Adriaan Campo

Magnetic Resonance Imaging and Spectroscopy Reveal Differential Hippocampal Changes in Anhedonic and Resilient Subtypes of the Chronic Mild Stress Rat Model

BACKGROUND Repeated exposure to mild stressors induces anhedonia-a core symptom of major depressive disorder-in up to 70% of the stress-exposed rats, whereas the remaining show resilience to stress. This chronic mild stress (CMS) model is well documented as an animal model of major depressive disorder. We examined the morphological, microstructural, and metabolic characteristics of the hippocampus in anhedonic and stress resilient rats that may mark the differential behavioral outcome. METHODS Anhedonic (n = 8), resilient (n = 8), and control (n = 8) rats were subjected to in vivo diffusion kurtosis imaging, high-resolution three-dimensional magnetic resonance imaging and proton magnetic resonance spectroscopy. RESULTS Diffusion kurtosis parameters were decreased in both CMS-exposed groups. A significant inward displacement in the ventral part of the right hippocampus was apparent in the resilient subjects and an increase of the glutamate:total creatine ratio and N-acetylaspartylglutamate:total creatine was observed in the anhedonic subjects. CONCLUSIONS Diffusion kurtosis imaging discloses subtle substructural changes in the hippocampus of CMS-exposed animals irrespective of their anhedonic or resilient nature. In contrast, proton magnetic resonance spectroscopy and magnetic resonance imaging-based shape change analysis of the hippocampus allowed discrimination of these two subtypes of stress sensitivity. Although the precise mechanism discriminating their behavior is yet to be elucidated, the present study underlines the role of the hippocampus in the etiology of depression and the induction of anhedonia. Our results reflect the potency of noninvasive magnetic resonance methods in preclinical settings with key translational benefit to and from the clinic.

Non-invasive technique for assessment of vascular wall stiffness using laser Doppler vibrometry

It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter is best known when estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery in the groin, but may also be determined locally from short-distance measurements on a short vessel segment. In this work, we propose a novel, non-invasive, non-contact laser Doppler vibrometry (LDV) technique for evaluating PWV locally in an elastic vessel. First, the method was evaluated in a phantom setup using LDV and a reference method. Values correlated significantly between methods (R <= 0.973 (p <= 0.01)); and a Bland-Altman analysis indicated that the mean bias was reasonably small (mean bias <= -2.33 ms). Additionally, PWV was measured locally on the skin surface of the CCA in 14 young healthy volunteers. As a preliminary validation, PWV measured on two locations along the same artery was compared. Local PWV was found to be between 3 and 20 m s(-1), which is in line with the literature (PWV = 5-13 m s(-1)). PWV assessed on two different locations on the same artery correlated significantly (R = 0.684 (p < 0.01)). In summary, we conclude that this new non-contact method is a promising technique to measure local vascular stiffness in a fully non-invasive way, providing new opportunities for clinical diagnosing.

Digital image correlation for full-field time-resolved assessment of arterial stiffness

Abstract. Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19  m/s as measured with DIC and between 5.14 and 6.58  m/s as measured with US, with a maximum absolute difference of 2.78  m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid–structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics.

Dual-beam laser Doppler vibrometer for measurement of pulse wave velocity in elastic vessels

When a fluid flowing through an elastic vessel is subjected to a sudden change in pressure gradient, pressure pulses will propagate through the fluid. Velocity of these pulse waves (PWV) can be determined by simultaneous detection of wall distension on two separate points on the vessel wall, along its trajectory. PWV depends on wall stiffness, and under certain circumstances, wall stiffness can be calculated from the propagation velocity. Optical interferometry is a noncontacting technique that allows measurement of wall distension on discrete locations. In this work we propose a miniaturized dual-beam laser Doppler vibrometer (LDV) to measure wall distension simultaneously at two locations. Our dual-beam LDV is based on a single laser source and one acousto-optic modulator with as much as possible of the interferometer optics shared among the different beams. The dual-beam LDV was used for simultaneous detection of wall distension of several elastic vessels of different stiffness. We found that PWV as measured in elastic vessels agrees well with theoretically expected values, and measurement precision is better than 5%. Moreover, the dual-beam LDV performs almost as good as commercial systems for detection of PWV. The dual-beam LDV can have applications in cardiovascular risk management. Stiffness of large arteries has a very good predictive value for cardiovascular disease and overall mortality. This parameter can be estimated from arterial PWV. Current methods to measure arterial PWV suffer from several shortcomings. A dual-beam LDV can offer substantial advantages over existing techniques.

Laser Doppler vibrometry for assessment of arteriosclerosis: A first step towards validation

It has been shown that in cardiovascular risk management, stiffness of large arteries has a very good predictive value for cardiovascular disease and mortality. This parameter can be estimated from the pulse wave velocity (PWV) measured between the common carotid artery (CCA) in the neck and femoral artery (FA) in the groin. However PWV can also be measured locally in the CCA, using non-invasive methods such as ultrasound (US) or laser Doppler vibrometry (LDV). Potential of the latter approach was already explored in previous research, and in this work a first step towards clinical validation is made. 50 hypertension II/III patients aged between 30 and 65 participate in the study. Patients were asked to remain sober for 4 hours prior to the measurements. The trajectory of the CCA in the neck was determined by a trained clinician guided by an US probe. 3 laser Doppler vibrometer (LDV) systems were aimed along the CCA. PWV was then calculated from the distance between beams and the time-shift between wavefo...

Application of a new four-channel vibrometer for determination of atherosclerosis: Further advances towards a handheld device

Cardiovascular diseases (CD) are the leading cause of death worldwide and their prevalence is expected to rise. Important in the etiology of CD is the stiffening of the large arteries (arteriosclerosis) and plaque formation (atherosclerosis) in the common carotid artery (CCA). Increasing evidence shows that both arteriosclerosis and atherosclerosis can be detected by assessing pulse wave velocity (PWV) in the CCA, and several techniques focus on the detection of PWV in this structure. In previous studies, laser Doppler vibrometry (LDV) was proposed as an approach to detect arterial stiffness. In the present work, a compact four-channel LDV system is introduced for PWV detection. Four phantom arteries were assessed mimicking real life cardiovascular pathologies. Due to the high sensitivity and the increased spatial and temporal resolution of the LDV system, PWV could be assessed, and even local changes in phantom architecture could be detected. The system could potentially be used to detect arteriosclerosis and arterial plaque during cardiovascular screening.

Application of a four-channel vibrometer system for detection of arterial stiffness

Cardiovascular diseases (CD) are the most important cause of death in the world and their prevalence is only rising. A significant aspect in the etiology of CD is the stiffening of the large arteries (arteriosclerosis) and plaque formation (atherosclerosis) in the common carotid artery (CCA) in the neck. As shown by increasing evidence, both conditions can be detected by assessing pulse wave velocity (PWV) in the CCA, and several approaches allow local detection of PWV, including ultrasound (US) and magnetic resonance imaging (MRI). In previous studies, laser Doppler vibrometry (LDV) was introduced as an approach to assess arterial stiffness. In the present work, a new, compact four-channel LDV system is used for PWV detection in four phantom arteries mimicking real life CCA conditions. The high sensitivity of the LDV system allowed PWV to be assessed, and even local changes in phantom architecture could be detected. This method has potential for cardiovascular screening, as it allows arteriosclerosis ass...

Digital Image Correlation for Full-Field High Resolution Assessment of Leaf Growth

Changes in shape and size of the leaves are driven by several transient growth parameters. Being able to assess resulting changes at a high temporal and spatial resolution is a necessary tool for studying biochemical principles of leaf development, and for construction of leaf growth models. In this short communication, a technique based on the use of 2D digital image correlation (DIC) is presented to track leaf growth. A speckle pattern with orange fluorescent paint was applied on three leaves of the sycamore maple (Acer pseudoplatanus) at an arbitrary point in growth. For ten consecutive days, images of the growing leaves were analyzed with DIC, revealing leaf growth patterns. The patterns were similar for three leaves, and results corresponded both with literature data of leaf growth and with leaf area measurements using manual segmentation of leaf images. We demonstrate that DIC can be applied for tracking leaf growth. Based on the results, a detailed macro-model for leaf growth can be developed or environmental effects on leaf growth can be assessed, amongst other possible applications.

High Speed Fringe Pattern Topography for Detection of the Arterial Pulse Wave in Vivo

Cardiovascular disease is one of the most important health problems worldwide and its prevalence is expected to rise [1]. A screening method to detect risk for cardiovascular events is much sought after. A major factor in cardiovascular problems is increased arterial stiffness, or arteriosclerosis [2]. Every heartbeat, a pulse wave emerges from the heart, propagating through the arteries at a velocity in the range of 5-13m/s in a healthy person: the pulse wave velocity (PWV). PWV is proportional to arterial stiffness, and PWV has a strong predictive value for cardiovascular disease and overall mortality. A possible approach to detect arteriosclerosis is to measure PWV locally, at the common carotid artery (CCA) in the neck. The CCA is easily accessible, and it has great physiological importance in onset and progress of cardiovascular health problems [3]. In the proposed work, PWV is assessed in the CCA using fringe pattern topography (FPT).