PURPOSE:Identification of new enhancing lesions is a major endpoint of longitudinal brain magnetic resonance (MR) studies of multiple sclerosis (MS). To date, this is a visual, time-consuming procedure. We present here a supervised automated procedure (SAP) aimed at reducing the time needed to identify new MS enhancing lesions.MATERIALS AND METHODS:The SAP uses an algorithm including Cartesian coordinates of the lesions to be compared, their area and a constant (k). The procedure was validated for enhancing lesions on T1-weighted spin-echo images after intravenous administration of 0.1 mmol/kg of paramagnetic contrast agent, randomly selected from a dataset of a longitudinal MR study on ten relapsing-remitting MS patients followed for 2-5 years. During the validation session, two readers decided by consensus whether two lesions, present on the same slice of two examinations performed on subsequent dates, were the same or not. In this way, k was calibrated to obtain the same result from both visual inspection and automatic algorithm output.RESULTS:After evaluating of 25+/-5 (mean+/-standard deviation) lesions in each of ten different sessions with correction of k value, the k value became a stable value (0.45+/-0.05).CONCLUSIONS:Once the suitable value of k was found, SAP was able to identify new enhancing lesions, avoiding visual inspection, which is usually a lengthy procedure.

La valutazione non invasiva della dominanza emisferica per il linguaggio è una delle più promettenti applicazioni cliniche della risonanza magnetica funzionale, specie nei pazienti destinati alla neurochirurgia. In questo studio sono state eseguite due prove linguistiche in un gruppo di giovani volontari sani (8 destrimani, 12 non destrimani): una di fluenza fonemica ed una di associazione semantica. Tra i voxels statisticamente attivati nei due emisferi sono stati calcolati tre indici di asimmetria (emisferico, frontale e temporoparietale) in ogni soggetto e per ogni prova. Nel complesso, la prova di fluenza fonemica attivava fortemente il lobo frontale, mentre la prova di associazione semantica determinava un pattern di attivazione piu distribuito, che comprendeva anche il giro temporale medio ed il giro angolare. Per quanto riguarda gli indici di asimmetria, nei destrimani quello emisferico e quello frontale indicavano sempre l'attivazione prevalente dell'emisfero sinistro. Un solo soggetto ambidestro ha presentato nella prova di fluenza fonemica indici di asimmetria emisferico e frontale espressivi di lateralizzazione destra. D'altra parte, l'indice di asimmetria temporoparietale deponeva per una lieve revalenza dell'emisfero destro in un destrimane ed per una chiara lateralizzazione destra in un non destrimane. La risonanza magnetica funzionale appare dunque metodica sensibile ed appropriata nella valutazione della dominanza emisferica per il linguaggio. L'impiego di indici di asimmetria lobari può meglio evidenziare il differente contributo alla dominanza emisferica delle aree frontali rispetto a quelle temporoparietali. Infine, l'individuazione delle aree corticali correlate con la funzione linguistica è uno strumento potenzialmente utile per il neurochirurgo nel programmare resezioni di aree limitrofe.

La cosiddetta risonanza stocastica (RS) è un fenomeno statistico recentemente studiato in un'ampia gamma di sistemi fisici non lineari. Secondo la RS esisterebbe un livello ottimale di rumore per il quale il contenuto informativo di segnali deboli sotto soglia può essere rilevato. Questo studio analizza le possibilità della RS nel sistema visivo umano in termini di capacità soggettiva di riconoscere parametri in condizioni ottimali di rumore per stabilire le possibilita della fRM nell'obbiettivizzazione dei risultati.

Stochastic resonance (SR) is a statistical phenomenon recently studied in rr wide range of non linear physical systems. According to SR, there exists nn optimal noise level for which the information content of weak sub-threshold signals cml he detected. This study investigated SR in the human visual system in terms of subjective capacity, to recognise patterns under optimal noise conditions to Establish the possibilities of fMR1 techniques in making results objective.

Non invasive evaluation of hemispheric dominance for language is one of rile most promising clinical applications of the functional Magnetic Resonance Imaging, particularly in patients candidate to neurosurgery. In this study two language tasks were performed in a healthy group of young volunteers (8 right-handed, 12 non right-handed): i) a phonemic fluency task and ii) a semantic judgement task. Among rile statistically activated voxels in the two hemispheres cs, three asymmetry indexes (i.e. hemispheric, frontal, and temporoparietal) were compounded in each subject and for each task. In summary, phonemic fluency strongly activated rile frontal lobe, while semantic judgement caused a more widespread activation pattern, involving the medium temporal and angular gyri. Concerning the asymmetry indexes, the hemispheric and frontal indexes always showed main activation of the left hemisphere in right handers. Only one ambidextrous subject showed hemispheric and frontal right lateralisation ill phonemic fluency. On the other hand, temporoparietal asymmetry index showed a mild right lateralisation in a right handers and a strong right lateralisation in a non-right hander. Therefore, functional Magnetic Resonance Imaging is sensitive and appropriate in the evaluation of language dominance. Use of asymmetry lobar indexes could better distinguish the contribute to hemispheric dominance between frontal and temporoparietal areas. Finally localisation of the language-related areas could be useful to the neurosurgeon in the resection planning of neighbouring tissues.

Psychophysics experiments on the human visual system have established that the sensitivity for the detection of fine detail in noise contaminated images can be quantitatively and repeatably measured using stochastic resonance as a tool. Optimal noise results in maximal sensitivity. Does this mean simply that the retina is averaging out the noise, or instead is the visual cortex involved in some level of computation? We report results of functional magnetic resonance imaging experiments which indicate the latter. (C) 1999 Elsevier Science B.V. All rights reserved.

In fMRI the key problem of data analysis is to detect the weak BOLD signal component (about 2–5%) in the MR signal. Standard approaches, that typically use cross-correlation analysis or statistical parametric mapping, imply a presumptive knowledge of the expected stimulus-response pattern, which is not available in spontaneous events like hallucinations, sleep, or epileptic seizures. To evidence the possibility of analyzing these events by means of fMRI, we investigated a computational approach based on a self-organizing neural network (Neural Gas) that detects timedependent alterations in the regional intensity of the functional signal.

The goal of this study is to investigate the possibility of analyzing spatio-temporal organization of the human cortical activity during different complex tasks, by means of fMRI. To evidence cortical areas synchronization we propose a computational approach based on a self-organizing neural networks (“neural gas”) that detects time-dependent alterations in the regional intensity of the functional signal. Results of the application of such approach are reported and are compared with the results obtained with a standard statistical package (SPM96). Future experimental investigations will be aimed at the analysis of spatio-temporal structures of cortical activity in pathological conditions, such as epilepsy.

The effects of X-ray irradiation on as-grown YBa2Cu3O7 − x single crystals were investigated, in order to test the effects of radiation-induced defects during the subsequent annealing in O2, and to verify if short-circuits for diffusion could be provided that improve the oxygen enrichment of the specimens. X-ray irradiation was found to have a favourable effect on the homogeneity of the oxygen enrichment of the samples, as stated by the high reproducibility of resistance measurements carried out on specimens grown, irradiated and annealed under the same conditions. Even if X-ray irradiation seems unable to determine a significant reduction of the time needed for annealing, and it could not consequently be regarded as a totally resolutive step during the production of high-quality monocrystalline superconductors, the observed homogenization of lattice oxygen distribution seems to be exploitable.

In this work as-grown YBCO single crystals were irradiated using the radiation of a Mo anticathode as a X-ray source. The effects of X-ray irradiation were investigated in order to improve the oxygen enrichment during the subsequent annealing in O-2. X-ray irradiation was found to have a favourable effect on the homogeneity in the oxygen enrichment of the samples, as stated by the high reproducibility of resistance measurements carried out on specimens grown, irradiated and annealed under the same conditions.

Ruthenium ophthalmic applicators are energetic beta ray sources, supplied in several shapes and dimensions, and used in intraocular tumor therapy. Because of their small dimensions, the determination of dosimetric characteristics represents a technical challenge. We developed a semiautomatic method to define surface dose, dose distribution, and percentage depth dose of such applicators using radiochromic dosimetric media. These detectors consist of a thin (7 microns) radiation sensitive layer on polyester base (100 microns total thickness) changing color as a function of radiation exposure. Transmission images of exposed films were then grabbed with a TV-digitizer system to obtain a gray-level image from which dosimetric characteristics such as isodose distribution, dose values, and homogeneity of nuclide distribution were derived. Good agreement between experimental results and Monte Carlo simulation performed using the GEANT 3 code, appear to be a confirmation of the validity of the method. Moreover while manufacturer specifications of absolute and relative dose rates present a standard deviation error of +/- 30% on dose rate and +/- 6% on accuracy of relative dose values, the proposed method reduces the errors to +/- 10% and +/- 4%, respectively.

Radioisotopes employing in medical laboratory, nuclear medicine techniques for imaging and therapy, radioscopic investigations in surgery need extremity irradiation monitoring of workers.Frequently, gamma - emitting radioisotopes differing for energy range are manipolated by the same person. Extremity dose is therefore due to different radiation contribution.

Modem CT systems allow examinations with both multiscan and volumetric techniques. This study on image quality and dose distribution was carried out varying the operating conditions (step and slice thickness) for each technique. To describe the physical image quality two basic parameters were taken into account: spatial resolution and noise. The measurements were performed using an acrylic phantom, which includes a series of inserts for the response to spatial frequencies and a uniform insert for noise evaluation. The phantom images recorded on the film by a multiformat laser printer were acquired with a TV digitiser system and processed with a customised software package. Dosimetric evaluations were performed along the longitudinal axis using an air density equivalent phantom holding the TL dosemeters at the desired location.

A personal dosimeter prototype, for static magnetic fields with three Hall probes, has been designed and built to provide a reliable instrument for long-term analysis. The probe output signals, proportional to the magnetic flux density components of the vector B, are filtered, sampled, and stored in a buffer memory sufficient to cover a whole worker shift. The data sampling rate is high enough to record the operator movements within the fringes of the magnetic field. The content of the buffer memory is then transferred on a personal computer and registered on individual dosimetric cards. The data can be used for personal exposure monitoring.

Segmental wall motion abnormalities of the left ventricle frequently occur in ischemic heart disease. An objective, quantitative method is required to ensure the reproducibility of the assessment of left ventricular regional function, especially in evaluating the changes induced by diagnostic and therapeutic interventions. In 32 normal subjects we obtained 30 degrees right anterior oblique left ventriculograms and developed a method based on the following observations. The method should reflect the symmetric uniform motion of the left ventricular silhouette. Only actual contractile motion should be taken into account; therefore, rotatory and translational motion should be compensated for. Passive systolic movement of aortic and mitral valves accounts for the contraction of neighbouring myocardial segments. Left ventricular wall excursion is most often measured by a coordinate system: since the cavity of the left ventricle becomes relatively longer during systole, left ventricular walls contract neither toward a single central point nor toward the long axis; therefore the appropriate origin of the coordinate system will be a segment. Furthermore, as more elongated left ventricular end-diastolic silhouettes appear to show a greater extent of systolic lengthening (we show evidence of this), the length of the segment must be related to the end-diastolic shape. The basic steps of the method are: 1) identification of a symmetry line, from the aortic mid-point to the apex, by connecting the mid-point of 19 diameters perpendicular to the long axis; 2) roto-translation of the end-systolic silhouette so that the end-systolic apex and aortic mid-point lie on the symmetry line.(ABSTRACT TRUNCATED AT 250 WORDS)