Biomedical subjects

J H C Reiber

Publications and source records attributed to J H C Reiber.

11 recordsLinked to original sources

PubMed2004

Automatic segmentation and plaque characterization in atherosclerotic carotid artery MR images.

In vivo MRI provides a means to non-invasively image and assess the morphological features of atherosclerotic carotid arteries. To assess quantitatively the degree of vulnerability and the type of plaque, the contours of the lumen, outer boundary of the vessel wall and plaque components, need to be traced. Currently this is done manually, which is time-consuming and sensitive to inter- and intra-observer variability. The goal of this work was to develop an automated contour detection technique for tracing the lumen, outer boundary and plaque contours in carotid MR short-axis black-blood images. Seventeen patients with carotid atherosclerosis were imaged using high-resolution in vivo MRI, generating a total of 50 PD- and T1-weighted MR images. These images were automatically segmented using the algorithm presented in this work, which combines model-based segmentation and fuzzy clustering to detect the vessel wall, lumen and lipid core boundaries. The results demonstrate excellent correspondence between automatic and manual area measurements for lumen (r = 0.92) and outer (r = 0.91), and acceptable correspondence for fibrous cap thickness (r = 0.71). Though further optimization is required, our algorithm is a powerful tool for automatic detection of lumen and outer boundaries, and characterization of plaque in atherosclerotic vessels.

Aged↗

PubMed2004

Patients with type 3 severe von Willebrand disease are not protected against atherosclerosis: results from a multicenter study in 47 patients.

BACKGROUND: The results of a number of studies in pigs and mice suggest that absence of von Willebrand factor (vWF) protects against the development of atherosclerosis. We studied whether patients with a complete deficiency of vWF (type 3 von Willebrand disease [vWD]) develop fewer atherosclerotic vessel wall changes than healthy controls. METHODS AND RESULTS: This study included 47 individuals with type 3 vWD and 84 healthy controls. Early atherosclerotic changes were assessed by measuring the thickness of the intima-media in the carotid and femoral arteries by B-mode ultrasonography. Advanced atherosclerotic changes were quantified by summing the maximal thickness of atherosclerotic plaques in the carotid and femoral arteries and were expressed as a plaque score. Established risk factors were determined to adjust for possible differences between the groups. We found no substantial difference in intima-media thickness between vWD patients and controls (adjusted difference for carotid artery 0.007 mm, 95% CI -0.022 to 0.036 mm; femoral artery 0.069 mm, 95% CI -0.056 to 0.19 mm). Similar proportions of patients and controls had atherosclerotic plaques (19% and 17%, respectively). No difference was found in the plaque score between groups (adjusted difference -0.22 mm, 95% CI -0.69 to 0.26). Among vWD patients, we found no effect of treatment with vWF concentrates on intima-media thickness or plaque score. CONCLUSIONS: The results of this study indicate that vWF does not play a substantial role in human atherogenesis.

Adult↗

PubMed2004

Serial six year quantitative angiographic follow up in asymptomatic patients following successful coronary angioplasty.

OBJECTIVE: To evaluate long term (six years) lumen changes after balloon angioplasty by using quantitative coronary angiography. METHODS: Complete serial quantitative coronary angiography (before and after angioplasty and at six months, three years, and six years) was performed in 100 patients with successful angioplasty and without subsequent repeated revascularisation. In all, 198 dilated segments were compared with 395 non-dilated segments that were obtained from non-target arteries of study patients. RESULTS: From six months to three years after angioplasty, minimum lumen diameter (MLD) increased significantly by 0.13 (0.28) (mean (SD)) mm in dilated segments and decreased significantly by 0.04 (0.27) mm in non-dilated segments. From three years to six years, MLD remained stable in dilated segments but decreased further (by 0.04 (0.28) mm) in non-dilated segments. Consequently, the DeltaMLD between six months and six years was larger in dilated segments than in non-dilated segments (0.12 (0.32) v -0.08 (0.34); p < 0.001). Further, DeltaMLD from six months to six years correlated positively with the percentage diameter stenosis (DS) at six months in each group (dilated segments r = 0.47, p < 0.0001; non-dilated segments r = 0.49, p < 0.0001). Multivariate analysis showed that the only independent predictor of DeltaMLD over six years for each group was the DS at six months. CONCLUSIONS: Lesion regression occurs within the first three years after angioplasty and reaches a plateau thereafter. Moreover, the stenosis severity at six months predicts the magnitude of late regression after angioplasty.

Adult↗

PubMed2004

Evaluation of three pose estimation algorithms for model-based roentgen stereophotogrammetric analysis.

Model-based roentgen stereophotogrammetric analysis (RSA) uses a three-dimensional surface model of an implant in order to estimate accurately the pose of that implant from a stereo pair of roentgen images. The technique is based on minimization of the difference between the actually projected contour of an implant and the virtually projected contour of a model of that same implant. The advantage of model-based RSA over conventional marker-based RSA is that it is not necessary to attach markers to the implant. In this paper, three pose estimation algorithms for model-based RSA are evaluated. The algorithms were assessed on the basis of their sensitivities to noise in the actual contour, to the amount of drop-outs in the actual contour, to the number of points in the actual contour and to shrinkage or expansion of the actual contour. The algorithms that were studied are the iterative inverse perspective matching (IIPM) algorithm, an algorithm based on minimization of the difference (DIF) between the actual contour and the virtual contour, and an algorithm based on minimization of the non-overlapping area (NOA) between the actual and virtual contour. The results of the simulation and phantom experiments show that the NOA algorithm does not fulfil the high accuracy that is necessary for model-based RSA. The IIPM and DIF algorithms are robust to the different distortions, making model-based RSA a possible replacement for marker-based RSA.

Algorithms↗

PubMed2003

Automated segmentation and analysis of vascular structures in magnetic resonance angiographic images.

The accurate assessment of the presence and extent of vascular disease, and planning of vascular interventions based on MRA requires the determination of vessel dimensions. The current standard is based on measuring vessel diameters on maximum intensity projections (MIPs) using calipers. In order to increase the accuracy and reproducibility of the method, automated analysis of the 3D MR data is required. A novel method for automatically determining the trajectory of the vessel of interest, the luminal boundaries, and subsequent the vessel dimensions is presented. The automated segmentation in 3D uses deformable models, combined with knowledge of the acquisition protocol. The trajectory determination was tested on 20 in vivo studies of the abdomen and legs. In 93% the detected trajectory followed the vessel. The luminal boundary detection was validated on contrast-enhanced (CE) MRA images of five stenotic phantoms. The results from the automated analysis correlated very well with the true diameters of the phantoms used in the in vitro study (r = 0.999, P < 0.001). MRA and x-ray angiography (XA) of the phantoms also correlated well (r = 0.895, P < 0.001). The average unsigned difference between the MRA and XA measurements was 0.08 +/- 0.05 mm. In conclusion, the automated approach allows the accurate assessment of vessel dimensions in MRA images.

Abdomen↗

PubMed2003

Multi-View Active Appearance Models: application to X-ray LV angiography and cardiac MRI.

This paper describes a Multi-View Active Appearance Model (AAM) for coherent segmentation of multiple cardiac views. Cootes' AAM framework was adapted by considering shapes and intensities from multiple views, while eliminating trivial difference in object pose in different views. This way, the coherence in organ shape and intensities between different views is modeled, and utilized during image search. The method is validated in two substantially different and novel applications: segmentation of combined end-diastolic and end-systolic left ventricular X-ray angiograms, and simultaneous segmentation of a combination of four chamber, two chamber and short-axis cardiac MR views.

Algorithms↗

PubMed2003

A new model-based RSA method validated using CAD models and models from reversed engineering.

Roentgen stereophotogrammetric analysis (RSA) was developed to measure micromotion of an orthopaedic implant with respect to its surrounding bone. A disadvantage of conventional RSA is that it requires the implant to be marked with tantalum beads. This disadvantage can potentially be resolved with model-based RSA, whereby a 3D model of the implant is used for matching with the actual images and the assessment of position and rotation of the implant. In this study, a model-based RSA algorithm is presented and validated in phantom experiments. To investigate the influence of the accuracy of the implant models that were used for model-based RSA, we studied both computer aided design (CAD) models as well as models obtained by means of reversed engineering (RE) of the actual implant. The results demonstrate that the RE models provide more accurate results than the CAD models. If these RE models are derived from the very same implant, it is possible to achieve a maximum standard deviation of the error in the migration calculation of 0.06 mm for translations in x- and y-direction and 0.14 mm for the out of plane z-direction, respectively. For rotations about the y-axis, the standard deviation was about 0.1 degrees and for rotations about the x- and z-axis 0.05 degrees. Studies with clinical RSA-radiographs must prove that these results can also be reached in a clinical setting, making model-based RSA a possible alternative for marker-based RSA.

Algorithms↗

PubMed2003

Lipoprotein(a) and ultrasonographically determined early atherosclerotic changes in the carotid and femoral artery.

Recent studies suggest that high lipoprotein(a) [Lp(a)] plasma levels are associated with symptomatic ischemic cardiovascular disease. We examined whether Lp(a) plasma levels are associated with early atherosclerotic vessel wall changes in a group of asymptomatic subjects. In a group of 142 asymptomatic men, the intima-media thickness (IMT) in the common carotid artery, the carotid bifurcation and the common femoral artery was determined by B-mode ultrasonography. In addition to Lp(a) levels, established risk factors, such as blood pressure and cholesterol levels were determined. Lipoprotein(a) values ranged from 2 mg L(-1) to 900 mg L(-1) (median 145 mg L(-1)). Linear regression analysis showed a clear association of IMT with the established risk factors but not with Lp(a) [regression coefficient carotid artery -0.0003, 95% confidence interval (CI) -0.002-0.001; regression coefficient femoral artery -0.0003, 95% CI -0.004-0.003]. We found no increased intima-media thickness in the carotid or femoral artery at high levels of Lp(a). Lipoprotein(a) levels are not associated with early atherosclerotic vessel wall changes in the carotid or femoral artery.

Adult↗

PubMed2003

Correlation between annual change in health status and computer tomography derived lung density in subjects with alpha1-antitrypsin deficiency.

BACKGROUND: There is increasing recognition that questionnaires of health status and lung density measurements are more sensitive tools for assessing progression of emphysema than forced expiratory volume in 1 second (FEV(1)) and transfer coefficient (KCO). A study was undertaken to investigate prospectively the correlation between annual change in health status and computer tomography (CT) derived lung density in subjects with alpha(1)-antitrypsin deficiency. METHODS: Twenty two patients of mean (SD) age 40.7 (9.2) years with ZZ type alpha(1)-antitrypsin deficiency were investigated at baseline and 30 months later by FEV(1) and KCO, St George Respiratory Questionnaire (SGRQ), and by a spiral CT scan of the chest. CT data of chest images were analysed using software designed for automated lung contour detection and lung density measurements. The density data were corrected for changes in inspiration levels. RESULTS: Changes in lung density, expressed as 15th percentile point or relative area below -950 HU, correlated well with changes in health status (SGRQ total score): R = -0.56, p = 0.007 or R = 0.6, p = 0.003. Neither changes in health status nor changes in lung density correlated significantly with changes in FEV(1) or changes in KCO. CONCLUSIONS: The SGRQ total score (which is a global measure in COPD) and lung density (a specific measure of emphysema) are sensitive to deterioration in patients with alpha(1)-antitrypsin deficiency. This finding may facilitate future studies with new drugs specific for emphysema, a frequently occurring component of COPD.

Adult↗

PubMed2002

Arterial intima-media thickness and its relationship with cardiovascular disease and atherosclerosis: a possible contribution of medium-sized arteries.

The intima-media thickness (IMT) of the arterial wall, measured by B-mode ultrasonography, has been related to cardiovascular disease and atherosclerosis in many studies, most of which have considered carotid and common femoral arteries. No study has related the IMT of medium-sized arteries (e.g. brachial) to the atherosclerotic process. The aim of this study was to evaluate whether more peripheral arteries (e.g. brachial, superficial femoral and popliteal) represent a good model in studies of arterial wall IMT, as well as carotid artery. Twenty-six male patients with demonstrated coronary artery disease (median age 63 yrs; range 41-70) and twenty-four male controls (median age 62 yrs; range 53-74) were studied. The far-wall IMT of the common carotid, brachial, superficial femoral and popliteal arteries was measured by high-resolution B-mode ultrasonography. Its relationship with ischemic cardiovascular disease and the presence of atherosclerotic plaques in all the arteries was also evaluated. Mean IMT values were higher in patients than controls, more so in superficial femoral artery (IMT difference 0.08 mm [95% confidence interval 0.02 - 0.14]) and popliteal artery (0.08 [0.01-0.15]) than in common carotid artery (0.02 [-0.07-0.11]) or brachial artery (0.01[-0.01-0.03]). The difference did not change after adjustment for age. The prevalence of plaques was consistently higher in patients than controls, except for brachial artery, in which no plaque was found either in patients and controls. In all the arteries except brachial we found an association between increase in IMT and number of plaques. Age was strongly related to the presence of plaques in the carotid artery, and less markedly in superficial femoral and popliteal arteries. The brachial artery does not seem a good model to study atherosclerosis by ultrasound measurements of arterial IMT, whereas superficial femoral and popliteal arteries might be chosen for these studies besides carotid artery.

Adult↗

PubMedDate not supplied

Relationship of peripheral arterial compliance and standard cardiovascular risk factors.

Abnormalities of peripheral arterial compliance are clinically useful markers of atherosclerosis and risk of vascular events. Local peripheral arterial compliance can be easily and accurately assessed in the clinic by computer-controlled pulse volume recordings (air plethysmography). The purpose of this study was to investigate the relationship between clinical cardiovascular risk factors, a surrogate of atherosclerotic burden, and peripheral arterial compliance in the thigh and calf determined by quantification of local pulse volume recordings in patients undergoing coronary angiography. Peripheral arterial compliance in the thigh and calf was measured in 346 patients undergoing diagnostic cardiac catheterization at 4 centers. Demographic and cardiovascular risk factor data were collected, and their relationship to local arterial compliance examined using a new device that assesses maximal local arterial volume change in an extremity segment. Pulse volume recordings detected decreased local arterial compliance in the thigh associated with a history of hypertension (p < 0.0001), diabetes mellitus (p = 0.0001), and hyperlipidemia (p = 0.0007). In the calf, this arterial compliance measure was associated with a history of hypertension (p < 0.0001) and diabetes mellitus (p = 0.002). Females had lower arterial compliance than males in the thigh (p = 0.003) and calf (p < 0.0001). Limited evidence of lower arterial compliance in the thigh was found for those with obesity (p = 0.07). This procedure also demonstrated that subjects with multiple cardiovascular risk factors had lower arterial compliance in the thigh than subjects with no or 1 risk factor (p = 0.0001). Peripheral arterial compliance determined by air plethysmography is strongly associated with standard cardiovascular risk factors. The noninvasive measurement of local arterial compliance by regional pulse volume recording may be a useful adjunct for cardiovascular risk stratification early in the course of the disease as well as for monitoring vascular response to therapy.

Aged↗