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At least 109 records · Page 6Linked to original sources
PubMed1982

Increase in apparent compressibility of cytochrome c upon oxidation.

The apparent molal adiabatic compressibilities of ferri- and ferrocytochrome c have been determined from measurements of density and sound velocity. The values found were +2.99 X 10(-8) and -2.40 X 10(-8) cm5 mol-1 dyne-1 for the ferri and ferro forms, respectively. Experiments were performed on identical solutions containing either the oxidized or reduced form of protein. Solutions of ferricytochrome c were found to have significantly greater adiabatic compressibility than equivalent solutions of ferrocytochrome c at 25 degrees C and pH 7.15. The remarkable similarity of the three-dimensional structures of the ferri and ferro proteins [Takano, T. & Dickerson, R.E. (1980) Proc. Natl. Acad. Sci. USA 77, 6371-6375] strongly suggests that this difference in compressibility is due to an increase in volume fluctuations within ferricytochrome c relative to the ferro form rather than a change in equilibrium structure or hydration. Such a difference in the dynamic properties of the structures is consistent with both the crystallographic thermal B factors and the observed increase in amide hydrogen exchange kinetics when ferrocytochrome c is oxidized. The relative magnitude of the root mean square volume fluctuations is approximated from an ideal solution treatment of the compressibility data and yields a ratio of delta Vrms (ferri cyt c)/ delta Vrms (ferro cyt c) = 1.3.

Animals↗
PubMed1989

Evaluation of routine telephone transmission of nuclear medicine studies.

Rapid and reliable transmission of nuclear medicine studies using conventional telephone lines and commercially available modems and computer systems has been accomplished through use of software developed within the authors' hospital. Original digital images of all-night and weekend studies, acquired on any of the acquisition computers from different manufacturers, are now routinely sent for remote reading at the physician's home. Data, software, and letters are routinely exchanged using modems and standard telephone lines with a sister institution in Haifa, Israel. The software has been designed to achieve no loss data compression and minimal turnaround time loss. Thus, an average lung perfusion image or gallbladder study requires about 1-3 minutes of transmission time. Full analysis and display software is available on the remote computer.

Computer Communication Networks↗
PubMed1985

Radiological image compression: full-frame bit-allocation technique.

A full-frame bit-allocation technique has been developed for radiological image compression based on encoding the cosine transform of the image. Six different types of diagnostic images were used to examine this technique, and the results have been encouraging. Reconstructed images from compressed-image data with compression ratios of 4:1, 8:1, 12:1, and 16:1 did not have excessive visual degradation. It is concluded that this technique is suitable for diagnostic image compression.

Computers↗
PubMed1989

Foot strike and the properties of the human heel pad.

Many force-plate records of human locomotion show an impulse (the foot strike) shortly after ground contact. The authors' hypothesis is that this results from the rapid deceleration of a mass (the 'effective foot') under forces which compress the heel pad. The quantitative implications are investigated through an illustrative calculation. The observations used are (a) the peak force reached in foot strike (b) the vertical velocity of the foot immediately before ground contact and (c) the properties of the heel pad in compression. Data for (a) and (b) are available in the literature; measurements for (c) are presented here. The deductions are: (a) the time taken to reach peak force is about 5.4 ms, which agrees with published measurements; (b) the mass of the effective foot is about 3.6 kg. The effective foot thus includes a substantial portion of the leg: this seems reasonable. The models used for the calculations clarify the relationship between the foot strike and the shock wave, which it generates.

Biomechanical Phenomena↗
PubMedDate not supplied

Background of the demonstrated IMAGIS activities and future expectations.

In The Netherlands a national PACS development programme has been started, supported by the Dutch Society of Radiology and funded by the Dutch Department of Health because of the national character of the project. Three main partners are cooperating in this development: the Utrecht University Hospital (AZU), BAZIS and Philips International (Product Division Medical Systems), with the Delft University of Technology as the main BAZIS subcontractor. The non-profit foundation BAZIS, developing and supporting the ZIS Hospital Information System (in use in some 30 Dutch hospitals, over 15,000 acute beds), initiated its current IMAGe Information System (IMAGIS) projects in 1984. The activities were later integrated into the Dutch PACS project started in 1986. The final goal of the project is to achieve a PACS which is fully integrated with already existing hospital information systems (HIS). The development and operation of a HIS-PACS include many aspects of technical and clinical. The current efforts of BAZIS are concentrated on three main issues: diagnostic image quality evaluation (e.g. effects of data compression); modelling, software simulation and technology assessment of a prototype PACS (both general and detailed aspects); and coupling and integration of PACS and HIS (e.g. the BAZIS ZIS). Philips, Hamburg, is supplying equipment, particularly prototype components. A systematic clinical evaluation will take place at the Utrecht University Hospital.2+ We outline the background of the intermediate results as demonstrated during the 6th EuroPACS Conference:the psychophysical software package for Feature Evaluation And System Inspection By Logged Experiments (FEASIBLE); the modelling and simulation software package for Medical Image Representation, Archiving and Communication, Learned by Extensive Simulation (MIRACLES); and first results of the coupling experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Communication Networks↗
PubMed1991

[Thyroid carcinoma as cystic nodule. The diagnostic role of cytology by needle aspiration].

195 patients affected by a cystic thyroid lesion were studied by a Fine Needle Aspiration biopsy (FNAb). 42 patients were operated on account of clinical data, compressive phenomena or cytologic results suggesting a neoplasia. Out of the operated patients, 3 were affected by a carcinoma in the cystic lesion (one "pure" cystic nodule and two "mixed" ones), while three more patients with multinodular goiters showed a carcinomatous lesion in a nodule different from the cystic one. Macroscopic characteristics of the aspirated fluid (quantity and quality) didn't affect the cytologic diagnosis. Cytology was useful in the preoperative diagnosis of benign thyroid nodules (only two false positives out of 42 patients) and was diagnostic in all the three patients affected by a carcinoma in the cystic nodule.

Adolescent↗
PubMed1991

Digital imaging and picture archiving and communication systems.

Great progress has been made in digital imaging of the chest. Most studies are dealing with computed radiography. Chest radiography in the intensive care unit may, in most cases, be performed using computed radiography. However, subtle pulmonary interstitial disease can be demonstrated less confidently using computed radiography. Significantly better detection of calcified lung nodules can be obtained by using simplified single-exposure dual-energy technique that uses storage phosphor. The wide latitude of computed radiography permits images of high quality in areas other than chest radiography. Encouraging results are presented especially in the diagnostic evaluation of scoliosis and other musculoskeletal abnormalities. An important technical innovation in digital radiography is an improved method for single-exposure dual-energy digital imaging using prefiltration with gadolinium, a cassette consisting of four photostimulable phosphor plates, spatially dependent scatter and beam hardening corrections, and noise reduction algorithm. Other groups tested algorithms for enhancement of digital images that allowed significant data compression. The implementation of picture archiving and communication systems (PACS) is inevitable; the question concerning PACS implementation is not why, but when. A comparison of the cost-effectiveness of PACS with conventional film archiving and communication systems shows that PACS should provide indirect savings when regarding the hidden costs of conventional systems. Much more experience will be needed before there is general agreement on the best design for the radiologist's workstation. Teleradiology should contribute to radiologic consultation for remote locations, because it improves the efficacy of management of patients in such locations.

Child↗
PubMed1989

Shape description in osteology using automatic Fourier analysis. Example of the human atlas.

An image analysing procedure for the shape characterisation in osteology is described. We used expansion in Fourier series of an equiangular polar representation of the contour. Fourier analysis is an information preserving technique, and it is therefore possible to reconstruct the original contour from the shape descriptors (Fourier coefficients and descriptors). The properties of the truncated expansion of the Fourier series can be used for smoothing effect and noise reduction, for interpolated reconstruction, and for data compression. Fourier analysis also allows a quantitative description of the shape. The first components describe the gross feature, the following ones the fine details.

Cervical Atlas↗
PubMed1989

[Diagnostic limitations of isolated axiography interpretation].

Axiographic images of eccentric condylar paths can be more reliably interpreted by considering the clinical function data, compression test results and the MPI. In the case presented the abnormal position of the right condyle would have gone unnoticed without such a combined approach to the problem.

Cephalometry↗
PubMed1988

Towards a digital model for an electron-microscope image.

An image model is defined based on the boundaries between image regions with different textures and series of descriptions of those textures. Six models of texture are studied under the categories of pixel-based and region-based models. Several techniques for the determination of the unit-cell of textures are presented. The model is applied to the consideration of (a) image correction, (b) the classification of image texture, (c) image enhancement including averaging of detail in periodic specimens, and (d) image data compression. A floating point format, which provides a significant simplification for the Huffman code, is also introduced.

Algorithms↗
PubMedDate not supplied

Adaptive predictive coding with applications to radiographs.

Picture archiving and communications systems (PACS) require storage and transmission of vast amounts of data. For design/cost considerations, it is desirable to reduce the size of these data without sacrificing the integrity of the stored information. The major considerations in designing a data-compression scheme for a PACS system are discussed: fidelity of the reconstructed image, bit rate, hardware complexity, and processing time. The basic principles of conventional nonadaptive differential pulse-code modulation (DPCM) are reviewed and compared with adaptive techniques. The effect of adaptive quantization on radiographic images is examined. Special consideration is given to block-adaptive DPCM or the "switched quantizer," which greatly enhances the system performance as compared with nonadaptive techniques, and conservatively has a 5:1 compression ratio. Sample radiographs substantiate the results.

Bone and Bones↗
PubMed1985

Analysis of biomedical signals by means of linear modeling.

The recording and subsequent analysis of electrical signals of physiological origin constitutes an important aspect of current biomedical research. A versatile method for the analysis of such signals is based on linear, i.e., autoregressive (moving average) modeling. These techniques are based on fitting a hypothetical model to the signal under observation. These models are capable of generating the original signal by a linear combination of past observations and past and present noise samples. High resolution spectral estimates can be obtained in this way. Also, the often small number of model coefficients offer a concise description of the signal and may be used for classification purposes. Other applications entail the detection of nonstationarities, data-compression, and signal enhancement. In this review, linear modeling methods for the analysis of electroencephalograms, electro- and phono-cardiograms, electromyograms, and gastrointestinal signals are surveyed.

Digestive System Physiological Phenomena↗
PubMed1983

A computer-based system for the study of ECG/VCG variability.

A description is given of a computer-based system for electrocardiogram and vectorcardiogram analysis. Its main purpose is to provide a basic research and study tool of the variability occurring in electrocardiographic activity when the observation time is of the order of 30 min. System/operator interaction is designed to allow the user to validate or correct the identifications executed by the program. Special attention is given to graphic representation techniques suitable for synthesizing a great many numerical results. Data acquisition and analysis are performed by two different PDP 11 systems. The acquisition programs are written in ASSEMBLER, the analysis programs are in FORTRAN. Intermediate files are structured by a data compression technique. At present the program is oriented to study normal subjects. A new version to study bundle-branch blocks is now available.

Computers↗
PubMed1975

Computer signal processing of long duration biotelemetric brain data.

The EEG represents brain processing under diverse physiological conditions. A complete system involving acquisition and quantitation of this important information about brain function is described. The time-domain EEG and other biological signals are obtained using a multichannel PAM/FM biotelemeter mounted on the head of the experimental animal. This data is transmitted, demodulated and recorded by electronic recording techniques. A computer-based EEG analysis system is described for acquiring the primary data and transforming it into the frequency domain using Fourier methods. The computing system is developed to semi-automatically signal process about 4 h of eight channel EEG records. Data compression by plotting in a quasi-three-dimensional spectral profile allows visual correlations of pattern features to drug manipulations, etc. The software programs are briefly described for each step in signal processing. The feasibility of the complete system approach is demonstrated using biotelemetry to acquire low voltage EEG signals without behavioral distortions or introduction of artifacts by cables.

Animals↗
PubMedDate not supplied

Data predictability for compression of digital fluorography images.

Images obtained by digital fluorography were checked for compressability. These images include images of coronary vessels and images of peripheral vessels. These images have a very low signal-to-noise ratio compared to the optical images usually used for developing compression methods. Configurational entropy was used to represent the information content of these images. Reversible prediction algorithms were extensively checked in a search for minimal residual information, enabling more efficient reversible compression. Optimal results were obtained for algorithms based on two or three neighboring pixels and a semiempirical rule, based on the noise level, was found which decides on the best approach. It was found that raw data images are more predictable than subtracted images although the latter are visually preferred.

Algorithms↗
PubMed1991

Computerised method for acquisition and display of gastrointestinal motility data.

A computerised system is developed for the acquisition and display of gastrointestinal motility data which utilises a purpose developed software program called 'PC-motil', running on an IBM compatible microcomputer. 'PC-motil' displays data during collection, writes data to disk file and compresses all data at the end of a study on to a single monitor screen for convenient overview. Any area of interest, in single or multiple channels, may be selected and expanded for detailed examination. This system is tested by the recording of gastric and jejunal motility patterns of 11 healthy volunteers in fasting and fed states. All antral and jejunal migrating motor complexes (MMCs) in fasting studies, as well as all fed motility patterns were recognisable in both 'compressed' and 'expanded' form. The reproduction of motility patterns by the computer based system was indistinguishable from that of a conventional analogue chart recorder. This computerised system provides a convenient and cost-effective means of acquisition, storage and display of motility data in digital form.

Adult↗