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PubMed1991

Management and clinical utilization of computed tomography, magnetic resonance imaging, and angiography in Hokkaido University Hospital picture archiving and communication system.

We made a preliminary assessment of the Hokkaido University picture archiving and communication system (HU-PACS). Data access time from either imaging machines or data base to workstations was 1.5 minutes, which is great benefit for data communication in routine examinations. Image quality of the work station was estimated in terms of brain computed tomography (CT) and digitized cerebral angiograms. Cerebral infarction was definitely observed on the cathode-ray tube (CRT) monitor of the work station. Although the picture quality of CRT was acceptable, we had to manipulate window level and width for CRT diagnosis of cerebral angiography. Data compression was routinely used without significant degradation of those image quality. Nevertheless, further improvement of maneuverability of the workstation should be considered.

Angiography, Digital Subtraction↗

PubMed1997

Neural networks in higher levels of abstraction.

Existing artificial neural network models are not very successful in understanding or generating natural language texts. Therefore it is proposed to design novel neural network structures in higher levels of abstraction. This concept leads to a hierarchy of network layers which extract and store local details in every layer and transfer the remaining nonlocal context information to higher levels. At the same time data compression is provided from layer to layer. The use of the same network elements (meta-words) in higher levels for different word series in the basis level is introduced and discussed for grammatical identity or similarity. Thus text can be compressed to forms which are almost free of redundancy. Possible applications are storage, transmission, understanding, generating and translation of texts.

Cybernetics↗

PubMed1986

High pressure volumetric measurements in dipalmitoylphosphatidylcholine bilayers.

The one previously reported high pressure volumetric experiment on a phospholipid bilayer investigated a region of pressure between 0 and 25 MPa and obtained isothermal compressibility values for the liquid crystal and intermediate phases which differed by more than a factor of ten. We report new volumetric measurements around the main transition in dipalmitoylphosphatidylcholine (DPPC) from 0 to 100 MPa. The isothermal compressibility data for the two phases are of the same order of magnitude, and the experimentally determined coexistence curve, specific volume dependence, and volume discontinuity values are compared with the predictions of the phenomenological theory according to Sugar and Tarjan ((1982) Sov. Phys. Crystallogr. 27, 4-5). Significant discrepancies between this theory and experiment are found. Finally, the data indicate that steric interactions play a more dominant role in the main transition of phospholipid bilayers than in transitions in most thermotropic liquid crystals.

Atmospheric Pressure↗

PubMed1979

A computer feedback system for clinical research.

This paper presents a computerized data base management and information retrieval system for a heroin addiction research clinic, which has potential application for any type of clinical research. It describes data input checking programs, file structures, and output programs. The system contains several interesting features: built-in feedback error detection and correction; patient month matrix formatting and data compression; and a virtual blocking system to reduce the size of the files.

Computers↗

PubMed1994

Pattern recognition and interpretation of electromyogram data from cat jaw muscle.

This study investigates the effect of emotional behavior on the masseteric muscle EMG response patterns. Two experimental protocols are utilized: (1) does not elicit emotional behavior (stick chewing) and (2) elicits emotional behavior (hypothalamic stimulation). The Karhunen-Loève transform is used to compute features which exactly represent the correlated patterns of mean-zero observations, with data compression and noise immunity. Using nonparametric tests, it is found that the populations of biting and hissing features are significantly different (p < 0.05), with increased statistical significance as the size of the training set is increased. No statistically significant difference is seen in a test of the two biting populations.

Animals↗

PubMed1987

Power spectral analysis of normal and pathological brainstem auditory evoked potentials.

The brainstem auditory evoked potential (BAEP) recording has become a powerful investigational tool in neurological diagnosis. The BAEPs of patients have different latencies and morphologies when compared to those of normals. In this paper the power spectra (PS) of BAEPs of 21 normals, 17 patients with multiple sclerosis (MS) and 12 patients with head injury (HI) computed by Blackman-Tukey (BT) and Maximum Entropy (ME) methods are examined for their frequency composition. Three major peaks appear at approximately 170 Hz, 520 Hz and 950 Hz in PS of normal BAEPs. The average power contained in the frequency bands spread around these frequency bands for BAEPs of patients differed significantly (P less than 0.05) from those of normal BAEPs. The peaks observed in ME spectra were found to match those computed using BT method. The model order for representing both normal and patient BAEPs is greater than 40 and data compression afforded by modelling the BAEPs is of the order of 5:1.

Adolescent↗

PubMedDate not supplied

The CODATA/IUIS Hybridoma Data Bank: development of a hybrid system to handle complex data relationships.

System design for the Hybridoma Data Bank, a database of comprehensive information on immunoreagents for use by scientists in diverse disciplines, is described. Unique problems include: use of nomenclature from diverse fields that is neither static nor standard; the need for two representations of the database--textual for readability and numeric for complex search capabilities, analysis and data compression; and a method of translating between the two representations of the database.

Animals↗

PubMed1989

Assessing the evolution of the evoked potential average: a new color display method.

A new method to control the averaging process and to check the stability of evoked potential (EP) components is described. The principle of the method is based on the display of the consecutive averages of the EP after each stimulus in a color-coded picture. In this way the evolution of the process is visualised instead of only the last average. The colors are assigned according to the amplitudes. The resulting picture initially consists of erratic colors. However, with increasing numbers of stimuli, tracks of one color soon emerge, indicating stable components. The number of stimuli necessary to generate a stable peak and the duration of stability can easily be quantified. Details with regard to the methods of extraction of essential data and data compression to record the picture are described. The color display method was evaluated with the analysis of 18 somatosensory evoked potentials and 17 visual evoked potentials of controls and 33 EPs of 18 patients. It is shown that this method preserves essential information about the averaging process: the stability of the EP components can be quantified and consequently the optimum number of stimuli to be applied. Furthermore, 14 of the 33 patient recordings showed artifacts, which could be traced with the average-evolution method, but not from the final average alone.

Color↗

PubMed1994

Clinical experience of Hokkaido University-PACS and FCR-angiography.

Three years' experience with Hokkaido University-PACS (HU-PACS) is reported. In particular, this paper describes the suitability of FCR-angiography for HU-PACS, which has been in clinical use since March 1991. Image quality of FCR-arteriograms was evaluated in the head-and-face region and the abdominal region independently. The image quality in both regions was excellent. Quality of transferred images to image workstation for HU-PACS with 10:1 data compression was also evaluated, and no appreciable image degradation or loss of information was found in the transferred images. There was no significant difference in the examination time required for one patient in abdominal angiography between conventional angiography and FCR-angiography. In summary, FCR-angiography is suitable for HU-PACS as its image acquisition modality.

Abdomen↗

PubMedDate not supplied

Non-linear CT windows.

The display of computerized tomographic (CT) data requires data compression because of the limited shades of grey which the eye can differentiate. This may lead to information loss which can be minimized by a more efficient utilization of the available levels of grey than that afforded by conventional linear windows. Automated histogram equalization for grey level assignment has not been satisfactory because of the underlying assumption that the information content at any given CT level is proportional to the number of pixels at that level. For four different anatomic regions; the lumber spine, abdomen, brain and chest, an empiric graph of the clinical information content vs CT levels was integrated to yield the shape of a graph assigning shades of grey vs CT level i.e. a non-linear window. This non-linear window curve was utilized in the same manner as the linear window, namely the window center and width were under the direct control of the observer through the window center and width knobs. Each non-linear window was implemented on images of its anatomic region and interactively optimized on the screen till a maximal display of information was obtained. These optimal non-linear windows compared favorably with linear windows in most cases. This method provides the means to display more information on a CT image with no extra processing time, additional equipment or special training.

Brain↗

PubMed1996

Computationally efficient sub-band coding of ECG signals.

A data compression technique is presented for the compression of discrete time electrocardiogram (ECG) signals. The compression system is based on sub-band coding, a technique traditionally used for compressing speech and images. The sub-band coder employs quadrature mirror filter banks (QMF) with up to 32 critically sampled sub-bands. Both finite impulse response (FIR) and the more computationally efficient infinite impulse response (IIR) filter banks are considered as candidates in a complete ECG coding system. The sub-bands are threshold, quantized using uniform quantizers and run-length coded. The output of the run-length coder is further compressed by a Huffman coder. Extensive simulations indicate that 16 sub-bands are a suitable choice for this application. Furthermore, IIR filter banks are preferable due to their superiority in terms of computational efficiency. We conclude that the present scheme, which is suitable for real time implementation on a PC, can provide compression ratios between 5 and 15 without loss of clinical information.

Algorithms↗

PubMed2004

Pathological theta oscillations in idiopathic generalised epilepsy.

OBJECTIVE: To investigate spectral power, inter- and intra-hemispheric coherence in the interictal scalp electroencephalography (EEG) of 41 patients with idiopathic generalised epilepsy. METHODS: Two minutes of eyes-closed waking interictal EEG activity was analysed. Fast Fourier transformation was performed. Raw and age-regressed, Z-transformed values were computed for 19 electrodes and 4 frequency bands: absolute power (AP, ZAP), percent power (RP, ZRP), band mean frequency (MF, ZMF), inter-hemispheric (CO, ZCO) and intra-hemispheric (IC, ZIC) coherence. Compressed values (scalp averages) were computed for each parameter and 4 frequency bands. Compressed data of the patients (GE group) and the healthy controls (C group) were compared. RESULTS: ZAP across the entire 1.5-25.0 Hz range was greater in the GE than in the C group. Delta and theta ZRP was greater, alpha ZRP was less in GE than in C. ZMF and ZIC was about the same in the GE and C groups. The crucial, band-specific finding was significantly greater theta-ZCO in the GE group, in contrast to normal or decreased ZCO in the other bands. In addition, within-group correlation between ZAP of the frequency bands, correlation of ZAP and ZCO, correlation of ZIC and ZCO were different for the two groups. CONCLUSIONS: The pattern of enhanced ZAP, ZRP, ZCO, together with normal ZIC and ZMF in the theta range was a peculiar, novel finding in GE. It was incompatible with any of the known patterns of altered power and coherence due to lesional or metabolic aetiology. This pattern presumably indicates the presence of a powerful, diffuse, hypersynchronous, hypercoherent theta oscillation at the thalamo-cortical level of the brain. The role of inter-hemispheric connections in maintaining this oscillation was suggested. The other findings suggest disturbed central regulation of EEG power and coherence in the interictal state.

Adolescent↗

PubMed2006

Data reduction and representation in drug discovery.

Pre-clinical drug discovery relies increasingly on huge volumes of inter-related multivariate data. To make sense of these data and enable quality decision-making based on this plethora of information they must be presented in an interpretable form. Reducing the dimensionality of the data often leaves a data set that is too complex to interpret readily, so intuitive visualization methods are needed. Bioinformatics has provided much of the impetus for visualizing complex data, the cheminformatics community has been aggressive with the data-reduction problem. The increasing appreciation of the inter-related multifactorial nature of pre-clinical drug discovery makes visualization a burgeoning and active field that spans biosciences, mathematics and visual psychology.

Computational Biology↗

PubMed2004

Managing patient dose in digital radiology. A report of the International Commission on Radiological Protection.

Digital techniques have the potential to improve the practice of radiology but they also risk the overuse of radiation. The main advantages of digital imaging, i.e. wide dynamic range, post processing, multiple viewing options, and electronic transfer and archiving possibilities, are clear but overexposures can occur without an adverse impact on image quality. In conventional radiography, excessive exposure produces a 'black' film. In digital systems, good images are obtained for a large range of doses. It is very easy to obtain (and delete) images with digital fluoroscopy systems, and there may be a tendency to obtain more images than necessary. In digital radiology, higher patient dose usually means improved image quality, so a tendency to use higher patient doses than necessary could occur. Different medical imaging tasks require different levels of image quality, and doses that have no additional benefit for the clinical purpose should be avoided. Image quality can be compromised by inappropriate levels of data compression and/or postprocessing techniques. All these new challenges should be part of the optimisation process and should be included in clinical and technical protocols. Local diagnostic reference levels should be re-evaluated for digital imaging, and patient dose parameters should be displayed at the operator console. Frequent patient dose audits should occur when digital techniques are introduced. Training in the management of image quality and patient dose in digital radiology is necessary. Digital radiology will involve new regulations and invoke new challenges for practitioners. As digital images are easier to obtain and transmit, the justification criteria should be reinforced. Commissioning of digital systems should involve clinical specialists, medical physicists, and radiographers to ensure that imaging capability and radiation dose management are integrated. Quality control requires new procedures and protocols (visualisation, transmission, and archiving of the images).

Body Burden↗

PubMed2004

Interaction forces between polyethylene oxide-polypropylene oxide ABA copolymers adsorbed to hydrophobic surfaces.

Block and graft copolymers are frequently used as stabilizing agents in colloidal dispersions. One common material is the range of polymers known as "Pluronics," which is a BASF trade name for ABA block copolymers composed of a propylene oxide anchoring block (B block) and two ethylene oxide buoy or stabilizing blocks (A block); the equivalent ICI (Uneqima) trade name is Synperonic. In the work presented here the interactions between adsorbed layers of these materials immersed in 10(-2) M sodium sulfate solutions are presented. The block copolymers investigated had an approximately fixed molecular weight of around 3250 Da for the anchoring B block, whilst the molecular weight of the stabilizing polyethylene oxide chains varies around 800-6500 Da. Hydrophobic glass surfaces were used as the test substrate. It was found that in the absence of polymer a long ranged attractive interaction is observed, typical for the interaction between hydrophobic surfaces in aqueous media, but that in the presence of the polymers a repulsion was observed. The repulsion became longer ranged as the molecular weight of the ethylene oxide chain increased. On separation of the surfaces, the interaction was slightly longer ranged, suggesting that the two polymer layers intertwine and stretch each other on separation. This effect was more noticeable for the higher molecular weight polymers. The compression data were well described using a scaling analysis for the interaction between polymer brushes.

Adsorption↗

PubMed2005

A new polysaccharidic gel matrix for drug delivery: preparation and mechanical properties.

A new type of hydrogel was prepared, under controlled conditions, by diffusion of Ca(II) ions into a solution of the carboxylated derivative of Scleroglucan (Sclerox). The obtained hydrogel was loaded with Theophylline (TPH) and Myoglobin (MGB), two model drugs of remarkably different steric hindrance, and also used, after freeze drying, for the preparation of tablets. Release studies were carried out on both the freshly prepared gel and on the tablets. As far as the gel systems experiments are concerned, the delivery profiles resulted to be deeply dependent on the molecular dimensions of the loaded molecules; TPH was easily released while the larger tested molecule (MGB) remained partially entrapped within the three-dimensional network. Furthermore, in the case of MGB, the release was dependent also on polymer concentration (c(p)): at the highest investigated c(p) value a corresponding lowest delivery of the guest molecule was observed. This effect of polymer concentration on the rate of delivery was studied applying three different mathematical approaches: the one that better fitted the experimental release profile allowed to support the explanation of the mechanism involved in the observed two-step delivery that has been related to the drug trapping inside the clusters of the gel network. The delivery profiles from the tablets showed how the release, in this case, could be related, essentially, to the molecular dimensions of the guest molecules, independently on the c(p) used to prepare the starting hydrogel. TPH was completely delivered in a few hours while the MGB was almost unable to diffuse out of the matrix and more than 80% resulted entrapped in the network for at least 24 h. The novel hydrogel, at different c(p), was also characterized by means of a texture analyzer to inspect its mechanical properties. According to the compression data, the hardness, the work of cohesion and the work of adhesion of the networks were estimated. Furthermore, by means of relaxation experiments, analysed applying the generalized Maxwell model, the gels can be classified as solid viscoelastic materials and the mechanical spectra indicated a predominance of the viscous behaviour, while the Young modulus, E0, as expected, was found to increase with polymer concentration.

Drug Delivery Systems↗

PubMedDate not supplied

Morphological analysis and modeling of neuronal dendrites.

Morphological data on two classes of neurons from mammalian midbrain have quantitatively been analyzed for dendritic shape parameters. Their frequency distributions were used to optimize the parameters of a dendritic growth model which describes dendritic morphology by a stochastic growth process of segment branching. The model assumes randomness with respect to both the selection of the branching segment out of the tree segments and the occurrence of the branching event in time. Model-generated trees have shape properties closely matching the observed ones. The dendritic trees of each of the two classes of neurons are represented by a specific set of growth model parameters, thus achieving morphological data compression.

Animals↗

PubMed2005

A fuzzy theory of cortical computation: neuropoietic engrams, fuzzy hypercubes, and the nature of consciousness.

We apply fuzzy logic to a theory of memory representation and computation in the human cerebral cortex. The theory termed neuropoiesis is based on the hypothetical transfer of mRNA polyribosomes from the post-synaptic dendritic spine of cortical pyramidal neurons to the presynaptic boutons of connecting axons through a hypothetical process termed retroduction. The net effect of this process is a vast increase in predicted memory storage. The fuzzification of memory engrams permits this expansion in memory capacity and requires multiplex signaling which, in turn, requires the formation of a spike packet whose length is determined by the EEG frequencies generated by the thalamo-cortical rhythm generators. The role of the EEG frequencies is to provide a wavelet-like transform of the multiplex signal which in turn determines the degree of data compression that is required for memory recruitment at a given level of vigilance during cortical computation. In this conceptual model cortical computation is hypothesized to be a form of cluster analysis that can be represented by a fuzzy hypercube in which each dimension of the unit hypercube represents an apical dendrite of a layer 5 pyramidal cell in a cortical fascicle. The tuftal area of the apical dendrite in cortical layer one corresponds to the MIN or zero point of the hypercube's dimension and the cell body in layer 5 corresponds to the MAX or one point of that dimension in the unit hypercube. The neuroanatomical location of synapses on the apical dendrites in the fascicle is mapped onto the fuzzy hypercube. These synapses form clusters composed of both bottom-up and top-down signals represented as metasynaptic fuzzy sets-as-points in the hypercube. Soft winner-take-all gating by inhibitory neurons is proposed to supply the only non-linear operation needed for cortical computation. Feed-forward inhibition is envisioned to play the decisive role of spicing or de-fuzzifying the output signal. Proper transmission of the multiplex signal that carries the fuzzy engram requires synchrony of neuronal firing. For this fuzzy cortical model, synchrony of firing, multiplex signaling, winner-take-all gating, and the known spectrum of EEG frequencies are all derivable from the fundamental mechanism termed synaptopoiesis as described in the theory of neuropoiesis. Finally, this theory predicts that the neural correlate of consciousness must include inhibitory subcortical connections and that its function is largely that of limiting coherence to a narrow range of cortical engrams.

Cerebral Cortex↗