Peter Brands - Academia.edu (original) (raw)

Papers by Peter Brands

Proceedings of Spie the International Society For Optical Engineering, 2009

Ultrasonic Imaging, Oct 1, 2001

The reciprocal of the arterial pulse wave velocity contains crucial information about the mechani... more The reciprocal of the arterial pulse wave velocity contains crucial information about the mechanical characteristics of the arterial wall but is difficult to assess noninvasively in vivo. In this paper, a new method to assess local pulse wave velocity (PWV) is presented. To this end, multiple adjacent distension waveforms are determined simultaneously along a short arterial segment, using a single 2D-vessel wall tracking system with a high frame rate (651 Hz). Each B-mode image consists of 16 echo lines spanning a total width of 15.86 mm. Dedicated software has been developed to extract the end-diastolic diameter from the B-mode image and the distension waveforms from the underlying radiofrequency (rf) information for each echo-line. The PWV is obtained by determining the ratio of the temporal and spatial gradient of adjacent distension velocity waveforms. The proposed method is verified in a phantom and in the common carotid artery (CCA) of humans. Phantom experiments show a high concordance between the PWV obtained from 2D distension velocity waveforms (4.21 +/- 0.02 m/s) and the PWV determined using two pressure catheters (4.26 +/- 0.02 m/s). Assuming linear spatial gradients, the PWV can also be obtained in vivo for CCA and averages to 5.5 +/- 1.5 m/s (intersubject variation, n = 23), which compares well to values found in literature. Furthermore, intrasubject PWV compares well with those calculated using the Bramwell-Hill equation. It can be concluded that the PWV can be obtained from the spatial and temporal gradient if the spatial gradient is linear over the observed length of the artery, i.e. the artery should be homogenous in diameter and distension and the influence of reflections must be small.

Archives of Acoustics, 2014

Journal of Hypertension Supplement Official Journal of the International Society of Hypertension, Jul 31, 1992

To determine whether there are inhomogeneities in arterial wall distensibility with age and hyper... more To determine whether there are inhomogeneities in arterial wall distensibility with age and hypertension. It has been known for some years that arteries lose their elasticity with increasing age and that they are less distensible in subjects with established and borderline hypertension than in age-matched controls. In the carotid artery changes in arterial wall properties are not homogeneously distributed along the bifurcation. Both in older subjects and in those with borderline hypertension the loss of distensibility is most pronounced in the carotid artery bulb, while in borderline hypertensives the proximal part of the bulb, where the baroreceptors are predominantly located, is more affected than other parts of the bulb. The loss of distensibility in the bulb may explain the diminished baroreceptor sensitivity observed in older subjects. The pronounced involvement of the proximal part of the bulb in the decreased distensibility in borderline hypertensives suggests that local stiffening, probably leading to disturbed baroreceptor sensitivity, may contribute to the development of hypertension in these patients. The pattern of inhomogeneities in wall distensibility in borderline hypertensives at a relatively young age (average 38 years) is similar to that seen in older normotensive subjects (average age 57 years), supporting the idea that arteries age faster in hypertensives than in normotensives. In management of the borderline hypertensive patient, consideration should be given to preventing early ageing of the arterial wall rather than following arterial blood pressure.

Archives des maladies du coeur et des vaisseaux

ABSTRACT

European Journal of Ultrasound

European journal of ultrasound : official journal of the European Federation of Societies for Ultrasound in Medicine and Biology, 1999

To integrate methods for non-invasive assessment of vessel wall properties (diastolic diameter, d... more To integrate methods for non-invasive assessment of vessel wall properties (diastolic diameter, distension waveform and intima-media thickness) and hemodynamic properties (blood flow velocity and shear rate distribution) of large arteries by means of dedicated ultrasound signal processing. we have developed an arterial laboratory (ART-lab) system. ART-lab consists of software running on a standard personal computer, equipped with a data acquisition card for the acquisition of radio frequency (RF) ultrasound signals obtained with a conventional echo scanner. It operates either (1) off-line or (2) in real-time. Real-time operation is restricted to the assessment of vessel wall properties because of limitations in computational power. This paper provides an overview of ART-lab ultrasound radio frequency data acquisition and dedicated RF-signal processing methods. The capabilities of the system are illustrated with some typical applications. ART-lab in real-time mode is a useful tool fo...

IFMBE Proceedings, 2009

ABSTRACT An algorithm for performing fully automatic morphological analysis of the common carotid... more ABSTRACT An algorithm for performing fully automatic morphological analysis of the common carotid artery (CCA) in longitudinal ultrasound (US) B-mode scans is introduced. Arterial position, curvature and diameter are automatically estimated offline without human supervision. The CCA is automatically recognized by applying a method based on decimation, template matching and clustering to the first pair of US frames. This allows automatic placement of seed points in the CCA lumen. Next a sustain-attack filter (SAF) is applied in order to get raw estimates for CCA wall positions, used to deduct the CCA centerline in a region of interest (ROI). Arterial orientation and curvature are estimated by fitting a second order polynomial through the centerline. Subsequently the lines of sight in the ROI are vertically re-aligned based on the centerline so that the arterial walls shift to an approximately horizontal position, allowing subsequent lateral smoothing with horizontal kernels. This directional preprocessing attenuates speckle modulation without blurring perpendicularly to CCA walls. The SAF is then re-applied, yielding smooth delineation of both near and far wall. CCA diameter, orientation and curvature radius are calculated within the ROI. Automatic tracking of CCA movements is performed frame-by-frame. The method is tested on 30 US recordings (duration 6 seconds each) from 10 healthy volunteers. The algorithm successfully detects, without any user interference, CCA position, curvature and diameter for every subject considered. Comparison of results with and without curvature-compensated lateral smoothing shows significant decreases in the standard deviation of wall position estimates when the proposed pre-processing is applied. Correcting for local orientation at each line of sight yields the real CCA diameter, eliminating the error due to a non-perpendicular US beam orientation.

Ultrasound in Medicine & Biology, 1994

Ultrasound in medicine & biology, 2010

Transcutaneous ultrasound measurements of common carotid artery (CCA) diameter and intima-media t... more Transcutaneous ultrasound measurements of common carotid artery (CCA) diameter and intima-media thickness (IMT) give insight on arterial dynamics and anatomy, both correlating well with atherosclerosis and risk of cardiovascular disease. We propose a novel automatic algorithm to estimate CCA diameter and IMT in ultrasound (US) images, based on separate analysis of anterior and posterior CCA walls and able to distinguish internal (intima-intima) and external (adventitia-adventitia) diameter. The method combines off-line signal- and image-processing techniques to accommodate echo images acquired at a frame rate of 30 Hz and composed directly from RF data, circumventing digital video-grabbing. Segmentation consists of automatic CCA recognition, followed by adventitial delineation performed with a sustain-attack filter with exponentially decaying reference functions. Intimal delineation is then based on the multiscale anisotropic barycenter (MAB), which is an extension of a known deline...