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Biomedical subjects

G Valli

Publications and source records attributed to G Valli.

At least 19 recordsLinked to original sources
PubMed1992

Neural network synthesis of spin echo multiecho sequences.

Spin echo multiecho sequences are not frequently used in clinical practice, because they allow the observation of one single slice, imaged at different echo times, for each acquisition. To limit examination time, multislice sequences that include only images derived from one or two echoes are usually acquired. Nevertheless, the strong T2 dependence of multiecho sequences can be used effectively to enhance the contrast between tissues with different T2 and to gather useful diagnostic information. Artificial neural networks can offer new interesting facilities to the radiologist. In fact, the learning capabilities of neural networks allow them to extract the prototypical behavior of a system from a set of examples. After learning, artificial neural networks can emulate the system behavior even in the presence of new inputs, as far as these are not too different from those included in the training set. A conveniently trained neural network can synthesize a multiecho sequence for each slice of a multislice sequence, requiring only two images for each slice to achieve reliable results. When compared with a true multiecho sequence, the images generated by the network preserve the contrast characteristics of the original ones and have a better signal-to-noise (SNR) ratio. In this paper we report the results achieved by using a neural network to reconstruct synthetic spin echo multiecho images of the brain.

Image Processing, Computer-Assisted↗
PubMed1992

A neural network architecture for understanding discrete three-dimensional scenes in medical imaging.

Magnetic resonance and computed tomography produce sets of tomograms which are termed discrete 3D scenes. Usually, discrete 3D scenes are analyzed in two dimensions by observing each tomogram on a screen so that the three-dimensional information contained in the scene can be recovered only partially and qualitatively. The three-dimensional reconstruction of the shape of biological structures from discrete 3D scenes would allow a complete and quantitative recovery of the available information, but this task has proved hard for conventional processing techniques. In this paper we present a system architecture based on neural networks for the fully automated segmentation and recognition of structures of interest in discrete 3D scenes. The system includes a retina and two main processing modules, an Attention-Focuser System and a Region-Finder System, which have been implemented by using feed-forward nets trained with the back-propagation algorithm. This architecture has been tested on computer-simulated structures and has been applied to the reconstruction of the spinal cord and the brain from sets of tomograms.

Humans↗
PubMed1992

Artificial vision approach to the understanding of heart motion.

To overcome the major drawbacks of conventional descriptive methods, we have developed a computer vision approach to aid understanding of heart motion from a series of sequential X-ray images. The computation is addressed of local descriptors of the heart pumping function from ventricular contours. Physical constraints are exploited such as spatial smoothness of the displacement field and shape correspondence between ventricular boundaries during the beat. A computational method is proposed for the estimation of the displacement field of the left ventricular boundary. Moreover, the spatial arrangement of the estimated motion field is rendered explicit so that it may be utilized in the medical clinic (or for high-level symbolic processing). This is achieved using a grouping criterion which allows the clustering of contiguous points of the left ventricular outline into curve segments which have homogeneous motion properties.

Algorithms↗
PubMed1992

Influence of corticosterone acetate on the spleen in intact and ovariectomized rats.

Increasing evidence of the interaction of glucocorticoids and ovarian steroids prompted the current study. Effects of exogenously administered corticosterone acetate (3.5 mg/100 g b.w/day for one week) were examined on splenic nucleic acids, protein, lactate, and on lactate dehydrogenase (LDH) specific activity and its isozymes in ovariectomized and ovary-intact Wistar rats (65-75 days old). Ovariectomy resulted in no significant change in the parameters studied except DNA which increased significantly. The administration of corticosterone to these rats did not produce any remarkable change in the ovariectomy caused increase in splenic DNA content. Nevertheless, it decreased the ratio of heart type subunits (H)/muscle type subunits (M) [H/M] of LDH isozymes. In the case of ovary-intact rats, corticosterone produced an increase in the concentration of splenic lactate but a decrease in the H/M ratio. Exogenously administered corticosterone exerts selective synergistic interaction with ovarian hormones on splenic lactate. The specific activity of LDH and the concentrations of RNA and protein remained unchanged during the interaction between ovarian hormones and corticosterone.

Analysis of Variance↗
PubMed1992

[Radon levels in interiors in Valtellina, on the Angera hills and in the high valley of the Cervo river].

The results are reported of an investigation carried out from 1988 to 1990 in many houses in various sites in Lombardy and Piedmont. Measurements were actually carried out in Valtellina, in Angera--on the Lombard side of lake Maggiore--and in the high valley of the river Cervo, north of Biella. The patterns of radon immission in houses due to buildings materials and also to soil emissions are described. Average values of radon levels were obtained using track-etch detectors, whereas fluctuations were recorded daily with a unit capable of detecting alpha particles in real time. Some of the values obtained in 28 Valtellina towns were quite high--e.g., about 1,000 Bq/m3 in towns along the Insubrica fault. The area around Bormio and the Masino valley did not exhibit high radioactivity levels. A total number of nearly 100 houses were investigated in Angera; the highest radon concentrations were observed in cellars and especially in the areas where fractures are bigger and more diffuse. One particular house was accurately examined with real-time analysis of radon fluctuations. Four small towns in the pluton area were investigated in the valley of the river Cervo. In this instance, values were generally high (mean concentration: 842 Bq/m3); the highest concentrations were found in cellars and in ground-floor rooms.

Air Pollutants, Radioactive↗
PubMed1991

Three-dimensional knowledge driven reconstruction of coronary trees.

A knowledge-driven approach to the three-dimensional reconstruction of coronary artery trees by means of two X-ray projections is proposed. The spatial reconstruction of the tree skeleton is discussed. A binary tree model of the arterial structure and its projections is employed. Consequently, the reconstruction of the three-dimensional tree skeleton is achieved by (a) matching the skeletons of corresponding pairs of vascular segments in the two views and (b) back-projecting the coupled skeleton projections. From a geometrical point of view, the matching problem is, in general, ill-conditioned. For this reason, additional information sources were used. Thus, the matching phase is accomplished by using both the imaging geometry information, as well as anatomical and topological knowledge, about the coronary arteries coded in a rule base. As far as the back-projection phase is concerned, an algorithm was developed based on: (1) the imaging geometry, (2) the bounding of the back-projection error and (3) a contiguity criterion.

Algorithms↗
PubMed1991

Knowledge-based system for the diagnosis and treatment of hypertension.

A knowledge-based system to assist the physician in the diagnosis and treatment of hypertension has been developed as the result of cooperation between the Department of Electronic Engineering of the University of Florence and the Interuniversity Centre of Clinical Chronobiology. The system input consists of the data recorded over a 24 h (or longer) period by monitoring (automatically or through self-measurements) the blood pressure of the subject undergoing the system analysis, and the associated anamnestic data. The process results in a report that states from which kind of hypertensive syndrome, if any, the subject is suffering and which anti-hypertensive therapy appears to be most suitable. The system consists of three modules: the first diagnoses hypertension by applying cluster analysis to a set of parameters derived from the principal components of the time series resulting from the subject's blood pressure monitoring; the other two classify hypertension and offer advice about the most advisable treatment, respectively, by using high-level data representation and processing. The knowledge embedded in the system is internally represented by means of frames and rules. This paper describes the structure of the system, illustrates the techniques that have been used for its development and discusses the results of its application.

Artificial Intelligence↗
PubMed1988

Clinical and neurophysiologic features in paraneoplastic polyneuropathy.

Three of 8,954 in- patients have been selected as affected by paraneoplastic polyneuropathy. In all of them the polyneuropathy had a steadily progressive course, with symptoms beginning in the lower limbs and spreading to the upper limbs in a few months. An increase in protein content of the cerebrospinal fluid was evident in each case. No other possible causes of polyneuropathy were found, and the association with malignancy was histologically proved in all 3 cases. A bronchogenic ("oat cell") carcinoma was present in the first patient, who had an almost exclusively motor neuropathy. An osteosarcoma was diagnosed in the second case, and its association with a polyneuropathy seems to be exceptional. A sigmoid adenocarcinoma was discovered in the third patient. Neurophysiologic investigations were indicative of a polyneuropathy with predominant axonic involvement in all 3 cases.

Action Potentials↗
PubMed1987

Myasthenia gravis treatment: twelve years experience on 110 patients.

The clinical conditions of 110 patients affected by myasthenia gravis (MG) were followed from two to twelve years. Patients with thymectomy showed a statistically higher percentage of clinical remissions than patients without thymectomy. In patients without clinical remission immunosuppressive drugs were prescribed in different schedule; the greater percentage of pharmacological remissions with less adverse effects was obtained with administration of prednisone 50-75 mg/die initially, than gradually reduced to smaller dosage in alternate day, associated to azathioprine. Plasmapheresis, performed in six cases not responders to immunosuppressive drugs, always showed a positive and even prolonged effect.

Azathioprine↗
PubMed1979

Progressive extrinsic ophthalmoplegia with peripheral neuropathy and storage of muscle glycogen.

A case of progressive extrinsic ophthalmoplegia associated with peripheral neuropathy and hypertriglyceridemia type IV is described. Motor and sensory conduction velocities of the spinal nerves were severely decreased, while the EMG of the facial muscles was more suggested of a myopathic disorder. Electron microscopic study of biopsies of biceps and peroneus brevis muscles disclosed many ragged red fibers, mainly type I, which contained typical abnormal mitochondria. Other fibers, all type II, contained increased amounts of glycogen between myofibrils or beneath the sarcolemmal membrane, but the mitochondria were normal. These fibers were more abundant in the peroneus brevis than in the biceps muscle. Nerve biopsy revealed marked loss of myelinated fibers, but neither mitochondrial changes nor glycogen storages were evident in Schwann's cells. Biochemical investigations confirmed the increased amount of glycogen in both muscle biopsies and revealed a decrease of guanilcyclase. Phosphorylase, phosphorylase b kinase, adenilcyclase, and carnitine concentrations were all normal. The pathogenesis of this syndrome is discussed and the relationship between mitochondrial abnormalities and glycogen accumulation in muscle tissue are considered.

Adult↗
PubMed1977

Quantitative EMG and histological carrier detection of Duchenne muscular dystrophy.

Seventy-nine women known as, or suspected to be, carriers of the Duchenne type of muscular dystrophy were examined. The 15 known carriers had an estimation of the CPK serum level and a manual quantitative EMG, which gave the high detection rate of 93%. The 64 suspected carriers had CPK determination and quantitative EMG, or CPK and muscle biopsy, and the value of each technic is discussed. The problem of giving a reassuring answer to women considered to be possible carriers on genetic criteria, but who are not really carriers, is solved if the results of all three tests are negative.

Action Potentials↗
PubMed1977

[The quantitative cineangiography. Part II. Computerized analysis of the left ventricular volumes in man (author's transl)].

The values of left ventricular volumes (EDV and ESV) were determined in 35 patients with various heart diseases by computerized reading technique utilizying both the area-length and the slice methods. The data thus obtained were compared both with those derived manually and with those obtained following injection of 113mIn into the left ventricle and monitoring by external counting the dilution curve. Good agreement among the data obtained by the various methods was found. It appears, then, in the clinical practice, the computerized method has definite advantages over the others since it allows quick determination of the data and therefore examination of multiple frames.

Adolescent↗
PubMed1977

[Quantitative cineangiography. Part I. Computerized volumetry of ventricular models (author's transl)].

A computerized system for cineangiograms analysis is described. Each selected frame is displayed by a TV camera on a TV monitor, allowing the physician to draw the left ventricular contour using a light-pen. The coordinates of selected points are sent to a small size digital computer to be processed. The processing techniques are outlined, while particular evidence is given to the operating procedure. Left ventricular volume is evaluated using both area-length and slice methods. Results obtained on models yield an estimation of the accuracy of the volume measurements.

Angiocardiography↗
PubMed1976

Quantitative electromyography in the detection of the carriers in Duchenne type muscular dystrophy.

The quantitative EMG technique was used to detect Duchenne muscular dystrophy carriers. The tests were carried out, measuring the parameters of M.U. potentials (the duration, the phase, and the 0 index according to Van den Bosch, modified by Gardner-Medwin), and using the Willison analyzer, in a group of carriers and normal subjects. Ten M.U. potentials from the deltoid, biceps brachii and quadriceps muscles were photographed and measured in each subject, and the right and the left biceps were examined with the Willison analyzer. An high detection rate was obtained by manual EMG, measuring traditional values such as mean number of phases, A.P. duration and 0 index. The Willison analyzer was significant in 2 known carriers. The total EMG detection rate was higher than the CPK tests both in the known carriers and the possible carriers. It is concluded that the quantitative EMG technique is an useful and specific test to detect carriers of the gene of Duchenne muscular dystrophy.

Action Potentials↗