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Biomedical subjects

J Cornelis

Publications and source records attributed to J Cornelis.

At least 19 recordsLinked to original sources
PubMed2000

Multipole approach to the inverse problem in electrocardiology: convergence of the multipole equivalent generator on the inhomogeneous body conductor.

The multipole approach to the inverse electrocardiological problem consists of estimating the multipole components of the cardiac electric generator, starting from the measured body surface potential. This paper presents a critical investigation of the basic premise for the applicability of the multipole approach, namely the convergence of the multipole equivalent generator for the heart on the surface of an inhomogeneous body conductor. As an extension to multipole theory, a criterion for the convergence is derived. Based on realistic models for the body conductor and the cardiac electric generator, we observe that the criterion is not strictly satisfied in realistic conditions. Numerical simulations with the same models point out that the multipole equivalent generator is indeed not convergent in the strict mathematical sense. On the other hand, we show that the multipole equivalent generator yields a rather close approximation of the electrocardiological potential for intermediate values of the order of the multipole generator. A discussion is given on how to explain the apparently ambiguous results for the estimation of cardiac multipole components.

Computer Simulation↗
PubMed2000

Reconstruction of MR images from data acquired on a general nonregular grid by pseudoinverse calculation.

A minimum-norm least-squares image-reconstruction method for the reconstruction of magnetic resonance images from non-Cartesian sampled data is proposed. The method is based on a general formalism for continuous-to-discrete mapping and pseudoinverse calculation. It does not involve any regridding or interpolation of the data and therefore the methodology differs fundamentally from existing regridding-based methods. Moreover, the method uses a continuous representation of objects in the image domain instead of a discretized representation. Simulations and experiments show the possibilities of the method in both radial and spiral imaging. Simulations revealed that minimum-norm least-squares image reconstruction can result in a drastic decrease of artifacts compared with regridding-based reconstruction. Besides, both in vivo and phantom experiments showed that minimum-norm least-squares image reconstruction leads to contrast improvement and increased signal-to-noise ratio compared with image reconstruction based on regridding. As an appendix, an analytical calculation of the raw data corresponding to the well-known Shepp and Logan software head phantom is presented.

Humans↗
PubMed1999

Oncogenic transformation-dependent expression of a transcription factor NF-Y subunit.

As a result of differential splicing, one subunit of the nuclear factor Y (NF-Y) consists of two major isoforms designated short (NF-YaS) and long (NF-YaL). In proliferating normal human fibroblasts, NF-YaL is by far the more expressed isoform. Surprisingly, NF-YaS was found by immunoblotting to be as prominent as NF-YaL in simian virus 40 (SV40)-transformed cell derivatives. As a consequence, two NF-Y/DNA complexes, one containing the long and the other the short isoform, were formed with extracts from transformed cells and a target promoter element in electrophoretic mobility-shift assays. Only the complex containing NF-YaL was detected with extracts from normal fibroblasts. Furthermore, the NF-Y recognition motif contributed to promoter activation in SV40-transformed cells but not in normal, cells. Our finding links transcription stimulation in transformed cells to quantitative changes in the expression of an NF-Ya subunit.

Animals↗
PubMed1999

Wavelet-based lossless compression of coronary angiographic images.

The final diagnosis in coronary angiography has to be performed on a large set of original images. Therefore, lossless compression schemes play a key role in medical database management and telediagnosis applications. This paper proposes a wavelet-based compression scheme that is able to operate in the lossless mode. The quantization module implements a new way of coding of the wavelet coefficients that is more effective than the classical zerotree coding. The experimental results obtained on a set of 20 angiograms show that the algorithm outperforms the embedded zerotree coder, combined with the integer wavelet transform, by 0.38 bpp, the set partitioning coder by 0.21 bpp, and the lossless JPEG coder by 0.71 bpp. The scheme is a good candidate for radiological applications such as teleradiology and picture archiving and communications systems (PACS's).

Algorithms↗
PubMed1999

Wavelet image compression--the quadtree coding approach.

Perfect reconstruction, quality scalability, and region-of-interest coding are basic features needed for the image compression schemes used in telemedicine applications. This paper proposes a new wavelet-based embedded compression technique that efficiently exploits the intraband dependencies and uses a quadtree-based approach to encode the significance maps. The algorithm produces a losslessly compressed embedded data stream, supports quality scalability, and permits region-of-interest coding. Moreover, experimental results obtained on various images show that the proposed algorithm provides competitive lossless/lossy compression results. The proposed technique is well suited for telemedicine applications that require fast interactive handling of large image sets, over networks with limited and/or variable bandwidth.

Algorithms↗
PubMed1993

Modeling radon progeny absorbed in glass.

The depth distribution of 214Pb and 210Pb in glass was calculated from 218Po and 214Po deposited on the surface. The activity is found in a very narrow zone near the surface (< 100 nm). A fraction of the absorbed 214Po is capable of reaching the surface by decay into 210Pb. This fraction amounts to 29.8%.

Absorption↗
PubMed1991

Do you also have problems with the file format syndrome?

In a biomedical data processing environment, an essential requirement is the ability to integrate a large class of standard modules for the acquisition, processing and display of the (image) data. Our approach to the management and manipulation of the different data formats is based on the specification of a common standard for the representation of data formats, called 'data nature descriptions' to emphasise that this representation not only specifies the structure but also the contents of data objects (files). The idea behind this concept is to associate each hardware and software component that produces or uses medical data with a description of the data objects manipulated by that component. In our approach a special software module (a format convertor generator) takes care of the appropriate data format conversions, required when two or more components of the system exchange data.

Electronic Data Processing↗
PubMed1990

A monoclonal antibody to Ly-6 gene product inhibits generation of functionally active T cells and recognizes single antigenic specificity whose expression is up-regulated in virus-transformed rat fibroblast.

In order to elucidate the relationship between the structure and function of proteins encoded for by the Ly-6 gene complex, a cDNA was constructed for a Ly-6.2 specificity and then monoclonal antibodies (mAb) generated to bacterially synthesized protein. The addition of one of these mAb, designated Pb-19, inhibited the proliferative response of T cells to concanavalin A (Con A) or major histocompatability complex (MHC) alloantigens. Reactivity of Pb-19 to the Ly-6 specificity was blocked by a known anti-Ly-6.A.2 mAb but not by an anti-Ly-6.E.1 mAb. This mAb detected a Ly-6.A.2 specificity (a 33,000 MW antigen) whose expression was increased in a transformed rat fibroblast containing the entire genome of bovine papillomavirus.

Animals↗
PubMed1985

[Reactivation of gamma-ray irradiated parvovirus H-1 in cells of patients with ataxia telangiectasia and Huntington's chorea].

Parvovirus H-1 was used to probe the cellular radiosensitivity of two human degeneration syndromes AT and HC. No difference in the survival of gamma irradiated H-1 was detected between skin fibroblasts from such patients and from a normal individual. However, AT and normal cells were distinguished by the fact that the reactivation of irradiated H-1 could be increased by UV or X-irradiation of the latter but not of the former cells.

Animals↗
PubMed1984

[Simultaneous high performance liquid chromatographic determination of 8 anti-epileptics and sedatives in plasma. Use of a radial compression column system].

The authors describe a method of assaying anti-epileptic and sedative drugs by high performance liquid chromatography. This method allows for simultaneous separation and quantification of these drugs (Ethosuximide, Primidone, Phenobarbital, Beclamide, Prominal, Diphenylhydantoin, Glutethimide, Carbamazepine) in a relatively short analysis time, by means of a system of radial compression of the column. The serum is acidified and extracted by ethyl acetate. After evaporation, the residue is taken up in the mobile phase. The various drugs are eluted in a 10 micron Rad-Pak C 18 column with a mobile phase consisting of a mixture of methanol and water with a flow rate of 4 ml/min. The chromatograph is read at 200 nm and the separation is effective in about 16 minutes. The yield is between 75 and 100 per cent and the repeatability of the method is good (C. V. less than 9 per cent). The originality of the method resides in the assay of drugs such as beclamide, methylphenobarbital and glutethimide at the same time as the major anti-epileptics.

Anticonvulsants↗
PubMed1976

An active probe for electrocardiography.

In order to improve the signal to noise ratio during the recording of electrocardiographic maps from moving patients, the effect of using active electrodes with built-in amplifiers was investigated. Two kinds of electrodes using different technologies were developed: a miniature printed circuit and a thin film circuit. The first method was found to be suitable for the fabrication of small quantities in a normally equipped electronics workshop while the second, requiring highly specialised equipment, is intended for industrial manufacture in large quantities.

Amplifiers, Electronic↗
PubMedDate not supplied

Ultraviolet-irradiated simian virus 40 activates a mutator function in rat cells under conditions preventing viral DNA replication.

The UV-irradiated temperature-sensitive early SV40 mutant tsA209 is able to activate at the nonpermissive temperature the expression of mutator and recovery functions in rat cells. Unirradiated SV40 activates these functions only to a low extent. The expression of these mutator and recovery functions in SV40-infected cells was detected using the single-stranded DNA parvovirus H-1 as a probe. Because early SV40 mutants are defective in the initiation of viral DNA synthesis at the nonpermissive temperature, these results suggest that replication of UV-damaged DNA is not a prerequisite for the activation of mutator and recovery functions in mammalian cells. The expression of the mutator function is dose-dependent, i.e., the absolute number of UV-irradiated SV40 virions introduced per cell determines its level. Implications for the interpretation of mutation induction curves in the progeny of UV-irradiated SV40 in permissive host cells are discussed.

Animals↗