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Biomedical subjects

B Meffert

Publications and source records attributed to B Meffert.

13 recordsLinked to original sources
PubMed2006

Infrared-monitored cold response in the assessment of Raynaud's phenomenon.

BACKGROUND: Evaluation of treatments for Raynaud's phenomenon (RP) requires objective response parameters in addition to clinical activity scores. Thermographic monitoring of fingertip re-warming after cold challenge has been widely used but usually requires sophisticated equipment. We have previously shown that fingertip re-warming after cold challenge follows a first-order transient response curve that can be described by a single variable, designated tau. OBJECTIVES: Here, we describe a novel device termed a duosensor, which records the tau value upon cold challenge in an automated manner. METHODS: We determined tau values in healthy probands, patients with primary or secondary RP associated with autoimmune disease and patients with scleroderma-associated RP following cold challenge, to determine assay variability, sensitivity and specificity. RESULTS: Duosensor-based thermography exhibited low intraindividual variability in healthy probands. As expected, tau values in RP patients were significantly increased compared with controls (8.08 +/- 3.65 min vs. 3.23 +/- 1.65 min). The duosensor-determined tau value yielded a specificity of 94.6% and predictive value of 95.3% for the presence of RP in a retrospective analysis of 139 patients. Furthermore, in a cohort of scleroderma patients with RP, patient self-assessment of RP severity correlated with tau values. CONCLUSIONS: Taken together, the present data suggest that tau value determination provides a suitable outcome measure for clinical studies of novel RP treatments. As the duosensor is a simple stand-alone device requiring no supporting equipment and minimal personnel attention, it should allow RP activity monitoring even in clinical settings with minimal technical infrastructure.

Body Temperature↗
PubMed2000

[Optical radiation and its effect on the skin].

Optical radiation ranges from short wave ultraviolet via visible light to the far infra-red. Both natural and artificial light sources may cause desired and undesired effects, both on the skin and on the organism as a whole. The nature and extent of such effects depend primarily on the energy of the photons, the absorption capacity of the chromophores, the mean depth of penetration, and on the density and dose of the radiation. The present paper discusses the mechanisms of action and desired and undesired effects in the organism, including therapeutic applications, separately for ultraviolet radiation, visible light and infrared radiation.

Dose-Response Relationship, Radiation↗
PubMed1995

[Signal smoothing and differentiation with a single operator].

For the filtering and subsequent processing of of very noisy force curves obtained in studies of isolated heart muscles, an operator derived from the rules used in the construction of Bézier curves has been tested. The advantage of using the latter is that despite major changes in one sample as compared with another, the resulting curve changes only slightly. The derived operator permits either smoothing only or can be extended for both smoothing and differentiation simultaneously. With the filtering operation "smoothing and differentiation", even very noisy signals can be successfully processed. The operator is insensitive to signal interference and has advantages in terms of speed and complexity.

Computer Graphics↗
PubMed1991

Effects of a multiple mild infra-red-A induced hyperthermia on central and peripheral pulse waves in hypertensive patients.

The paper reports on the effects of multiple whole-body infra-red-A irradiational (IRA) on 13 male patients known to have stage I or stage II essential arterial hypertension (WHO definition). The peripheral blood pressure was decreased significantly by IRA exposures. The lowered diastolic blood pressure lasted into posttreatment time. This effect is regarded as a consequence of an improvement in peripheral haemodynamics. A measure of this improvement is the different shape of the blood pressure pulse waves. Calculation and comparison of the spectral components of the recorded pulse signals show that these components are useful for a prediction of the blood pressure lowering effect.

Adult↗
PubMed1990

Classification of brain tumours by CT-image Walsh spectra.

Besides clinical and anamnestic data, image information from CT-image data in the tumour border was used for classification of brain tumours. If the image regions are properly selected a classification rate of 85% is obtained with a hierarchic classifier, although our study is based on only 139 patients.

Algorithms↗
PubMed1989

[Grading of brain tumors using computer-assisted analysis of CT images and anamnestic data].

For the classification of various brain tumours data from 139 patients with histologically proven diagnosis were used. With linear discriminant analysis and hierarchic classification of clinical and anamnestic data and features obtained by Walsh-transformation of image data presently 7 classes of tumours are differentiated with an estimated classification rate of 85% and reclassification rate of 92%.

Brain Neoplasms↗
PubMed1977

[Interpretation of pulse curves by means of the Walsh analysis].

A method for classification of medical data using the Walsh transformation is demonstrated. The Walsh spectrum was obtained by the algorithm of Andrews-Kane-Pratt. The spectral points were used to declare the signals normal or abnormal. The example described in this paper shows that in the case of pulse wave the classification is successful in 93 percent.

Carotid Arteries↗