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At least 163 records · Page 9Linked to original sources
PubMed1997

Multimedia image display: a view to the future.

The development of multimedia image review stations offers the cardiologist the ability to review multiple image sets in a single setting rather than moving from one review station to another. To accomplish this goal there are three essential barriers: 1) memory requirements for digital images; 2) standardization of data format; and 3) practical user interfaces. Image compression algorithms can be used to overcome the digital barrier; however, these must be used cautiously so as to not adversely affect image quality. The lack of standardization is being addressed by the implementation of the Digital Communication in Medicine (DICOM) standard, and practical user interfaces are being developed every day with the widespread implementation of World Wide Web technology. These solutions will allow the clinician to review all of a patient's image data in one location, such as in the office, on the nursing unit, or at home.

Computer Communication Networks↗
PubMed1995

Discrimination of multichannel-compressed speech in noise: long-term learning in hearing-impaired subjects.

OBJECTIVE: It takes time for an individual to obtain optimal benefit from a new hearing aid. This research examines the possibility that similar long-term learning can be seen in consecutive laboratory studies of multichannel compression (MCC). DESIGN: Three studies of different parameters of MCC processing, carried out over the period of 1 yr, included the same 15 hearing-impaired subjects and one identical MCC-processing condition. The full-range MCC had 8, 12, or 16 independent frequency channels, using a Robinson-Huntington compression algorithm. The City University of New York nonsense syllable test was modified to facilitate digital signal processing and control of the experiments. The subjects discriminated nonsense syllables (a female and a male voice) in speech spectrum noise at -5 to 15 dB signal-to-noise ratios (S/N). Conditions were not ideal for learning: subjects' experience with MCC-processed speech was limited to the laboratory and no trial-by-trial feedback was provided. Percent correct syllable discrimination and consonant confusion matrices were compared across experiments to observe the subjects' learning to listen with MCC processing. RESULTS: All subjects combined, and 14 of 15 individual subjects, showed significant improvement across experiments. For the subject showing the maximum learning, the percent correct difference between the first and third experiments was equivalent to a 9.8 dB increase in S/N. The average learning for all subjects was equivalent to +3 dB S/N. The difference between the consonant-confusion matrices for the first and third experiments indicated that improved discrimination occurred for both manner and place information. The pattern of changes in the confusion matrices was consistent with improved use of the high-frequency information supplied by the MCC signal processing. A brief comparison of the results of the first experiment with a fourth experiment indicated that the learning was specific to MCC processing because it did not generalize to frequency-shaped linear amplification which was also studied in those two experiments. CONCLUSIONS: These results indicate that specific long-term learning occurred for hearing-impaired subjects listening to nonsense syllables in noise with 8- to 16-channel MCC processing. Since previous experiments have provided subjects with much less listening experience, the results suggest that MCC with large numbers of channels may be much more beneficial for the hearing-impaired individuals than the results of previous experiments had indicated.

Aged↗
PubMedDate not supplied

Microcomputer-based coronary care unit central station.

A four-bed central station that can be connected to any commercial intensive-care bedside monitor was developed. The system is based on a personal computer (IBM-AT compatible) as a local unit and on a microcontroller Intel 8031 as a remote unit. Four ECG signals are low-pass filtered, multiplexed, sampled at 256-Hz per channel, 8-bit A/D converted, preprocessed, and converted to a serial format RS-232 by the remote unit. The real-time display of the signals is at the standard speed of 25 and 50 mm/sec. Heartrate, alarms, trend plots, and general patient data are shown on an Olivetti M280 and EGA 13'' color monitor as the local unit. The communication speed was set at 57.6 Kbaud full duplex. Additionally, to reach standard monitoring sweep rates using a 13'' screen with 640 x 350 pixels, an ECG data-compression algorithm was implemented in the remote unit. This unit can support up to eight input channels and can work with any personal computer, via RS-232, with the appropriate software. It also allows other signal preprocessing software that could be developed, such as QRS detection or ST segment quantification, to be loaded into its random access memory and to be run under PC command. The development of this system demonstrated the use of a widespread piece of commercial equipment, the PC, in a very specific application, CCU monitoring, assuring low-cost system implementation. This feature is particularly attractive in upgrading existing CCU units in less developed countries.

Biomedical Engineering↗
PubMed2000

Is random close packing of spheres well defined?

Despite its long history, there are many fundamental issues concerning random packings of spheres that remain elusive, including a precise definition of random close packing (RCP). We argue that the current picture of RCP cannot be made mathematically precise and support this conclusion via a molecular dynamics study of hard spheres using the Lubachevsky-Stillinger compression algorithm. We suggest that this impasse can be broken by introducing the new concept of a maximally random jammed state, which can be made precise.

Journal Article↗
PubMed2005

Lossy data compression with random gates.

We introduce a new protocol for a lossy data compression algorithm which is based on constraint satisfaction gates. We show that the theoretical capacity of algorithms built from standard parity-check gates converges exponentially fast to the Shannon's bound when the number of variables seen by each gate increases. We then generalize this approach by introducing random gates. They have theoretical performances nearly as good as parity checks, but they offer the great advantage that the encoding can be done in linear time using the survey inspired decimation algorithm, a powerful algorithm for constraint satisfaction problems derived from statistical physics.

Journal Article↗
PubMed1991

Compression of the ambulatory ECG by average beat subtraction and residual differencing.

We implemented a method for compression of the abulatory ECG that includes average beat subtraction and first differencing of residual data. Our previous investigations indicated that this method is superior to other compression methods with respect to data rate as a function mean-squared-error distortion. Based on previous results we selected a sample rate of 100 samples per second and a quantization step size of 35 microV. These selections allow storage of 24 h of two-channel ECG data in 4 Mbytes of memory with a minimum rms distortion. For this sample rate and quantization level, we show that estimation of beat location and quantizer location can significantly affect compression performance. Improved compression resulted when beats were located with a temporal resolution of 5 ms and coarse quantization was performed in the compression loop. For the 24-h MIT/BIH arrhythmia database our compression algorithm coded a single-channel of ECG data with an average data rate of 174 bits per second.

Algorithms↗
PubMed2000

The weighted diagnostic distortion (WDD) measure for ECG signal compression.

In this paper, a new distortion measure for electrocardiogram (ECG) signal compression, called weighted diagnostic distortion (WDD) is introduced. The WDD measure is designed for comparing the distortion between original ECG signal and reconstructed ECG signal (after compression). The WDD is based on PQRST complex diagnostic features (such as P wave duration, QT interval, T shape, ST elevation) of the original ECG signal and the reconstructed one. Unlike other conventional distortion measures [e.g. percentage root mean square (rms) difference, or PRD], the WDD contains direct diagnostic information and thus is more meaningful and useful. Four compression algorithms were implemented (AZTEC, SAPA2, LTP, ASEC) in order to evaluate the WDD. A mean opinion score (MOS) test was applied to test the quality of the reconstructed signals and to compare the quality measure (MOSerror) with the proposed WDD measure and the popular PRD measure. The evaluators in the MOS test were three independent expert cardiologists, who studied the reconstructed ECG signals in a blind and a semiblind tests. The correlation between the proposed WDD measure and the MOS test measure (MOSerror) was found superior to the correlation between the popular PRD measure and the MOSerror.

Algorithms↗
PubMed2005

Tile-boundary artifact reduction using odd tile size and the low-pass first convention.

It is well known that tile-boundary artifacts occur in wavelet-based lossy image coding. However, until now, their cause has not been understood well. In this paper, we show that boundary artifacts are an inescapable consequence of the usual methods used to choose tile size and the type of symmetric extension employed in a wavelet-based image decomposition system. This paper presents a novel method for reducing these tile-boundary artifacts. The method employs odd tile sizes (2N + 1 samples) rather than the conventional even tile sizes (2N samples). It is shown that, for the same bit rate, an image compressed using an odd tile length low-pass first (OTLPF) convention has significantly less boundary artifacts than an image compressed using even tile sizes. The OTLPF convention can also be incorporated into the JPEG 2000 image compression algorithm using extensions defined in Part 2 of this standard.

Algorithms↗
PubMed2003

Scalable medical data compression and transmission using wavelet transform for telemedicine applications.

In this paper, a novel medical data compression algorithm, termed layered set partitioning in hierarchical trees (LSPIHT) algorithm, is presented for telemedicine applications. In the LSPIHT, the encoded bit streams are divided into a number of layers for transmission and reconstruction. Starting from the base layer, by accumulating bit streams up to different enhancement layers, we can reconstruct medical data with various signal-to-noise ratios (SNRs) and/or resolutions. Receivers with distinct specifications can then share the same source encoder to reduce the complexity of telecommunication networks for telemedicine applications. Numerical results show that, besides having low network complexity, the LSPIHT attains better rate-distortion performance as compared with other algorithms for encoding medical data.

Algorithms↗
PubMed1996

The effects of lossy compression on the detection of subtle pulmonary nodules.

We examined the ability of radiologists to detect pulmonary nodules in computed radiographic (CR) chest images subjected to lossy image compression. Low-contrast 1-cm diameter targets simulating noncalcified pulmonary nodules were introduced into clinical images and presented to ten radiologists in a series of two-alternative forced-choice (2AFC) observer experiments. The percentages of correct observer responses obtained while viewing noncompressed images (1:1) were compared with those obtained for the same images compressed 7:1, 16:1, 44:1, and 127:1. The images were compressed using a standard full-frame discrete cosine transform (DCT) technique. The degree of compression was determined by quantizing Fourier components in various frequency channels and then Huffman encoding the result. The data show a measurable decline in performance for each compression ratio. Through signal-to-noise ratio (SNR) analysis, we found that the reduction in performance was due primarily to the compression algorithm that increased image noise in the frequency channels of the signals to be detected.

Algorithms↗
PubMed2003

Digital slide and virtual microscopy based routine and telepathology evaluation of routine gastrointestinal biopsy specimens.

AIMS: To evaluate a recently developed digital slide and virtual microscope system, and to compare this method with optical microscopy on routine gastrointestinal biopsy specimens in both local and remote access modes. METHODS: A fully computer controlled commercial microscope was used. The scanning program included object detection, autofocus, and image compression algorithms. The overall hard disk space for a gastric biopsy was between 30 and 50 MB and the scanning time was between 20 and 40 minutes. Haematoxylin and eosin stained routine gastric (61) and colon (42) biopsy specimens were selected, scanned, and evaluated by two specialists on an optical (OM) and virtual microscope (VM). RESULTS: The overall concordance of VM and OM with the consensus diagnosis was 95.1% and 97%, respectively. Clinically important concordance was 96.1% and 98% for VM and OM, respectively. The two methods showed concordance in 92% of cases and clinically important concordance in 94.1% of cases. The reasons for discordance were image quality (one case), interpretation difference (three cases), and insufficient clinical information (three cases). Remote evaluation of the digital slides through the Internet has the advantages of the previously used static and dynamic telepathology methods. CONCLUSIONS: Diagnostic concordance was found between OM and VM. The digital slide and the virtual microscope can be alternative techniques in the computerisation of the histology laboratory and in teleconsultation services after further evaluation of time and storage constraints.

Algorithms↗
PubMed1995

Computer-based radiology information system: from floppy disk to CD-ROM.

The authors have developed a comprehensive computer-based radiology information system known as "Radiology Resource and Review" (R3). The content is divided into 10 radiology information categories spanning the entire human body and presently includes more than 4 Mbytes of text, 9,000 topics, and 6,000 images. The R3 software and the information content are stored on compact disk, read-only memory (CD-ROM) media. The images are compressed by using a standard compression algorithm. Images and text are cross-indexed with more than 13,000 key words, which can be linked together in searches by using Boolean logic. Four different retrieval interfaces support browsing of text and image information, diagnosis decision making, self-study, and teaching file preparation. The 10-year university-funded evolution of R3 is an example of the transition in storage media from floppy disk to CD-ROM.

CD-ROM↗
PubMed1996

Radiology information and image management system: new approach to PACS with hypermedia capabilities of personal computers.

A system for archiving patient data and images was developed, installed, and evaluated in a radiology department. The system was developed with a relational database program for use with commercially available computers linked with an Ethernet network. The main options of the system are those of a conventional radiology information system: scheduling, registration, examination execution, reporting, archives and statistics, and system administration. However, the main feature of the system is the image archiving capability. Images are associated with patient records after capture by direct acquisition of the video signal or by scanning. Only relevant pathologic images are archived and a commonly employed compression algorithm is used, reducing the total memory requirement for each case to 200-600 kbytes. The diagnosis is still made by reading the original images. The low-resolution images stored in the system have an important role in teaching and consultation and as a first-line archive. Good results have been obtained with this system, which is used by medical and nonmedical staff without any special training.

Humans↗
PubMed1994

Thoracic CT images: effect of lossy image compression on diagnostic accuracy.

PURPOSE: To evaluate the effects of lossy image (noninvertible) compression on diagnostic accuracy of thoracic computed tomographic images. MATERIALS AND METHODS: Sixty images from patients with mediastinal adenopathy and pulmonary nodules were compressed to six different levels with tree-structured vector quantization. Three radiologists then used the original and compressed images for diagnosis. Unlike many previous receiver operating characteristic-based studies that used confidence rankings and binary detection tasks, this study examined the sensitivity and predictive value positive scores from nonbinary detection tasks. RESULTS: At the 5% significance level, there was no statistically significant difference in diagnostic accuracy of image assessment at compression rates of up to 9:1. CONCLUSION: The techniques presented for evaluation of image quality do not depend on the specific compression algorithm and provide a useful approach to evaluation of the benefits of any lossy image processing technique.

Humans↗
PubMed1994

A multiprocessor architecture for medical image compression in a PACS environment.

We present a new multiprocessor architecture for medical image compression using digital signal processors. The system has been designed to be used in a NuBus-based workstation and to apply different image compression algorithms to medical images. The system has been tested with a full-frame cosine transform and bit allocation table on several imaging modalities ranging from ultrasound to magnetic resonance imaging. Results show that image quality is acceptable when the allocation tables are calculated for each specific image modality. Implementation of algorithms such as wavelet transforms and vector quantization which respond to the characteristics of each type of image is in progress.

Algorithms↗
PubMed1995

Multimedic system for telepathology and interdisciplinary councils between doctors and various hospitals.

At present, the exchange of information between clinicians and pathologists are limited to mail, telefax and telephone. The bi-directional video communication using at least two digitized phone lines (ISDN) is an additional medium for video-conference and for image exchange. The MECOM system (Medical Communication) has been set up in the department of pathology of Aixla-Chapelle Hospital (Germany) and has routinely used for two years between 4 local hospitals. Now it is mainly used for staff discussions between pathologists and practitioners involved in different oncological fields. Mecom can transmit any kind of high resolution images (x rays films, scanner images, histologic slides...) which are useful or necessary during medical staff discussions. This system requires only two phone lines to be operative. However it can turn on up to twelve parallel ISDN lines which allow to transmit 768 kbytes/sec. It manages the SG3, HVQ and H320 compression algorithms and allows the transmission of still images at a resolution varying from 256/240 to 512/480 pixels. Mecom is a modulable system which adapts to the needs. It has the following advantages. Emergency inter-disciplinary conferences. Real time images, discussion between a pathologist and an expert to confirm histo-pathological diagnosis. Abolition of distances. That is specially useful or necessary in countries with low medical population and poor transportation network.

Computer Communication Networks↗
PubMed1996

Imaging system architectures for picture archiving and communication systems.

Picture archiving and communications systems (PACS) provide for the intraelectronic management of acquired digital image examination. Mini-PACS are image-management systems focused on specific applications. Computer architecture to be applied to radiology applications includes pipelining to improve the speed of the central processing unit, client and server architecture for distributed radiology applications, and image file servers. Image-compression algorithms provide increased digital storage and increased image transmission speeds. Throughput rates can be improved by identifying the bottlenecks.

Algorithms↗
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↗