Computer-aided diagnosis: automatic detection of malignant masses in digitized mammograms

A computerized method to automatically detect malignant masses on digital mammograms based on bilateral subtraction to identify asymmetries between left and right breast images was developed. After the digitization, in order to align left and right mammograms the breast border and nipple were automatically detected. Images were corrected to avoid differences in brightness due to the recording procedure. Left and right mammograms were subtracted and a threshold was applied to obtain a binary image with the information of suspicious areas. The suspicious regions or asymmetries were delimited by a region growing algorithm. Size and eccentricity tests were used to eliminate false-positive responses and texture features were extracted from suspicious regions to reject normal tissue regions. The scheme, tested in 70 pairs of digital mammograms, achieved a true-positive rate of 71% with an average number of 0.67 false positives per image. Computerized detection was evaluated by using free-response operating characteristic analysis (FROC). An area under the AFROC (A1) of 0.667 was obtained. Our results show that the scheme may be helpful to the radiologists by serving as a second reader in mammographic screening. The low number of false positives indicates that our scheme would not confuse the radiologist by suggesting normal regions as suspicious.

Intra- and intermolecular charge transfer in aggregates of tetrathiafulvalene-triphenylmethyl radical derivatives in solution

An extensive investigation of aggregation phenomena occurring in solution for a family of electron donor-acceptor derivatives, based on polychlorotriphenylmethyl radicals (PTM) linked via a vinylene-bridge to tetrathiafulvalene (TTF) units, is presented. A large set of temperature and/or concentration dependent optical absorption and electron spin resonance (ESR) spectra in a solution of dyads bearing different number of electrons and/or with a hydrogenated PTM residue offer reliable information on the formation of homo dimers and mixed valence dimers. The results shed light on the reciprocal influence of intramolecular electron transfer (IET) within a dyad and the intermolecular charge transfer (CT) occurring in a dimer between the TTF residues and are rationalized based on a theoretical model that describes both interactions.

Computer-assisted diagnosis: the classification of mammographic breast parenchymal patterns

We have developed a method for the quantification of breast texture by using different algorithms to classify mammograms into the four patterns described by Wolfe (N1, P1, P2 and Dy). The computerized scheme employs craniocaudal views of conventional screen-film mammograms, which are digitized by a laser scanner. We used discriminant analysis to select among different feature-extraction techniques, including Fourier transform, local-contrast analysis, and grey-level distribution and quantification. The method has been evaluated on 117 clinical mammograms previously classified by five radiologists as to mammographic breast parenchymal patterns (MBPPS). The results show differences in agreement among radiologists and computer classification, depending on the Wolfe pattern: excellent for Dy (kappa = 0.77), good for P2 (kappa = 0.52) and N1 (kappa = 0.52) and poor for P1 (kappa = 0.22). Our quantitative texture measure as calculated from digital mammograms may be valuable to radiologists in their assessment of MBPP and therefore useful in establishing an index of risk for developing breast carcinoma.

Pulmonary nodules: improved detection with vascular segmentation and extraction with spiral CT. Work in progress

PURPOSE

To determine whether extraction of pulmonary vessels from computed tomographic (CT) images with automated segmentation improves the detection of pulmonary nodules.

MATERIALS AND METHODS

Simulated nodules were superimposed on normal spiral CT images. Eight patients referred for CT assessment of pulmonary nodules were selected for clinical evaluation. Vessels were extracted from both the simulation and clinical study with a three dimensional seeded region-growing algorithm. Three experienced radiologists were asked to locate the nodules and assign a level of confidence to their findings. Sensitivity and proportion of false-positive results per case (FPC) were calculated. Observer performance was evaluated by alternate free-response receiver operating characteristic analysis.

RESULTS

Extraction of vascular structures from CT scans improved sensitivity from 63% to 84% in the simulation study and from 58% to 78% in the clinical study. The proportion of FPC decreased from 52% to 24% and from 55% to 12%, respectively. Radiologists performed consistently better with the segmented images than with the original images in both the simulation (P = .006) and the clinical (P = .0013) study.

CONCLUSION

Automated vessel subtraction and extraction improves detection of pulmonary nodules.

Automatic detection of breast border and nipple in digital mammograms

Advances in the area of computerized image analysis applied to mammography may have very important practical applications in automatically detecting asymmetries (masses, architectural distortions, etc.) between the two breasts. We have developed a fully automatic technique to detect the breast border and the nipple, this being a necessary prerequisite for further image analysis. To detect the breast border, an algorithm that computes the gradient of gray levels was applied. To detect the nipple, three algorithms were compared (maximum height of the breast border, maximum gradient, and maximum second derivative of the gray levels across the median-top section of the breast). A combined method was also designed. The algorithms were tested on 156 digitized mammograms. The breast segmentation results were evaluated by two expert radiologists and one physicist. In 89% of the mammograms, the computed border was in close agreement with the radiologist's estimated border. Segmentation results were acceptable to be used in computer-aided diagnostic schemes. The mean distance between the position of the nipple indicated by two radiologists by consensus and the position calculated by the computer was 6 mm.

Breathing-Dependent Redox Activity in a Tetrathiafulvalene-Based Metal-Organic Framework

"Breathing" metal-organic frameworks (MOFs) that involve changes in their structural and physical properties upon an external stimulus are an interesting class of crystalline materials due to their range of potential applications including chemical sensors. The addition of redox activity opens up a new pathway for multifunctional "breathing" frameworks. Herein, we report the continuous breathing behavior of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, showing a reversible swelling (up to ca. 40% of the volume cell) upon solvent adsorption. Importantly, the planarity of the TTF linkers is influenced by the breathing behavior of the MOF, directly impacting on its electrochemical properties and thus opening the way for the development of new electrochemical sensors. Quantum chemical calculations and Raman spectroscopy have been used to provide insights into the tunability of the oxidation potential.

A highly stable and hierarchical tetrathiafulvalene-based metal-organic framework with improved performance as a solid catalyst

A highly stable Metal–Organic Framework with a hierarchical structure based on the Fe₃O cluster and a TTF-based ligand is presented.

Herein we report the synthesis of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, which shows a non-interpenetrated hierarchical crystal structure with mesoporous one-dimensional channels of ca. 3 nm and orthogonal microporous channels of ca. 1 nm. This highly stable MOF (aqueous solution with pH values ranging from 2 to 11 and different organic solvents), which possesses the well-known [Fe₃(μ₃-O)(COO)₆] secondary building unit, has proven to be an efficient catalyst for the aerobic oxidation of dibenzothiophenes.

A wavelet-based algorithm for detecting clustered microcalcifications in digital mammograms

A computerized scheme to detect clustered microcalcifications in digital mammograms has been developed. Detection of individual microcalcifications in regions of interest (ROIs) was also performed. The mammograms were previously classified into fatty and dense, according to their breast tissue. The most appropriate wavelet basis and reconstruction levels were selected. To select the wavelet basis, 40 profiles of microcalcifications were decomposed and reconstructed using different types of wavelet functions and different combinations of wavelet coefficients. The symlets with a basis of length 8 were chosen for fatty tissue. For dense tissue, the Daubechies' wavelets with a four-element basis were employed. Two methods to detect individual microcalcifications were evaluated: (a) two-dimensional wavelet transform, and (b) one-dimensional wavelet transform. The second technique yielded the best results, and was used to detect clustered microcalcifications in the complete mammogram. When detecting individual microcalcifications by using two-dimensional wavelet transform we have obtained, for fatty ROIs, a sensitivity of 71.11% at a false positive rate of 7.13 per image. For dense ROIs the sensitivity was 60.76% and the false positive rate, 7.33. The areas (A1) under the AFROC curves were 0.33+/-0.04 and 0.28+/-0.02, respectively. The one-dimensional wavelet transform method yielded 80.44% of sensitivity and 6.43 false positives per image (A1=0.39+/-0.03) for fatty ROIs, and 62.17% and 5.82 false positives per image (A1=0.37+/-0.02) for dense ROIs. For the detection of clusters of microcalcifications in the entire mammogram, the sensitivity was 80.00% with 0.94 false positives per image (A1=0.77+/-0.09) for fatty mammograms, and 72.85% of sensitivity at a false positive detection rate of 2.21 per image (A1=0.64+/-0.07) for dense mammograms. Globally, a sensitivity of 76.43% at a false positive detection rate of 1.57 per image was obtained.

Automatic calculation of total lung capacity from automatically traced lung boundaries in postero-anterior and lateral digital chest radiographs

Total lung capacity (TLC) is a very important parameter in the study of pulmonary function. In the pulmonary function laboratory, it is normally obtained using plethysmography or helium dilution techniques. Several authors have developed methods of calculating the TLC using postero-anterior (PA) and lateral chest radiographs. These methods have not been often used in clinical practice. In the present work, we have developed and automated computer-based method for the calculation of TLC, by determining the pulmonary contours from digital PA and lateral radiographs of the thorax. The automatic tracing of the pulmonary borders is carried out using: (1) a group of reference lines is determined in each radiograph; (2) a family of rectangular regions of interest (ROIs) defined, which include the pulmonary borders, and in each of them the pulmonary border is identified using edge enhancement and thresholding techniques; (3) removing outlaying points from the preliminary boundary set; and (4) the pulmonary border is corrected and completed by means of interpolation, extrapolation, and arc fitting. The TLC is calculated using a computerized form of the radiographic ellipses method of Barnhard. The pulmonary borders were automatically traced in a total of 65 normal radiographs (65 PA and 65 lateral views of the same patients). Three radiologists carried out a subjective evaluation of the automatic tracing of the pulmonary borders, with a finding of no error or only one minor error in 67.7% of the PA evaluations, and in 75.9% of the laterals. Comparing the automatically traced borders with borders traced manually by an expert radiologists, we obtained a precision of 0.990 +/- 0.001 for the PA view, and 0.985 +/- 0.002 for the lateral. The values of TLC obtained by the automatic calculation described here showed a high correlation (r = 0.98) with those obtained by applying the manual Barnhard method.

Effects of clozapine on the activity of central dopaminergic and noradrenergic neurons

The effects of clozapine on the spontaneous firing rate of noradrenergic (NE, locus coeruleus), dopaminergic (DA, zona compacta, ventral tegmental area) and non-dopaminergic (zona reticulata) neurons was studied in chloral hydrate anesthetized rats. Clozapine administered intraperitoneally significantly increased the spontaneous activity of NE and DA neurons. After a cumulative dose of 8 mg/kg clozapine, the increase of mean firing rate per min of zona compacta and ventral tegmental area neurons attained almost similar values. Amphetamine reversed the clozapine-induced stimulation of NE and DA neurons. Zona reticulata neurons were depressed by clozapine. Neither amphetamine nor physostigmine were effective in antagonizing the inhibition. Our results suggest that clozapine blocks central NE and DA receptors. Furthermore, they fail to reveal a smaller sensitivity of the striatum as compared to the limbic system to the effects of clozapine.

Tuning the Rectification Ratio by Changing the Electronic Nature (Open-Shell and Closed-Shell) in Donor-Acceptor Self-Assembled Monolayers

This Communication describes the mechanism of charge transport across self-assembled monolayers (SAMs) of two donor-acceptor systems consisting of a polychlorotriphenylmethyl (PTM) electron-acceptor moiety linked to an electron-donor ferrocene (Fc) unit supported by ultraflat template-stripped Au and contacted by a eutectic alloy of gallium and indium top contacts. The electronic and supramolecular structures of these SAMs were well characterized. The PTM unit can be switched between the nonradical and radical forms, which influences the rectification behavior of the junction. Junctions with nonradical units rectify currents via the highest occupied molecular orbital (HOMO) with a rectification ratio R = 99, but junctions with radical units have a new accessible state, a single-unoccupied molecular orbital (SUMO), which turns rectification off and drops R to 6.

Antagonism by d,1-propranolol of imipramine effects in mice

Three agents with known or suspected antidepressant activity, imipramine, salbutamol and dexamphetamine, were active in animal tests predictive of an antidepressant effect in man: antagonism of the hypothermia induced by reserpine, by oxotremorine or by a high dose of apomorphine, and the potentiation of the yohimbine-induced toxicity. These effects were antagonized by d,1-propranolol, suggesting that the stimulation of beta-adrenergic receptors could be a common mechanism underlying their effects. These results agree with the noradrenergic hypothesis of the pathophysiology of affective disorders.

Design of cost-efficient and photocatalytically active Zn-based MOFs decorated with Cu2O nanoparticles for CO2methanation

Here we show for the first time a MOF that is photocatalytically active for light-assisted CO₂methanation under mild conditions (215 °C), which can be further improved with the inclusion of metallic nanoparticles.

Electronic, Structural and Functional Versatility in Tetrathiafulvalene-Lanthanide Metal-Organic Frameworks

Tetrathiafulvalene-lanthanide (TTF-Ln) metal-organic frameworks (MOFs) are an interesting class of multifunctional materials in which porosity can be combined with electronic properties such as electrical conductivity, redox activity, luminescence and magnetism. Herein a new family of isostructural TTF-Ln MOFs is reported, denoted as MUV-5(Ln) (Ln=Gd, Tb, Dy, Ho, Er), exhibiting semiconducting properties as a consequence of the short intermolecular S⋅⋅⋅S contacts established along the chain direction between partially oxidised TTF moieties. In addition, this family shows photoluminescence properties and single-molecule magnetic behaviour, finding near-infrared (NIR) photoluminescence in the Yb/Er derivative and slow relaxation of the magnetisation in the Dy and Er derivatives. As such properties are dependent on the electronic structure of the lanthanide ion, the immense structural, electronic and functional versatility of this class of materials is emphasised.

Enhancement of chest and breast radiographs by automatic spatial filtering

The authors present a new algorithm to enhance the edges and contrast of chest and breast radiographs while minimally amplifying image noise. The algorithm consists of a linear combination of an original image and two smoothed images obtained from it by using different masks and parameters, followed by the application of nonlinear contrast stretching. The result is an image which retains the high median frequency local variations (edge and contrast-enhancing).

Scatter in computed radiography

The effects of scatter radiation on images obtained with storage phosphor computed radiography (CR) were evaluated. The scatter degradation factor was extended to account separately for forward scatter and backscatter. Values for the ratios of forward scatter to primary radiation (sf/p) and backscatter to primary radiation (sb/p) were measured for various x-ray tube potentials, phantom thicknesses, and field sizes for CR imaging plates (IPs). Similar measurements were made for a common screen-film system. The sb/p values for the IPs were 0.05-3.80. Standard CR cassettes do not have lead foil behind the IP to control backscatter; the results of this study indicate that such control is needed. The sf/p values were 40%-70% higher in IPs (50%-120% higher when backscatter was included) than those in the conventional screen-film system. This difference is attributed to the differences in the K-absorption edges of barium and gadolinium and the fact that scatter has lower effective energy than the primary beam as they exit the patient.

Three Redox States of a Diradical Acceptor-Donor-Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization

The diradical acceptor-donor-acceptor triad 1(••), based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)-vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1(•-), and triradical cation species, 1(•••+), obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.

Charge-transfer interactions between fullerenes and a mesoporous tetrathiafulvalene-based metal-organic framework

The design of metal-organic frameworks (MOFs) incorporating electroactive guest molecules in the pores has become a subject of great interest in order to obtain additional electrical functionalities within the framework while maintaining porosity. Understanding the charge-transfer (CT) process between the framework and the guest molecules is a crucial step towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C₆₀) in a mesoporous tetrathiafulvalene (TTF)-based MOF. The CT process between the electron-acceptor C₆₀ guest and the electron-donor TTF ligand is studied in detail by means of different spectroscopic techniques and density functional theory (DFT) calculations. Importantly, gas sorption measurements demonstrate that sorption capacity is maintained after encapsulation of fullerenes, whereas the electrical conductivity is increased by two orders of magnitude due to the CT interactions between C₆₀ and the TTF-based framework.

TTF–PTM dyads: from switched molecular self assembly in solution to radical conductors in solid state

Dyads formed by tetrathiafulvalene (TTF) linked to perchlorotriphenylmethyl (PTM) radicals exhibit interesting physical properties such as bistability in solution or conductivity in solid state.

The circadian optimal time for hepatectomy in the study of liver regeneration

Standardized (light from 0600 to 1800) C3HS mice, hepatectomized at different circadian stages, were killed at 1400 (the peak time of mitotic activity in intact mice). The higher values of mitotic index were those of mice operated at 1400, 48 hr before. The curve of mitotic activity of the regenerating liver of mice operated at 1400 and that of mice operated at 0200 (an opposite time in the circadian stage) are, both, grossly in phase with the curves of mitotic index in young and adult mice liver. The amplitude of the first peak of mitotic activity in mice operated at 0200 was dramatically lower than that of animals operated at 1400. The same applies to hepatocytes as well as to the sinusoid litoral population of cells. It is concluded that 1400 hr, as contrast to 0200 hr, is an optimal time for hepatectomy if one wants to obtain the highest mitotic index first peak during regeneration in a normal phase position (the position of the mitotic index peak in the liver of normal young and adult mice).