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At least 469 records · Page 26Linked to original sources

PubMed2003

Medical image security in a HIPAA mandated PACS environment.

Medical image security is an important issue when digital images and their pertinent patient information are transmitted across public networks. Mandates for ensuring health data security have been issued by the federal government such as Health Insurance Portability and Accountability Act (HIPAA), where healthcare institutions are obliged to take appropriate measures to ensure that patient information is only provided to people who have a professional need. Guidelines, such as digital imaging and communication in medicine (DICOM) standards that deal with security issues, continue to be published by organizing bodies in healthcare. However, there are many differences in implementation especially for an integrated system like picture archiving and communication system (PACS), and the infrastructure to deploy these security standards is often lacking. Over the past 6 years, members in the Image Processing and Informatics Laboratory, Childrens Hospital, Los Angeles/University of Southern California, have actively researched image security issues related to PACS and teleradiology. The paper summarizes our previous work and presents an approach to further research on the digital envelope (DE) concept that provides image integrity and security assurance in addition to conventional network security protection. The DE, including the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header, can be embedded in the background area of the image as an invisible permanent watermark. The paper outlines the systematic development, evaluation and deployment of the DE method in a PACS environment. We have also proposed a dedicated PACS security server that will act as an image authority to check and certify the image origin and integrity upon request by a user, and meanwhile act also as a secure DICOM gateway to the outside connections and a PACS operation monitor for HIPAA supporting information.

California↗

PubMed1999

Variational learning in nonlinear gaussian belief networks.

We view perceptual tasks such as vision and speech recognition as inference problems where the goal is to estimate the posterior distribution over latent variables (e.g., depth in stereo vision) given the sensory input. The recent flurry of research in independent component analysis exemplifies the importance of inferring the continuous-valued latent variables of input data. The latent variables found by this method are linearly related to the input, but perception requires nonlinear inferences such as classification and depth estimation. In this article, we present a unifying framework for stochastic neural networks with nonlinear latent variables. Nonlinear units are obtained by passing the outputs of linear gaussian units through various nonlinearities. We present a general variational method that maximizes a lower bound on the likelihood of a training set and give results on two visual feature extraction problems. We also show how the variational method can be used for pattern classification and compare the performance of these nonlinear networks with other methods on the problem of handwritten digit recognition.

Depth Perception↗

PubMed1999

[Dorsal metacarpal flap with an extensive retrograde pedicle. Anatomic study and 22 clinical cases].

The dorsal digitometacarpal flap or extended distal pedicled dorsal metacarpal flap is a new skin flap, useful in reconstructing large distal defects on the dorsal aspect of the digits. It is raised on the dorsum of the hand, over an intermetacarpal space. Its vascularisation is provided by proximal dorsal cutaneous branches of the digital collateral arteries through the rich, anastomotic arterial network of the webspace. This flap is a useful flap compared to others flaps harvested from the dorsum of the hand, such as the reverse metacarpal flaps. The operative procedure preserves the dorsal interosseous muscles aponeurosis, the junctura tendinum and the dorsal metacarpal artery. Its vascularisation depends on the webspace arterial network; it is constant contrary to the dorsal metacarpal arteries of the ulnar spaces. This flap is indicated to cover distal defects on the dorsum of the digits because of its large rotation arc. The anatomical basis and operative technique of the flap are described. Two out of 22 clinical cases were selected to illustrate the ability of this flap for reconstruction of digital defects.

Adult↗

PubMed1988

Preferential distribution of leukocytes in rat mesentery microvessel networks.

Distribution of leukocytes in rat mesenteric microvessel networks was studied using intravital fluorescence video microscopy. A digital image analysis system was used to measure vessel diameters, flow velocities and leukocyte fluxes in 306 capillaries of 8 networks. Capillaries were defined as vessel segments connecting divergent to convergent branch points. Their topological position within the network was quantified by a generation number defined as the number of bifurcations between the capillary and the arteriole feeding the network. Proximal capillaries (generation numbers 4 and 5) were slightly but significantly smaller in diameter (8.9 +/- 0.4 micron, mean +/- SEM) than distal ones (generation numbers 20 and 21, 10.1 +/- 0.4 micron). Average capillary flow velocity decreased markedly from 2.0 +/- 1.0 mm.s-1 in proximal to 0.41 +/- 0.06 mm.s-1 in distal capillaries. Average leukocyte concentration was 3.4 +/- 0.5.10(9) 1(-1) and thus significantly below systemic values (6.0.10(9) 1(-1] in proximal capillaries, and above in distal ones (11.7 +/- 2.6.10(9) 1(-1). The analysis of flow and leukocyte flux partition at 138 bifurcations showed preferential distribution of leukocytes to the daughter capillary with higher flow rate. This suggests a tentative explanation for the observed leukocyte accumulation along the microvascular tree: due to their low fractional flow, proximal capillaries draw relatively leukocyte-poor blood from the arteriole feeding the network; this leads to an increased leukocyte concentration in distal capillaries. As a consequence of the concomitant increase of capillary diameter with increasing generation number, leukocytes are preferentially flowing through larger capillaries and are excluded from small ones.

Animals↗

PubMed2005

Semi-synthetic mammalian gene regulatory networks.

In recent years gene network engineers have celebrated spectacular success: Genetic devices such as epigenetic toggle switches and oscillating networks have been engineered and pioneered a new ever-increasing scientific community known as synthetic biology. While synthetic biology was until recently restricted to network assembly and testing in prokaryotes, decisive advances have been achieved in eukaryotic systems based on current availability of different human-compatible transgene control technologies. Most prominent examples include the epigenetic gene network enabling metastable fully inheritable transgene expression states in mice, artificial regulatory cascades managing multi-level expression control and Boolean-type BioLogic gates supporting near-digital expression readout. The majority of transgene control networks available to date are fully synthetic and integrate artificial extracellular signals in a desired host metabolism-independent manner. Yet, in order to develop their full anticipated therapeutic potential, synthetic transgene control circuits need to be well interconnected with the host cell's regulatory networks in order to enable physiologic control of prosthetic molecular expression units. We have designed three semi-synthetic transcription control networks able to integrate physiologic oxygen levels and artificial antibiotic signals to produce expression readout with NOT IF or NOR-type Boolean logic or discrete multi-level control of several intracellular and secreted model product proteins. Subtle differences in the regulation performance of the endogenous oxygen-sensing system in CHO-K1 and human HT-1080 switched the semi-synthetic network's readout from a classic four-level (high, medium, low, basal) regulatory cascade to a network enabling six discrete transgene expression levels. These findings are in excellent correspondence with a mathematical model. Prosthetic networks, precisely embedded in host regulatory networks and co-fine-tuned by physiologic as well as pharmacologic input signals, will foster future advances in gene therapy and tissue engineering.

Animals↗

PubMed2005

Digital imaging in pathology: the case for standardization.

The process of digital imaging in microscopy is a series of operations, each contributing to the quality of the final image that is displayed on the computer monitor. The operations include sample preparation and staining by histology, optical image formation by the microscope, digital image sampling by the camera sensor, postprocessing and compression, transmission across the network and display on the monitor. There is an extensive literature about digital imaging and each step of the process is fairly well understood. However, the complete process is very hard to standardize or even to understand fully. The important concepts for pathology imaging standards are: (1) systems should be able to share image files, (2) the standards should allow the transmission of information on baseline colours and recommended display parameters, (3) the images should be useful to the pathologist, not necessarily better or worse than direct examination of a slide under the microscope, (4) a mechanism to evaluate image quality objectively should be present, (5) a mechanism to adjust and correct the minor errors of tissue processing should be developed, (6) a public organization should support pathologists in the development of standards.

Image Interpretation, Computer-Assisted↗

PubMed2000

Effects of MPEG compression on the quality and diagnostic accuracy of digital echocardiography studies.

The advantages of digital echocardiography studies include ease of retrieval, review, comparison, duplication, and quantitation as well as the potential for moving studies over networks. However, the large amounts of data associated with digital echocardiography studies have posed new problems. Reduction of the amount of data can be accomplished with image compression, in particular MPEG-1 (Moving Pictures Expert Group), which is designed for dynamic image sequences. However the effects of different levels of compression on the quality and diagnostic content of echocardiographic images need to be established. Digital sequences of single cardiac cycles were acquired in 40 consecutive patients, MPEG-1-compressed at different effective ratios (60:1, 80:1, 120:1, 200:1, 300:1, 370:1, 500:1), reviewed, and scored for endocardial visualization. The overall visualization scores and percentages of nonvisualized segments in the compressed images were not different from the uncompressed images up to a compression ratio of 200:1. Differential effects of compression were noted on a segmental basis and also varied with baseline image quality. The ability to correctly identify regional wall motion abnormalities did not decrease until compression ratios of 1:200 or higher were used. Digital echocardiography loops, MPEG-1-compressed at an effective ratio of 200:1, demonstrate no degradation in endocardial visualization quality or diagnostic content. Compression at this ratio has the potential to reduce the storage size of digital echocardiography studies to less than 1% of their current size.

Echocardiography↗

PubMed2006

Network analysis of online bidding activity.

With the advent of digital media, people are increasingly resorting to online channels for commercial transactions. The online auction is a prototypical example. In such online transactions, the pattern of bidding activity is more complex than traditional offline transactions; this is because the number of bidders participating in a given transaction is not bounded and the bidders can also easily respond to the bidding instantaneously. By using the recently developed network theory, we study the interaction patterns between bidders (items) who (that) are connected when they bid for the same item (if the item is bid by the same bidder). The resulting network is analyzed by using the hierarchical clustering algorithm, which is used for clustering analysis for expression data from DNA microarrays. A dendrogram is constructed for the item subcategories; this dendrogram is compared to a traditional classification scheme. The implication of the difference between the two is discussed.

Journal Article↗

PubMed1992

Digital imaging in pediatric hospitals.

Thirty-nine of 65 children's hospitals in North America responded to a questionnaire regarding their use of digital fluoroscopy and computed radiography (CR) systems. Both digital modalities are very favorably rated by institutions that have them. Budget constraints limit purchases in the other institutions. Picture archiving and communication systems (PACS) networking is not the primary reason for installation of digital systems. Fourteen of 39 hospitals have digital fluoroscopy and another 9 plan installation within 12 months. The three most highly rated benefits of digital fluoroscopy were decreased radiation dose, immediate visualization of the acquired image on the monitor, and the ability to alter image contrast and density. Four of 39 hospitals have computed radiography. The three most highly rated benefits of computed radiography were more stable image quality, ability to alter contrast and density, and PACS networking.

Child↗

PubMed2004

Does computation provide a model for creativity? An epistemological perspective in neuroscience.

In 1939 Alan Turing, a major scholar in the field of mechanical computation, described a system whose computational power was beyond that of a discrete, finite state machine (Turing Machine). The composition of this system was likely the first example of what is now called an hybrid computational system. Since then, development of neural networks and brain automata has made aware that forms of computation might exist that are likely to go beyond Turing's limits. Natural systems, like the central nervous system in Mammals and man, are likely to use such a type of computation, especially to perform highly integrating activities, like feedback controls and mental creative processes. The latter are usually understood as processes that involve infinitary procedures, ending up in a complex information network, the computational maps, in which both digital, Turing-like computation and continuous, analog forms of calculus are expected to occur. Pictorial representation may be a fruitful example, mostly metaphorical, to analyze the use of this hybrid forms of computation by higher order computational maps, and the possible role of these types of computational processes in painting creativity is briefly analyzed in comparing 15th vs 16th century Renaissance Art. An open challenge for neuroscience in the 21st century is to clarify whether a hybrid neural learning network might represent a reasonable clue to scientifically interpret the theme of "creativity".

Art↗

PubMed1998

Neural network for sleep EEG K-complex detection.

The paper presents the development and application of an automatic system used to detect and classify the K-complexes aperiodic, waveforms found in electroencephalograms of patients during stage two sleep. The slow-wave transient K-complex is evoked by auditory or somatosensory stimulation being an event related potential. The analysis of this transitory waveform contributes to the assessment of sleep stages used by controlled learning during sleep. In our work we used a TMS320C30 DSP to implement an automatic detection procedure based on features extraction and classification using a feed-forward neural network.

Analog-Digital Conversion↗

PubMed1994

ID number recognition of X-ray films by a neural network.

Results of ID number recognition of X-ray films using the neuro-computing technique implemented on a conventional engineering workstation are reported. The neural network was trained to identify the ten digits of arabic numerals and two roman letters printed on X-ray films. We used 22 sheets of films for the training set and 23 sheets for the test set. Each sheet of film contains 25 characters. A 99.5% recognition rate on the character base was achieved.

Algorithms↗

PubMed1990

Design and operation of a nuclear medicine picture archiving and communication system.

Construction of a new Veterans Administration Medical Center provided a unique opportunity to design and implement a state-of-the-art nuclear medicine department in a large teaching and research hospital. The new medical center allowed the acquisition of all new gamma cameras and computer systems without any historical need to patch together a system of old and new equipment. The picture archiving and communication system (PACS) was designed to link five gamma cameras to four image viewing areas, followed by digital archive on an optical disc. The gamma cameras' computers and viewing areas' computers are linked to a central networking computer in a manner that provides nine independent but digitally communicating image computers. Each nuclear medicine computer is capable of acquiring gamma camera data while possibly also performing up to three other simultaneous tasks: analysis of image data, transfer of image data from node to node, and patient database manipulation. The nine image computers each appear to the user as a digital file cabinet, containing various folders, which in turn contain patient studies. To transfer a patient study from one location to another, the user simply queues a transfer request by selecting a file drawer-folder combination for the source and destination locations. It takes only a few seconds to queue a transfer request, and the transfer is complete about a minute later without any further user intervention. A computer genie awakens during the early morning off-hours and performs housekeeping tasks, including movement of patient studies (based on date of acquisition) from active viewing folders to inactive archive folders. All scheduling, workload data, patient image reports, etc, are handled by a patient textual information database system. Patient reports and scheduling information are transmitted to the medical center's central computer where they are made readily available throughout the medical center. The PACS, in clinical use since the spring of 1988, is practical and well-received by technologists, nuclear medicine physicians, and more importantly, our consumer, the referring physicians.

Hospital Information Systems↗

PubMed2001

Fractal branching pattern in the pial vasculature in the cat.

Arborization pattern was studied in pial vascular networks by treating them as fractals. Rather than applying elaborate taxonomy assembled from measures from individual vessel segments and bifurcations arranged in their branching order, the authors' approach captured the structural details at once in high-resolution digital images processed for the skeleton of the networks. The pial networks appear random and at the same time having structural elements similar to each other when viewed at different scales--a property known as self-similarity revealed by the geometry of fractals. Fractal (capacity) dimension, Dcap, was calculated to evaluate the network's spatial complexity by the box counting method (BCM) and its variant, the extended counting method (XCM). Box counting method and XCM were subject to numerical testing on ideal fractals of known D. The authors found that precision of these fractal methods depends on the fractal character (branching, nonbranching) of the structure they evaluate. Dcaps (group mean +/- SD) for the arterial and venous pial networks in the cat (n = 6) are 1.37 +/- 0.04, 1.37 +/- 0.02 by XCM, and 1.30 +/- 0.04, 1.31 +/- 0.03 by BCM, respectively. The arterial and venous systems thus appear to be developed according to the same fractal generation rule in the cat.

Animals↗

PubMed1996

Salvage of a devascularized digit with free arterialized venous flap: a case report.

Significant soft tissue and vascular loss is always encountered in salvage of a devascularized digit that has sustained crush or avulsion injury. Ideal reconstruction should include repair of the vascular defect and provision of stable soft tissue coverage simultaneously in a single operation to facilitate early recovery and early rehabilitation. A venous flap is a composite cutaneous flap that contains a segment of vein traversing it. A free venous flap is used in a devascularized digit to cover the soft tissue defect and restore the digital circulation by perfusion of arterial blood through the flap's venous network (i.e., free arterialized venous flap). Satisfactory result, both for the flap and for the digit, is obtained. The free arterialized venous flap is a useful, up-to-date option for such dual-purpose reconstruction.

Debridement↗

PubMed2002

Nanocontroller update: building a better artificial neuron.

Recent progress in microprocessor design has produced sophisticated 8-bit single-chip microcontrollers in small packages. These user-programmable "nanocontrollers", some with as few as eight pins, now include a variety of linear on-chip components. Miniscule complex mixed digital and analog systems are now possible. This paper outlines some of these advances, then describes how using these new microcontroller features to create a better artificial neuron have improved the author's ten-year-old neural network design.

Analog-Digital Conversion↗

PubMed1994

Classification of chromosomes using a probabilistic neural network.

This paper describes the application of a probabilistic neural network (PNN) to the classification of normal human chromosomes. The inputs to the network are 30 different features extracted from each chromosome in digitized images of metaphase spreads. The output is 1 of 24 different classes of chromosomes (the 22 autosomes plus the sex chromosomes X and Y). An updating procedure was implemented to take advantage of the fact that in a normal somatic cell only two chromosomes can be assigned to each class. The network has been tested using the Copenhagen, Edinburgh, and Philadelphia databases of digitized images of human chromosomes. The recognition rates achieved in this study are superior to those reported using either the maximum likelihood or back propagation neural network techniques.

Chromosomes, Human↗

PubMed1992

Telepathology: a new tool of pathology? Presentation of a French national network.

The field of pathology is constantly growing and the responsibility of the pathologists has progressively increased in the decision of application of some efficient but aggressive therapies. They justify the increasing necessity of discussion between pathologists about the diagnoses of difficult or rare or severe lesions. It is now possible to discuss at distance on good definition digitized images transmitted through I.S.D.N. A French experimental network between 12 workstations has been introduced since 2 years. Difficult or severe diagnoses have been immediately solved in 85% of the discussed cases. It remain legal problems and the necessity of an evaluation protocol which could be discussed at a European level. The increase of technical progress and, above all, the decrease of the costs might favour the development of telepathology. The workstation of the pathologist in the year 2000 could be the combination of a microscope, a HD-TV-camera and a personal computer with many softwares allowing treatment and transmission of numerous pictures.

Equipment Design↗