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At least 235 records · Page 13Linked to original sources

PubMed1991

Effect of moisture content on compression properties of two dextrose-based directly compressible diluents.

Moisture sorption characteristics and the effect of moisture content on the compression properties of two dextrose-based directly compressible diluents, namely, Emdex (diluent A) and Sweetrex (diluent B) were studied. Both diluents sorbed moisture rapidly at relative humidities greater than 60%. For both the diluents, pressures required to compress tablets to the same relative density decreased with increasing moisture content. Yield pressures calculated from linear Heckel plots obtained from the compression data of both diluents reflected decreasing values with increasing moisture content. Three-way surface profile graphs of moisture content versus tablet parameters such as crushing force, relative density, and compression pressure give a unique overall picture of the compression properties of a diluent and offer the tablet formulator a useful tool for diluent comparison.

Chemical Phenomena↗

PubMedDate not supplied

The formal specification of an electrocardiogram compressor.

Remote telemonitoring of physiological parameters is being used increasingly both for medical research and for clinical management. However, the technique entails the collection of large volumes of information for transmission and storage which necessitates efficient means of data compression. This paper presents a simple mathematical model of the lossy compression of physiological signals. The model is developed in a top-down style making design decisions progressively. First a general model of lossy compression is developed and some lemmas presented. Then the model is refined to take advantage of inherent cyclicity in many types of physiological signal. Finally the model is specialized to the compression of electrocardiograms. An algorithm is described for implementing the model. The algorithm is a table-based method capable of achieving very low output bit rates (50 bps) with reasonable fidelity. This compares favourably with the results obtained by other workers and holds promise for further evaluation. The generality of the model should ultimately allow a coherent approach to the compression of the various types of physiological signal currently being recorded.

Algorithms↗

PubMed2025

SKiM: accurately classifying metagenomic ONT reads in limited memory.

MOTIVATION: Oxford Nanopore Technologies' devices, such as MinION, permit affordable, real-time DNA sequencing, and come with targeted sequencing capabilities. Such capabilities create new challenges for metagenomic classifiers that must be computationally efficient yet robust enough to handle potentially erroneous DNA reads, while ideally inspecting only a few hundred bases of a read. Currently available DNA classifiers leave room for improvement with respect to classification accuracy, memory usage, and the ability to operate in targeted sequencing scenarios. RESULTS: We present SKiM: Short K-mers in Metagenomics, a new lightweight metagenomic classifier designed for ONT reads. Compared to state-of-the-art classifiers, SKiM requires only a fraction of memory to run, and can classify DNA reads with higher accuracy after inspecting only their first few hundred bases. To achieve this, SKiM introduces new data compression techniques to maintain a reference database built from short k-mers, and treats classification as a statistical testing problem. AVAILABILITY AND IMPLEMENTATION: SKiM source code, documentation, and test data are available from: https://gitlab.com/SCoRe-Group/skim.

Metagenomics↗

PubMedDate not supplied

Automated electrocardiogram analysis: the state of the art.

The overwhelming number of electrocardiograms (ECGs) now recorded routinely has prompted the development of computer analysis which in turn has benefited electrocardiography with important technological advances. All automated ECG analysis systems adopt a similar approach: a measurement program and a program that interprets the clinical significance of these measurements along with a rhythm analysis algorithm. Measurement, selection and classification of parameters vary according to the program used. Data compression is applied to the signal to reduce processing time and allow long-term storage. Diagnostic accuracy, however, is not greatly improved over that of experienced cardiologists. Programs studied using a validated data bank provided by an international group of cardiologists show a variability not only in parameter measurement but also in diagnostic statement and in the way in which such statements are expressed. Recommendations for measurement standards have been made to fulfil the need for exchange of diagnostic criteria. No recommendations concerning the selection of parameters have been proposed, and so new parameters or combinations of parameters can be introduced with the ultimate aim of increased diagnostic performance.

Diagnosis, Computer-Assisted↗

PubMed2001

Long-term data storage in DNA.

This article discusses how DNA might be used to store data. It is argued that, at present, DNA would be best employed as a long-term repository (thousands or millions of years). How data-containing DNA might be packaged and how the data might be encrypted, with particular attention to the encryption of written information, is also discussed. Various encryption issues are touched on, such as how data-containing DNA might be differentiated from genetic material, error detection, data compression and reading frame location. Finally, this article broaches the difficulty of constructing very large pieces of DNA in the laboratory and highlights some complications that might arise when attempting to transmit DNA-encrypted data to recipients who are a long period of time in the future.

Base Sequence↗

PubMed1992

Teleradiology via narrow-band integrated services digital network (N-ISDN) and Joint Photographic Experts Group (JPEG) image compression.

The importance of remote access to both radiological images and medical information has stimulated many demonstration projects that use a variety of telecommunications providers' offerings. Teleradiology, through modest cost channels, can achieve adequate response times using a combination of narrow-band integrated services digital network (N-ISDN) and data compression. A demonstration project, developed in collaboration with Southwestern Bell Technology Resources, Inc, uses the aggregate bandwidth of two B channels (achieving a rate of 120 kilobits per second) and a block-oriented discrete cosine transform compression/decompression implementation based on the Joint Photographic Experts Group Standard for Still Image Compression. System response measurements for an Inquiry and Display Station accessing the Mallinckrodt Institute of Radiology's Radiology Image and Information Management Testbed via the N-ISDN connection show response times to be within 20 seconds. Viewing applications have been shown at sites within St Louis and at Radiological Society of North America, 1990, in Chicago.

Computer Communication Networks↗

PubMed2003

[Complexity evaluation of data transfer in the Z-axis direction in 4-row multislice spiral CT using fractal dimension analysis].

Image reconstruction in multislice spiral/helical computed tomography (MSCT) consists of a package of data on the arbitrary direction of the Z-axis that can be collected by active detector arrays. Thus the recombined data vary with each spiral pitch. In certain cases of spiral pitch, data compression can occur, and the spiral artifacts that are characteristic of MSCT would change. In our study, we evaluated image complications by fractal dimensions, because the geometrical patterns from a conic phantom are closely related to data transfer in the direction of the Z-axis in spiral pitches. We hoped to establish useful spiral pitches and slice collimation for clinical use in a 4-row MSCT scanner. By employing a conic phantom of 120 mm in diameter and a cone angle of 100 degrees, we measured the fractal dimension of the conic phantom image by making a binary to outline from 2.0 to 8.0 of various slice collimations. Moreover, in order to evaluate the correlation between fractal dimensions and image artifacts, we confirmed the influence of spiral pitch and reconstruction slice thickness for clinical use. We found that, when the reconstruction slice thickness was the same, the cross section of the conic phantom that was from thin-slice collimations was more similar to an actual circle than that of wide-slice collimations. The former deserved a low value and showed slight changes, and, therefore, its fractal dimensions were fixed. As a phenomenon worthy of attention, when we employed wide-slice collimations (4x5.0 mm) during peculiar low spiral pitches of 2.5 to 3.0 fractal dimensions remained low and similar to an actual circle. By these analyses of the influence of data transfer in the direction of the Z-axis, we found that spiral pitch influenced the rate of slice collimation used for data acquisition closely to the reconstruction slice thickness. Based on these findings, when slice collimations and reconstruction slice thickness should be made equal, we estimated that spiral pitches of low image artifacts in 4row MSCT ranged from 2.5 to 3.0 using fractal dimensions. We consider that a new adaptation of fractal dimension analysis is possible when it is used as an index in determining protocols.

Artifacts↗

PubMed1997

Clinical assessment of Hokkaido University PACS.

The paper describes the hardware and software used in the Hokkaido University picture archiving and communication system (HUPACS), which has been in use for the past two years. An evaluation of the system is also included. Fuji computed radiography completely replaces conventional X-ray radiographs, and 10:1 data compression is routinely employed. The PACS LAN is connected to the hospital information system through the main-frame computer and it is linked, not only to the radiology department, but also to the outpatient clinics. Image data have been steadily stored in the optical disc library, which contains more than 200,000 images. The original image can be accessed within 1 min. Image quality on a cathode ray tube (CRT) is clinically acceptable. Nevertheless, the transfer time of a newly made image is prolonged in some cases, during periods of heavy usage of the system. During scheduled radiology conferences, image reading tends to take more time on a CRT than on film. An improvement in the ease of operation of the workstations is necessary for full acceptance of CRT diagnoses. Generally speaking, however, HUPACS is working well and is appreciated by most of the clinicians.

Computer Systems↗

PubMed1990

Perimeter encoding for teleradiology.

Perimeter encoding is a technique of data compression that is done simply by outlining the area of interest on an examination. In a sample of 92 emergency room examinations (excluding chest, abdomen, and pelvic exams), 304 films were interpreted by a resident radiologist who indicated the area of interest by marking four corners of a rectangle. The adequacy of the area of interest was determined by a staff osteoradiologist during subsequent review of the films. The amount of data reduction was measured by determining the ratio of the area of interest inside a rectangle to the area of the film (compression ratio). The overall average compression ratio was 3 to 1. This preliminary study suggests that further evaluation of perimeter encoding is warranted.

Emergency Medical Service Communication Systems↗

PubMedDate not supplied

Beyond principal component analysis: canonical component analysis for data reduction in classification of EPs.

The authors tested a new procedure for the discrimination of EPs obtained in different stimulus situations. In contrast with principal component analysis (PCA) used so far for the purpose of data compression, the method referred to as canonical component analysis (CCA) is optimal for the purpose of discrimination. To illustrate this, the authors performed both PCA and CCA for the same material, then after carrying out discriminant analysis ( SWDA ) for the data transformed in this way, compared the performance of the two procedures in discrimination. In view of both the theoretical and practical considerations, the authors recommend that in the future researchers use CCA instead of PCA in EP studies for data reduction carried out for discrimination.

Computers↗

PubMed1999

Multimedia electronic medical record systems.

A wide range of imaging technologies are becoming increasingly important to the practice of medicine. In addition, many medical specialties are highly visual, independent of their use of new imaging modalities. Because today's medical record contains text, images, and physiologic signals, it is inherently multimedia in nature. However, most electronic medical record systems handle only the textual portion of the patient record, resulting in a fragmentation of the database that physicians need to make timely, effective clinical decisions. Advances in database-, storage-, data-compression, and networking technologies will facilitate the development of multimedia electronic medical record systems for the 21st century. These systems will become widely used over the next decade, and in addition to enhancing patient care, will also present new opportunities for using clinical imaging data for biomedical research and education.

Forecasting↗

PubMed1994

Nonuniform sampling of urodynamic signals: a comparison of different methods.

Several different techniques for urodynamic signal compression have been proposed in the last few years. Using these techniques it is possible to reduce the requirements for digital storage or transmission. There are a number of applications where it is essential to use such techniques in diagnostic and ambulatory urodynamics. The purpose of this study is to compare different techniques of urodynamic data compression. The so-called FAN, voltage triggered, two point projection and second difference methods. The comparison between the methods is based on 65 pressure, 46 uroflow and 18 surface electromyogram signals. The reduction ratio achieved for different allowable errors between the original and compressed signals is calculated and compared for the different techniques. Results show that it is possible to store urodynamic signals accurately at a low sampling rate, where FAN and voltage triggered methods seem to be superior to the rest.

Algorithms↗

PubMed1995

Variations in cardiopulmonary resuscitation techniques: past, present and future.

OBJECTIVE: To review the major changes and advances in cardiopulmonary resuscitation (CPR) since its first description over 100 years ago. DATA SOURCES: A MEDLINE search of the English literature (1966 to 1994) was done using the key words 'cardiopulmonary resuscitation', 'CPR', 'heart massage', 'techniques' and 'methods'. STUDY SELECTION: Articles were selected based on content related to promising CPR techniques and specifically on alternate methods of closed chest compression. DATA EXTRACTION: Performed independently by the authors. DATA SYNTHESIS: Over the past three and a half decades, the importance of rapid institution of CPR has become increasingly recognized. This has led to a strenuous effort to educate the public in CPR delivery in addition to making definitive treatment with emergency medical systems more readily accessible. Furthermore, as the physiology of closed chest massage has become better understood, investigators have been able to focus their efforts appropriately to exploit the mechanisms that are operative during CPR. As a result, several modifications have been proposed in adjuvant therapies administered concomitantly with CPR, as well as in new, innovative methods of CPR delivery. Many of these changes and new methods show promise for improving vital organ perfusion and patient survival. CONCLUSIONS: CPR has become increasingly recognized as an important element in the chain of survival for victims of cardiopulmonary arrest. Several advances in delivery and technique have resulted in improved resuscitation of cardiopulmonary arrest victims. However, despite these advances, additional research is needed to improve further the still dismal overall survival of victims of cardiopulmonary arrest.

Cardiopulmonary Resuscitation↗

PubMed1999

Seamless multiresolution display of portable wavelet-compressed images.

Image storage, display, and distribution have been difficult problems in radiology for many years. As improvements in technology have changed the nature of the storage and display media, demand for image portability, faster image acquisition, and flexible image distribution is driving the development of responsive systems. Technology, such as the wavelet-based multiresolution seamless image database (MrSID) portable image format (PIF), is enabling image management solutions that address the shifting "point-of-care." The MrSID PIF employs seamless, multiresolution technology, which allows the viewer to determine the size of the image to be viewed, as well as the position of the viewing area within the image dataset. In addition the MrSID PIF allows control of the compression ratio of decompressed images. This capability offers the advantage of very rapid image recall from storage devices and portability for rapid transmission and distribution using the internet or wide-area networks. For example, in teleradiology, the radiologist or other physician desiring to view images at a remote location has full flexibility in being able to choose a quick display of an overview image, a complete display of a full diagnostic quality image, or both without compromising communication bandwidth. The MrSID algorithm will satisfy Joint Photographic Experts Group (JPEG) 2000 standards, thereby being compatible with future versions of the Digital Imaging and Communications in Medicine (DICOM) standard for image data compression.

Algorithms↗

PubMedDate not supplied

Digital echocardiography and telemedicine applications in pediatric cardiology.

Digital echocardiography offers several advantages over videotape, including easy review, comparison, storage, postprocessing, and sharing of studies, quantitative analysis, and superior resolution. Newer echocardiography systems can write digital data to computer hardware, whereas older systems require digitization of analog data. Clinical and digital data compression is required to reduce study size. Clinical compression has been validated in several adult studies and one pediatric study. JPEG and MPEG digital compression ratios of 26:1 and 200:1, respectively, approximate S-videotape quality. JPEG is the DICOM 3.0 standard and is ideal for short loops, serial comparisons, and quantitative analysis. MPEG (the motion picture standard) lends itself to digitization of video streams and may be more attractive to pediatric cardiologists. Options for data storage and transfer range from limited local review to multiple offline review stations linked by a wide-area network. Telemedicine expands the capabilities of digital echocardiography in a "store and forward" or "real-time" format. Real-time neonatal telecardiology is accurate, impacts patient care, is cost-effective, and does not increase utilization. Cost, increased reliance on sonographers' skills, lack of accepted standards, and legal, licensure, and billing issues are obstacles to widespread acceptance of digital echocardiography and telemedicine.

Echocardiography↗

PubMed2001

Validation of a clinical decision aid to discontinue in-hospital cardiac arrest resuscitations.

CONTEXT: Most patients undergoing in-hospital cardiac resuscitation do not survive to hospital discharge. In a previous study, we developed a clinical decision aid for identifying all patients undergoing resuscitation who survived to hospital discharge. OBJECTIVE: To validate our previously derived clinical decision aid. DESIGN, SETTING, AND PARTICIPANTS: Data from a large registry of in-hospital resuscitations at a community teaching hospital in Georgia were analyzed to determine whether patients would be predicted to survive to hospital discharge (ie, whether their arrest was witnessed or their initial cardiac rhythm was either ventricular tachycardia or ventricular fibrillation or they regained a pulse during the first 10 minutes of chest compressions). Data from 2181 in-hospital cardiac resuscitation attempts in 1987-1996 involving 1884 pulseless patients were analyzed. MAIN OUTCOME MEASURE: Comparison of predictions based on the decision aid with whether patients were actually discharged alive from the hospital. RESULTS: For 327 resuscitations (15.0%), the patient survived to hospital discharge. For 324 of these resuscitations, the patients were predicted to survive to hospital discharge (sensitivity = 99.1%, 95% confidence interval, 97.1%-99.8%). In 269 resuscitations, patients did not satisfy the decision aid and were predicted to have no chance of being discharged from the hospital. Only 3 of these patients (1.1%) were discharged from the hospital (negative predictive value = 98.9%), none of whom were able to live independently following discharge from the hospital. CONCLUSION: This decision aid can be used to help physicians identify patients who are extremely unlikely to benefit from continued resuscitative efforts.

Aged↗

PubMed1999

Wavelet analysis of neuroelectric waveforms: a conceptual tutorial.

This paper presents a nontechnical, conceptually oriented introduction to wavelet analysis and its application to neuroelectric waveforms such as the EEG and event related potentials (ERP). Wavelet analysis refers to a growing class of signal processing techniques and transforms that use wavelets and wavelet packets to decompose and manipulate time-varying, nonstationary signals. Neuroelectric waveforms fall into this category of signals because they typically have frequency content that varies as a function of time and recording site. Wavelet techniques can optimize the analysis of such signals by providing excellent joint time-frequency resolution. The ability of wavelet analysis to accurately resolve neuroelectric waveforms into specific time and frequency components leads to several analysis applications. Some of these applications are time-varying filtering for denoising single trial ERPs, EEG spike and spindle detection, ERP component separation and measurement, hearing-threshold estimation via auditory brainstem evoked response measurements, isolation of specific EEG and ERP rhythms, scale-specific topographic analysis, and dense-sensor array data compression. The present tutorial describes the basic concepts of wavelet analysis that underlie these and other applications. In addition, the application of a recently developed method of custom designing Meyer wavelets to match the waveshapes of particular neuroelectric waveforms is illustrated. Matched wavelets are physiologically sensible pattern analyzers for EEG and ERP waveforms and their superior performance is illustrated with real data examples.

Brain↗

PubMedDate not supplied

Fundamentals of image processing for personal computers.

Photographic images make an important contribution to medical education. Conventional means of display have included 35-mm projection, film, videotape, and more recently, analog videodiscs that accompany computer-based text. The availability of compact discs, with their enormous storage capacity, and of powerful central processing units now permits consideration of digital storage of visual images for display by the personal computer. The data processing required for the representation and transfer of high-quality images is forbidding, however, even with today's technology. The problem is compounded if one anticipates display of full-motion video. In this tutorial we first review the nature of analog signals and the process of capturing them in digital format. We then consider mass storage and the concept of compressing data into smaller amounts of information that can be processed and transferred by personal computers with the use of optical disc drives. A look into the future provides a vision of high-definition television-quality video in digital format.

Analog-Digital Conversion↗