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At least 145 records · Page 8Linked to original sources
PubMed2005

LF-NMR and multivariate data analysis: compression of data to classify hydrogel contact lenses.

Hydrogel contact lenses swollen in viscoelastic artificial tears solution have been studied, measuring transversal relaxation times of water molecules using LF-NMR techniques. Data were processed by classical multiexponential fitting, by principal component analysis and by SLICING, a multi-way analysis method. The reason for using multivariate data analysis was not to obtain a better fitting, but rather more effective data description. The single-sample relaxation curves were projected in a space spanned by the loading curves, and in this space it was simpler to compare data. In particular, it contributed to the description of the variability of motion characteristics of the water molecule 'families' contained in the studied samples. Applying multivariate techniques, we were able to group lenses with different Equilibrium Water Content (EWC) and with the same water content but different compositions. Accordingly, we were able to point out that, if the lenses are swollen first in physiological solution and then in viscoelastic artificial tears solution, hydration characteristics remained unchanged in all the studied samples, except for 38% EWC lenses.

Algorithms↗
PubMed2003

Effect of data compression on proximal caries detection: observer performance with DenOptix photostimulable phosphor images.

OBJECTIVES: To study the effect of lossy image compression on caries detection. Null hypothesis states no difference in caries detection efficacy among observers using original digital images versus images compressed at various rates of compression. METHODS: Digital images of 41 extracted posterior teeth were obtained with a storage phosphor DenOptix (Gendex DenOptix Imaging system) system. Images were exported in Tagged Image File Format (TIFF) and compressed with Joint Photographic Experts Group File Interchange Format (JFIF), as provided by the software of the imaging system. The compressions options JFIF100%, JFIF75% and JFIF50% resulted in reducing the image size to 1:2, 1:11 and 1:16, respectively. Eight observers evaluated the presence or absence of caries on a 5-point confidence scale. The actual caries status of each proximal surface was determined by ground section histology. Responses were evaluated by receiver operating characteristic (ROC) analysis. Areas under the curves (Az) were assessed using analysis of variance (ANOVA). RESULTS: The mean Az scores were 0.85 for original/uncompressed images, and 0.89 for JFIF100%, 0.88 for JFIF75% and 0.88 for JFIF50% images. These differences were not statistically significant (P = 0.26). Differences between observers were also not statistically significant (P = 0.12). CONCLUSIONS: JFIF compression at the level of 1:16 can be used without significant deterioration in diagnostic accuracy for proximal caries detection.

Analysis of Variance↗
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↗
PubMed2001

Effect of wavelet compression on data transmission in a multipurpose wireless telemedicine system.

We have developed a novel emergency telemedicine system which allows the transmission of physiological data (electrocardiogram, oximetry, blood pressure and temperature) and still images of the patient. The transmission is performed through wireless links using either GSM mobile phones or satellite. Because of the low bandwidth available through these links, data compression is required to allow realtime transmission of electrocardiographic (ECG) data. A new integrated design approach for an optimal zonal wavelet compression (OZWC) method was implemented for the ECG data. The performance of the mobile system with compressed ECG data segments was evaluated in terms of the percentage root-mean-square difference and visual inspection. The optimum wavelet algorithm achieved a maximum compression ratio of 18:1 with low distortion.

Algorithms↗
PubMed2005

Computed Quality Assessment of MPEG4-compressed DICOM Video Data.

Digital Imaging and Communication in Medicine (DICOM) has become one of the most popular standards in medicine. This standard specifies the exact procedures in which digital images are exchanged between devices, either using a network or storage medium. Sources for images vary; therefore there exist definitions for the exchange for CR, CT, NMR, angiography, sonography and so on. With its spreading, with the increasing amount of sources included, data volume is increasing, too. This affects storage and traffic. While for long-time storage data compression is generally not accepted at the moment, there are many situations where data compression is possible: Telemedicine for educational purposes (e.g. students at home using low speed internet connections), presentations with standard-resolution video projectors, or even the supply on wards combined receiving written findings. DICOM comprises compression: for still image there is JPEG, for video MPEG-2 is adopted. Within the last years MPEG-2 has been evolved to MPEG-4, which squeezes data even better, but the risk of significant errors increases, too. Within the last years effects of compression have been analyzed for entertainment movies, but these are not comparable to videos of physical examinations (e.g. echocardiography). In medical videos an individual image plays a more important role. Erroneous single images affect total quality even more. Additionally, the effect of compression can not be generalized from one test series to all videos. The result depends strongly on the source. Some investigations have been presented, where different MPEG-4 algorithms compressed videos have been compared and rated manually. But they describe only the results in an elected testbed. In this paper some methods derived from video rating are presented and discussed for an automatically created quality control for the compression of medical videos, primary stored in DICOM containers.

Algorithms↗
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↗
PubMed2003

Wavelet: a new trend in chemistry.

Since 1989, wavelet transform (WT) has attracted much interest of chemists working on signal and image processing, and the WT-based techniques have been successfully applied to the chemical signal processing. This approach has been demonstrated as fast in computation with localization and having quick decay properties, in contrast to the popular methods existing, especially to the fast Fourier transform. More than 370 papers have been published up to the year 2002 which covered applications of WT in various fields of chemistry, including analytical chemistry, chemical physics, and quantum chemistry. In this paper, we report on applications of WT to data compression, data smoothing and denoising, baseline and background correction, resolution of multicomponent overlapping signals, regression and classification, and analytical images processing in analytical chemistry. Through this report we wish to induce greater interest of chemists in WT and to obtain greater benefits from using the WT-based techniques.

Journal Article↗
PubMed2001

CT data storage reduction by means of compressing projection data instead of images: feasibility study.

The authors developed and evaluated a technique of compressing raw projection data at computed tomography (CT). Raw projection data acquired at CT were compressed and decompressed and then used for image reconstruction. For comparison, original images were compressed by comparable ratios. Projection data files were more compressible than image files. Projection data compression is a promising, efficient method to reduce data file size and thus to facilitate retrospective image reconstruction.

Algorithms↗
PubMed2004

Wavelet-based ultra-high compression of multidimensional NMR data sets.

The application of a lossy data compression algorithm based on wavelet transform to 2D NMR spectra is presented. We show that this algorithm affords rapid and extreme compression ratios (e.g., 800:1), providing high quality reconstructed 2D spectra. The algorithm was evaluated to ensure that qualitative and quantitative information are retained in the compressed NMR spectra. Whilst the maximum compression ratio that can be achieved depends on the number of signals and on the difference between the most and the least intense peaks (dynamic range), a compression ratio of 80:1 is affordable even for the challenging case of homonuclear 2D experiments of large biomolecules.

Algorithms↗