Biomedical subjects

E J Delp

Publications and source records attributed to E J Delp.

4 recordsLinked to original sources

PubMed1990

Nonlinear methods in electrocardiogram signal processing.

Electrocardiographic (ECG) signals are frequently corrupted by impulsive noise due to muscle activities, and background normalization is often needed to correct for patient motion and respiration. Nonlinear signal processing methods are effective alternatives to conventional linear filtering methods when dealing with impulsive noise or noise types that are difficult to characterize. The class of nonlinear filtering methods studied in this article operate by moving a window of finite width along the input data sequence. At each position, the filter output is obtained from the input samples inside the window. Nonlinear operators differ from linear filters in that the output is not a simple linear combination of the input samples. Three classes of nonlinear operators--median filters, morphologic operators, and the alpha-trimmed mean filter--are briefly introduced and algorithms using them for ECG signal processing are presented. Empirical results indicate that the nonlinear operators are good candidates for impulsive noise suppression and background normalization in ECG signal processing.

Algorithms↗

PubMed1989

Impulsive noise suppression and background normalization of electrocardiogram signals using morphological operators.

A new approach to impulsive noise suppression and background normalization of digitized electrocardiogram signals is presented using mathematical morphological operators that incorporate the shape information of a signal. A brief introduction to these nonlinear signal processing operators, as well as a detailed description of the new algorithm, is presented. Empirical results show that the new algorithm has good performance in impulsive noise suppression and background normalization.

Algorithms↗

PubMed1985

Automatic segmentation and quantification of electron micrographs: extracellular components.

Extracellular glycosaminoglycans when precipitated by tannic acid, appear in electron micrographs as amorphous reticulate masses or fragments sometimes finely beaded and often associated with collagen fibrils. An algorithm for automatic classification, segmentation, and quantification of the amount of tannic acid-precipitable material (TAPM) and collagen in electron microscopic images is presented. Small patches of a region are initially located and the patch boundaries are traced using a binary contour tracing algorithm. The patches are then grown out and merged together to form one large area. This area is classified using a two-dimensional feature vector into one of two classes: a region with TAPM and collagen, or one with cell bodies and/or processes. Once these areas are classified and segmented, the distribution of TAPM is measured. The algorithm was tested on several TAPM images displaying varying amounts and configurations of TAPM with good results. It may also be adapted to process other electron microscopic images containing elements of interest which have complex or amorphous form.

Animals↗

PubMed1985

Difference picture algorithms for the analysis of extracellular components of histological images.

A computer-assisted method for objectively identifying and displaying the distribution of molecules that can only be positively identified by a combination of staining characteristics and susceptibility to specific enzymatic digestion or chemical degradation is presented. The visual image of an enzymatically digested tissue section is subtracted from that of an adjacent buffer-incubated control section and the distribution of the extracellular molecules removed from the tissue section displayed. Photomicrographs are taken using white light and narrow bandwidth filters of wavelengths at or near the maximum absorbance for the dye products used to visualize the extracellular matrix and cells. Each negative is standardized using reference gray levels. The cell and matrix images of both digested and undigested sections are then registered. The locations of cells in both control and digested sections are identified and set to an undefined gray level value in the matrix images. The cell-removed images of the control and digested sections are then registered and the difference in gray levels between the two images calculated and displayed. The validity of results obtained is primarily dependent on the soundness of the histological visualization and digestion techniques used, but is independent of investigator interpretation.

Animals↗