Craig Lanning - Academia.edu (original) (raw)
Papers by Craig Lanning
ASME 2011 Summer Bioengineering Conference, Parts A and B, 2011
Input Impedance Accurately Quantifies Both Structural and Strain Stiffening of the Pulmonary Arterial Wall in the Chronically Hypoxic Neonatal Calf
B57. ENGINEERING THE LUNG: BIOMECHANICS OF THE LUNG CIRCULATION, 2009
Journal of Biomechanical Engineering
Clinical imaging methods are highly effective in the diagnosis of vascular pathologies, but they ... more Clinical imaging methods are highly effective in the diagnosis of vascular pathologies, but they do not currently provide enough detail to shed light on the cause or progression of such diseases, and would be hard pressed to foresee the outcome of surgical interventions. Greater detail of and prediction capabilities for vascular hemodynamics and arterial mechanics are obtained here through the coupling of clinical imaging methods with computational techniques. Three-dimensional, patient-specific geometric reconstructions of the pediatric proximal pulmonary vasculature were obtained from x-ray angiogram images and meshed for use with commercial computational software. Two such models from hypertensive patients, one with multiple septal defects, the other who underwent vascular reactivity testing, were each completed with two sets of suitable fluid and structural initial and boundary conditions and used to obtain detailed transient simulations of artery wall motion and hemodynamics in...
Validation of a Second-Generation Echo PIV System in Patient-Specific Carotid Artery Models: In Vitro Studies Using Pulsatile Flow
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT Echo Particle Image Velocimetry (Echo PIV), a novel opaque flow velocimetry technique de... more ABSTRACT Echo Particle Image Velocimetry (Echo PIV), a novel opaque flow velocimetry technique developed in our laboratory, has been shown to be an effective 2-D flow measurement velocimetry method in prior studies for both steady and pulsatile flow conditions [1,2]. However, certain limitations remained in the first-generation system. These include inconsistent spatial resolution caused by the phased array transducer, and the relatively low frame rate (i.e., lower temporal resolution) [2]. To overcome these limitations, we developed a second-generation Echo PIV system with a custom-designed linear array transducer (5–14MHz, center frequency 10MHz) and customized post-processing of backscatter data. In vascular applications, the new system can provide frame rates up to 1428 fps (temporal resolution of 0.7 ms). The transducer has a consistent axial resolution of 150um, which brings a maximal velocity field resolution around 500um in axial direction. An ECG module was also integrated to enable the capture of ensemble data over the cardiac cycle.
Dynamic three-dimensional reconstruction and modeling of cardiovascular anatomy in children with congenital heart disease using biplane angiography
Biomedical sciences instrumentation, 2004
Modeling and simulation of cardiovascular biomechanics and fluid dynamics from patient-specific d... more Modeling and simulation of cardiovascular biomechanics and fluid dynamics from patient-specific data is a continuing topic of research investigation. Several methodologies utilizing CT, MRI and ultrasound to re-create the three-dimensional anatomy of the cardiovascular system have been examined. Adaptation of these models to pediatric applications has not been studied as extensively. There is significant need for such techniques in pediatric congenital heart disease since local anatomy may exhibit highly unusual geometry, and three-dimensional information would be of significant use for surgical and interventional planning, biomechanical and fluid dynamic simulation, and patient counseling. We report here on the adaptation and application of a three-dimensional reconstruction technique that utilizes bi-plane angiographic images as the base data sets. The method has been validated in a variety of adult imaging situations including coronary artery imaging and intervention. The method ...
Elastin Remodeling Of The Pulmonary Conduit Arteries Reduces The Physiological Impacts Of Collagen Stiffening In The Hypoxic Calf Model Of Pulmonary Hypertension
D59. PULMONARY VASCULAR MECHANICS AND VASOREACTIVITY, 2010
University of Colorado /, Aurora, CO, United States of America, University of Colorado Denver, Au... more University of Colorado /, Aurora, CO, United States of America, University of Colorado Denver, Aurora, CO, United States of America, 1 ... University of Colorado, Boulder, CO, United States of America, University of Colorado, Denver /, Aurora, CO, United States of America
Free Recovery Effects of Shape-Memory Polymers for Cardiovascular Stents
MRS Proceedings, 2005
ABSTRACT The shape-memory effect was examined in polymer stents intended for cardiovascular appli... more ABSTRACT The shape-memory effect was examined in polymer stents intended for cardiovascular applications. Four polymer networks were synthesized from poly(ethylene glycol) dimethacrylate and tert-butyl acrylate with 10 wt% and 20 wt% crosslinker, and with glass transition temperatures (Tg) of 52°C and 55°C. Solid and 50% porous stents were manufactured and tested for free strain recoverability at temperatures at or just above 37°C. Stents with lower glass transition temperatures and a higher degree of crosslinking recovered faster than their counterparts. Lower deformation (packaging) temperatures and higher recovery temperatures induce more rapid recovery. The presence of geometrical features, such as pores, initiated recovery sooner, but had negligible influence on overall recovery.
Echo particle image velocimetry (Echo Piv): a novel ultrasound-based method for the in vivo measurement of wall shear stress in human carotid arteries
In-Vivo Pulmonary Vascular Stiffness Obtained From Color M-Mode Tissue Doppler Imaging And Pressure Measurements Predicts Clinical Outcomes Better Than Indexed Pulmonary Vascular Resistance In Pediatric Patients With Pulmonary Arterial Hypertension
D26. PULMONARY VASCULAR AND RIGHT HEART PHYSIOLOGY, 2011
Journal of functional biomaterials, 2012
Tissue engineering strategies employing biomaterials have made great progress in the last few dec... more Tissue engineering strategies employing biomaterials have made great progress in the last few decades. However, the tissues of the brain and spinal cord pose unique challenges due to a separate immune system and their nature as soft tissue. Because of this, neural tissue engineering for the brain and spinal cord may require re-establishing biocompatibility and functionality of biomaterials that have previously been successful for tissue engineering in the body. The goal of this review is to briefly describe the distinctive properties of the central nervous system, specifically the neuroimmune response, and to describe the factors which contribute to building polymer hydrogels compatible with this tissue. These factors include polymer chemistry, polymerization and degradation, and the physical and mechanical properties of the hydrogel. By understanding the necessities in making hydrogels biocompatible with tissue of the brain and spinal cord, tissue engineers can then functionalize t...
BMC anesthesiology, 2014
Endotracheal tubes are frequently used to establish alternate airways. Precise placement of the t... more Endotracheal tubes are frequently used to establish alternate airways. Precise placement of the tubes must be maintained to prevent serious complications. Several methods for fixation of endotracheal tubes are available. Available methods vary widely in form and functionality. Due to the unpredictable and dynamic nature of circumstances surrounding intubation, thorough evaluation of tube restraints may help reduce airway accidents such as tube dislodgement and unplanned extubation. Seven different tube-restraint combinations were compared against themselves and one another at a series of discrete angles (test points) covering a hemisphere on the plane of the face. Force values for tube motion of 2 cm and 5 cm (or failure) were recorded for 3 pull tests, at each angle, for each method of tube fixation. All methods showed variation in the force required for tube motion with angle of force application. When forces were averaged over all test points, for each fixation technique, differe...
Measurement of Valve Lesion Morphology and Aorta / Flow-Jet Patterns in Bicuspid Aortic Valve Patients
ASME 2009 Summer Bioengineering Conference, Parts A and B, 2009
ABSTRACT Bicuspid aortic valve (BAV) patients are identified by a lesion of the tricuspid aortic ... more ABSTRACT Bicuspid aortic valve (BAV) patients are identified by a lesion of the tricuspid aortic leaflets in which only two ‘functional’ leaflets are visibly present. This lesion occurs in 0.5–2% of the population and is accompanied by a significant incidence of morbidity and mortality related to aortic valve dysfunction, aortic dilatation, aortic aneurysm, and aortic dissection. [1] The pathogenesis of the malformation has been postulated to be the result of a congenital or inflammatorily-mediated fusion of two of the three aortic leaflets. In addition, BAV is accompanied by a variety of heterogeneous complications and is considered a complex disease with many cofactors, the importance of which continue to be debated. Among these cofactors, the most commonly identified vascular manifestation is aortic dilatation. [1] There are two hypotheses for this manifestation: the first postulates the coexistence of BAV and genetically-based aortic fragility; the second proposes that BAV morphology and incomplete valve opening induces hemodynamic forces that influence structure and function at the aorta.
Use of Cardiac Phase-Contrast MRI to Examine Hemodynamics and Wall Deformation Within the Aortic Root for Patients With Bicuspid Aortic Valves
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT
Initial Investigation of Reduced Wall Shear Stress in the Pulmonary Arteries of Hypertension Patients Using Phase Contrast MRI
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT A number of concomitant factors are thought to contribute to an increase in the mean pul... more ABSTRACT A number of concomitant factors are thought to contribute to an increase in the mean pulmonary arterial pressure (MPAP) of pulmonary arterial hypertension (PAH) patients, such as increased pulmonary vascular resistance (PVR), increased blood flow (due to septal defects), and a decrease in wall distensibility.[1] This is in contrast to the normal pulmonary circuit, which is characterized by compliant artery walls and a low PVR, resulting in a low MPAP with little flow and pressure wave reflection. The influence of pathologic MPAP’s on proximal hemodynamic factors such as artery size, flow pulse waveforms, and wall shear stress (WSS) is unclear. Since these factors are known pathophysiological stimuli in the production of molecules that alter vascular tone and matrix properties,[2] we set out to quantify the geometry, flow, and WSS of the left, right and main pulmonary arteries (LPA, RPA, & MPA) of control and PAH patients using phase-contrast magnetic resonance imaging (PC-MRI).
Proceedings - IEEE Ultrasonics Symposium, 2009
Recent in-vitro and in-vivo validation studies confirmed the accuracy of echo particle image velo... more Recent in-vitro and in-vivo validation studies confirmed the accuracy of echo particle image velocimetry (echo PIV), a simple non-invasive means of measuring multi-component blood velocity vectors. Echo PIV should also be useful for direct measurement of wall shear stress (WSS) in clinical studies. However, calculation of WSS requires accurate delineation of vessel walls in ultrasound images, which may be problematic when conventional segmentation techniques are used. In this paper, we proposed two methods for segmenting contrast enhanced B-mode images. The first is based on the intensity profile of ultrasound images, termed intensity-based edge detection (IBED) and the second based on the movement of microbubbles, termed movement-based quadratic difference (MBQD). The parameters related with the two methods were optimized over large sets of microbubble images acquired from human carotid vessels using an echo PIV system (Illumasonix LLC, Boulder, CO). A validation study on the two algorithms was carried out against manual delineations on both common carotid artery (CCA) and carotid bifurcation images, with 20 frames for each group. The inter-observer variability of three manual delineations, in pixels (about 80 µm/pixel), was 0.9±0.4, 1.3±0.6, 1.3±0.6 on CCA images, and 2.5±1.0, 3.9±1.1, 2.3±1.1 on bifurcation images. The absolute difference (mean±SD) between each computer-generated contour and the ground truths, taken as the average of three manual delineations, were 1.3±0.8, 3.8±0.8, 5.3±0.5 on CCA images, and 2.3±0.9, 4.6±1.3, 6.3±0.6 on bifurcation images, for the MBQD, IBED and active contour methods, respectively. The MBQD method shows comparable performance with manual delineations on particle images even with poor intima-media layer quality.
Conduit Arteries In The Rat And Calf Express Different Material Property Changes In Response To Hypoxia-Induced Pulmonary Hypertension
D59. PULMONARY VASCULAR MECHANICS AND VASOREACTIVITY, 2010
University of Colorado, Boulder, CO, United States of America, University of Colorado /, Aurora, ... more University of Colorado, Boulder, CO, United States of America, University of Colorado /, Aurora, CO, United States of America, University 1 ... Corresponding author's email: steven.lammers@colorado.edu ... Rationale: While it has long been established that the ...
Quantitative Measures Of Collagen And Elastin Microstructure In Health And Pulmonary Hypertension
C61. PULMONARY HYPERTENSION: EXPERIMENTAL MODELS II, 2011
/ Thematic Poster Session / Tuesday, May 17/8:15 AM-4:30 PM ... / Area H, Hall B (Upper Level), C... more / Thematic Poster Session / Tuesday, May 17/8:15 AM-4:30 PM ... / Area H, Hall B (Upper Level), Colorado Convention Center ... Quantitative Measures Of Collagen And Elastin Microstructure In Health And Pulmonary Hypertension ... , K. Hunter , L. Tian , P. Kao , H. Qi , C. ...
2010 IEEE International Ultrasonics Symposium, 2010
Echo Particle Image Velocimetry (Echo PIV) has great potential as a non-invasive, simple-to-use h... more Echo Particle Image Velocimetry (Echo PIV) has great potential as a non-invasive, simple-to-use hemodynamic vascular profiling technique. Results generated through the analysis of radio frequency (RF) data have shown to be accurate under in vitro and in vivo testing settings. However, most ultrasound (US) imaging systems do not provide RF data but provide image output using the DICOM standard. An important issue when analyzing DICOM-coded images using the Echo PIV method is how to reduce the effects of noise introduced during postprocessing. In this work, a new Echo PIV analysis algorithm was developed to analyze DICOM images. In the algorithm, a quasilinear transform first operates on the cross-correlation maps of each interrogation window, after which a modified ensemble average method is used to estimate time-averaged velocity field from multiple image pairs. This approach was validated against theory using measurements of fully developed laminar pipe flow, thus indicating that DICOM-image based Echo PIV is possible. We further demonstrate that the instantaneous velocity maps of certain pulsatile flow configurations were actually improved by the new method compared to the RF-based Echo PIV results.
Patient-Specific Fluid Structure Interaction Simulation Applied to Evaluating Hemodynamics Within the Total Cavopulmonary Connection
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT Congenital heart disease (CHD), a life-threatening birth disorder, is the most common ge... more ABSTRACT Congenital heart disease (CHD), a life-threatening birth disorder, is the most common genetic disorder with an incidence rate as high as 1% in neonates (36,000 cases in 2006). Amongst these children, one out of four has single ventricle anomaly. As a palliative rather than a curative means for vascular reconstruction, the “Fontan” palliation has been used to produce stable hemodynamic states, at least for a limited period of time. However, the majority of post-Fontan patients faces a high risk of mortality and morbidity [1], and will have to undergo heart transplant eventually due to the excess load imposed on the single ventricle by the systemic resistance.
Measurement of In-Vivo Pulmonary Vascular Impedance in Two Animal Models of Pulmonary Hypertension
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT Pulmonary vascular input impedance has been increasingly promoted as an important diagno... more ABSTRACT Pulmonary vascular input impedance has been increasingly promoted as an important diagnostic for pulmonary arterial hypertension (PAH) [1,2]. The gold-standard clinical diagnostic for the disease, pulmonary vascular resistance (PVR), quantifies only the mean resistance to flow but ignores the impact of vascular stiffness and flow pulsatility, which in PAH can represent up to 40% of the total load presented to the right ventricle. PVR has also been found to be only a moderate predictor of PAH outcomes [3]. The first of these deficiencies is not present in impedance; clinical studies have found the sum of its 1st and 2nd harmonic moduli to have good correlation (r2 = 0.812) with global pulmonary vascular stiffness (PVS) [2], a hemodynamically-measured quantifier of vascular stiffness. Additionally, the 0th harmonic modulus of impedance has excellent correlation to PVR (r2 = 0.974); thus, it also quantifies the resistive load. Moreover, because PVS has recently been found as a valuable determinant of mortality in PAH [4], we believe that impedance, as a combined measure of PVR and PVS, might be an excellent predictor of disease outcomes.
ASME 2011 Summer Bioengineering Conference, Parts A and B, 2011
Input Impedance Accurately Quantifies Both Structural and Strain Stiffening of the Pulmonary Arterial Wall in the Chronically Hypoxic Neonatal Calf
B57. ENGINEERING THE LUNG: BIOMECHANICS OF THE LUNG CIRCULATION, 2009
Journal of Biomechanical Engineering
Clinical imaging methods are highly effective in the diagnosis of vascular pathologies, but they ... more Clinical imaging methods are highly effective in the diagnosis of vascular pathologies, but they do not currently provide enough detail to shed light on the cause or progression of such diseases, and would be hard pressed to foresee the outcome of surgical interventions. Greater detail of and prediction capabilities for vascular hemodynamics and arterial mechanics are obtained here through the coupling of clinical imaging methods with computational techniques. Three-dimensional, patient-specific geometric reconstructions of the pediatric proximal pulmonary vasculature were obtained from x-ray angiogram images and meshed for use with commercial computational software. Two such models from hypertensive patients, one with multiple septal defects, the other who underwent vascular reactivity testing, were each completed with two sets of suitable fluid and structural initial and boundary conditions and used to obtain detailed transient simulations of artery wall motion and hemodynamics in...
Validation of a Second-Generation Echo PIV System in Patient-Specific Carotid Artery Models: In Vitro Studies Using Pulsatile Flow
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT Echo Particle Image Velocimetry (Echo PIV), a novel opaque flow velocimetry technique de... more ABSTRACT Echo Particle Image Velocimetry (Echo PIV), a novel opaque flow velocimetry technique developed in our laboratory, has been shown to be an effective 2-D flow measurement velocimetry method in prior studies for both steady and pulsatile flow conditions [1,2]. However, certain limitations remained in the first-generation system. These include inconsistent spatial resolution caused by the phased array transducer, and the relatively low frame rate (i.e., lower temporal resolution) [2]. To overcome these limitations, we developed a second-generation Echo PIV system with a custom-designed linear array transducer (5–14MHz, center frequency 10MHz) and customized post-processing of backscatter data. In vascular applications, the new system can provide frame rates up to 1428 fps (temporal resolution of 0.7 ms). The transducer has a consistent axial resolution of 150um, which brings a maximal velocity field resolution around 500um in axial direction. An ECG module was also integrated to enable the capture of ensemble data over the cardiac cycle.
Dynamic three-dimensional reconstruction and modeling of cardiovascular anatomy in children with congenital heart disease using biplane angiography
Biomedical sciences instrumentation, 2004
Modeling and simulation of cardiovascular biomechanics and fluid dynamics from patient-specific d... more Modeling and simulation of cardiovascular biomechanics and fluid dynamics from patient-specific data is a continuing topic of research investigation. Several methodologies utilizing CT, MRI and ultrasound to re-create the three-dimensional anatomy of the cardiovascular system have been examined. Adaptation of these models to pediatric applications has not been studied as extensively. There is significant need for such techniques in pediatric congenital heart disease since local anatomy may exhibit highly unusual geometry, and three-dimensional information would be of significant use for surgical and interventional planning, biomechanical and fluid dynamic simulation, and patient counseling. We report here on the adaptation and application of a three-dimensional reconstruction technique that utilizes bi-plane angiographic images as the base data sets. The method has been validated in a variety of adult imaging situations including coronary artery imaging and intervention. The method ...
Elastin Remodeling Of The Pulmonary Conduit Arteries Reduces The Physiological Impacts Of Collagen Stiffening In The Hypoxic Calf Model Of Pulmonary Hypertension
D59. PULMONARY VASCULAR MECHANICS AND VASOREACTIVITY, 2010
University of Colorado /, Aurora, CO, United States of America, University of Colorado Denver, Au... more University of Colorado /, Aurora, CO, United States of America, University of Colorado Denver, Aurora, CO, United States of America, 1 ... University of Colorado, Boulder, CO, United States of America, University of Colorado, Denver /, Aurora, CO, United States of America
Free Recovery Effects of Shape-Memory Polymers for Cardiovascular Stents
MRS Proceedings, 2005
ABSTRACT The shape-memory effect was examined in polymer stents intended for cardiovascular appli... more ABSTRACT The shape-memory effect was examined in polymer stents intended for cardiovascular applications. Four polymer networks were synthesized from poly(ethylene glycol) dimethacrylate and tert-butyl acrylate with 10 wt% and 20 wt% crosslinker, and with glass transition temperatures (Tg) of 52°C and 55°C. Solid and 50% porous stents were manufactured and tested for free strain recoverability at temperatures at or just above 37°C. Stents with lower glass transition temperatures and a higher degree of crosslinking recovered faster than their counterparts. Lower deformation (packaging) temperatures and higher recovery temperatures induce more rapid recovery. The presence of geometrical features, such as pores, initiated recovery sooner, but had negligible influence on overall recovery.
Echo particle image velocimetry (Echo Piv): a novel ultrasound-based method for the in vivo measurement of wall shear stress in human carotid arteries
In-Vivo Pulmonary Vascular Stiffness Obtained From Color M-Mode Tissue Doppler Imaging And Pressure Measurements Predicts Clinical Outcomes Better Than Indexed Pulmonary Vascular Resistance In Pediatric Patients With Pulmonary Arterial Hypertension
D26. PULMONARY VASCULAR AND RIGHT HEART PHYSIOLOGY, 2011
Journal of functional biomaterials, 2012
Tissue engineering strategies employing biomaterials have made great progress in the last few dec... more Tissue engineering strategies employing biomaterials have made great progress in the last few decades. However, the tissues of the brain and spinal cord pose unique challenges due to a separate immune system and their nature as soft tissue. Because of this, neural tissue engineering for the brain and spinal cord may require re-establishing biocompatibility and functionality of biomaterials that have previously been successful for tissue engineering in the body. The goal of this review is to briefly describe the distinctive properties of the central nervous system, specifically the neuroimmune response, and to describe the factors which contribute to building polymer hydrogels compatible with this tissue. These factors include polymer chemistry, polymerization and degradation, and the physical and mechanical properties of the hydrogel. By understanding the necessities in making hydrogels biocompatible with tissue of the brain and spinal cord, tissue engineers can then functionalize t...
BMC anesthesiology, 2014
Endotracheal tubes are frequently used to establish alternate airways. Precise placement of the t... more Endotracheal tubes are frequently used to establish alternate airways. Precise placement of the tubes must be maintained to prevent serious complications. Several methods for fixation of endotracheal tubes are available. Available methods vary widely in form and functionality. Due to the unpredictable and dynamic nature of circumstances surrounding intubation, thorough evaluation of tube restraints may help reduce airway accidents such as tube dislodgement and unplanned extubation. Seven different tube-restraint combinations were compared against themselves and one another at a series of discrete angles (test points) covering a hemisphere on the plane of the face. Force values for tube motion of 2 cm and 5 cm (or failure) were recorded for 3 pull tests, at each angle, for each method of tube fixation. All methods showed variation in the force required for tube motion with angle of force application. When forces were averaged over all test points, for each fixation technique, differe...
Measurement of Valve Lesion Morphology and Aorta / Flow-Jet Patterns in Bicuspid Aortic Valve Patients
ASME 2009 Summer Bioengineering Conference, Parts A and B, 2009
ABSTRACT Bicuspid aortic valve (BAV) patients are identified by a lesion of the tricuspid aortic ... more ABSTRACT Bicuspid aortic valve (BAV) patients are identified by a lesion of the tricuspid aortic leaflets in which only two ‘functional’ leaflets are visibly present. This lesion occurs in 0.5–2% of the population and is accompanied by a significant incidence of morbidity and mortality related to aortic valve dysfunction, aortic dilatation, aortic aneurysm, and aortic dissection. [1] The pathogenesis of the malformation has been postulated to be the result of a congenital or inflammatorily-mediated fusion of two of the three aortic leaflets. In addition, BAV is accompanied by a variety of heterogeneous complications and is considered a complex disease with many cofactors, the importance of which continue to be debated. Among these cofactors, the most commonly identified vascular manifestation is aortic dilatation. [1] There are two hypotheses for this manifestation: the first postulates the coexistence of BAV and genetically-based aortic fragility; the second proposes that BAV morphology and incomplete valve opening induces hemodynamic forces that influence structure and function at the aorta.
Use of Cardiac Phase-Contrast MRI to Examine Hemodynamics and Wall Deformation Within the Aortic Root for Patients With Bicuspid Aortic Valves
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT
Initial Investigation of Reduced Wall Shear Stress in the Pulmonary Arteries of Hypertension Patients Using Phase Contrast MRI
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT A number of concomitant factors are thought to contribute to an increase in the mean pul... more ABSTRACT A number of concomitant factors are thought to contribute to an increase in the mean pulmonary arterial pressure (MPAP) of pulmonary arterial hypertension (PAH) patients, such as increased pulmonary vascular resistance (PVR), increased blood flow (due to septal defects), and a decrease in wall distensibility.[1] This is in contrast to the normal pulmonary circuit, which is characterized by compliant artery walls and a low PVR, resulting in a low MPAP with little flow and pressure wave reflection. The influence of pathologic MPAP’s on proximal hemodynamic factors such as artery size, flow pulse waveforms, and wall shear stress (WSS) is unclear. Since these factors are known pathophysiological stimuli in the production of molecules that alter vascular tone and matrix properties,[2] we set out to quantify the geometry, flow, and WSS of the left, right and main pulmonary arteries (LPA, RPA, & MPA) of control and PAH patients using phase-contrast magnetic resonance imaging (PC-MRI).
Proceedings - IEEE Ultrasonics Symposium, 2009
Recent in-vitro and in-vivo validation studies confirmed the accuracy of echo particle image velo... more Recent in-vitro and in-vivo validation studies confirmed the accuracy of echo particle image velocimetry (echo PIV), a simple non-invasive means of measuring multi-component blood velocity vectors. Echo PIV should also be useful for direct measurement of wall shear stress (WSS) in clinical studies. However, calculation of WSS requires accurate delineation of vessel walls in ultrasound images, which may be problematic when conventional segmentation techniques are used. In this paper, we proposed two methods for segmenting contrast enhanced B-mode images. The first is based on the intensity profile of ultrasound images, termed intensity-based edge detection (IBED) and the second based on the movement of microbubbles, termed movement-based quadratic difference (MBQD). The parameters related with the two methods were optimized over large sets of microbubble images acquired from human carotid vessels using an echo PIV system (Illumasonix LLC, Boulder, CO). A validation study on the two algorithms was carried out against manual delineations on both common carotid artery (CCA) and carotid bifurcation images, with 20 frames for each group. The inter-observer variability of three manual delineations, in pixels (about 80 µm/pixel), was 0.9±0.4, 1.3±0.6, 1.3±0.6 on CCA images, and 2.5±1.0, 3.9±1.1, 2.3±1.1 on bifurcation images. The absolute difference (mean±SD) between each computer-generated contour and the ground truths, taken as the average of three manual delineations, were 1.3±0.8, 3.8±0.8, 5.3±0.5 on CCA images, and 2.3±0.9, 4.6±1.3, 6.3±0.6 on bifurcation images, for the MBQD, IBED and active contour methods, respectively. The MBQD method shows comparable performance with manual delineations on particle images even with poor intima-media layer quality.
Conduit Arteries In The Rat And Calf Express Different Material Property Changes In Response To Hypoxia-Induced Pulmonary Hypertension
D59. PULMONARY VASCULAR MECHANICS AND VASOREACTIVITY, 2010
University of Colorado, Boulder, CO, United States of America, University of Colorado /, Aurora, ... more University of Colorado, Boulder, CO, United States of America, University of Colorado /, Aurora, CO, United States of America, University 1 ... Corresponding author's email: steven.lammers@colorado.edu ... Rationale: While it has long been established that the ...
Quantitative Measures Of Collagen And Elastin Microstructure In Health And Pulmonary Hypertension
C61. PULMONARY HYPERTENSION: EXPERIMENTAL MODELS II, 2011
/ Thematic Poster Session / Tuesday, May 17/8:15 AM-4:30 PM ... / Area H, Hall B (Upper Level), C... more / Thematic Poster Session / Tuesday, May 17/8:15 AM-4:30 PM ... / Area H, Hall B (Upper Level), Colorado Convention Center ... Quantitative Measures Of Collagen And Elastin Microstructure In Health And Pulmonary Hypertension ... , K. Hunter , L. Tian , P. Kao , H. Qi , C. ...
2010 IEEE International Ultrasonics Symposium, 2010
Echo Particle Image Velocimetry (Echo PIV) has great potential as a non-invasive, simple-to-use h... more Echo Particle Image Velocimetry (Echo PIV) has great potential as a non-invasive, simple-to-use hemodynamic vascular profiling technique. Results generated through the analysis of radio frequency (RF) data have shown to be accurate under in vitro and in vivo testing settings. However, most ultrasound (US) imaging systems do not provide RF data but provide image output using the DICOM standard. An important issue when analyzing DICOM-coded images using the Echo PIV method is how to reduce the effects of noise introduced during postprocessing. In this work, a new Echo PIV analysis algorithm was developed to analyze DICOM images. In the algorithm, a quasilinear transform first operates on the cross-correlation maps of each interrogation window, after which a modified ensemble average method is used to estimate time-averaged velocity field from multiple image pairs. This approach was validated against theory using measurements of fully developed laminar pipe flow, thus indicating that DICOM-image based Echo PIV is possible. We further demonstrate that the instantaneous velocity maps of certain pulsatile flow configurations were actually improved by the new method compared to the RF-based Echo PIV results.
Patient-Specific Fluid Structure Interaction Simulation Applied to Evaluating Hemodynamics Within the Total Cavopulmonary Connection
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT Congenital heart disease (CHD), a life-threatening birth disorder, is the most common ge... more ABSTRACT Congenital heart disease (CHD), a life-threatening birth disorder, is the most common genetic disorder with an incidence rate as high as 1% in neonates (36,000 cases in 2006). Amongst these children, one out of four has single ventricle anomaly. As a palliative rather than a curative means for vascular reconstruction, the “Fontan” palliation has been used to produce stable hemodynamic states, at least for a limited period of time. However, the majority of post-Fontan patients faces a high risk of mortality and morbidity [1], and will have to undergo heart transplant eventually due to the excess load imposed on the single ventricle by the systemic resistance.
Measurement of In-Vivo Pulmonary Vascular Impedance in Two Animal Models of Pulmonary Hypertension
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT Pulmonary vascular input impedance has been increasingly promoted as an important diagno... more ABSTRACT Pulmonary vascular input impedance has been increasingly promoted as an important diagnostic for pulmonary arterial hypertension (PAH) [1,2]. The gold-standard clinical diagnostic for the disease, pulmonary vascular resistance (PVR), quantifies only the mean resistance to flow but ignores the impact of vascular stiffness and flow pulsatility, which in PAH can represent up to 40% of the total load presented to the right ventricle. PVR has also been found to be only a moderate predictor of PAH outcomes [3]. The first of these deficiencies is not present in impedance; clinical studies have found the sum of its 1st and 2nd harmonic moduli to have good correlation (r2 = 0.812) with global pulmonary vascular stiffness (PVS) [2], a hemodynamically-measured quantifier of vascular stiffness. Additionally, the 0th harmonic modulus of impedance has excellent correlation to PVR (r2 = 0.974); thus, it also quantifies the resistive load. Moreover, because PVS has recently been found as a valuable determinant of mortality in PAH [4], we believe that impedance, as a combined measure of PVR and PVS, might be an excellent predictor of disease outcomes.