Biomedical subjects

S K Jespersen

Publications and source records attributed to S K Jespersen.

4 recordsLinked to original sources

PubMed2000

In vitro spatial compound scanning for improved visualization of atherosclerosis.

A new off-line multiangle ultrasound (US) compound scanner has been built with the purpose of investigating possible improvements in visualization of vascular structure. Images of two formalin-fixed human atherosclerotic plaques removed by carotid endarterectomy were recorded from seven insonification angles over a range of 42 degrees and the individual images were combined (averaged) into a single image (spatial compounding). Compared to conventional B-mode imaging, this multiangle compound imaging (MACI) method features images with reduced angle-dependence, reduced random variation (speckle) and improved delineation of the plaque outline. With the MACI approach, it is, thus, easier to assess e.g., a possible residual lumen of an atherosclerotic artery as well as the level of echogenicity for the different plaque constituents.

Arteriosclerosis↗

PubMed1998

Quantitative analysis of ultrasound B-mode images of carotid atherosclerotic plaque: correlation with visual classification and histological examination.

This paper presents a quantitative comparison of three types of information available for 52 patients scheduled for carotid endarterectomy: subjective classification of the ultrasound images obtained during scanning before operation, first-and second-order statistical features extracted from regions of the plaque in still ultrasound images from three orthogonal scan planes and finally a histological analysis of the surgically removed plaque. The quantitative comparison was made with the linear model and with separation of the available data into training and test sets. The comparison of subjective classification with features from still ultrasound images revealed an overall agreement of 60% for classification of echogenicity and 70% for classification of structure. Comparison of the histologically determined relative volume of soft materials with features from the still images revealed a correlation coefficient of r = -0.42(p = 0.002). for mean echogenicity of the plaque region. The best performing feature was of second order and denoted Contrast (r = -0.5). Though significant, the latter correlation is probably not strong enough to be useful for clinical prediction of relative volume of soft materials for individual patients. Reasons for this is discussed in the paper, together with suggestions for improvements.

Arteriosclerosis↗

PubMed1998

Multi-angle compound imaging.

This paper reports on a scanning technique, denoted multi-angle compound imaging (MACI), using spatial compounding. The MACI method also contains elements of frequency compounding, as the transit frequency is lowered for the highest beam angles in order to reduce grating lobes. Compared to conventional B-mode imaging MACI offers better defined tissue boundaries and lower variance of the speckle pattern, resulting in an image with reduced random variations. Design and implementation of a compound imaging system is described, images of rubber tubes and porcine aorta are shown and effects on visualization are discussed. The speckle reduction is analyzed numerically and the results are found to be in excellent agreement with existing theory. An investigation of detectability of low-contrast lesions shows significant improvements compared to conventional imaging. Finally, possibilities for improving diagnosis of atherosclerotic diseases using MACI are discussed.

Animals↗

PubMed1997

Influence of tissue preservation methods on arterial geometry and echogenicity.

Thoracic porcine aortas from 5 pigs were investigated with 7.5-MHz ultrasound in vitro at low and high transmural pressure before and after the following tissue preservation methods were applied: 1. Storage in frozen condition (-12 degrees C) for 24 h followed by thawing; 2. fixation in formalin at zero transmural pressure for 24 h; and 3. fixation with formalin for 24 h while applying 74 mmHg of transmural pressure from within the lumen and a tensile force to longitudinally stretch the artery. Fixation in formalin at zero transmural pressure resulted in swelling of the arterial wall (25 +/- 40%, p < 0.02, at low transmural measurement pressure) and in decreased echogenicity (-23 +/- 38%, p < 0.01) of the arterial vessel wall. No changes in this respect were found after storage in a frozen condition nor after fixation in formalin at high transmural pressure which, therefore, are more appropriate procedures for fixation of arteries prior to in vitro ultrasound examination if geometry is important.

Animals↗