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PubMed1992

PACS mini refresher course. Wide area network strategies for teleradiology systems.

Teleradiology systems require the use of wide area networks (WANs). Design and implementation of a WAN depend on the number of images to be transmitted, desired digital image throughput (based on signaling rate), and cost of the communications link. Image transmission load must be estimated before the communications link can be selected. Communications links used in WANs include T-1 carrier point-to-point service, digital service (DS)-1 dial-up service, DS-3 point-to-point service, DS-0 dial-up service, digital microwave, fiberoptic local loop carriers, and metropolitan area networks (MANs). Depending on the distance between sites, T-1 service may be less costly than DS-1 service; however, for distances more than 200 miles, DS-1 service can be less expensive and more flexible. Both of these services and DS-0 service have lower signaling rates than DS-3 service, which is the fastest and most expensive link. Microwave and fiberoptic links are less expensive but have distance limitations of 14 and 30 miles, respectively. MANs are still being developed but hold the promise of higher signaling rates at lower costs.

Computer Communication Networks↗
PubMed1985

Localization of cell surface glycoproteins in membrane domains associated with the underlying filament network.

To visualize the localization of cell surface constituents in relation to the plasma membrane-associated filament network, we developed a method based on a combination of immunogold labeling and dry-cleaving. For labeling we used trinitrophenyl-derivatized ligand, anti-TNP antibodies, and protein A-coated colloidal gold. Dry-cleaving (Mesland, D. A. M., H. Spiele, and E. Roos, 1981, Exp. Cell Res., 132: 169-184) involves cleavage of lightly fixed critical point-dried cells by means of adhesive tape. Since cells cleave close to the cell surface, the remaining layer is thin enough to be examined in transmission electron microscopy. Using this method, we studied concanavalin A-binding constituents on the medium-facing surface of H35 hepatoma cells. The distribution of the gold particles, which was partly dispersed and partly patchy, coincided strikingly with membrane-associated filaments, and label was virtually absent from areas overlying openings in the filament network. In stereo pairs we observed the label to be localized to areas of somewhat enhanced electron density at the plane of the membrane. These areas were interconnected in a pattern congruent with the filament network. Preliminary observations on wheat germ agglutinin receptors on the hepatoma cells as well as concanavalin A receptors on isolated hepatocytes yielded comparable results. It thus appears that surface glycoproteins, although seemingly randomly distributed as observed in thin sections, may actually be localized to particular membrane domains associated with underlying filaments.

Actin Cytoskeleton↗
PubMedDate not supplied

[Diagnostic image management and communication systems: experience at the University of Pisa].

Our work was aimed at implementing and validating a system for the acquisition, local management and remote transmission of diagnostic images. Integration of imaging equipment was performed in each of the two sites (5 km apart) in which the Department of Radiology of the University of Pisa is divided. Teleradiology was carried out using 64 Kbit/s lines as well as a 140 Mbit/s Metropolitan Area Network compliant with the Distributed Queue Dual Bus standard. Application domains included remote expert consultation and teleprocessing of diagnostic images. Remote expert consultation was performed in particular by using the 34 Mbit/s interconnection with the Metropolitan Area Network of Florence. Remote processing of diagnostic images using the high speed link allowed the cooperative work with scientific institutions in a field often limited by the complexity of image transfer and by the lack of a timely feed-back concerning the clinical value of processed images. Advanced processing of diagnostic images was performed in the field of stereographic display of CT and MR data sets. Moreover, experience was gained in the visualization, on a single composite image, of the multiparametric data obtained by means of different MR sequences (T1, Spin Density, T2), thus allowing to summarize, by using false colors, different tissue contrast information.

Computer Communication Networks↗
PubMed2003

Behavior of ectopic surface: effects of beta-adrenergic stimulation and uncoupling.

By using both experimental and theoretical means, we have addressed the progression of ectopic activity from individual cardiac cells to a multicellular two-dimensional network. Experimental conditions that favor ectopic activity have been created by local perfusion of a small area of cardiomyocyte network (I-zone) with an isoproterenol-heptanol containing solution. The application of this solution initially slowed down and then fully blocked wave propagation inside the I-zone. After a brief lag period, ectopically active cells appeared in the I-zone, followed by evolution of the ectopic clusters into slowly propagating waves. The changing pattern of colliding and expanding ectopic waves confined to the I-zone persisted for as long as the isoproterenol-heptanol environment was present. On restoration of the control environment, the ectopic waves from the I-zone broke out into the surrounding network causing arrhythmias. The observed sequence of events was also modeled by FitzHugh-Nagumo equations and included a cell's arrangement of two adjacent square regions of 20 x 20 cells. The control zone consisted of well-connected, excitable cells, and the I-zone was made of weakly coupled cells (heptanol effect), which became spontaneously active as time evolved (isoproterenol effect). The dynamic events in the system have been studied numerically with the use of a finite difference method. Together, our experimental and computational data have revealed that the combination of low coupling, increased excitability, and spatial heterogeneity can lead to the development of ectopic waves confined to the injured network. This transient condition appears to serve as an essential step for the ectopic activity to "mature" before escaping into the surrounding control network.

Adrenergic beta-Agonists↗
PubMed2005

Integrating regression formulas and kernel functions into locally adaptive knowledge-based neural networks: a case study on renal function evaluation.

OBJECTIVE: In many medical areas, there exist different regression formulas to predict/evaluate a medical outcome on the same problem, each of them being efficient only in a particular sub-space of the problem space. The paper aims at the development of a generic, incremental learning model that includes all available regression formulas for a particular prediction problem to define local areas of the problem space with their best performing formula along with useful explanation rules. Another objective of the paper is to develop a specific model for renal function evaluation using nine existing formulas. METHODS AND MATERIALS: We have used a connectionist neuro-fuzzy approach and have developed a knowledge-based neural network model (KBNN) which incorporates and adapts incrementally several existing regression formulas and kernel functions. The model incorporates different non-linear regression functions as neurons in its hidden layer and adapts these functions through incremental learning from data in particular local areas of the space. More specifically, each hidden neural node has a pair of functions associated with it--one regression formula, that represents existing knowledge and one Gaussian kernel function, that defines the sub-space of the whole problem space, in which the formula is locally adapted to new data. All these functions are aggregated and changed through incremental learning. The proposed KBNN model is illustrated using a medical dataset of observed patient glomerular filtration rate (GFR) measurements for renal function evaluation. In this case study, the regression function for each cluster is selected by the model from nine formulas commonly used by medical practitioners to predict GFR. 441 GFR data vectors from 141 patients taken from 12 sites in Australia and New Zealand have been used as a case study experimental data set. RESULTS: The proposed GFR prediction model, based on the proposed generic KBNN model, outperforms at least by 10% accuracy any of the individual regression formulas or a standard neural network model. Furthermore, we have derived locally adapted regression formulas to perform best on local clusters of data along with useful explanatory rules. CONCLUSION: The proposed KBNN model manifests better accuracy then existing regression formulas or neural network models for renal function evaluation and extracts modified formulas that perform well in local areas of the problem space.

Algorithms↗
PubMed2003

[EMI net--electronic medical record sharing in local community for home care medicine].

An electronic medical information network (EMI net) includes patient records from more than 40 facilities in Matsudo City and it is now used especially to improve the communication between doctors and nurses who visit patients' homes. This fact suggests the importance of a medical information sharing system in a local area for home care medicine. An infrastructure connecting facilities to share the database of the patient records is essential for home care medicine performed by a multidisciplinary team beyond one medical facility.

Community Networks↗
PubMed1984

Hypoxic reduction in blood flow velocity in pulmonary arterioles and capillaries.

A small ring chamber (I.D. = 6 mm) was placed on the exposed lung of anaesthetized bullfrogs. A localized hypoxia was induced in the ring chamber by introducing nitrogen in it. Blood flow velocity in pulmonary microvessels was measured by means of a laser Doppler microscope. The mean blood flow velocity was 1.98 +/- 0.45 and 1.52 +/- 0.10 mm/sec during the control condition in arterioles and capillaries, respectively. It was then reduced by the localized hypoxia to 1.63 +/- 0.32 and 1.33 +/- 0.08 mm/sec in arterioles and capillaries, respectively. The reduction, when expressed in the percentage ratio to the control flow velocity in each blood vessel group, was significantly larger in arterioles than in capillaries. A phase delay in the pulsation of the flow velocity contour was detected only in arterioles. These differences between pulmonary arterioles and capillaries in response to the localized hypoxia may be attributed to the dense interconnection of capillary network extending beyond the localized hypoxic area to the normoxic area.

Animals↗
PubMed1999

Spatio-temporal analysis of electric brain activity during semantic and phonological word processing.

There is an ongoing debate in cognitive neuroscience about the time course and the functional independence of the different processes involved in encoding written language material. New data indicate very fast and highly parallel language analysis networks in the brain. Here we demonstrate a methodological approach to study the temporal dynamics of this network by searching for time periods where different task demands emphasize different aspects of the network. Multi-channel event related potentials (ERPs) were recorded during a semantic and a phonological reading task from 14 healthy subjects. Signals were analyzed exclusively on the basis of the spatial configuration of the electric potential distributions (ERP maps), since differences in these spatial patterns directly reflect changes in the configuration of the active sources in the brain. This analysis did not reveal any differences of the evoked brain electric fields between the two tasks up to 280 ms post-stimulus. The ERP maps then differed for a brief period between 280 and 380 ms, before they were similar again. The analysis of the maps using a global linear localization procedure revealed a network of areas, active in both tasks, that mainly involved the left postero-temporal and left antero-temporal regions. The left posterior activation was found already around 100 ms post-stimulus, indicating that language-specific functions appear early in time. We therefore conclude that phonological and semantic processing are essentially performed in both tasks and that only late decision-related processes influence the relative strength of activity of the different modules in the complex language network.

Adult↗
PubMed2002

Developmental event-related gamma oscillations: effects of auditory attention.

This study describes maturational changes in topographical patterns, stability, and functional reactivity of auditory gamma band (31-63 Hz) responses (GBRs) as brain electrical correlates relevant for cognitive development during childhood. GBRs of 114 healthy children from 9 to 16 years were elicited in an auditory focused attention task requiring motor responding to targets, and analyzed by means of the wavelet transform (WT). The effects of age and task variables (attended side and stimulus type relevance) were examined for GBR power and phase-locking within 120 ms after stimulation. Similar to the spontaneous gamma band power, the power and phase-synchronization of GBRs did not depend on the age. However, the functional reactivity of GBRs at specific locations changed in the course of development. In 9-12-year-old children, GBRs at frontal locations were larger and better synchronized to target than to nontarget stimulus type, and were larger over the left hemisphere (contralateral to the responding hand), thus manifesting sensitivity to external stimulus features and motor task. In 13-16-year-old adolescents, GBRs at parietal sites were enhanced by active attending to the side of stimulation, thus being associated with a maintenance of attentional focus to stimulus location. The results indicate that (i) specific aspects of task-stimulus processing engage distinct spatially localized gamma networks at functionally relevant areas, and (ii) the neuronal substrates of gamma band networks and the ability to synchronize them in relation to task-specific processes are available in all age groups from 9 to 16 years. However, the mode and efficiency with which gamma networks can be entrained depends on the age. This age-dependent reactivity of GBRs to different task variables may reflect a transition in processing strategies emerging at approximately 12-13 years in relation to the maturation of cognitive and executive brain functions.

Acoustic Stimulation↗
PubMed1992

Picture archiving and communication systems: an overview.

Organizational techniques that enable small departments to function efficiently often fail as departments become larger. With the recent growth in imaging technology, the capacity of film-based systems to meet the increasing needs of radiology departments has decreased. Electronic picture archiving and communication systems (PACS) have been developed in an attempt to provide economical storage, rapid retrieval of images, access to images acquired with multiple modalities, and simultaneous access at multiple sites. Input to a PACS may come from digital or analog sources (when the latter have been digitized). A PACS consists primarily of an image acquisition device (an electronic gateway to the system), data management system (a specialized computer system that controls the flow of information on the network), image storage devices (both short- and long-term archives), transmission network (which serves local or wide areas), display stations (which include a computer, text monitor, image monitors, and a user interface), and devices to produce hard-copy images (currently, a multiformat or laser camera). The goals of PACS are to improve operational efficiency while maintaining or improving diagnostic ability.

Radiology Information Systems↗
PubMed1997

Evaluation of electrosurgical interference to low-power spread-spectrum local area net transceivers.

OBJECTIVE: To study whether an electrosurgery device interferes with the operation of a low-power spread-spectrum wireless network adapter. METHODS: Nonrandomized, unblinded trials with controls, conducted in the corridor of our institution's operating suite using two portable computers equipped with RoamAbout omnidirectional 250 mW spread-spectrum 928 MHz wireless network adapters. To simulate high power electrosurgery interference, a 100-watt continuous electrocoagulation arc was maintained five feet from the receiving adapter, while device reported signal to noise values were measured at 150 feet and 400 feet distance between the wireless-networked computers. At 150 feet range, and with continuous 100-watt electrocoagulation arc five feet from one computer, error-corrected local area net throughput was measured by sending and receiving a large file multiple times. RESULTS: The reported signal to noise (N = 50) decreased with electrocoagulation from 36.42+/-3.47 (control) to 31.85+/-3.64 (electrocoagulation) (p < 0.001) at 400 feet inter-adapter distance, and from 64.53+/-1.43 (control) to 60.12+/-3.77 (electrocoagulation) (p < 0.001) at 150 feet inter-adapter distance. There was no statistically significant change in network throughput (average 93 kbyte/second) at 150 feet inter-adapter distance, either transmitting or receiving during continuous 100 Watt electrocoagulation arc. CONCLUSIONS: The manufacturer indicates "acceptable" performance will be obtained with signal to noise values as low as 20. In view of this, while electrocoagulation affects this spread spectrum network adapter, the effects are small even at 400 feet. At a distance of 150 feet, no discernible effect on network communications was found, suggesting that if other obstructions are minimal, within a wide range on one floor of an operating suite, network communications may be maintained using the technology of this wireless spread spectrum network adapter. The impact of such adapters on cardiac pacemakers should be studied. Wireless spread spectrum network adapters are an attractive technology for mobile computer communications in the operating room.

Electricity↗
PubMed2005

Genetic enhancement of visual learning by activation of protein kinase C pathways in small groups of rat cortical neurons.

Although learning and memory theories hypothesize that memories are encoded by specific circuits, it has proven difficult to localize learning within a cortical area. Neural network theories predict that activation of a small fraction of the neurons in a circuit can activate that circuit. Consequently, altering the physiology of a small group of neurons might potentiate a specific circuit and enhance learning, thereby localizing learning to that circuit. In this study, we activated protein kinase C (PKC) pathways in small groups of neurons in rat postrhinal (POR) cortex. We microinjected helper virus-free herpes simplex virus vectors that expressed a constitutively active PKC into POR cortex. This PKC was expressed predominantly in glutamatergic and GABAergic neurons in POR cortex. This intervention increased phosphorylation of five PKC substrates that play critical roles in neurotransmitter release (GAP-43 and dynamin) or glutamatergic neurotransmission (specific subunits of AMPA or NMDA receptors and myristoylated alanine-rich C kinase substrate). Additionally, activation of PKC pathways in cultured cortical neurons supported activation-dependent increases in release of glutamate and GABA. This intervention enhanced the learning rate and accuracy of visual object discriminations. In individual rats, the numbers of transfected neurons positively correlated with this learning. During learning, neuronal activity was increased in neurons proximal to the transfected neurons. These results demonstrate that potentiating small groups of glutamatergic and GABAergic neurons in POR cortex enhances visual object learning. More generally, these results suggest that learning can be mediated by specific cortical circuits.

Animals↗
PubMed1997

Rural health network development: public policy issues and state initiatives.

Rural health networks are a potential way for rural health care systems to improve access to care, reduce costs, and enhance quality of care. Networks provide a means for rural providers to contract with managed care organizations, develop their own managed care entities, share resources, and structure practice opportunities to support recruitment and retention of rural physicians and other health care professionals. The results of early network development initiatives indicate a need for state officials and others interested in encouraging network development to agree on common rural health network definitions, to identify clearly the goals of network development programs, and to document and analyze program outcomes. Future network development efforts need to be much more comprehensive if they are to have a significant impact on rural health care. This article analyzes public policy issues related to integrated rural health network development, discusses current efforts to encourage network development in rural areas, and suggests actions that states may take if they desire to support rural health network development. These actions include adopting a formal rural health network definition, providing networks with alternatives to certain regulatory requirements, and providing incentives such as matching grants, loans, or technical assistance. Without public sector support for networks, managed care options may continue to be unavailable in many less densely populated rural areas of the country, and locally controlled rural health networks are unlikely to develop as an alternative to the dominant pattern of managed care expansion by large urban entities. Implementation of Medicare reform legislation could provide significant incentives for the development of rural health networks, depending on the reimbursement provisions, financial solvency standards, and antitrust exemptions for provider-sponsored networks in the final legislation and federal regulations.

Antitrust Laws↗
PubMed2000

The involvement of recurrent connections in area CA3 in establishing the properties of place fields: a model.

Strong constraints on the neural mechanisms underlying the formation of place fields in the rodent hippocampus come from the systematic changes in spatial activity patterns that are consequent on systematic environmental manipulations. We describe an attractor network model of area CA3 in which local, recurrent, excitatory, and inhibitory interactions generate appropriate place cell representations from location- and direction-specific activity in the entorhinal cortex. In the model, familiarity with the environment, as reflected by activity in neuromodulatory systems, influences the efficacy and plasticity of the recurrent and feedforward inputs to CA3. In unfamiliar, novel, environments, mossy fiber inputs impose activity patterns on CA3, and the recurrent collaterals and the perforant path inputs are subject to graded Hebbian plasticity. This sculpts CA3 attractors and associates them with activity patterns in the entorhinal cortex. In familiar environments, place fields are controlled by the way that perforant path inputs select among the attractors. Depending on the training experience provided, the model generates place fields that are either directional or nondirectional and whose changes when the environment undergoes simple geometric transformations are in accordance with experimental data. Representations of multiple environments can be stored and recalled with little interference, and these have the appropriate degrees of similarity in visually similar environments.

Animals↗
PubMed2003

Preoperative melanoma thickness determination by 20-MHz sonography and digital videomicroscopy in combination.

OBJECTIVE: To identify accurately thick melanomas preoperatively by means of a combined approach based on sonography and clinical-videomicroscopic evaluation. DESIGN: Ultrasonographic thickness measurement, obtained by means of a 20-MHz B-scanner, and identification of clinical and videomicroscopic variables useful in distinguishing between thick and thin melanomas were performed on a training set of 40 melanomas. An algorithm based on echographic, clinical, and videomicroscopic criteria was constructed to develop a method for preoperative evaluation of melanoma thickness and was validated on a test set of 48 melanomas. SETTING: University medical department. PATIENTS: Eighty-eight patients affected by primary cutaneous melanoma. MAIN OUTCOME MEASURES: Sensitivity and specificity of the algorithm, with the use of sonographic, clinical, and videomicroscopic data, in thick melanoma identification. RESULTS: Echographic thickness was calculated for each lesion. On the training set, 2 clinical and 7 videomicroscopic features were identified for distinction between thick and thin melanomas: nonpalpability, central pigment network, central brown globules, and blotches were characteristic of thin melanomas; clinical regression, localized peripheral pigment network, veil, grayish polygonal areas, and blood vessels were characteristic of thick ones. A coefficient was attributed to each variable and a score was obtained for each lesion. The algorithm, developed for preoperative thickness prediction, was validated on the test set, enabling the distinction of thick melanomas with an 86.7% sensitivity and a 100% specificity. CONCLUSION: The correct classification of all thin melanomas as such renders this approach suitable in clinical practice.

Algorithms↗
PubMed1990

Seroprevalence and risk factors for HIV transmission among female prostitutes: a community survey.

To estimate the prevalence of HIV-1, HIV-2 and HTLV-I among female prostitutes, and to identify possible risk factors for HIV transmission in this collective, sera and epidemiological information from 71 prostitutes were obtained. Using the local network of a well-defined area in southern Catalonia, all prostitution bars were identified and their working women interviewed using a previously validated questionnaire. Eight sera were found positive for HIV-1 antibodies. Of those, 7 sera were also positive in the HIV-2 assay, probably as a result of cross-reactivity between the two viruses. All sera were negative for HTLV-I antibodies. In our area, where intravenous drug users (IVDUs) account for the majority of AIDS cases, the use of drugs by the prostitutes or by their steady sexual partners seems to be the most important risk factor for HIV infection in that group.

Adolescent↗
PubMed2006

Structure mapping and semantic integration in a construction-based neurolinguistic model of sentence processing.

The current research provides a theoretical, computational and neurophysiological framework in which particular aspects of sentence comprehension and non-linguistic sequence transformation processing are implemented by a common neural mechanism for structure mapping. The theoretical context is derived from construction grammar theory in which language is considered in terms of a structured inventory of form to meaning mappings. Computationally, the construction grammar concept is implemented in a hybrid neural network model that is derived from functional neuroanatomical studies. In particular, based on data from Hoen et al. (2006, this issue), the generalized structure mapping capability is attributed to a local cortical network that includes Brodmann's area (BA) 44, while the integration of semantic structure into this transformation mechanism relies on BA 45.

Brain↗
PubMed1975

The "starry night" splenic angiogram. Contrast material opacification of the malpighian body marginal sinus circulation in spleen trauma.

In traumatized human spleens, focal 0.3-1 cm. areas of contrast material staining appear to represent the malpighian marginal sinus circulation. This circulation, when seen, is static or very slow moving. Extravasation of blood and contrast material also may be present in the marginal sinus network. The identification of diffuse or localized small areas of contrast material in the splenic angiogram of the traumatized patient suggests splenic contusion, intrasplenic hematoma, or both. The splenic angiographic appearance described may be compared to the globular appearance of stars, as depicted by van Gogh in his painting "The Starry Night."

Abdominal Injuries↗