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J G Bosch

Publications and source records attributed to J G Bosch.

7 recordsLinked to original sources
PubMed2000

Ultrasound assessment of atherosclerotic vessel wall changes: reproducibility of intima-media thickness measurements in carotid and femoral arteries.

RATIONALE AND OBJECTIVES: Ultrasonography is widely used in cardiovascular research to quantify early atherosclerotic vessel wall changes. In this article, we examined the short- and long-term reproducibility of this technique in the common carotid artery, carotid bifurcation, common femoral artery, and superficial femoral artery. Furthermore, we assessed the effect of progressed atherosclerosis on reproducibility. METHODS: Repeated ultrasound examinations were performed by one observer on 15 healthy individuals and 18 patients suffering from coronary heart disease. Intima-media thickness was determined by B-mode ultrasonography. The examinations were repeated by the same observer after a short time interval (short-term) and after a few weeks (long-term) and expressed as the mean difference between the measurements and the coefficient of variation (CV). RESULTS: The reproducibility of the intima-media thickness determination turned out to be best in the common carotid artery and the superficial femoral artery when performed in healthy controls (CV 5.6% and 5.5%, respectively). Reproducibility was less in patients with clinical atherosclerosis; this especially affected the reliability of the superficial femoral artery measurement (CV in healthy controls was 5.5%; in coronary heart disease patients, 17.5 %). The reliability of the intima-media thickness measurements in the common carotid artery (CV in healthy controls was 5.6%; in coronary heart disease patients, 9.5%) proved to be least affected by progressed atherosclerosis. A longer time interval between measurements did not affect the reproducibility of intima-media thickness measurements in healthy controls, whereas in the patients it led to some decrease of reproducibility and to a major decrease in reproducibility of the superficial femoral artery measurements (CV changed from 12.7% to 17.5%). CONCLUSIONS: Ultrasonography is a reliable and accurate technique to determine intima-media thickness in superficial arteries. In studies in which the intima-media thickness determination is used as a marker for generalized and coronary atherosclerosis, the common carotid artery should always be included, whereas the benefit of inclusion of other arteries depends on age and the expected extent of atherosclerosis in the individuals studied.

Adult↗
PubMed1999

Anatomical model matching with fuzzy implicit surfaces for segmentation of thoracic volume scans.

Many segmentation methods for thoracic volume data require manual input in the form of a seed point, initial contour, volume of interest etc. The aim of the work presented here is to further automate this segmentation initialization step. In this paper an anatomical modeling and matching method is proposed to coarsely segment thoracic volume data into anatomically labeled regions. An anatomical model of the thorax is constructed in two steps: 1) individual organs are modeled with blended fuzzy implicit surfaces and 2) the single organ models are grouped into a tree structure with a solid modeling technique named constructive solid geometry (CSG). The combination of CSG with fuzzy implicit surfaces allows a hierarchical scene description by means of a boundary model, which characterizes the scene volume as a boundary potential function. From this boundary potential, an energy function is defined which is minimal when the model is registered to the tissue-air transitions in thoracic magnetic resonance imaging (MRI) data. This allows automatic registration in three steps: feature detection, initial positioning and energy minimization. The model matching has been validated in phantom simulations and on 15 clinical thoracic volume scans from different subjects. In 13 of these sets the matching method accurately partitioned the image volumes into a set of volumes of interest for the heart, lungs, cardiac ventricles, and thorax outlines. The method is applicable to segmentation of various types of thoracic MR-images, provided that a large part of the thorax is contained in the image volume.

Heart↗
PubMed1995

Automated contour detection and acoustic quantification.

Echocardiographic left and right ventricular sequences are usually interpreted visually, but current quantitation techniques have been found to be tedious, time-consuming and associated with significant inter- and intra-observer variabilities. In an attempt to eliminate these problems, we have developed the Echocardiographic Analysis System (EAS) which uses robust automated border detection techniques both for single frames as well as for sequences. Comparison of LV cross-sectional area with the semi-automated border detection (AUTO) and those assessed from manual tracings (MAN) yielded a systematic difference (MAN-AUTO) of -6.6% (p < 0.001), and a random difference (standard deviation of paired signed differences) of 11.8%. Current developments are directed towards real-time automated border detection with an Accelerator board, integration of Acoustic Quantification (AQ) data as edge information into EAS, and intravascular echocardiographic applications.

Computers↗
PubMed1994

Relation of plasma coagulation factor VII and fibrinogen to carotid artery intima-media thickness.

Plasma clotting factor VII and plasma fibrinogen have been claimed as independent risk factors for occlusive cardiovascular disease. The aim of this study was to investigate whether these coagulation parameters affect early atherosclerosis, additional to their possible effect on arterial thrombosis. We used high-resolution quantitative ultrasonography to measure carotid intima-media thickness in 121 healthy volunteers, aged 18 to 56 years. It has previously been demonstrated that an increased artery wall thickness is seen in advanced atherosclerosis. To validate our methodology for relatively young individuals, we assessed the association of intima-media thickness with the risk-factor status of our subjects, by including classical cardiovascular risk factors, e.g. age, sex, serum cholesterol, smoking habits and blood pressure. Thereafter, we studied the effect of factor VII and fibrinogen plasma levels on carotid intima-media thickness, as well as that of polymorphisms of the factor VII and fibrinogen genes. All classical risk factors except smoking and family history were associated with intima-media thickness. When adjusted for by multivariate linear regression analysis, age, blood pressure and cholesterol appeared to be independent determinants of intima-media thickness. Factor VII and fibrinogen levels showed no association in multivariate analysis with intima-media thickness. We conclude that artery wall thickness measurement by ultrasound is a useful tool to investigate the role of clotting factors in early atherosclerosis. Factor VII and fibrinogen levels in young and middle-aged volunteers have no association with early artherosclerotic vessel wall changes.

Adult↗
PubMed1989

Early and recent intraluminal ultrasound devices.

The history of intraluminal echography dates back to the very beginning of diagnostic ultrasound. Over the years many fascinating ideas and applications of catheter tip or gastroscopic tube tip mounted transducers have been described. This chapter surveys these methods, subdividing them into a) measurements; b) Doppler and c) imaging. The survey ranges from early work of Cieszynski on the feasibility of echocardiography to more recent intra-arterial catheter tip Doppler with guidewire and balloon as described by Serruys. Examples of ultrasound catheter tip echography in combination with other techniques such as angioscopy, laser ablation and spark erosion are also described. Today practical approaches are limited to imaging only. The three major approaches for catheter tip echo imaging are described and compared. This paper concludes with the results of automatic contour analysis of the inner arterial boundaries.

Cardiac Catheterization↗
PubMedDate not supplied

Evaluation of a semiautomatic contour detection approach in sequences of short-axis two-dimensional echocardiographic images.

Quantitative analysis of echocardiographic sequences has been limited by time-consuming and strenuous manual tracing approaches. To circumvent these disadvantages, we have developed the EchoCardiographic Measurement System (ECHO-CMS). ECHO-CMS employs the robust, model-based Minimum Cost Contour Tracking technique for semiautomatic detection of left ventricular (LV) endocardial contours in sequences of consecutive echocardiographic images. An evaluation study was carried out on 20 short-axis patient studies (10 transesophageal and 10 transthoracic studies), each consisting of 16 consecutive images covering approximately one cardiac cycle. The LV endocardial contours in the 320 images were analyzed both by manual tracing and semiautomatically. In addition, interobserver and intraobserver variabilities were determined for both techniques in two patients (32 images). Manual editing was required in only 57 (18%) of all 320 contours detected. Average processing time per patient for manual tracing was 25 minutes (of which 18 1/2 minutes was for drawing and corrections) and for semiautomatic tracing it was only 5 1/2 minutes (of which just 1 1/2 minutes was for corrections). Regression analysis showed excellent correspondence between manual and semiautomatic tracing: semiautomatic = 1.01 manual + 5.58%; r = 0.989; standard error of the estimate = 11.9% (n = 320 contours). Interobserver and intraobserver variabilities were smaller for semiautomatic than for manual tracing, although not in all cases statistically significant. In conclusion, semiautomatic LV short-axis endocardial contour detection by ECHO-CMS provides contours that are highly similar to those drawn by an expert; it is five to 10 times faster than manual tracing and reduces intraobserver and interobserver variabilities. This demonstrates that ECHO-CMS is a useful tool for clinical echocardiographic research studies.

Echocardiography↗