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 37 records · Page 2Linked to original sources
PubMed1989

Image data compression in magnification hand radiographs.

A study was conducted on the use of an irreversible compression technique, Fourier quantization, to reduce the amount of digital data needed for an image. The effect of image compression was studied in radiographs obtained to diagnose subperiosteal bone resorption. Magnification radiographs of 44 hands were digitized to an array size of 4,096 X 4,096 X 12 bits. Selected subregions containing a single middle phalanx were compressed and reconstructed. A subset of the resultant 12-bit uncompressed and 8-, 7-, and 6-bit compressed images were read by four radiologists whose responses were analyzed with receiver operating characteristic (ROC) techniques. There were 81 images used in the ROC analysis, of which 48 were normal and 33 showed subperiosteal resorption. No statistically significant loss of diagnostic quality was detected for 8- or 7-bit compressed images, with average compression ratios of 16:1 and 28:1, respectively. Diagnostic quality was lost with 6-bit images, with an average compression ratio of 107:1.

Arthritis↗
PubMed1989

Data compression applied to dynamic electrocardiography.

We have tested some techniques of ECG compression on the BIH/MIT Arrhythmias database. We have applied the following methods: (1) method of differences; (2) compression by prediction; (3) sample skipping methods; with the following kinds of errors: amplitude error, amplitude and delay error, area error. In the first and second method the average code length found after application of the Huffmann encoding has been found to be about 4 bits sample-1. For the third method the final compression ratio varies according to the allowed error; with a limited error threshold, however, we have reached an average compression a little lower than 1:5.

Ambulatory Care↗
PubMed1991

Image data compression using a new floating-point digital signal processor.

A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.

Algorithms↗
PubMed1989

A report-coding system for integration into a digital radiology department.

Report-coding systems allow the radiologist to generate a typewritten radiographic report with a computer. Typically, the report is generated by selecting bar codes, speaking key words, or selecting items on a screen. MAMM REPORT is a report-coding system for mammography, developed by radiologists, that runs on a microcomputer (Amiga, Commodore Co., West Chester, PA). MAMM REPORT speaks questions to the radiologist, who responds by pressing one of two buttons on a computer mouse, thus generating the report. MAMM REPORT allows labeling of digital images and reduction of data required to store the report in computer memory (data compression). Data compression is useful for improving computer operating speed. Digital image labeling and data compression facilitate use of MAMM REPORT on a future digital radiology workstation for an all-digital radiology department. Sixty mammographic reports, reviewed by a radiologist who is not a specialist in mammography, were entered into MAMM REPORT. The mammography specialists who dictated the original reports then judged whether the reports generated by MAMM REPORT would be acceptable replacements on the basis of descriptions of findings, diagnoses, and recommendations for further study. Data compression was measured by calculating the ratio of the number of bytes for storage of the reports in original form to a standard storage form (Huffman encoding) and to the MAMM REPORT coded form. All 60 coded reports were acceptable replacements for the original reports. For computer storage, MAMM REPORT produced a compression ratio of 135 to 1 and Huffman encoding, 1.1 to 1. Huffman encoding did not compress most reports because of their brevity. The results indicate that report coding can produce data compression of radiographic reports. The standard method of text storage, Huffman encoding, is not suitable for application to mammographic reports, which tend to be brief.

Electronic Data Processing↗
PubMed1978

Progress curve analysis in enzyme kinetics: model discrimination and parameter estimation.

The method of progress curve analysis for enzyme-catalyzed reactions (Duggleby, R.G. and Morrison, J.F. (1977) Biochim. Biophys. acta 481, 297--312) has been extended to a two substrate, reversible reaction through the use of enzyme-catalyzed recycling of one of the products. The reaction investigated was that catalyzed by aspartate aminotransferase (L-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1) and the product, alpha-ketoglutarate was recycled to glutamate using NADH and NH4Cl in the presence of glutamate dehydrogenase. The values determined for the kinetic parameters of the aminotransferase were found to agree well with those obtained from steady-state velocity measurements. The standard errors of the parameters, as calculated by the procedure originally described, were found to underestimate the observed variation between different experiments. Therefore, a procedure of data compression was devised which leads to more realistic values for standard errors. The compressed data obtained with aspartate aminotransferase have been fitted to the integrated rate equations that describe a variety of kinetic mechanisms. The best fit was obtained with the Ping-Pong model which is applicable to the aspartate aminotransferase reaction. Thus, progress curve analysis may be used to determine the kinetic mechanism of, and values of the kinetic parameters associated with, an enyzme-catalyzed reaction.

Aspartate Aminotransferases↗
PubMed1990

High compression of nuclear medicine dynamic studies.

As data compression plays now an important role in the development of medical PACS, a technique has been developed for medical image sequences storage and transmission in order to obtain very high compression ratio: in dynamic nuclear medicine studies it can achieve a compression ratio as high as 100:1 without significant degradation. The implemented technique combines two methods which multiply their effects. In a first step, a principal component analysis (PCA) of the image series is performed. It extracts a limited number of principal components and their associated images. For data compression it is not necessary to perform an oblique factor analysis to estimate the so-called 'physiological functions' and their spatial distributions as in factor analysis of dynamic structures (FADS). In a second step, the principal images are compressed by means of a transform coding procedure: an adaptive block-quantization technique using the 2D discrete cosine transform (DCT) is implemented, followed by a statistical quantization method to encode the DCT coefficients. To reconstruct the principal images, an inverse DCT is applied. Then the original series is computed from the reconstructed images combined with the principal components which have been stored without any modification. The reconstructed series is compared to the original series, as well as the time activity curves generated on different regions of interest (ROI) and the factor estimates obtained using FADS performed on the two series. Method and evaluation are illustrated on an example of first pass radionuclide angiocardiography.

Humans↗