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PubMed2006

Redistribution of the neurosensory retina in inferior limited macular translocation: an evaluation using image registration.

BACKGROUND: The present work aims to demonstrate the role of redistribution of the neurosensory retina (RNR)-that is, retinal tissue stretching and compression-in inferior limited macular translocation (LMT), to perform displacement mapping all over the area centralis, and to try and improve displacement evaluation precision. METHODS: Using piecewise linear image registration (through Matlab) on indocyanine green angiographic frames, we have evaluated the deformation (on both the retinal and choroido-scleral layer) of a pre-operative grid superimposed on the area centralis, plotted displacement vectors all over the area centralis, and calculated a scale ratio between pre- and post-operative frames. The scale ratio tests whether or not the same physical distance is represented by the same distance on these frames. RESULTS: The choroido-scleral layer is not deformed following surgery. The retinal layer shows areas of stretching and compression, demonstrating the RNR. Displacement vectors feature a rotating pattern around the optic disk (except if a macular fold exists) and a positive naso-temporal gradient. The median scale ratio is 3.8% (2.5% to 5.8%). CONCLUSIONS: LMT involves RNR accounting for inferior retinal displacement, despite the supposedly limited internal scleral shortening. Our study confirms that the optic disk temporal edge is the displacement axis (except if a macular fold exists). Our method, unaffected by a non-zero scale ratio, provides more precision than previously published.

Aged↗
PubMed2004

[Changes in the management of cardiac arrest].

NEW RECOMMENDATIONS: for cardio-pulmonary resuscitation Methods such as mouth to mouth or the search for a pulse, until now the fundamental preliminaries, have now become second line. Everything must be organised to allow for defibrillation as rapidly as possible. NEW MODALITIES FOR CARDIAC MASSAGE: The frequency of compressions recommended is currently 100 per minute in the adult with a rhythm of compression-ventilation reaching 15/2 before intubation. Concerning the haemodynamic agents for cardiac arrest, the efficacy of high doses of adrenalin is not greater than with conventional doses. Vasopressin is not superior to intravenous adrenalin regarding survival at 24 hrs exepet in case of asystoly. Dopamine at a "renal" dose is no longer used. ANTIARRYTHMICS: Amiodarone is part of the decisional tree in the case of ventricular fibrillation or ventricular tachycardia without a pulse. Semi-automatic defibrillator accessibility should be generalized. INFUSED SOLUTIONS: Sodium bicarbonate does not improve the survival except in particular cases. Physiological serum should be preferred to glucosed serum during reanimation.

Adult↗
PubMed2002

Preparation of highly efficient manganese catalase mimics.

The series of compounds [Mn(bpia)(mu-OAc)](2)(ClO(4))(2) (1), [Mn(2)(bpia)(2)(muO)(mu-OAc)](ClO(4))(3).CH(3)CN (2), [Mn(bpia)(mu-O)](2)(ClO(4))(2)(PF(6)).2CH(3)CN (3), [Mn(bpia)(Cl)(2)](ClO)(4) (4), and [(Mn(bpia)(Cl))(2)(mu-O)](ClO(4))(2).2CH(3)CN (5) (bpia = bis(picolyl)(N-methylimidazol-2-yl)amine) represents a structural, spectroscopic, and functional model system for manganese catalases. Compounds 3 and 5 have been synthesized from 2 via bulk electrolysis and ligand exchange, respectively. All complexes have been structurally characterized by X-ray crystallography and by UV-vis and EPR spectroscopies. The different bridging ligands including the rare mono-mu-oxo and mono-mu-oxo-mono-mu-carboxylato motifs lead to a variation of the Mn-Mn separation across the four binuclear compounds of 1.50 A (Mn(2)(II,II) = 4.128 A, Mn(2)(III,III) = 3.5326 and 3.2533 A, Mn(2)(III,IV) = 2.624 A). Complexes 1, 2, and 3 are mimics for the Mn(2)(II,II), the Mn(2)(III,III), and the Mn(2)(III,IV) oxidation states of the native enzyme. UV-vis spectra of these compounds show similarities to those of the corresponding oxidation states of manganese catalase from Thermus thermophilus and Lactobacillus plantarum. Compound 2 exhibits a rare example of a Jahn-Teller compression. While complexes 1 and 3 are efficient catalysts for the disproportionation of hydrogen peroxide and contain an N(4)O(2) donor set, 4 and 5 show no catalase activity. These complexes have an N(4)Cl(2) and N(4)OCl donor set, respectively, and serve as mimics for halide inhibited manganese catalases. Cyclovoltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentials to more positive values. To our knowledge, complex 1 is the most efficient binuclear functional manganese catalase mimic exhibiting saturation kinetics to date.

Algorithms↗
PubMed2001

Clinical and laboratory diagnosis of deep vein thrombosis: new cost-effective strategies.

Diagnosis of deep vein thrombosis (DVT) has been made easier, less invasive, and somewhat safer over the past 2 decades. This has been due mainly to the development of venous compression ultrasonography (US). The prevalence of the disease in patients clinically suspected of DVT has steadily decreased during the past 10 years, likely as a consequence of the accurate noninvasive test, ultrasound imaging. This has led to the development of diagnostic tools that aim at reducing the number of unnecessary US exams. These include clinical probability assessment and fibrin D-dimer. Several strategies combining these tools have been validated in large-outcome studies and compared in a formal cost-effectiveness analysis. The results indicate that they should now be implemented in daily practice, taking into account local facilities and expertise.

Algorithms↗
PubMed2005

Powder functionality test: a methodology for rheological and mechanical characterization.

In most pharmaceutical formulations, the part of the excipients, in quantity and number, is larger than that of active principles, justifying particular attention to their characteristics to ensure quality, efficacy, and reproducibility of final forms. Whereas chemical specifications are described in Pharmacopeias, physical characteristics, up to now, have not been sufficiently considered. Nevertheless, there is a need for tests to objectively compare technological performances of products and justify composition of medicinal products. The powder functionality test described in this article is based on the analysis of the global behavior of materials under pressure. The powder compression is performed using an instrumented uniaxial press, Lloyd 6000R, and a compression cell of 1 cm3 in volume, allowing a complete and early characterization with a few grams of material. Indices characterizing packing, densification energies, energetic yields, and deformation mode of the particles are proposed from the analysis of compression cycles. Cohesion and energy of rupture are deduced from the diametral rupture cycles of the compacts. Application of this methodology to supplied celluloses has shown better flow properties of microcrystalline celluloses due to their higher bulk density and particle size. The energy fraction lost as frictions is very important and independent of the type of celluloses, whereas elastic energy is higher for powdered celluloses P100 and G250. Finally the efficacy to convert compaction energy into cohesion is higher for products with a small degree of polymerization, i.e., microcrystalline celluloses, except A301 and A302, which also are distinguished by their low porosity.

Algorithms↗
PubMed1995

Asymptomatic deep venous thrombosis in the trauma patient: is an aggressive screening protocol justified?

The incidence and sequelae of deep venous thrombosis (DVT) in trauma patients are unclear because the majority of patients who develop DVT are asymptomatic. This study evaluated the incidence, risk factors, and efficacy of prophylaxis for DVT in trauma patients over a 5-year period. Trauma patients at high risk for DVT were evaluated biweekly with lower extremity venous duplex scans. The DVT prophylaxis was instituted on admission with low-dose heparin therapy and pneumatic compression. The incidence of asymptomatic DVT identified by duplex screening was 10% (45 of 458); one pulmonary embolus occurred. Five variables were significant from bivariate and multiple logistic regression analysis: age (p = 0.005), Injury Severity Score (p = 0.005), length of stay (p = 0.004), Trauma and Injury Severity Score (p = 0.01), and spinal injury (p = 0.014). This analysis documents that trauma patients with these risk factors are at increased risk for the development of asymptomatic DVT, despite prophylaxis, and warrant surveillance with venous duplex sonography.

Adult↗
PubMed2005

Flow rate of some pharmaceutical diluents through die-orifices relevant to mini-tableting.

The effects of cylindrical orifice length and diameter on the flow rate of three commonly used pharmaceutical direct compression diluents (lactose, dibasic calcium phosphate dihydrate and pregelatinised starch) were investigated, besides the powder particle characteristics (particle size, aspect ratio, roundness and convexity) and the packing properties (true, bulk and tapped density). Flow rate was determined for three different sieve fractions through a series of miniature tableting dies of different orifice diameter (0.4, 0.3 and 0.2 cm) and thickness (1.5, 1.0 and 0.5 cm). It was found that flow rate decreased with the increase of the orifice length for the small diameter (0.2 cm) but for the large diameter (0.4 cm) was increased with the orifice length (die thickness). Flow rate changes with the orifice length are attributed to the flow regime (transitional arch formation) and possible alterations in the position of the free flowing zone caused by pressure gradients arising from the flow of self-entrained air, both above the entrance in the die orifice and across it. Modelling by the conventional Jones-Pilpel non-linear equation and by two machine learning algorithms (lazy learning, LL, and feed-forward back-propagation, FBP) was applied and predictive performance of the fitted models was compared. It was found that both FBP and LL algorithms have significantly higher predictive performance than the Jones-Pilpel non-linear equation, because they account both dimensions of the cylindrical die opening (diameter and length). The automatic relevance determination for FBP revealed that orifice length is the third most influential variable after the orifice diameter and particle size, followed by the bulk density, the difference between bulk and tapped densities and the particle convexity.

Algorithms↗
PubMed1996

A representation for mammographic image processing.

Mammographic image analysis is typically performed using standard, general-purpose algorithms. We note the dangers of this approach and show that an alternative physics-model-based approach can be developed to calibrate the mammographic imaging process. This enables us to obtain, at each pixel, a quantitative measure of the breast tissue. The measure we use is h(int) and this represents the thickness of 'interesting' (non-fat) tissue between the pixel and the X-ray source. The thicknesses over the image constitute what we term the h(int) representation, and it can most usefully be regarded as a surface that conveys information about the anatomy of the breast. The representation allows image enhancement through removing the effects of degrading factors, and also effective image normalization since all changes in the image due to variations in the imaging conditions have been removed. Furthermore, the h(int) representation gives us a basis upon which to build object models and to reason about breast anatomy. We use this ability to choose features that are robust to breast compression and variations in breast composition. In this paper we describe the h(int) representation, show how it can be computed, and then illustrate how it can be applied to a variety of mammographic image processing tasks. The breast thickness turns out to be a key parameter in the computation of h(int), but it is not normally recorded. We show how the breast thickness can be estimated from an image, and examine the sensitivity of h(int) to this estimate. We then show how we can simulate any projective X-ray examination and can simulate the appearance of anatomical structures within the breast. We follow this with a comparison between the h(int) representation and conventional representations with respect to invariance to imaging conditions and the surrounding tissue. Initial results indicate that image analysis is far more robust when specific consideration is taken of the imaging process and the h(int) representation is used.

Breast Diseases↗
PubMed2004

Rapid D-dimer test combined a clinical model for deep vein thrombosis. Validation with ultrasonography and clinical follow-up in 383 patients.

An optimal approach to the diagnosis of deep vein thrombosis (DVT) in lower limbs in the emergency department is still unknown. In this prospective cohort study, we aimed to evaluate the accuracy of the widely available plasma D-dimer test (VIDAS) and establish the usefulness of combining D-dimer testing with a clinical model to reduce the need for serial ultra-sonographies and improve the diagnostic strategy of DVT. We performed a cohort study in 383 consecutive outpatients referred to the emergency department of Hospital La Princesa, with clinical suspicion of DVT. The patients were stratified into three pre-test probability categories using an explicit clinical model (Wells score), and underwent a quantitative automated ELISA D-dimer assay (VIDAS D-Dimer bioMérieux). Patients were managed according to the diagnostic strategy based on clinical probability and compression ultrasonography (CU). Patients for whom DVT was considered a high pre-test probability with negative ultrasonographic findings in the initial CU, returned the following week for repeat ultrasonography. All patients with DVT excluded did not receive anticoagulant therapy, and were followed up for three months to monitor the development of venous thromboembolic complications. DVT was confirmed in 102 patients (26.6%): 95 in the initial test, four in the second test, and three who developed venous thromboembolic complications in the three-month follow-up period. The calculated D-dimer cut-off level was 1 micro g/ml. One hundred patients (98%) with DVT had positive D-dimer. D-dimer had a sensitivity of 98% and a negative predictive value of 98.6%. Among the high-probability patients with positive D-dimer tests and initial negative CU, 9.75% had DVT on repeat CU at one week. The study results suggest that the addition of VIDAS D-dimer to this diagnostic algorithm could improve the management of patients with suspected DVT in daily practice. A diagnostic approach of DVT based on D-dimer (cut-off > or =1 microg/ml) as the first diagnostic tool for the exclusion of DVT, and the clinical probability model as the tool that identifies those patients requiring a second ultrasonography is useful and suitable for daily medical practice.

Aged↗
PubMed1998

A method for quantifying time dependent changes in MR signal intensity of articular cartilage as a function of tissue deformation in intact joints.

A method is proposed to determine accurately the signal intensity changes of the articular cartilage from sectional MR images and its related cartilage deformation under compression in an intact joint. Image processing methods are developed to delineate and register the cartilage boundaries in consecutive MR images in order to track corresponding tissue sectors during the loading experiment. Regions of interest can then be defined and traced during the compression, making a spatial and temporal analysis of signal intensity changes possible. In addition, the cartilage deformation is calculated in the respective tissue sectors and is related to the MR signal changes. Using a fat-suppressed FLASH 3D sequence, the preliminary results showed location-dependent slight changes of the signal intensity varying from individual to individual. The quantitative analysis of the signal intensity changes as a function of cartilage deformation with magnetic resonance imaging (MRI) aims to characterize microstructural properties of the articular cartilage that may lead to a better understanding of degenerative joint disease.

Adult↗
PubMed2003

Gray scale registration of mammograms using a model of image acquisition.

A parametric technique is proposed to match the pixel-value distributions of two mammograms of the same woman. It can be applied to mammograms of the left and the right breast, or, more effectively, to temporal mammograms, e.g., from two screening rounds. The main reason to match mammograms is to lessen irrelevant differences between images due to acquisition: by varying breast compression, different film types, et cetera. Firstly, a technique like this might reduce the radiologist's efforts to detect relevant differences like abnormal growth in breast tissue that signals breast cancer. Secondly, though not the aim of this study, applications might be found in subtraction radiology or in the computer aided detection of abnormalities in temporal mammograms. Instead of arbitrarily shifting and/or scaling the pixel-values of one image to match the other or directly mapping one histogram to the other, the proposed method is based on general aspects of acquisition. This encompasses (1) breast compression; (2) exposure time; (3) incident radiation intensity; and, (4a) film properties and digitization for screen-film mammograms, or (4b) detector response for unprocessed digital mammograms. The method does not require a priori knowledge about specific settings of acquisition to match histograms; the degrees of freedom are estimated from the pixel-value distributions of the two mammograms themselves. By the method it is possible to match digitized screen-film mammograms (in the next also referred to as analog mammograms) as well as unprocessed digital mammograms in any of the four possible combinations: analog to analog, analog to digital, digital to analog, and digital to digital.

Algorithms↗
PubMed2002

Continuous twin screw extrusion for the wet granulation of lactose.

The suitability of continuous twin screw extrusion for the wet granulation of alpha-lactose monohydrate was studied and compared with conventional high shear granulation. The influence of process parameters (screw speed and total input rate) and formulation variables (water and polyvinylpyrrolidone (PVP) concentration) on the properties of granules (yield, particle size distribution, friability and compressibility) and tablets (tablet tensile strength, friability and disintegration time) was investigated. Variation of the formulation and process parameters had a major effect on the process feasibility. Optimization of these parameters is required to allow continuous processing and to ensure a high yield. Total input rate, screw speed and water concentration had a minor influence on the granule and the tablet properties. The addition of PVP had no major influence on the granule properties, but significantly affected the tablet characteristics. For granules formulated with and without PVP a yield above 50%, a friability below 30% and a compressibility below 15% was obtained. Tablets without PVP showed a tensile strength below 0.6 MPa, a friability above 1% and a disintegration time below 3 min, whereas tablets with PVP showed a tensile strength above 0.6 MPa, a friability below 1% and a disintegration time ranging from 8 to 15 min. High shear granulation was only possible when PVP was added and it required a higher amount of water. It was concluded that wet granulation of alpha-lactose monohydrate using continuous twin screw extrusion is a robust process and might offer a suitable alternative for high shear granulation in the pharmaceutical industry.

Algorithms↗
PubMed2006

New indices to characterize powder flow based on their avalanching behavior.

Use of powder avalanches in the study of flow properties of pharmaceutical excipients has yet to be popularized even though it is rather simple to use and yields comparatively reliable results. Commonly employed flow assessment methods include compressibility studies and shear cell and repose angle measurements. Though widely accepted, these methods are not without limitations and inadequacies. More often than not, experimental and environmental conditions lead to a considerable amount of variability in the results obtained. The primary objective of this current work is to propose two new indices, avalanche flow index (AFI) and cohesive interaction index (CoI) based on the avalanche flow behaviors of powders. Not only were these two indices able to describe the ease of powder flow but they also provided a simpler means of quantifying the extent of cohesive interactions within the powder mass without elaborate mathematical functions.

Algorithms↗
PubMed1994

Nucleic acid modeling tool (NAMOT): an interactive graphic tool for modeling nucleic acid structures.

The helical nature of the molecule (almost all of the DNA and a significant portion of the RNA) makes the modeling of nucleic acids a unique task. Unlike other biopolymers (proteins, lipids, etc.), the integrity the structure of a nucleic acid molecule depends strongly on the maintenance of the base pairing within the molecule. Structural alterations (bending, stretching, compressing, etc.), in general, should not disturb the base pairings. A custom-made molecular modeling tool is developed taking into consideration this specific property of the molecule. Instead of Cartesian coordinates, the modeling is carried out on a set of reduced coordinates developed here in our laboratory. One of the advantages using this set of reduced coordinates is the readiness of maintaining the base pairings while altering the structure. A graphic routine is incorporated into the package to display the image of the molecule while the modeling work is being executed. The program is written in C using XView tool kit with Xlib routines to ensure portability to different workstations.

Algorithms↗
PubMed2004

Beyond average protein secondary structure content prediction using FTIR spectroscopy.

This paper demonstrates that secondary structure information beyond purely protein secondary structure content can be predicted from FTIR (Fourier transform infrared spectroscopy) spectra of proteins with a high degree of accuracy. Both neural networks and adaptive neuro-fuzzy inference systems (ANFISs) were employed to predict helix/sheet segment information. The best results were achieved using ANFISs with fuzzy subtractive clustering based on normalised, compressed amide I data with an average SEP (standard error of prediction, root mean of squared errors) of 1.51. Predictions for average helix/sheet length based merely on the amide I band maximum position in combination with the full-width at half-height resulted in a comparable average SEP of 1.62. This suggests the importance of information on the position and width of the amide I band maximum for the prediction of helix/sheet segment information. Finally, the most promising pattern recognition approaches found in this study were applied to a protein with an as yet unknown x-ray structure: native a1-antichymotrypsin (a1-ACT).

Algorithms↗
PubMed2006

Management and algorithm for focal nodular hyperplasia of the liver in children.

PURPOSE: The aim of this study was to determine an appropriate management plan for childhood and adolescent FNH, in particular to establish an algorithm for preoperative diagnosis and treatment. PATIENTS AND METHODS: Between 1985 and 2003, 4 children with FNH were diagnosed. Of these 4 patients, 3 (Group A) underwent tumor resection, and 1 (Group B) was treated by conservative management. Clinical data, pathological findings and follow-up were evaluated retrospectively. RESULTS: The 3 patients in Group A were symptomatic, while the 1 patient in Group B was asymptomatic. In 3 of 4 patients, a homogeneous tumor with a central stellate area was noted on abdominal ultrasonography, CT scan and MR imaging. In case 2, SPIO-enhanced MR imaging was useful for differentiating FNH from hepatocellular carcinoma. Though percutaneous needle biopsy was performed in case 3, a pathologically definitive diagnosis was impossible. An open biopsy was performed in case 4 and FNH was diagnosed. In case 4 treated by conservative management, the tumor size did not change during the 7 years after the diagnosis of FNH. CONCLUSION: FNH is usually treated conservatively because of the good evolutionary outcome of the lesion. Surgery is indicated in cases of complications, compressed adjacent organs, lesion progression, or for symptomatic patients. We advocate the use of less invasive SPIO-enhanced MR imaging instead of open biopsy when the diagnosis of focal liver lesions is not clear after contrast-enhanced CT scan and non-enhanced MR imaging.

Adolescent↗
PubMedDate not supplied

Are minidisc recorders adequate for the study of respiratory sounds?

Digital audio tape (DAT) recorders have become the de facto gold standard recording devices for lung sounds. Sound recorded on DAT is compact-disk (CD) quality with adequate sensitivity from below 20 Hz to above 20 KHz. However, DAT recorders have drawbacks. Although small, they are relatively heavy, the recording mechanism is complex and delicate, and finding one desired track out of many is inconvenient. A more recent development in portable recording devices is the minidisc (MD) recorder. These recorders are widely available, inexpensive, small and light, rugged, mechanically simple, and record digital data in tracks that may be named and accessed directly. Minidiscs hold as much recorded sound as a compact disk but in about 1/5 of the recordable area. The data compression is achieved by use of a technique known as adaptive transform acoustic coding for minidisc (ATRAC). This coding technique makes decisions about what components of the sound would not be heard by a human listener and discards the digital information that represents these sounds. Most of this compression takes place on sounds above 5.5 KHz. As the intended use of these recorders is the storage and reproduction of music, it is unknown whether ATRAC will discard or distort significant portions of typical lung sound signals. We determined the suitability of MD recorders for respiratory sound research by comparing a variety of normal and pathologic lung sounds that were digitized directly into a computer and also after recording by a DAT recorder and 2 different MD recorders (Sharp and Sony). We found that the frequency spectra and waveforms of respiratory sounds were not distorted in any important way by recording on the two MD recorders tested.

Algorithms↗
PubMed1994

Data compression by linear prediction for storage and transmission of EEG signals.

The EEG time series has been subjected to various formalisms of analysis to extract meaningful information regarding the underlying neural events. In this paper the linear prediction (LP) method has been used for analysis and presentation of spectral array data for the better visualisation of background EEG activity. It has also been used for signal generation, efficient data storage and transmission of EEG. The LP method is compared with the standard Fourier method of compressed spectral array (CSA) of the multichannel EEG data. The autocorrelation autoregressive (AR) technique is used for obtaining the LP coefficients with a model order of 15. While the Fourier method reduces the data only by half, the LP method just requires the storage of signal variance and LP coefficients. The signal generated using white Gaussian noise as the input to the LP filter has a high correlation coefficient of 0.97 with that of original signal, thus making LP as a useful tool for storage and transmission of EEG. The biological significance of Fourier method and the LP method in respect to the microstructure of neuronal events in the generation of EEG is discussed.

Algorithms↗