Search PubMed⌕ Search

Biomedical subjects

R Velu

Publications and source records attributed to R Velu.

3 recordsLinked to original sources
PubMed2001

Early clinical experience with color three-dimensional intravascular ultrasound in peripheral interventions.

PURPOSE: To report early clinical experiences with color 3-dimensional intravascular ultrasound (3-D IVUS) in assisting peripheral interventions. TECHNIQUE: A 3.5-F, 20-MHz IVUS catheter that utilizes ChromaFlo computer software to demonstrate blood flow in color was evaluated in over 100 peripheral interventions. ChromaFlo captures up to 30 conventional IVUS frames every second and generates "real-time" imaging. The software compares sequential axial IVUS images and interprets any differences in the position of echogenic blood particles, which are displayed as colorized flow in axial or 3-D renderings. CONCLUSIONS: ChromaFlo-enhanced IVUS demonstrates colorized blood flow inside the vessel lumen, which is helpful in distinguishing echolucent disease from luminal blood flow and can also be used to perform peripheral interventions in patients with renal failure or allergy, avoiding the use of contrast media.

Catheterization↗
PubMed1994

Testing for omitted variables and non-linearity in regression models for longitudinal data.

When fitting regression models to investigate the relationship between an outcome variable and independent variables of primary interest, there is often concern whether omitted variables or assuming a different functional relationship could have changed the conclusion or interpretation of the results. In longitudinal studies of aging, the concern with omitted variables is well known in the context of cohort and period effects, which refer to unmeasured variables systematically related to the individual's year of birth and secular trends in outcome, respectively. We present and compare three approaches to detecting omitted confounders and non-linearity in the random effects model for longitudinal data (Laird and Ware, 1982) with random slope and intercept across individuals. The first approach compares simple unweighted within and between regression coefficients, the second is the Hausman specification test for regression models, and the third approach involves testing directly the significance of functions of individual specific covariate means means i, in the random effects regression model. This last approach is motivated by the models that arise when cohort or period effects are ignored. We compare the three approaches, and illustrate their application.

Analysis of Variance↗