Biomedical subjects

K H Ting

Publications and source records attributed to K H Ting.

3 recordsLinked to original sources

PubMed2006

Automatic correction of artifact from single-trial event-related potentials by blind source separation using second order statistics only.

Event-related potentials (ERP) are in general masked by various kinds of artifacts. To attenuate the effects of artifacts, various schemes have been introduced, such as epoch rejection, electro-oculogram (EOG) regression and independent component analysis (ICA). However, none of the existing techniques can automatically remove various kinds of artifacts from a single ERP epoch. EOG regression cannot handle artifacts other than ocular ones. ICA incorporating higher order statistics (HOS) normally requires data with large number of time samples in order that the solution is robust. In this paper we blindly separate the multi-channel ERP into source components by estimating the correlation matrices of the data. Since only second order statistics (SOS) is involved, the process performs well at the single epoch level. Automatic artifact identification is performed in the source domain by introducing objective criteria for various artifacts. Criteria are based on time domain signal amplitude for blink and spurious peak artifact, scalp distribution of signal power for eye movement artifact and power distribution of frequency components for muscle artifact. The correction procedure can be completed by removing the identified artifactual sources from the raw multi-channel ERP.

Algorithms↗

PubMed1994

Interobserver agreement in defecography.

PURPOSE: This study was designed to test the reproducibility of the diagnostic assessment of defecographies in patients with a suspected disorder of defecation. METHODS: To evaluate interobserver agreement, 100 defecographic series of patients with complaints suggesting a disordered defecation were evaluated independently by three observers with a standardized questionnaire. After six weeks, a random sample of 35 of 100 defecographies was evaluated a second time with clinical data provided (history, proctologic examination). To evaluate whether the position of residual volume in the rectum would affect agreement, patients with substantial retention either in the upper or lower rectum were also evaluated separately. RESULTS: Total agreement regarding rectocele and internal prolapse was 0.81 and 0.75, respectively (1.0 = complete agreement), and was significantly higher than chance agreement. Total agreement regarding residual volume in the rectum at the end of defecography and clinical relevance of findings was not different from chance agreement, providing clinical data did not significantly improve agreement. When residual volume was situated in the lower rectum, agreement regarding incompleteness of emptying and its clinical relevance was much better (0.93). CONCLUSIONS: Interobserver agreement is good regarding the deformation of the rectum during defecography but not different from chance agreement regarding the completeness of evacuation.

Adult↗

PubMed1992

Is the volume retained after defecation a valuable parameter at defecography?

The intention of this study was to correlate the retained volume at the end of defecography to certain defecographic findings and to the sense of incomplete emptying. In 170 defecographic series, the retained barium was estimated planimetrically. No particular defecographic finding determined a higher or lower amount of remaining volume, and the sense of incomplete evacuation did not depend on the amount of retained volume. Thresholds of urge and perception on anorectal manometry did not differ between patients with and without the feeling of incomplete evacuation. A rectocele, isolated or combined with an internal prolapse, caused the retained volume to be in the lowermost part of the rectum, whereas, in the case of an isolated intussusception, the remaining volume was located in the middle or higher part of the rectum. It is concluded that defecographic findings do not in general explain incomplete emptying or the sense of incomplete emptying, but they may determine the localization of the retained volume.

Adult↗