Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Data Compression”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
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↗
PubMed1996

Teleradiology and telemedicine.

This article provides a historical perspective as well as an update on the current state of teleradiology and telemedicine in the United States. Technical implementation issues are discussed and enabling technologies are described. Considerations that impact network design are outlined including data transmission, data compression, applicable standards, and band-width requirements. Reimbursement, medicolegal, licensure, and regulatory issues related to the delivery of teleradiology and other telemedicine services are reviewed. Insight is provided into the role of teleradiology and telemedicine in a changing health care environment.

Computer Communication Networks↗
PubMed1996

Source localization and bioelectric imaging as it relates to continuous waveform analysis.

One of the goals of the mathematical analysis of scalp-recorded continuous EEG waveforms is to elucidate non-invasively the neural generators of these voltages. One way of accomplishing this is to simulate these generators by equivalent current sources and follow the apparent motion of these theoretical generators during the temporal evolution of the EEG. Another way of accomplishing this is to follow the changes in scalp or simulated cortical surface potential or Laplacian maps during the temporal evolution of the EEG. We first discuss the possible theoretical pitfalls of using linear techniques on an essentially nonlinear problem (the localization of the sources of the EEG), as well as possible computational pitfalls associated with realistic, but complex, conductive medium models simulating the head. Various mathematical source localization methods and bioelectric imaging techniques are then outlined. Later in this paper a collaborative project involving mathematicians, computer scientists, and clinical neuroscientists is described. In this project EEG waveform data will be analyzed, millisecond-to-millisecond, using the various mathematical techniques for localizing equivalent current sources and simulating cortical surface potential and Laplacian topographical maps mentioned above. One of the clinical aims of this research project is to localize epileptic foci without employing invasive recording procedures. Since the EEG datasets that will be analyzed are large (22 Mb, in some cases), data compression and parallel processing strategies will be important parts of this research project. Such strategies, as they may apply to continuous waveform analysis, are discussed in the two appendices at the end of this paper. Many of the presentations at the Symposium and the corresponding papers in this Supplement are related to the ideas and goals of this research project and the implementation of the mathematical/computational techniques for realizing these goals.

Brain↗
PubMed1996

Wavelets, adapted waveforms and de-noising.

This is a short summary of a talk given at the Frontier Science in EEG Symposium, Continuous Waveform Analysis, held on 9 October 1993 in New Orleans. We describe some new libraries of waveforms well-adapted to various numerical analysis and signal processing tasks. The main point is that by expanding a signal in a library of waveforms which are well-localized in both time and frequency, one can achieve both understanding of structure and efficiency in computation. We briefly cover the properties of the new "wavelet packet" and "localized trigonometric" libraries. The main focus will be applications of such libraries to the analysis of complicated transient signals: a feature extraction and data compression algorithm for speech signals which uses best-adapted time and frequency decompositions, and an adapted waveform analysis algorithm for removing fish noises from hydrophone recordings. These signals share many of the same properties as EEG traces, but with distinct features that are easier to characterize and detect.

Electricity↗
PubMed1997

Update on new technologies in pediatric echocardiography.

Advances in ultrasound technology will continue to expand the utility of echocardiography in the assessment of structural and functional cardiac disease in children. Tissue Doppler imaging and dobutamine stress echocardiography are 2 promising clinical applications that are expected to become increasingly used with time. Advances in data compression technology, including JPEG and MPEG techniques, will significantly affect digital archival and transmission of echocardiograms, which also have clinical implications, particularly in the expanding use of telemedicine. Continued research and clinical experience will further define the ultimate roles of these technologies in the future.

Cardiotonic Agents↗
PubMed1998

[The Monte Carlo method and parallel estimation in the drawing up of radiosurgery treatment plans].

PURPOSE: We investigated the practical application of a calculation algorithm based on the Monte Carlo method to stereotactic radiosurgery treatment planning. In radiosurgery, high dose gradients and the lack of electronic disequilibrium make high resolution matrices and high computing power and speed necessary to obtain accurate dose distribution. To date, the main obstacle to the wider-spread use of the Monte Carlo method has been the huge computing time necessary to obtain a dose distribution on current hardware. MATERIAL AND METHODS: In this project, developed within the ESPRIT program, funded by the European Union, a Parsytec CC (Cognitive Computing) computer was used with 9 processors (Power PC 604, 133 Mhz, RAM 64 Mb) with IBM AIX/EPX OS and availability for Fortran parallel codes compilation, connected to a PC for data input, results rendering, and dose distribution calculation with a conventional algorithm for comparison with the Monte Carlo code (an EGS4 user code). The module named Rapt Region Extractor performs data compression with an octree method without decreasing resolution, for RAM and computing time requirements to remain acceptable. A model of the 6 MV photon beam from Clinac 2100C Varian linear accelerator was devised, based on incident photon energy spectrum and, for each collimator dimension, on bidimensional dose distribution orthogonal to beam direction measured at SSd = SAD = 100 cm. RESULTS: Parallelization was carried out on event numbers, allowing a simulation speed to number of processor ratio close to unity. A new random number generator was used, capable of correctly running on the parallel architecture. The simulation procedure includes: 1) CT acquisition in DICOM 3.0 format, Analyze or with scanner; 2) Target delineation, treatment arc definition. 3) Dose calculation, with both conventional and Monte Carlo methods. 4) Dose distribution rendering on every transverse, sagittal or coronal planes overlapped in color wash on anatomical representation. Comparison between conventional and Monte Carlo algorithms were carried out on an anthropomorphic phantom and 10 real patients, with 2.5 mm anatomical resolution and standard deviation never exceeding 2%. A simulation with 10,000,000 events and 1% maximum variance can be run in 43'. When PTV is an homogeneous areas the differences between the two methods are around 5%, while when PTV is localized in dishomogeneous areas discrepancies reach 20% in the bone. CONCLUSIONS: In conclusion, the feasibility of direct simulation with the Monte Carlo method in radiosurgery has been demonstrated within time and hardware costs compatible with clinical practice.

Algorithms↗
PubMed1999

Effect of active compression-decompression resuscitation (ACD-CPR) on survival: a combined analysis using individual patient data.

Active compression decompression resuscitation (ACD-CPR) has been developed as an alternative to standard cardiopulmonary resuscitation (S-CPR). To determine the effect of ACD-CPR on survival and neurologic outcome in patients with out-of-hospital cardiac arrest, this combined analysis involved individual patient data from 2866 patients from seven separate randomized prospective prehospital studies who had received ACD-CPR or S-CPR after out-of-hospital cardiac arrest in seven international sites. Significant improvement in 1-h survival (odds ratio (OR) = 0.83; confidence interval (CI): 0.695-0.99; P < 0.05) was found with ACD-CPR (n = 1410) versus S-CPR (n = 1456). The odds ratio for hospital discharge after ACD-CPR was similar (OR = 0.82; CI: 0.609-1.107, P = NS), but this finding was not statistically significant. Using the chi2-test for trend, there was a significant improvement in overall survival with ACD-CPR (P < 0.05) versus S-CPR. This improvement was largely due to the influence of results from one study site. Neurological outcome and complication rates were comparable between groups. Further study is needed to determine which emergency medical services systems may benefit from out-of-hospital use of ACD-CPR.

Aged↗
PubMed1995

Real-time compression of myoelectric data utilising adaptive differential pulse code modulation.

The myoelectric signal, obtained by either surface or needle electrodes, is used in many areas of clinical research and diagnosis. The conventional method of storing such information is in digitised form on a computer. However, the bandwidth of the signal and the required resolution result in large memory requirements. Adaptive differential pulse code modulation is investigated as a method of reducing the memory requirements for myoelectric data storage. In this scheme, a 12-bit sample is reduced to four bits, thus reducing the memory requirements by a factor of three. In reality, this compression ratio is closer to 4:1 owing to the fact that the widths of most memories are organised as multiples of eight bits.

Computer Systems↗
PubMed1999

The diagnostic validity of digitally captured intraoperative transesophageal echocardiography examinations compared with analog recordings: A pilot study.

BACKGROUND: Digital acquisition and storage of echocardiographic studies offer many advantages over analog recordings, but the amount of computer memory required may be large. "Computer compression" of data is done by machines with various algorithms. "Clinical compression" involves limiting the recordings to 1-beat loops, and although it is commonly used, its diagnostic validity has not been demonstrated in the operating room. METHODS: This prospective pilot study looked at 51 patients undergoing transesophageal echocardiography during cardiac surgery. During continuous videocassette recording, we captured digital loops to demonstrate wall motion abnormalities, ventricular systolic function, aortic insufficiency, and mitral regurgitation. Experts reviewed the loops and tapes. We then compared the diagnoses from the 2 methods. RESULTS: There were major differences in the diagnosis of wall motion between loops and tapes in only 3.4% of myocardial segments. No major differences were seen in the diagnosis of systolic function, aortic insufficiency, or mitral regurgitation in any patients. CONCLUSION: We conclude that clinical compression is a suitable method to compress data in the operating room. Large numbers of patients are required to definitively demonstrate the small differences.

Chi-Square Distribution↗
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↗
PubMed1999

A uniform format for ocular imaging devices.

PURPOSE: To develop a uniform file format of ocular imaging data, including, but not limited to, ultrasound biomicroscopy, optical coherence tomography, and nerve fiber analyzer, capable of being transmitted via Internet or intranet for collaborative research and telemedicine use. METHOD: File filters were developed as dynamic link libraries (DLLs). These can read the original raw data format of each ocular imaging device. A data file format was also designed to describe these raw data uniformly in three different types of compression: noncompressed, run length compression, and differential pulse code modulation (DPCM). These three file formats were then tested in the following aspects: file size, speed of reading, and speed of writing. RESULTS: Run length compression failed to compress raw data, while DPCM compressed raw data successfully (< or =35.5%). The speed of reading and writing files was slowest in DPCM. However, the actual time of reading and writing was fast enough (<0.6 s) for daily work regardless of file compression methods. CONCLUSION: The format designed has robust potential to be the standard file format for transmission of any ocular imaging raw data.

Data Display↗
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↗