scholarly journals Optical Coherence Elastography Techniques for Carotid Arterial Wall Imaging

2021 ◽  
Author(s):  
Felix Nolte
Keyword(s):  
Axial Strain ◽  
Image Correlation ◽  
Arterial Blood Flow ◽  
Lateral Strain ◽  
Optical Coherence ◽  
Phantom Experiment ◽  
Arterial Blood ◽  
Speckle Patterns ◽  
Imaging Mode

In this thesis, elastography is evaluated in combination with optical coherence tomography (OCT). Two approaches to OCT based elastography, Digital image correlation (DIC) and Doppler optical coherence elastography (DOCE), are evaluated for an intravascular setup using in vivo images from a porcine carotid model. DIC tracks the displacement of speckle patterns in consecutive frames, allowing the calculation of axial and lateral strain. Rapid speckle decorrelation was observed in preprocessed structural images, affecting the tracking and limiting the feasibility of this algorithm. DOCE measures axial strain based on relative tissue velocities. Rotational movement of the imaging optical fibre was the biggest source of artefacts in this imaging mode, but could be removed with a newly developed algorithm, based on the phase change induced in a surrounding catheter. The standard deviation of phase after artefact removal, measured in a stationary phantom experiment, was ~0.2 rad, corresponding to a minimum detectable velocity of 792 μm/s at a Doppler angle of 20°. The sensitivity allowed the detection of arterial blood flow velocity and pattern and the detection of adjacent veins, but did not allow direct elastography.

scholarly journals Optical Coherence Elastography Techniques for Carotid Arterial Wall Imaging

2021 ◽  
Author(s):  
Felix Nolte
Keyword(s):  
Axial Strain ◽  
Image Correlation ◽  
Arterial Blood Flow ◽  
Lateral Strain ◽  
Optical Coherence ◽  
Phantom Experiment ◽  
Arterial Blood ◽  
Speckle Patterns ◽  
Imaging Mode

In this thesis, elastography is evaluated in combination with optical coherence tomography (OCT). Two approaches to OCT based elastography, Digital image correlation (DIC) and Doppler optical coherence elastography (DOCE), are evaluated for an intravascular setup using in vivo images from a porcine carotid model. DIC tracks the displacement of speckle patterns in consecutive frames, allowing the calculation of axial and lateral strain. Rapid speckle decorrelation was observed in preprocessed structural images, affecting the tracking and limiting the feasibility of this algorithm. DOCE measures axial strain based on relative tissue velocities. Rotational movement of the imaging optical fibre was the biggest source of artefacts in this imaging mode, but could be removed with a newly developed algorithm, based on the phase change induced in a surrounding catheter. The standard deviation of phase after artefact removal, measured in a stationary phantom experiment, was ~0.2 rad, corresponding to a minimum detectable velocity of 792 μm/s at a Doppler angle of 20°. The sensitivity allowed the detection of arterial blood flow velocity and pattern and the detection of adjacent veins, but did not allow direct elastography.

Abstract 249: Delayed Gene Transfer Increases Transgene Expression in Vein Grafts

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Liang Du ◽  
Jingwan Zhang ◽  
Alexander Clowes ◽  
David Dichek
Keyword(s):  
Gene Expression ◽  
Blood Flow ◽  
Gene Transfer ◽  
Transgene Expression ◽  
Ex Vivo ◽  
Arterial Blood Flow ◽  
Vein Grafts ◽  
Arterial Blood ◽  
En Face

Background Autogenous vein grafts are effective therapies for obstructive arterial disease. However, their long-term utility is limited by stenosis and occlusion. Genetic engineering of veins that prevents intimal hyperplasia and atherosclerosis could significantly improve the clinical utility of vein grafts. We recently reported that a helper-dependent adenoviral vector (HDAd) reduces atherosclerosis 4 wks after gene transfer in fat-fed rabbits and can express a therapeutic transgene (apo AI) in normal rabbit carotids for at least 48 wks. Use of HDAd for vein graft gene therapy will depend on achievement of similarly high and persistent transgene expression in grafted veins. Hypothesis We tested the hypothesis that Ad-mediated transgene expression in grafted veins (at an early time point) can be increased by varying the timing of gene transfer. Methods Rabbit external jugular veins were transduced by exposure to a beta galactosidase (b-gal)-expressing Ad: in situ either without (a) or with (b) immediate arterial grafting; c) ex vivo with grafting after overnight incubation with Ad; d) in vivo immediately after grafting and e) in vivo 4 wks after grafting (n = 6 - 19 veins/group). Transgene expression was measured in veins removed 3 d after Ad exposure by PCR quantitation of b-gal mRNA and by en-face planimetry of blue-stained area. Results B-gal transgene expression was higher in ungrafted veins than in veins grafted immediately after gene transfer (84 ± 17 vs 9.4 ± 2.0 arbitrary units (AU); P < 0.0001). Overnight incubation of veins with Ad increased gene expression ex vivo by 10-fold but neither this nor performing vector infusion immediately after grafting improved gene expression (11 ± 4.7 and 9.1 ± 1.8 AU; P > 0.9 for both vs immediately grafted veins). Delaying gene transfer until 4 wks after grafting significantly increased gene expression, to a level equivalent to transgene expression in ungrafted veins (61 ± 11 AU; P = 0.3 vs ungrafted veins). En face planimetry yielded similar results. Conclusions Exposure of a transduced vein to arterial blood flow is associated with significant loss of transgene expression. Transgene expression in grafted veins is significantly higher when gene transfer is performed 4 wks after exposure of the vein to arterial blood flow.

scholarly journals Speckle-modulating optical coherence tomography in living mice and humans

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Orly Liba ◽  
Matthew D. Lew ◽  
Elliott D. SoRelle ◽  
Rebecca Dutta ◽  
Debasish Sen ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Speckle Noise ◽  
Coherent Detection ◽  
Speckle Reduction ◽  
Optical Coherence ◽  
Coherent Noise ◽  
Speckle Patterns ◽  
Reduction Methods ◽  
Diagnostic Capabilities

Abstract Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner’s corpuscle in the human fingertip skin—features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Spiral Laminar Flow in Vivo

1996 ◽  
Vol 91 (1) ◽  
pp. 17-21 ◽  
Author(s):  
P. A. Stonebridge ◽  
P. R. Hoskins ◽  
P.L. Allan ◽  
J. F. F. Belch
Keyword(s):  
Blood Flow ◽  
Reverse Flow ◽  
Arterial Disease ◽  
Flow Patterns ◽  
Endothelial Damage ◽  
Arterial Blood Flow ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Blood Flow Patterns

1. Blood flow patterns are poorly understood despite their impact on arterial disease. There have been few measurements in vivo of the three-dimensional blood flow patterns; we present the results of such studies using a new non-invasive in-vivo method of examining biplanar arterial blood flow patterns. 2. Multiple colour Doppler ultrasound directional velocity images were obtained at two different beam target angles from the artery in the plane perpendicular to its axis. Ensemble average images were constructed; the absolute velocity and direction were calculated by compounding the left and right averaged images. Simple directional, non-directional velocity and vector maps were constructed. 3. Flow patterns were sampled in 11 healthy male volunteers at four points of the pulse cycle; peak systole, systolic downswing, diastolic reverse flow and diastolic forward flow and at three sites; the right common and distal superficial femoral and the left common femoral arteries. 4. Stable rotational flow was observed in all subjects, the direction of rotation varying between sides and individuals. 5. There are theoretical advantages to spiral laminar blood flow; the forward-directed, rotationally induced stability and reduction of laterally directed forces may reduce turbulence in the tapering branching arterial tree and at stenoses and have a beneficial effect on mechanisms of endothelial damage and repair.

scholarly journals Validation of the mean systemic filling pressure assessment with preserved arterial blood flow by comparing two methods of calculation 

2021 ◽  
Author(s):  
Roberto Alberto De Blasi ◽  
Stefano Finazzi
Keyword(s):  
Near Infrared ◽  
Venous Occlusion ◽  
Calculation Model ◽  
Arterial Blood Flow ◽  
Venous Compliance ◽  
Model Method ◽  
Arterial Blood ◽  
Methods Of Calculation ◽  
Multi Phase

Abstract Significance: We developed a method for measuring in vivo venular volumes and pressures in the limbs using near-infrared spectroscopy (NIRS).Aim: 36 We aimed to validate the NIRS methodology by comparing two independent methods of calculation based on different physiological approaches.Approach: Pressure-volumes curves were recorded following graded venous occlusion on the forearm. Values from a multi-phase model (method 1) were compared with data derived from a resistor-capacitance calculation model (method 2) based on arterial pressure and venous compliance. We tested these methods on 10 healthy participants at rest and during exercise and on 6 severely ill patients.Results: Pressure-volume curves measured by method 1 were comparable with those calculated by method 2. Venular volumes calculated using method 1 correlated linearly with those calculated using method 2 both in participants (R2 = 0.98, p < 0.001) and in patients (R2 = 0.94, p < 0.001). The Bland-Altman test showed a good agreement between methods with few values out of the range of ± 1.96 SD.Conclusions: Our findings showed that the NIRS methodology may be valid for the assessment of venular bed with no flow interruption. Further research will be required to confirm the relevance of methodology in the clinical setting.

Anterior Spinal Cord Contusion on Porcine Model

2014 ◽  
Author(s):  
Francis Cliche ◽  
Jean-Marc Mac-Thiong ◽  
Yvan Petit
Keyword(s):  
Spinal Cord ◽  
Porcine Model ◽  
Spinal Cord Injuries ◽  
Motor Evoked Potentials ◽  
Arterial Blood Flow ◽  
Bench Test ◽  
Arterial Blood ◽  
Compression Time ◽  
Spinal Cord Contusion

Animal models are commonly used to study spinal cord injuries (SCI). These models aim to better understand the traumatic behaviour of the spinal cord in vivo. However, experimental SCI models usually simulate a posterior contusion of the spinal cord on small animals, which do not reproduce completely the SCI mechanisms in humans. The objectives of the study are: 1) to develop an experimental anterior contusion of the spinal cord on porcine models, and 2) to compare biomechanical differences between ventral and dorsal approaches. A total of 6 specimens were tested in vivo with a drop weight bench test. Impacts were produced at T10 with 5mm diameter impactor of 50g and dropped from a height of 100mm. Compression time was set to 5min for 4 specimens (2 ventral, 2 dorsal) and 60min for 1 ventral and 1 dorsal. The outcome measures were the compression displacement, blood pressure, heart rate and macroscopic inspection of the spinal cord. This is the first study proposing an animal model of anterior SCI. Preliminary results suggest that there is a biomechanical difference between ventral and dorsal contusion approaches. A new bench test especially designed for ventral contusion will allow additional tests analyzing more variables, such as the motor evoked potentials and arterial blood flow.

A New Hexahedral Mesher for a Numerically Efficient Patient Specific Analysis of Arterial Blood Flow and Wall Shear Stress

2010 ◽  
Author(s):  
G. De Santis ◽  
P. Mortier ◽  
M. De Beule ◽  
P. Segers ◽  
P. Verdonck ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Imaging Techniques ◽  
Arterial Blood Flow ◽  
Patient Specific ◽  
Arterial Tree ◽  
Arterial Blood ◽  
Current Measuring ◽  
Wall Shear

Atherosclerosis depends on systemic risk factors but manifests itself as geometrically focal plaques, which appear in regions of the arterial tree experiencing low and/or oscillating Wall Shear Stress (WSS) such as outer edges of vessels bifurcations and highly curved vessels. Because direct measurements of WSS (differential quantity) in vivo are difficult due to limited spatial resolution offered by current measuring technologies (ultrasound, phase contrast MRI), an indirect approach is often taken, integrating medical imaging techniques (biplane angiography, CT, MRI) with Computational Fluid Dynamics (CFD) for patient specific WSS profiling.

Evidence for a rapid vasodilatory contribution to immediate hyperemia in rest-to-mild and mild-to-moderate forearm exercise transitions in humans

2004 ◽  
Vol 97 (3) ◽  
pp. 1143-1151 ◽  
Author(s):  
Natasha R. Saunders ◽  
Michael E. Tschakovsky
Keyword(s):  
Maximal Voluntary Contraction ◽  
Voluntary Contraction ◽  
Arterial Blood Flow ◽  
Vascular Conductance ◽  
Muscle Pump ◽  
Arterial Blood ◽  
Exercise Hyperemia ◽  
Forearm Vascular Conductance ◽  
Condition B

Controversy exists regarding the contribution of a rapid vasodilatory mechanism(s) to immediate exercise hyperemia. Previous in vivo investigations have exclusively examined rest-to-exercise (R-E) transitions where both the muscle pump and early vasodilator mechanisms may be activated. To isolate vasodilatory onset, the present study investigated the onset of exercise hyperemia in an exercise-to-exercise (E-E) transition, where no further increase in muscle pump contribution would occur. Eleven subjects lay supine and performed a step increase from rest to 3 min of mild (10% maximal voluntary contraction), rhythmic, dynamic forearm handgrip exercise, followed by a further step to moderate exercise (20% maximal voluntary contraction) in each of arm above ( condition A) or below ( condition B) heart level. Beat-by-beat measures of brachial arterial blood flow (Doppler ultrasound) and blood pressure (arterial tonometry) were performed. We observed an immediate increase in forearm vascular conductance in E-E transitions, and the magnitude of this increase matched that of the R-E transitions within each of the arm positions ( condition A: E-E, 52.8 ± 10.7 vs. R-E, 60.3 ± 11.7 ml·min−1·100 mmHg−1, P = 0.66; condition B: E-E, 43.2 ± 12.8 vs. R-E, 33.9 ± 8.2 ml·min−1·100 mmHg−1, P = 0.52). Furthermore, changes in forearm vascular conductance were identical between R-E and E-E transitions over the first nine contraction-relaxation cycles in condition A. The immediate and identical increase in forearm vascular conductance in R-E and E-E transitions within arm positions provides strong evidence that rapid vasodilation contributes to immediate exercise hyperemia in humans. Specific vasodilatory mechanisms responsible remain to be determined.

Sign in / Sign up

Export Citation Format

Share Document