only on the shadow density. Nevertheless, we show that both the volume depth and the shadow density affect the percentage of extracted particles.