23 research outputs found
Quantitative cardiac ultrasound
This thesis is about the various aspects of quantitative cardiac ultrasound. The first
four chapters are mainly devoted to the reproducibility of echocardiographic
measurements. These . are focussed on the variation of echocardiographic
measurements within patients. An important issue, since this variation determines the
distinction between a real change of the measurement in a single patient or a_
difference caused by chance. The problems of the estimation of the variation of
measurements within patients and its clinical implications are elaborated more
specifically for Doppler velocity measurements and for cardiac volume determinations
using cross-sectional echocardiography. Next, there are two chapters about
echocardiographically determined normal ranges of cardiac dimensions. These
reference ranges provide for the quantitative distinction between sickness and health.
The last two chapters of this thesis deal with the newest aspect of quantitative cardiac
ultrasound: non-invasive cardiac tissue characterisation using integrated backscatter
measurements. These chapters are focussed on the distinction between normal
myocardial tissue and acute ischemic cardiac muscl
The relative contributions of myocardial wall thickness and ischemia to ultrasonic myocardial integrated backscatter during experimental ischemia
Abstract
The purpose of this study was to assess the empirical relationship between myocardial integrated backscatter (IB) and myocardial wall thickness (WT) in normal myocardium. A second object was to estimate the additional contribution to acute ischemic integrated backscatter levels given this relationship. Myocardial IB measurements and simultaneous myocardial WT measurements were made in 16 open-chested pigs with intact coronary circulation (normal myocardium) and 10 min after the flow in the left anterior descending coronary artery had been reduced to 20% of its baseline value (ischemic myocardium). Measurements were made 50 times during one cardiac cycle and averaged over 10 cardiac cycles. IB and WT measurements were normalized with respect to the nonischemic end-diastolic values. The relationship between IB and WT in normal myocardium was estimated in every individual pig by simple linear regression. Estimates of IB during ischemia were calculated on the basis of this relationship and the ischemic WT measurements. Differences of the estimator and the actual measurement made during ischemia depict the actual contribution of the state of acute ischemia, without the influence of WT. The slope of the relationship between IB and WT during normal myocardial contraction ranged from −0.16 to 0.03 dB/% (mean = −0.036 dB/%, SD = 0.06 dB/%). The additional contribution of ischemia ranged from −3.84 to 5.56 dB (mean = 0.31 dB, SD = 2.72 dB). It was concluded that the average contribution of ischemia to IB measurements is insignificant if the IB dependency on WT is removed from the data and that the higher level of ischemic IB measurements can be explained by the decrease in wall thickness during ischemia and not by the ischemia itself
Influence of data processing on cyclic variation of integrated backscatter and wall thickness in stunned porcine myocardium
Influence of data processing on cyclic variation of integrated backscatter and wall thickness in stunned porcine myocardium
The relationship between myocardial integrated backscatter, perfusion pressure and wall thickness during isovolumic contraction: An isolated pig heart study
Validation of quantitative analysis of intravascular ultrasound images
This study investigated the accuracy and reproducibility of a computer-aided method for quantification of intravascular ultrasound. The computer analysis system was developed on an IBM compatible PC/AT equipped with a framegrabber. The quantitative assessment of lumen area, lesion area and percent area obstruction was performed by tracing the boundaries of the free lumen and original lumen. Accuracy of the analysis system was tested in a phantom study. Echographic measurements of lumen and lesion area derived from 16 arterial specimens were compared with data obtained by histology. The differences in lesion area measurements between histology and ultrasound were minimal (mean ± SD: -0.27±1.79 mm2, p>0.05). Lumen area measurements from histology were significantly smaller than those with ultrasound due to mechanical deformation of histologic specimens (-5.38±5.09 mm2, p0.05). Finally, intra- and interobserver variability of our quantitative method was evaluated in measurements of 100 in vivo ultrasound images. The results showed that variations in lumen area measurements were low (5%) whereas variations in lesion area and percent area obstruction were relatively high (13%, 10%, respectively). Results of this study indicate that our quantitative method provides accurate and reproducible measurements of lumen and lesion area. Thus, intravascular ultrasound can be used for clinical investigation, including assessment of vascular stenosis and evaluation of therapeutic intervention
An in vitro evaluation of the line pattern of the near and far walls of carotid arteries using B-mode ultrasound
Myocardial backscatter analysis in animal experiments
This Paper describes the instrumentation and data analysis procedures for cardiac tissue characterization by a backscatter method. Experimental results obtained with a 'button' transducer in direct contact with the myocardium are discussed