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At least 163 records · Page 9Linked to original sources
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↗
PubMed1983

[Generation of response functions of a NaI detector by using an interpolation technic].

A computer method is developed for generating response functions of a NaI detector to monoenergetic gamma-rays. The method is based on an interpolation between measured response curves by a detector. The computer programs are constructed for Heath's response spectral library. The principle of the basic mathematics used for interpolation, which was reported previously by the author, et al., is that response curves can be decomposed into a linear combination of intrinsic-component patterns, and thereby the interpolation of curves is reduced to a simple interpolation of weighting coefficients needed to combine the component patterns. This technique has some advantages of data compression, reduction in computation time, and stability of the solution, in comparison with the usual functional fitting method. The processing method of segmentation of a spectrum is devised to generate useful and precise response curves. A spectral curve, obtained for each gamma-ray source, is divided into some regions defined by the physical processes, such as the photopeak area, the Compton continuum area, the backscatter peak area, and so on. Each segment curve then is processed separately for interpolation. Lastly the estimated curves to the respective areas are connected on one channel scale. The generation programs are explained briefly. It is shown that the generated curve represents the overall shape of a response spectrum including not only its photopeak but also the corresponding Compton area, with a sufficient accuracy.

Gamma Rays↗
PubMed1995

SD filtering for enhancement of a nuclear medicine image sequence.

This paper explores the use of an image sequence processing algorithm, called the simultaneous diagonalization (SD) filter, which can be effectively applied to long noisy image sequences. This filter was developed to filter a spatially invariant image sequence to form one new image in which a desired feature is enhanced and one or more undesired features (and noise) are suppressed in the filtered image. This filtering technique, applied to a long noisy image sequence, can be used to achieve significant data compression for image storage and provide surprisingly good enhanced image reconstructions. For this investigation, SD filtering is applied to a temporal image sequence, a renogram, with compression of a very noisy 180-image sequence to a 4-image set. The renogram, a nuclear medicine technique, was chosen due to its low signal-to-noise ratio over a long image sequence. Before the application of the SD filter, classical image processing techniques, median and averaging filtering, are used as a preliminary method to reduce the image sequence noise content. Compared to any of the images in the original image sequence, the reconstructed images are remarkably good. The SD filter with prefiltering, thus, can collect information distributed over a 180-image temporal sequence with low signal-to-noise ratio.

Algorithms↗
PubMed1994

Femoral nerve palsy. An unusual complication of anterior lumbar interbody fusion.

SUMMARY OF BACKGROUND DATA: Compression neuropathy of the femoral nerve has been reported as an uncommon complication of bleeding into the iliopsoas muscle. OBJECTIVE: The authors detected anatomic reasons of direct injury to the femoral nerve at the lower lumbar level. METHODS: Keeping the hip in extension during the course of carrying out anterior fusion on a previously failed posterior fusion was considered another causative factor of femoral nerve injury. Anatomical dissection confirmed the likelihood of this injury being produced in this situation. RESULTS: Femoral nerve traction and compression can occur after prolonged compression of the nerve within the psoas muscle stretched between an immobile lower lumbar spine and the lesser trochanter when the hip is kept in extension. In the patients described no other reasons for direct or indirect injury were identified. CONCLUSION: Although uncommon, the complication should be kept in mind. It can be avoided by intraoperative hip flexion.

Cadaver↗
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↗
PubMed1993

Chromosome anomalies in mammary carcinoma from transgenic WAPRAS mice: compression with human data.

Transgenic WAPRAS mice, obtained by infection of the construct WAP promoter murine gene and the HRAS human protooncogene, develop mammary adenocarcinoma within 1-3 months after pregnancy. A cytogenetic analysis was performed on 17 tumors from 10 mice. Almost all detected anomalies were chromosome gains. The resulting trisomies affected recurrently chromosomes 1, 15, 19, 17, 7, and 12, in decreasing order of involvement. Although in situ hybridization showed that the transgene was integrated in chromosome 1, the duplication of this chromosome did not depend on the presence or absence of the transgene. Comparison with human data indicates that the 3 most frequently duplicated chromosomes in WAPRAS mice correspond to the human chromosome segments most frequently duplicated or amplified in breast cancer, i.e., 1q, 8q, and 11q13. None of the chromosome segments often deleted in human tumors were found to be duplicated in the mouse tumors.

Adenocarcinoma↗
PubMed1993

FASTPAT: a fast and efficient algorithm for string searching in DNA sequences.

A new string searching algorithm is presented aimed at searching for the occurrence of character patterns in longer character texts. The algorithm, specifically designed for nucleic acid sequence data, is essentially derived from the Boyer-Moore method (Comm. ACM, 20, 762-772, 1977). Both pattern and text data are compressed so that the natural 4-letter alphabet of nucleic acid sequences is considerably enlarged. The string search starts from the last character of the pattern and proceeds in large jumps through the text to be searched. The data compression and searching algorithm allows one to avoid searching for patterns not present in the text as well as to inspect, for each pattern, all text characters until the exact match with the text is found. These considerations are supported by empirical evidence and comparisons with other methods.

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↗
PubMed1981

Progress in computer analysis of the exercise electrocardiogram.

The potential advantages of digital computer processing of exercise electrocardiographic data include reduction of noise, compression of data, improved precision and application of optimal criteria. Most prior approaches to such processing required equipment that was both expensive and inconvenient. With the revolution in instrumentation brought about by the development of microcomputers, powerful dedicated computers can now be afforded by many exercise laboratories. There are many approaches to computerized management of exercise electrocardiographic data and various criteria for ischemia. Studies are necessary to validate computer algorithms so that these devices can be used diagnostically to best advantage. Cardiologists need some understanding of this field so that they can be discriminating users of computer systems. In addition, the results of studies correlating electrocardiographic changes with radionuclide methods of assessing myocardial perfusion and function should enable such assessments to be made from the electrocardiographic signals alone, particularly when aided by computer analysis of spatial shifts.

Angina Pectoris↗
PubMed1991

The effect of mechanical deformation on the movement of water in foods.

This study has shown the importance of relating NMR spectroscopic information on the water in model food structures to the mechanical properties of those structures. Analysis of the NMR relaxation data can be used to examine the distribution of water domain sizes, and this has been related to the mechanical properties of the samples. A novel NMR probe-head has been designed, which allows both the NMR and the mechanical data to be simultaneously measured during compression of the sample. This probe-head allows compressive stress/strain data to be obtained directly from the NMR sample, allowing changes in the distribution of the water to be directly correlated to changes in mechanical properties.

Chemical Phenomena↗
PubMed1989

Recurrent deep venous thrombosis: limitations of US.

Compression ultrasound (US) has become widely used to diagnose acute deep venous thrombosis (DVT). To determine the appearance of veins with previous DVT, 60 legs (58 patients) in which DVT had been diagnosed 6-31 months earlier (mean, 15.1 months) were reexamined with compression US. At reevaluation there was no indication of acute DVT. Thirty-two extremities had an appearance consistent with clot at the time of this study; 28 demonstrated normal findings. Variables that correlated with findings at follow-up US included age, location of clot, number of previous clots, pain, and augmentation of flow at compression. These preliminary data indicate that compression US may not be reliable as a follow-up study in patients in whom postphlebotic syndrome develops after an acute episode of DVT.

Follow-Up Studies↗
PubMed1992

An efficient algorithm for MR image reconstruction and compression.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Algorithms↗