Biomedical subjects

B Olstad

Publications and source records attributed to B Olstad.

7 recordsLinked to original sources

PubMed2001

Assessment of regional long-axis function during dobutamine echocardiography.

Echocardiographic analysis of regional left ventricular function is based upon the assessment of radial motion. Long-axis motion is an important contributor to overall function, but has been difficult to evaluate clinically until the recent development of tissue Doppler techniques. We sought to compare the standard visual assessment of radial motion with quantitative tissue Doppler measurement of peak systolic velocity, timing and strain rate (SRI) in 104 patients with known or suspected coronary artery disease undergoing dobutamine stress echocardiography (DbE). A standard DbE protocol was used with colour tissue Doppler images acquired in digital ciné-loop format. Peak systolic velocity (PSV), time to peak velocity (TPV) and SRI were assessed off-line by an independent operator. Wall motion was assessed by an experienced reader. Mean PSV, TPV and SRI values were compared with wall motion and the presence of coronary artery disease by angiography. A further analysis included assessing the extent of jeopardized myocardium by comparing average values of PSV, TPV and SRI against the previously validated angiographic score. Segments identified as having normal and abnormal radial wall motion showed significant differences in mean PSV (7.9 +/- 3.8 and 5.9 +/- 3.3 cm/s respectively; P < 0.001), TPV (84 +/- 40 and 95 +/- 48 ms respectively; P = 0.005) and SRI (-1.45 +/- 0.5 and -1.1 +/- 0.9 s(-1) respectively; P < 0.001). The presence of a stenosed subtending coronary artery was also associated with significant differences from normally perfused segments for mean PSV (8.1+/-3.4 compared with 5.7+/-3.7 cm/s; P < 0.001), TPV (78 +/- 50 compared with 92 +/- 45 ms; P < 0.001) and SRI (-1.35 +/- 0.5 compared with -1.20 +/- 0.4 s(-1); P = 0.05). PSV, TPV and SRI also varied significantly according to the extent of jeopardized myocardium within a vascular territory. These results suggest that peak systolic velocity, timing of contraction and SRI reflect the underlying physiological characteristics of the regional myocardium during DbE, and may potentially allow objective analysis of wall motion.

Adrenergic beta-Agonists↗

PubMed2000

Use of peak systolic strain as an index of regional left ventricular function: comparison with tissue Doppler velocity during dobutamine stress and myocardial ischemia.

OBJECTIVES: The goals of this study were to examine peak systolic strain as an index of regional function in an animal model of inotropic stress and ischemia, and to compare these results with peak systolic myocardial tissue Doppler velocity (MDV). BACKGROUND: Myocardial tissue Doppler velocity is an objective measure of regional left ventricular responses to inotropic stimulation and ischemia, but it is affected by tethering from adjacent segments and translational movement. Myocardial Doppler strain (epsilon, relative change in length) is a more local measure of contractility, which can now be derived noninvasively from MDV. METHODS: Eight dogs underwent graded dobutamine infusion followed by coronary occlusion. Epicardial 2-dimensional echocardiography and color MDV of the left ventricle were obtained and digitized from the short-axis view at baseline and with dobutamine doses of 2, 4, and 8 microg/kg per minute. These were repeated 0, 10, 20, 45, and 90 seconds after occlusion of the left anterior descending artery (LAD) (n = 3) or circumflex coronary artery (n = 5). Dobutamine was continued at 8 microg/kg per minute during coronary occlusion. The peak systolic radial MDV (cm/s) and systolic strain (epsilon(s), percent thickening) in the anterior and posterior walls were measured off-line at each stage. RESULTS: Dobutamine caused an increase in MDV (P =.0001) and epsilon(s) (P =.09) above baseline values. Coronary occlusion caused a reduction in wall motion; after 45 seconds, all nonperfused segments were hypokinetic. There was a corresponding decrease in MDV and epsilon(s), but this occurred earlier for epsilon(s), and the difference between ischemic and nonischemic segments was greater for epsilon(s) than for MDV (P <. 03). Nonischemic regions trended to an increase in epsilon(s) (compensatory hyperkinesis), whereas MDV trended downward, probably reflecting the global decrease in left ventricular function. CONCLUSION: Both MDV and epsilon(s) increase with dobutamine and decrease during ischemia. epsilon(s) appears to respond to local ischemia earlier than MDV, perhaps because it is a more local measure. Thus epsilon(s) may prove to be an accurate parameter for the clinical recognition of regional ischemia.

Animals↗

PubMed1999

Dynamic three-dimensional freehand echocardiography using raw digital ultrasound data.

In this paper, we present a new method for simple acquisition of dynamic three-dimensional (3-D) ultrasound data. We used a magnetic position sensor device attached to the ultrasound probe for spatial location of the probe, which was slowly tilted in the transthoracic scanning position. The 3-D data were recorded in 10-20 s, and the analysis was performed on an external PC within 2 min after transferring the raw digital ultrasound data directly from the scanner. The spatial and temporal resolutions of the reconstruction were evaluated, and were superior to video-based 3-D systems. Examples of volume reconstructions with better than 7 ms temporal resolution are given. The raw data with Doppler measurements were used to reconstruct both blood and tissue velocity volumes. The velocity estimates were available for optimal visualization and for quantitative analysis. The freehand data reconstruction accuracy was tested by volume estimation of balloon phantoms, giving high correlation with true volumes. Results show in vivo 3-D reconstruction and visualization of mitral and aortic valve morphology and blood flow, and myocardial tissue velocity. We conclude that it was possible to construct multimodality 3-D data in a limited region of the human heart within one respiration cycle, with reconstruction errors smaller than the resolution of the original ultrasound beam, and with a temporal resolution of up to 150 frames per second.

Adult↗

PubMed1998

Echocardiographic functional images based on tissue velocity information.

Tissue velocity information (TVI) is acquired by sampling of tissue Doppler velocity values at discrete points. The information is stored in an interfoiled format with gray scale imaging during one or several cardiac cycle at a high temporal resolution, > 60 Hz, giving signals that tolerate mathematical processing as derivation, integration and Fourier analysis of velocity profiles without distortions. The software enables the possibility to analyze multiple velocity profiles from any localization within the acquired scanned sector. The myocardial tissue velocity direction and color-coded numerical value can be computed along any chosen curve form (C-line) and be presented as a spatial function of velocities against time (C-mode). The velocity curves can also be presented in several new functional modes as color-coded running cineloops: phase imaging, time delay imaging, amplitude imaging, acceleration imaging, instantaneous phase imaging, wrapped phase imaging. The software also allows color or C-mode presentation of tissue contraction and expansion. This facilitates the differentiation between active and passive myocardial tissue movements, thus improving the ability to differentiate between healthy and diseased myocardial tissue. This article presents several applications of the software in normals and in cardiac patients.

Blood Flow Velocity↗

PubMed1998

Regional mean systolic myocardial velocity estimation by real-time color Doppler myocardial imaging: a new technique for quantifying regional systolic function.

A new color Doppler myocardial imaging (CDMI) system with high spatial and temporal resolution and novel postprocessing modalities has been developed that could allow quantifiable stress echocardiography. The purpose of this study was to determine whether regional myocardial systolic velocities could be accurately and reproducibly measured both at rest and during bicycle ergometry by using CDMI. Thirty normal subjects were examined with CDMI at rest, and peak mean systolic myocardial velocities (MSV) were measured for 34 predetermined left ventricular myocardial segments. Interobserver variability and intraobserver variability were established for all segments. Submaximal bicycle ergometry was performed in 20 normal subjects by using standardized weight-related increases in workload. MSV were measured at each step of exercise for 16 left ventricular stress echo segments. At rest, a base-apex gradient in regional MSV was recorded with highest longitudinal shortening velocities at the base. A similar pattern was noted for circumferential shortening MSV. Measurements were predictable and highly reproducible with low interobserver and intraobserver variability for 26 of 34 segments. Reproducibility was poor for basal anteroseptal segments in all views and mid anterior, anteroseptal, and septal segments in the short-axis views. During exercise, mid and basal segments of all walls showed a significant increase of MSV between each workload step and for apical segments between alternate steps. The resting base-apex velocity gradient observed at rest remained in all walls throughout ergometry. Thus a CDMI system with improved spatial and temporal resolution and postprocessing analysis modalities provided reproducible and accurate quantification of segmental left ventricular circumferential and longitudinal contraction both at rest and during exercise.

Adult↗

PubMed1995

Three-dimensional imaging of the brain cavities in human embryos.

A system for high-resolution three-dimensional imaging of small structures has been developed, based on the Vingmed CFM-800 annular array sector scanner with a 7.5-MHz transducer attached to a PC-based TomTec Echo-Scan unit. A stepper motor rotates the transducer 180 degrees and the complete three-dimensional scan consists of 132 two-dimensional images, video-grabbed and scan-converted into a regular volumetric data set by the TomTec unit. Three normal pregnancies with embryos of gestational age 7, 9 and 10 weeks received a transvaginal examination with special attention to the embryonic/fetal brain. In all three cases, it was possible to obtain high-resolution images of the brain cavities. At 7 weeks, both hemispheres and their connection to the third ventricle were delineated. The isthmus rhombencephali could be visualized. At 9 weeks, the continuous development of the brain cavities could be followed and at 11 weeks the dominating size of the hemispheres could be depicted. It is concluded that present ultrasound technology has reached a stage where structures of only a few millimeters can be imaged in vivo in three-dimensions with a quality that resembles the plaster figures used in embryonic laboratories. The method can become an important tool in future embryological research and also in the detection of early developmental disorders of the embryo.

Brain↗

PubMed1993

[Non-linear models for real time image processing and their applications in image enhancement, surface area determination and volume visualization].

This paper presents non-linear filter models that are suitable for real-time operations. The requirements imposed on these models by ultrasonic imaging are discussed. In particular, we study the characteristics of temporal filtering in cardiac imaging. Non-linear filter models incorporating these requirements are presented and compared with filtering schemes traditional in ultrasonic imaging. Furthermore, we illustrate how these filter models can be utilized to improve the quality and noise tolerance of automatic, real-time area detection algorithms. Finally, we present results from a 3D ultrasonic study of a foetus. The experiments illustrate how non-linear processing can increase the clinical information content that can be extracted from such investigations.

Body Surface Area↗