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Mutlu O, Salman HE, Al-Thani H, El-Menyar A, Qidwai UA, Yalcin HC. How does hemodynamics affect rupture tissue mechanics in abdominal aortic aneurysm: Focus on wall shear stress derived parameters, time-averaged wall shear stress, oscillatory shear index, endothelial cell activation potential, and relative residence time. Comput Biol Med 2023; 154:106609. [PMID: 36724610 DOI: 10.1016/j.compbiomed.2023.106609] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 01/19/2023] [Accepted: 01/22/2023] [Indexed: 01/24/2023]
Abstract
An abdominal aortic aneurysm (AAA) is a critical health condition with a risk of rupture, where the diameter of the aorta enlarges more than 50% of its normal diameter. The incidence rate of AAA has increased worldwide. Currently, about three out of every 100,000 people have aortic diseases. The diameter and geometry of AAAs influence the hemodynamic forces exerted on the arterial wall. Therefore, a reliable assessment of hemodynamics is crucial for predicting the rupture risk. Wall shear stress (WSS) is an important metric to define the level of the frictional force on the AAA wall. Excessive levels of WSS deteriorate the remodeling mechanism of the arteries and lead to abnormal conditions. At this point, WSS-related hemodynamic parameters, such as time-averaged WSS (TAWSS), oscillatory shear index (OSI), endothelial cell activation potential (ECAP), and relative residence time (RRT) provide important information to evaluate the shear environment on the AAA wall in detail. Calculation of these parameters is not straightforward and requires a physical understanding of what they represent. In addition, computational fluid dynamics (CFD) solvers do not readily calculate these parameters when hemodynamics is simulated. This review aims to explain the WSS-derived parameters focusing on how these represent different characteristics of disturbed hemodynamics. A representative case is presented for spatial and temporal formulation that would be useful for interested researchers for practical calculations. Finally, recent hemodynamics investigations relating WSS-related parameters with AAA rupture risk assessment are presented. This review will be useful to understand the physical representation of WSS-related parameters in cardiovascular flows and how they can be calculated practically for AAA investigations.
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Affiliation(s)
- Onur Mutlu
- Biomedical Research Center, Qatar University, Doha, Qatar
| | - Huseyin Enes Salman
- Department of Mechanical Engineering, TOBB University of Economics and Technology, Ankara, Turkey
| | - Hassan Al-Thani
- Department of Surgery, Trauma and Vascular Surgery, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha, Qatar
| | - Ayman El-Menyar
- Department of Surgery, Trauma and Vascular Surgery, Hamad General Hospital, Hamad Medical Corporation, P.O. Box 3050, Doha, Qatar; Clinical Medicine, Weill Cornell Medical College, Doha, Qatar
| | - Uvais Ahmed Qidwai
- Department of Computer Science Engineering, Qatar University, Doha, Qatar
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Doolette DJ, Mitchell SJ. Extended lifetimes of bubbles at hyperbaric pressure may contribute to inner ear decompression sickness during saturation diving. J Appl Physiol (1985) 2022; 133:517-523. [PMID: 35834629 DOI: 10.1152/japplphysiol.00121.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inner ear decompression sickness (IEDCS) may occur after upward or downward excursions in saturation diving. Previous studies in non-saturation diving strongly suggest IEDCS is caused by arterialization of small venous bubbles across intracardiac or intrapulmonary right-to-left shunts, and bubble growth through inward diffusion of supersaturated gas when they arrive in the inner ear. The present study used published saturation diving data, and models of inner ear inert gas kinetics and bubble dynamics in arterial conditions to assess whether IEDCS after saturation excursions could also be explained by arterialization of venous bubbles, and whether such bubbles might survive longer and be more likely to reach the inner ear under deep saturation diving conditions. Previous data show that saturation excursions produce venous bubbles. Modelling shows gas supersaturation in the inner ear persists longer than in the brain after such excursions, explaining why the inner ear would be more vulnerable to injury by arriving bubbles. Estimated survival of arterialized bubbles is significantly prolonged at high ambient pressure such that bubbles large enough to be filtered by pulmonary capillaries but able to cross right-to-left shunts are more likely to survive transit to the inner ear than at the surface. IEDCS after saturation excursions is plausibly caused by arterialization of venous bubbles whose prolonged arterial survival at deep depths suggests larger bubbles in greater numbers reach the inner ear.
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Affiliation(s)
- David J Doolette
- Department of Anaesthesiology, The University of Auckland, Auckland, New Zealand
| | - Simon J Mitchell
- Department of Anaesthesiology, The University of Auckland, Auckland, New Zealand
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3
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Takizawa Y, Song Y, Tani T, Yoshioka T, Takahashi K, Abe T, Ro-Mase T, Ishiko S, Sakai J, Minamide K, Akiba M, Tatsukawa T, Azuma N, Yoshida A. Retinal Blood Velocity Waveform Characteristics With Aging and Arterial Stiffening in Hypertensive and Normotensive Subjects. Transl Vis Sci Technol 2021; 10:25. [PMID: 34792557 PMCID: PMC8606851 DOI: 10.1167/tvst.10.13.25] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose We aimed to explore the velocity waveform characteristics of the retinal artery associated with age and the cardio-ankle vascular index (CAVI) as a conventional arterial stiffness marker by applying the Doppler optical coherence tomography (DOCT) flowmeter. Methods In this cross-sectional study, DOCT flowmeter imaging was performed in 66 participants aged 21 to 83 years (17 men, 49 women) with no history of eye diseases and no systemic diseases, except for hypertension. Retinal blood velocity waveform was analyzed where several parameters in time (upstroke time, T1, T2, T3, and T4) and area under the waveform (area elevation, area declination, A1, A2, A3, and A4) were extracted. Systolic blood pressure–adjusted Pearson's coefficients were calculated to determine the correlations of each parameter with age or CAVI. Results Corrected upstroke time (UTc) was the waveform parameter most positively correlated with age (r = 0.497, P < 0.001). Area declination was the waveform parameter most negatively correlated with age (r = −0.682, P < 0.001) and CAVI (r = −0.601, P < 0.001). Conclusions We extracted the waveform parameters associated with the risks of arterial stiffening. The velocity waveform analysis of the retinal artery with DOCT flowmeter potentially could become a new method for arterial stiffness identification. Translational Relevance DOCT flowmeter could evaluate arterial stiffening in a different way from the conventional method of measuring arterial stiffening using pressure waveform. Because the DOCT flowmeter can easily, quickly, and noninvasively provide a retinal blood velocity waveform, this system could be useful as a routine medical examination for arterial stiffening.
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Affiliation(s)
- Yoshitaka Takizawa
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Youngseok Song
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Tomofumi Tani
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Takafumi Yoshioka
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Kengo Takahashi
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Tsubasa Abe
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Tomoko Ro-Mase
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | - Satoshi Ishiko
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
| | | | | | | | - Takamitsu Tatsukawa
- Department of Vascular Surgery, Asahikawa Medical University, Asahikawa, Japan
| | - Nobuyoshi Azuma
- Department of Vascular Surgery, Asahikawa Medical University, Asahikawa, Japan
| | - Akitoshi Yoshida
- Department of Ophthalmology, Asahikawa Medical University, Asahikawa, Japan
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4
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Magor-Elliott SRM, Fullerton CJ, Richmond G, Ritchie GAD, Robbins PA. A dynamic model of the body gas stores for carbon dioxide, oxygen, and inert gases that incorporates circulatory transport delays to and from the lung. J Appl Physiol (1985) 2021; 130:1383-1397. [PMID: 33475459 PMCID: PMC8354828 DOI: 10.1152/japplphysiol.00764.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Many models of the body’s gas stores have been generated for specific purposes. Here, we seek to produce a more general purpose model that: 1) is relevant for both respiratory (CO2 and O2) and inert gases; 2) is based firmly on anatomy and not arbitrary compartments; 3) can be scaled to individuals; and 4) incorporates arterial and venous circulatory delays as well as tissue volumes so that it can reflect rapid transients with greater precision. First, a “standard man” of 11 compartments was produced, based on data compiled by the International Radiation Protection Commission. Each compartment was supplied via its own parallel circulation, the arterial and venous volumes of which were based on reported tissue blood volumes together with data from a detailed anatomical model for the large arteries and veins. A previously published model was used for the blood gas chemistry of CO2 and O2. It was not permissible ethically to insert pulmonary artery catheters into healthy volunteers for model validation. Therefore, validation was undertaken by comparing model predictions with previously published data and by comparing model predictions with experimental data for transients in gas exchange at the mouth following changes in alveolar gas composition. Overall, model transients were fastest for O2, intermediate for CO2, and slowest for N2. There was good agreement between model estimates and experimentally measured data. Potential applications of the model include estimation of closed-loop gain for the ventilatory chemoreflexes and improving the precision associated with multibreath washout testing and respiratory measurement of cardiac output. NEW & NOTEWORTHY A model for the body gas stores has been generated that is applicable to both respiratory gases (CO2 and O2) and inert gases. It is based on anatomical details for organ volumes and blood contents together with anatomical details of the large arteries. It can be scaled to the body size and composition of different individuals. The model enables mixed venous gas compositions to be predicted from the systemic arterial compositions.
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Affiliation(s)
| | | | - Graham Richmond
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, United Kingdom
| | - Grant A D Ritchie
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, United Kingdom
| | - Peter A Robbins
- Department of Physiology, Anatomy and Genetics, University of Oxford, United Kingdom
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5
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Steinlauf S, Hazan Shenberger S, Halak M, Liberzon A, Avrahami I. Aortic arch aneurysm repair - Unsteady hemodynamics and perfusion at different heart rates. J Biomech 2021; 121:110351. [PMID: 33794471 DOI: 10.1016/j.jbiomech.2021.110351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 02/22/2021] [Indexed: 11/27/2022]
Abstract
The aortic arch aneurysm is a complex disease that requires branching of one or more aortic arch vessels and can be fatal if left untreated. In this in vitro study, we examine the effect of the treatment approach on the unsteady hemodynamics and blood perfusion to the upper vessel's in models of an aortic arch aneurysm, and of the three common repair approaches: open-chest surgical repair, chimney, and hybrid approach. A particle image velocimetry method was used to quantify the unsteady hemodynamics in the four models simulated in a mock circulatory loop, to evaluate unsteady hemodynamic parameters and measure perfusion to the brain and the upper body. According to the findings, in terms of perfusion to the brain and upper body, the surgery model has the highest flow rate comparing to the other models in most heart-rate conditions. It also shows oscillatory parameters in the upper vessels which in normal arteries are correlated with a better arterial function. Between the two endovascular procedures, the hybrid model exhibits slightly better hemodynamic characteristics than the chimney model, with lower shear stresses and more oscillatory flow and WSS in the upper vessels. The hybrid model had lower perfusion flow rates to upper vessels during rest conditions (90BPM). However, unlike the other models, perfusion in the hybrid model increased with heart rate, thus at 135 BPM, it results in flow rate to upper vessels similar to that of the chimney model. The results of this study may shed light on future endograft' design and placement techniques.
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Affiliation(s)
- Shirly Steinlauf
- Department of Mechanical Engineering and Mechatronics, Ariel University, Israel; School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Moshe Halak
- Department of Vascular Surgery, the Chaim Sheba Medical Center, Tel Hashomer, Israel
| | - Alex Liberzon
- School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978, Israel
| | - Idit Avrahami
- Department of Mechanical Engineering and Mechatronics, Ariel University, Israel.
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De Nisco G, Gallo D, Siciliano K, Tasso P, Lodi Rizzini M, Mazzi V, Calò K, Antonucci M, Morbiducci U. Hemodialysis arterio-venous graft design reducing the hemodynamic risk of vascular access dysfunction. J Biomech 2020; 100:109591. [PMID: 31902610 DOI: 10.1016/j.jbiomech.2019.109591] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/04/2019] [Accepted: 12/18/2019] [Indexed: 11/18/2022]
Abstract
Although arterio-venous grafts (AVGs) represent the second choice as permanent vascular access for hemodialysis, this solution is still affected by a relevant failure rate due to graft thrombosis, and development of neointimal hyperplasia (IH) at the distal vein. As a key role in these processes has been attributed to the abnormal hemodynamics establishing in the distal vein, the optimization of AVGs design aimed at minimizing flow disturbances would reduce AVG hemodynamic-related risks. In this study we used computational fluid dynamics to investigate the impact of alternative AVG designs on the reduction of IH and thrombosis risk at the distal venous anastomosis. The performance of the newly designed AVGs was compared to that of commercially available devices. In detail, a total of eight AVG models in closed-loop configuration were constructed: two models resemble the commercially available straight conventional and helical-shaped AVGs; six models are characterized by the insertion of a flow divider (FD), straight or helical shaped, differently positioned inside the graft. Unfavorable hemodynamic conditions were analyzed by assessing the exposure to disturbed shear at the distal vein. Bulk flow was investigated in terms of helical blood flow features, potential thrombosis risk, and pressure drop over the graft. Findings from this study clearly show that using a helically-shaped FD located at the venous side of the graft could induce beneficial helical flow patterns that, minimizing flow disturbances, reduce the IH-related risk of failure at the distal vein, with a clinically irrelevant increase in thrombosis risk and pressure drop over the graft.
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Affiliation(s)
- Giuseppe De Nisco
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Diego Gallo
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Katia Siciliano
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Paola Tasso
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Maurizio Lodi Rizzini
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Valentina Mazzi
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | - Karol Calò
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy
| | | | - Umberto Morbiducci
- Polito(BIO)Med Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy.
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Yin O, Woods A, Koos B, DeVore G, Afshar Y. Central hemodynamics are associated with fetal outcomes in pregnancies of advanced maternal age. Pregnancy Hypertens 2019; 19:67-73. [PMID: 31923879 DOI: 10.1016/j.preghy.2019.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/17/2019] [Accepted: 12/23/2019] [Indexed: 10/25/2022]
Abstract
OBJECTIVES Age is a known risk factor for both maternal cardiovascular disease and adverse outcomes in pregnancy. We aimed to characterize the hemodynamic profiles in pregnancies of advanced maternal age (AMA) and correlate these with fetal outcomes. STUDY DESIGN This was a prospective observational study of pregnancies undergoing antenatal testing. Maternal hemodynamics were measured non-invasively using an imaging probe at the descending aorta and the Uscom BP + arm cuff utilizing pulse pressure wave analysis. The Wilcoxon rank-sum test, Fisher's exact test, and Spearman rank correlation test were used for statistical analysis in R. MAIN OUTCOME MEASURES Hemodynamic measurements, neonatal birthweight. RESULTS Twenty-one AMA and twenty-four control patients were enrolled. Mean age ± SD was 39 ± 3.22 in the AMA cohort and 28 ± 4.32 in the control cohort (p < 0.001). AMA patients were evaluated at a later gestational age (36 4/7 weeks) compared to control (34 1/7 weeks, p = 0.02). Between groups, there was no difference in BMI, race, hypertensive disease, diabetes, asthma, drug use, or indication for antenatal testing. 38% (AMA) and 37% (control) had hypertensive disorders of pregnancy. In AMA patients but not control patients, cardiac output (r = 0.52, p = 0.01), systemic vascular resistance (r = -0.53, p = 0.01), and systemic vascular resistance index (r = -0.62, p = 0.002) were significantly correlated with neonatal birthweight percentile. CONCLUSIONS Hemodynamic alterations consistent with a low output, high resistance cardiovascular circuit were associated with lower birthweight in AMA, but not in control pregnancies.
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Affiliation(s)
- Ophelia Yin
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, United States
| | - Allison Woods
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, United States
| | - Brian Koos
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, United States
| | - Greggory DeVore
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, United States
| | - Yalda Afshar
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, United States.
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Harloff A, Hagenlocher P, Lodemann T, Hennemuth A, Weiller C, Hennig J, Vach W. Retrograde aortic blood flow as a mechanism of stroke: MR evaluation of the prevalence in a population-based study. Eur Radiol 2019; 29:5172-5179. [PMID: 30877458 DOI: 10.1007/s00330-019-06104-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 02/07/2019] [Accepted: 02/12/2019] [Indexed: 10/27/2022]
Abstract
OBJECTIVES Retrograde blood flow from complex atheroma in the descending aorta (DAo) has only recently been described as a potential mechanism of stroke. However, prevalence of this mechanism in the general population and the exact factors influencing stroke risk are unclear. METHODS One hundred twenty-six consecutively recruited inhabitants of Freiburg, Germany, between 20 and 80 years of age prospectively underwent 3-T MRI. Aortic plaque location and thickness were determined by 3D T1 MRI (1 mm3). 4D flow MRI (spatial/temporal resolution 2 mm3/20 ms) and dedicated software were used to determine prevalence and extent of flow reversal and potential embolization from DAo plaques. Flow was correlated with baseline characteristics and echocardiographic and MRI parameters (aortic diameter, wall thickness, and pulse wave velocity). RESULTS The maximum length of retrograde blood flow connecting the DAo with the left subclavian artery (LSA) increased from 16.1 ± 8.3 mm in 20-29-year-old to 24.7 ± 11.7 mm in 70-80-year-old subjects, correlated with age (r = 0.37; p < 0.001), and was lower in females (p = 0.003). Age was the only independent predictor of increased flow reversal. Complex DAo plaques ≥ 4-mm thickness were found in eight subjects (6.3%) and were connected with the LSA, left common carotid artery, and brachiocephalic trunk in 8 (100%), 1 (12.5%), and 0 (0%) cases, respectively. CONCLUSIONS Retrograde blood flow from the DAo was very frequent. However, potential retrograde embolization was rare due to the low incidence of complex DAo plaques. The magnitude of flow reversal and prevalence of complex atheroma increased with age. Thus, older patients with aortic atherosclerosis are especially vulnerable to this stroke mechanism. KEY POINTS • 4D flow MRI allows in vivo visualization and quantification of individual and three-dimensional blood flow patterns within the thoracic aorta including retrograde components. • This population-based study showed that blood flow reversal from the proximal descending aorta to the brain-supplying great arteries is very frequent and able to reach all brain territories. The extent of such flow reversal increases with age and with the extent of aortic atherosclerosis. • The combination of blood flow reversal with plaque rupture in the proximal descending aorta constitutes a potential stroke mechanism that should be considered in future trials and in the management of stroke patients in clinical routine.
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Affiliation(s)
- Andreas Harloff
- Department of Neurology and Neurophysiology, Medical Center, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany. .,Faculty of Medicine, University of Freiburg, Freiburg, Germany.
| | - Paul Hagenlocher
- Department of Neurology and Neurophysiology, Medical Center, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thomas Lodemann
- Department of Neurology and Neurophysiology, Medical Center, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Anja Hennemuth
- Institute for Cardiovascular Computer-Assisted Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Cornelius Weiller
- Department of Neurology and Neurophysiology, Medical Center, University of Freiburg, Breisacherstr. 64, 79106, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jürgen Hennig
- Faculty of Medicine, University of Freiburg, Freiburg, Germany.,Department of Diagnostic Radiology, MR Physics, Medical Center - University of Freiburg, Freiburg, Germany
| | - Werner Vach
- Institute for Medical Biometry and Statistics, Medical Faculty and Medical Center, University of Freiburg, Freiburg, Germany.,Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland
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The Atheroprotective Nature of Helical Flow in Coronary Arteries. Ann Biomed Eng 2018; 47:425-438. [DOI: 10.1007/s10439-018-02169-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 11/15/2018] [Indexed: 12/20/2022]
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10
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Impaired cardiac output during exercise in adults operated for ventricular septal defect in childhood: a hitherto unrecognised pathophysiological response. Cardiol Young 2017; 27:1591-1598. [PMID: 28539128 DOI: 10.1017/s1047951117000877] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Recent studies have demonstrated that surgical ventricular septal defect closure in childhood is associated with reduced functional capacity and disruption of the right ventricular force-frequency relationship during exercise. To further describe long-term cardiac function, we performed a non-invasive assessment of cardiac index during exercise in adults having undergone surgery for ventricular septal defect in early childhood. METHODS A total of 20 patients (surgical age 2.1±1.4 years, age at examination 22.1±2.2 years) and 20 healthy, matched controls (23.4±2.1 years at examination) underwent continuous supine bicycle ergometry during MRI. Their blood flow was recorded in the ascending aorta and the pulmonary trunk at increasing exercise levels. Cardiac index, retrograde flow, and vessel diameters were determined by blinded, post hoc analyses. RESULTS The patient group had normal cardiac index at rest (2.9±0.7 L/minute/m2), which was comparable with that of the controls (3.0±0.6 L/minute/m2); however, they had a lower increase in cardiac index during exercise (reaching 7.3±1.3 L/minute/m2 at submaximal exercise) compared with controls (8.2±1.2 L/minute/m2), p<0.05. Patients had a significantly higher ascending aorta retrograde flow than controls at rest and throughout exercise. In the pulmonary artery, the retrograde flow was minimal at rest in both groups, but increased significantly in patients during exercise compared with controls. CONCLUSIONS Young adults with a surgically closed ventricular septal defect have a reduced cardiac index during exercise compared with healthy, young adults. The impaired cardiac index appears to be related to an increasing retrograde flow in the pulmonary artery with progressive exertion.
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11
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Nardi A, Avrahami I. Approaches for treatment of aortic arch aneurysm, a numerical study. J Biomech 2017; 50:158-165. [DOI: 10.1016/j.jbiomech.2016.11.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 11/02/2016] [Indexed: 10/20/2022]
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12
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Zhang Q, Gao B, Chang Y. Effect of Different Rotational Directions of BJUT-II VAD on Aortic Swirling Flow Characteristics: A Primary Computational Fluid Dynamics Study. Med Sci Monit 2016; 22:2576-88. [PMID: 27440399 PMCID: PMC4966492 DOI: 10.12659/msm.899313] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Background The BJUT-II VAD is a novel left ventricular assist device (LVAD), which is thought to have significant effects on the characteristics of aortic swirling flow. However, the precise mechanism of the rotational direction of BJTU-II VAD in the aortic swirling flow is unclear. Material/Methods A patient-specific aortic geometric model was reconstructed based on the CT data. Three pump’s output flow profiles with varied rotational direction, termed “counterclockwise”, “flat profile”, and “clockwise”, were used as the boundary conditions. The helicity density, area-weighted average of helicity density (Ha), localized normalized helicity (LNH), wall shear stress (WSS), and WSS spatial gradient (WSSG) were calculated to evaluate the swirling flow characteristics in the aorta. Results The results demonstrated that the swirling flow characteristics in the aorta and 3 branches are directly affected by the output blood flow of BJUT-II VAD. In the aortic arch, the helicity density, supported by the clockwise case, achieved the highest value. In the 3 branches, the flat profile case achieved the highest helicity density, whereas the maximum WSS and WSSG generated by clockwise case were lower than in other cases. Conclusions The outflow of the BJUT-II VAD has significant effects on the aortic hemodynamics and swirling flow characteristics. The helical blood profiles can enhance the strength of aortic swirling flow, and reduce the areas of low WSS and WSSG regions. The clockwise case may have a benefit for preventing development of atherosclerosis in the aorta.
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Affiliation(s)
- Qi Zhang
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
| | - Bin Gao
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
| | - Yu Chang
- School of Life Science and BioEngineering, Beijing University of Technology, Beijing, China (mainland)
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13
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Hashimoto J, Ito S. Aortic Blood Flow Reversal Determines Renal Function. Hypertension 2015; 66:61-7. [DOI: 10.1161/hypertensionaha.115.05236] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 03/13/2015] [Indexed: 01/09/2023]
Abstract
Aortic stiffness determines the glomerular filtration rate (GFR) and predicts the progressive decline of the GFR. However, the underlying pathophysiological mechanism remains obscure. Recent evidence has shown a close link between aortic stiffness and the bidirectional (systolic forward and early diastolic reverse) flow characteristics. We hypothesized that the aortic stiffening–induced renal dysfunction is attributable to altered central flow dynamics. In 222 patients with hypertension, Doppler velocity waveforms were recorded at the proximal descending aorta to calculate the reverse/forward flow ratio. Tonometric waveforms were recorded to measure the carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities, to estimate the aortic pressure from the radial waveforms, and to compute the aortic characteristic impedance. In addition, renal hemodynamics was evaluated by duplex ultrasound. The estimated GFR was inversely correlated with the aortic pulse wave velocity, reverse/forward flow ratio, pulse pressure, and characteristic impedance, whereas it was not correlated with the peripheral pulse wave velocity or mean arterial pressure. The association between aortic pulse wave velocity and estimated GFR was independent of age, diabetes mellitus, hypercholesterolemia, and antihypertensive medication. However, further adjustment for the aortic reverse/forward flow ratio and pulse pressure substantially weakened this association, and instead, the reverse/forward flow ratio emerged as the strongest determinant of estimated GFR (
P
=0.001). A higher aortic reverse/forward flow ratio was also associated with lower intrarenal forward flow velocities. These results suggest that an increase in aortic flow reversal (ie, retrograde flow from the descending thoracic aorta toward the aortic arch), caused by aortic stiffening and impedance mismatch, reduces antegrade flow into the kidney and thereby deteriorates renal function.
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Affiliation(s)
- Junichiro Hashimoto
- From the Division of Nephrology, Endocrinology and Vascular Medicine, Department of Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (J.H., S.I.)
| | - Sadayoshi Ito
- From the Division of Nephrology, Endocrinology and Vascular Medicine, Department of Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (J.H., S.I.)
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14
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Tanweer O, Wilson TA, Metaxa E, Riina HA, Meng H. A comparative review of the hemodynamics and pathogenesis of cerebral and abdominal aortic aneurysms: lessons to learn from each other. J Cerebrovasc Endovasc Neurosurg 2014; 16:335-49. [PMID: 25599042 PMCID: PMC4296046 DOI: 10.7461/jcen.2014.16.4.335] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Revised: 10/13/2014] [Accepted: 10/29/2014] [Indexed: 12/28/2022] Open
Abstract
OBJECTIVE Cerebral aneurysms (CAs) and abdominal aortic aneurysms (AAAs) are degenerative vascular pathologies that manifest as abnormal dilations of the arterial wall. They arise with different morphologies in different types of blood vessels under different hemodynamic conditions. Although treated as different pathologies, we examine common pathways in their hemodynamic pathogenesis in order to elucidate mechanisms of formation. MATERIALS AND METHODS A systematic review of the literature was performed. Current concepts on pathogenesis and hemodynamics were collected and compared. RESULTS CAs arise as saccular dilations on the cerebral arteries of the circle of Willis under high blood flow, high wall shear stress (WSS), and high wall shear stress gradient (WSSG) conditions. AAAs arise as fusiform dilations on the infrarenal aorta under low blood flow, low, oscillating WSS, and high WSSG conditions. While at opposite ends of the WSS spectrum, they share high WSSG, a critical factor in arterial remodeling. This alone may not be enough to initiate aneurysm formation, but may ignite a cascade of downstream events that leads to aneurysm development. Despite differences in morphology and the structure, CAs and AAAs share many histopathological and biomechanical characteristics. Endothelial cell damage, loss of elastin, and smooth muscle cell loss are universal findings in CAs and AAAs. Increased matrix metalloproteinases and other proteinases, reactive oxygen species, and inflammation also contribute to the pathogenesis of both aneurysms. CONCLUSION Our review revealed similar pathways in seemingly different pathologies. We also highlight the need for cross-disciplinary studies to aid in finding similarities between pathologies.
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Affiliation(s)
- Omar Tanweer
- Department of Neurosurgery, New York University School of Medicine, NY, United States
| | - Taylor A Wilson
- Department of Neurosurgery, New York University School of Medicine, NY, United States
| | - Eleni Metaxa
- Foundation for Research and Technology - Hellas Institute of Applied and Computational Mathematics, Crete, Greece
| | - Howard A Riina
- Department of Neurosurgery, New York University School of Medicine, NY, United States
| | - Hui Meng
- Toshiba Stroke Research Center, University at Buffalo, NY, United States. ; Department of Mechanical and Aerospace Engineering, University at Buffalo, NY, United States. ; Department of Neurosurgery, University at Buffalo, NY, United States
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15
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Ouss AJ, Riezebos RK. The tissue Doppler imaging derived post-systolic velocity notch originates at the aortic annulus. J Cardiovasc Ultrasound 2014; 22:23-7. [PMID: 24753805 PMCID: PMC3992344 DOI: 10.4250/jcu.2014.22.1.23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 02/05/2014] [Accepted: 02/18/2014] [Indexed: 11/22/2022] Open
Abstract
Background A distinct velocity pattern represented by a "notch" is observed during the time interval between the end of the systolic and the onset of the early diastolic velocity wave on longitudinal myocardial velocity curve. The origin of the post-systolic velocity notch (PSN) has not been resolved. Methods The high frame rate color tissue Doppler imaging of the apical longitudinal axis was performed in 32 healthy subjects. Results The time delays of the PSN onset at the posterior aortic wall (AW), the mid anteroseptal wall (MAS) and the posterior mitral annulus (MA) relatively to the anterior aortic annulus (AA) were found to be significantly longer than zero (5.1 ± 2.2, 6.0 ± 2.3, 6.8 ± 2.8 ms; p < 0.001). The amplitude was the highest at the AA when compared to the AW, the MAS and the MA (4.77 ± 1.28 vs. 2.88 ± 1.11, 2.15 ± 0.73, 2.44 ± 1.17 cm/s; p < 0.001). A second PSN spike was identifiable in 10/32 (31%) of the studied subjects at the AA. Of these, 9 (28%) exhibited a second PSN spike at the AW, 3 (9%) at the MAS and no one at the MA. Conclusion The AA represents the site of the earliest onset and maximal amplitude of the PSN on the longitudinal velocity curve suggesting its mechanism to be that of an energy release at the instant of the aortic valve closure causing an apically directed acceleration of the myocardium. A substantial number of healthy subjects exhibit a second PSN spike predominantly at the level of the AA. Its mechanism remains to be elucidated.
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Affiliation(s)
- Alexandre J Ouss
- Department of Cardiology, Onze Lieve Vrouwe Gasthuis Hospital, Amsterdam, the Netherlands
| | - Robert K Riezebos
- Department of Cardiology, Onze Lieve Vrouwe Gasthuis Hospital, Amsterdam, the Netherlands
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16
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Avrahami I, Dilmoney B, Azuri A, Brand M, Cohen O, Shani L, Nir RR, Bolotin G. Investigation of risks for cerebral embolism associated with the hemodynamics of cardiopulmonary bypass cannula: a numerical model. Artif Organs 2013; 37:857-65. [PMID: 24138494 DOI: 10.1111/aor.12094] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cerebral emboli originating in the ascending aorta are a major cause of noncardiac complications following cardiac surgery. The hemodynamics of the aortic cannula has been proven to play a significant role in emboli generation and distribution. The aim of the current study was to perform a thorough numerical investigation in order to examine the effect of the design and orientation of the cannula used during cardiopulmonary bypass on the risk to develop cerebral embolism. Hemodynamic analyses compared numerical models of 27 cases consisting of six different cannula orientations, four aortic anatomies, and three cannula designs. The cannula designs included a straight-tip (ST) cannula, a moderately curved tip cannula (TIP1 ), and a sharp-angle curved cannula (TIP2 ). Outcome measures included hemodynamic parameters such as emanating jet velocity, jet velocity drop, maximal shear stress, aortic wall reaction, emboli pathlines and distribution between upper and lower vessels, and stagnation regions. Based on these parameters, the risks for hemolysis, atheroembolism, and cerebral embolism were evaluated and compared. On one hand, the jet emerging from the ST cannula generated large wall-shear stress at the aortic wall; this may have triggered the erosion and distribution of embolic atheromatous debris from the aortic arch. On the other hand, it diverted more emboli from the clamp region to the descending aorta and thus reduced the risk for cerebral embolism. The TIP1 cannula demonstrated less shear stress on the aortic wall and diverted more emboli from the clamp region toward the upper vessels. The TIP2 cannula exhibited a stronger emanating jet, higher shear stress inside the cannula, and highly disturbed flow, which was more stagnant near the clamp region. Current findings support the significant impact of the cannula design and orientation on emboli generation and distribution. Specifically, the straight tip cannula demonstrated a reduced risk of cerebral embolism, which may be pivotal in the clinical setting.
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17
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Hashimoto J, Ito S. Aortic stiffness determines diastolic blood flow reversal in the descending thoracic aorta: potential implication for retrograde embolic stroke in hypertension. Hypertension 2013; 62:542-9. [PMID: 23798349 DOI: 10.1161/hypertensionaha.113.01318] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Aortic stiffening often precedes cardiovascular diseases, including stroke, but the underlying pathophysiological mechanisms remain obscure. We hypothesized that such abnormalities could be attributable to altered central blood flow dynamics. In 296 patients with uncomplicated hypertension, Doppler velocity pulse waveforms were recorded at the proximal descending aorta and carotid artery to calculate the reverse/forward flow ratio and diastolic/systolic flow index, respectively. Tonometric waveforms were recorded on the radial artery to estimate aortic pressure and characteristic impedance (Z0) and to determine carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities. In all subjects, the aortic flow waveform was bidirectional, comprising systolic forward and diastolic reverse flows. The aortic reverse/forward flow ratio (35 ± 10%) was positively associated with parameters of aortic stiffness (including pulse wave velocity, Z0, and aortic/peripheral pulse wave velocity ratio), independent of age, body mass index, aortic diameter, and aortic pressure. The carotid flow waveform was unidirectional and bimodal with systolic and diastolic maximal peaks. There was a positive relationship between the carotid diastolic/systolic flow index (28 ± 9%) and aortic reverse/forward flow ratio, which remained significant after adjustment for aortic stiffness and other related parameters. The Bland-Altman plots showed a close time correspondence between aortic reverse and carotid diastolic flow peaks. In conclusion, aortic stiffness determines the extent of flow reversal from the descending aorta to the aortic arch, which contributes to the diastolic antegrade flow into the carotid artery. This hemodynamic relationship constitutes a potential mechanism linking increased aortic stiffness, altered flow dynamics, and increased stroke risk in hypertension.
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Affiliation(s)
- Junichiro Hashimoto
- Department of Blood Pressure Research, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan.
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18
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Carr IA, Nemoto N, Schwartz RS, Shadden SC. Size-dependent predilections of cardiogenic embolic transport. Am J Physiol Heart Circ Physiol 2013; 305:H732-9. [PMID: 23792681 DOI: 10.1152/ajpheart.00320.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
While it is intuitively clear that aortic anatomy and embolus size could be important determinants for cardiogenic embolic stroke risk and stroke location, few data exist confirming or characterizing this hypothesis. The objective of this study is to use medical imaging and computational modeling to better understand if aortic anatomy and embolus size influence predilections for cardiogenic embolic transport and right vs. left hemisphere propensity. Anatomically accurate models of the human aorta and branch arteries to the head were reconstructed from computed tomography (CT) angiography of 10 patients. Blood flow was modeled by the Navier-Stokes equations using a well-validated flow solver with physiologic inflow and boundary conditions. Embolic particulate was released from the aortic root and tracked through the common carotid and vertebral arteries for a range of particle sizes. Cardiogenic emboli reaching the carotid and vertebral arteries appeared to have a strong size-destination relationship that varied markedly from expectations based on blood distribution. Observed trends were robust to modeling parameters. A patient's aortic anatomy appeared to significantly influence the probability a cardiogenic particle becomes embolic to the head. Right hemisphere propensity appeared dominant for cardiogenic emboli, which has been confirmed clinically. The predilections discovered through this modeling could represent an important mechanism underlying cardiogenic embolic stroke etiology.
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Affiliation(s)
- Ian A Carr
- Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, Illionis
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19
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Avrahami I, Dilmoney B, Hirshorn O, Brand M, Cohen O, Shani L, Nir RR, Bolotin G. Numerical investigation of a novel aortic cannula aimed at reducing cerebral embolism during cardiovascular bypass surgery. J Biomech 2013. [DOI: 10.1016/j.jbiomech.2012.11.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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20
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Hashimoto J, Ito S. Central pulse pressure and aortic stiffness determine renal hemodynamics: pathophysiological implication for microalbuminuria in hypertension. Hypertension 2011; 58:839-46. [PMID: 21968753 DOI: 10.1161/hypertensionaha.111.177469] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A significant link has been reported between aortic stiffening and renal microvascular damage, but the underlying mechanism remains poorly understood. We hypothesized that alterations in central and renal hemodynamics are responsible for this link. In 133 patients with hypertension, pressure waveforms were recorded on the radial, carotid, femoral, and dorsalis pedis arteries with applanation tonometry to estimate the aortic pressures and aortic (carotid-femoral) and peripheral (carotid-radial and femoral-dorsalis pedis) pulse wave velocities. Flow-velocity waveforms were recorded on the renal segmental arteries with duplex ultrasound to calculate the resistive index (RI) as [1 - (end-diastolic velocity/peak systolic velocity)] and on the femoral arteries to calculate the reverse/forward flow index and diastolic/systolic forward-flow ratio. Albuminuria was defined as urinary albumin/creatinine ratio ≥30 mg/g of creatinine. The renal RI (mean: 0.65±0.07) was strongly correlated (P<0.001) with the aortic pulse pressure (r=0.62), incident pressure wave (r=0.55), augmented pressure (r=0.49), and aortic pulse wave velocity (r=0.51), although not with the mean arterial pressure or peripheral pulse wave velocities. The correlations remained highly significant after consideration of confounders including age, cholesterol, hemoglobin A(1c), and glomerular filtration rate. The renal RI was inversely correlated with the femoral reverse and diastolic forward flow indices. Both aortic pulse pressure and renal RI correlated with the urinary albumin/creatinine ratio independent of confounders. Each 0.1 increase in renal RI was associated with a 5.4-fold increase in the adjusted relative risk of albuminuria. In conclusion, increased aortic pulse pressure causes renal microvascular damage through altered renal hemodynamics resulting from increased peripheral resistance and/or increased flow pulsation.
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Affiliation(s)
- Junichiro Hashimoto
- Department of Blood Pressure Research, Tohoku University Graduate School of Medicine, 1-1 Seiryo-cho, Aoba-ku, Sendai 980-8574, Japan.
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21
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Jeffery D, Emery DJ, Wilman AH. Effects of cardiac motion on 3D contrast-enhanced MR angiography of the carotid arteries. J Magn Reson Imaging 2011; 34:532-8. [DOI: 10.1002/jmri.22657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 04/28/2011] [Indexed: 11/10/2022] Open
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22
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Hashimoto J, Ito S. Pulse Pressure Amplification, Arterial Stiffness, and Peripheral Wave Reflection Determine Pulsatile Flow Waveform of the Femoral Artery. Hypertension 2010; 56:926-33. [DOI: 10.1161/hypertensionaha.110.159368] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Junichiro Hashimoto
- From the Department of Blood Pressure Research (J.H., S.I.) and Division of Nephrology, Endocrinology, and Vascular Medicine (S.I.), Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Sadayoshi Ito
- From the Department of Blood Pressure Research (J.H., S.I.) and Division of Nephrology, Endocrinology, and Vascular Medicine (S.I.), Tohoku University Graduate School of Medicine, Sendai, Japan
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23
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Brown R, Nguyen TD, Spincemaille P, Cham MD, Choi G, Winchester PA, Prince MR, Wang Y. Effect of blood flow on double inversion recovery vessel wall MRI of the peripheral arteries: quantitation with T2 mapping and comparison with flow-insensitive T2-prepared inversion recovery imaging. Magn Reson Med 2010; 63:736-44. [PMID: 20187182 DOI: 10.1002/mrm.22227] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Blood suppression in the lower extremities using flow-reliant methods such as double inversion recovery may be problematic due to slow blood flow. T(2) mapping using fast spin echo (FSE) acquisition was utilized to quantitate the effectiveness of double inversion recovery blood suppression in 13 subjects and showed that 25 +/- 12% of perceived vessel wall pixels in the popliteal arteries contained artifactual blood signal. To overcome this problem, a flow-insensitive T(2)-prepared inversion recovery sequence was implemented and optimal timing parameters were calculated for FSE acquisition. Black blood vessel wall imaging of the popliteal and femoral arteries was performed using two-dimensional T(2)-prepared inversion recovery-FSE in the same 13 subjects. Comparison with two-dimensional double inversion recovery-FSE showed that T(2)-prepared inversion recovery-FSE reduced wall-mimicking blood artifacts that inflated double inversion recovery-FSE vessel wall area measurements in the popliteal artery.
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Affiliation(s)
- Ryan Brown
- Department of Radiology, Weill Medical College of Cornell University, New York, New York 10016, USA.
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24
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Eriksson J, Carlhäll CJ, Dyverfeldt P, Engvall J, Bolger AF, Ebbers T. Semi-automatic quantification of 4D left ventricular blood flow. J Cardiovasc Magn Reson 2010; 12:9. [PMID: 20152026 PMCID: PMC2831022 DOI: 10.1186/1532-429x-12-9] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 02/12/2010] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The beating heart is the generator of blood flow through the cardiovascular system. Within the heart's own chambers, normal complex blood flow patterns can be disturbed by diseases. Methods for the quantification of intra-cardiac blood flow, with its 4D (3D+time) nature, are lacking. We sought to develop and validate a novel semi-automatic analysis approach that integrates flow and morphological data. METHOD In six healthy subjects and three patients with dilated cardiomyopathy, three-directional, three-dimensional cine phase-contrast cardiovascular magnetic resonance (CMR) velocity data and balanced steady-state free-precession long- and short-axis images were acquired. The LV endocardium was segmented from the short-axis images at the times of isovolumetric contraction (IVC) and isovolumetric relaxation (IVR). At the time of IVC, pathlines were emitted from the IVC LV blood volume and traced forwards and backwards in time until IVR, thus including the entire cardiac cycle. The IVR volume was used to determine if and where the pathlines left the LV. This information was used to automatically separate the pathlines into four different components of flow: Direct Flow, Retained Inflow, Delayed Ejection Flow and Residual Volume. Blood volumes were calculated for every component by multiplying the number of pathlines with the blood volume represented by each pathline. The accuracy and inter- and intra-observer reproducibility of the approach were evaluated by analyzing volumes of LV inflow and outflow, the four flow components, and the end-diastolic volume. RESULTS The volume and distribution of the LV flow components were determined in all subjects. The calculated LV outflow volumes [ml] (67 +/- 13) appeared to fall in between those obtained by through-plane phase-contrast CMR (77 +/- 16) and Doppler ultrasound (58 +/- 10), respectively. Calculated volumes of LV inflow (68 +/- 11) and outflow (67 +/- 13) were well matched (NS). Low inter- and intra-observer variability for the assessment of the volumes of the flow components was obtained. CONCLUSIONS This semi-automatic analysis approach for the quantification of 4D blood flow resulted in accurate LV inflow and outflow volumes and a high reproducibility for the assessment of LV flow components.
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Affiliation(s)
- Jonatan Eriksson
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Carl Johan Carlhäll
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Department of Clinical Physiology, Linköping University Hospital, Linköping, Sweden
| | - Petter Dyverfeldt
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Division of Applied Thermodynamics and Fluid Mechanics, Department of Management and Engineering, Linköping University, Linköping, Sweden
| | - Jan Engvall
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Department of Clinical Physiology, Linköping University Hospital, Linköping, Sweden
| | - Ann F Bolger
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Department of Medicine, University of California, San Francisco, California, USA
| | - Tino Ebbers
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
- Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
- Division of Applied Thermodynamics and Fluid Mechanics, Department of Management and Engineering, Linköping University, Linköping, Sweden
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25
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Misra S, Gadhinglajkar S. Unexpected air in the left ventricle after aortic cannulation in two patients with severe aortic insufficiency: possible mechanisms and clinical implications. J Cardiothorac Vasc Anesth 2009; 24:824-7. [PMID: 20006523 DOI: 10.1053/j.jvca.2009.09.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Indexed: 11/11/2022]
Affiliation(s)
- Satyajeet Misra
- Department of Anesthesiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Kerala, India.
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26
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Frydrychowicz A, Stalder AF, Russe MF, Bock J, Bauer S, Harloff A, Berger A, Langer M, Hennig J, Markl M. Three-dimensional analysis of segmental wall shear stress in the aorta by flow-sensitive four-dimensional-MRI. J Magn Reson Imaging 2009; 30:77-84. [PMID: 19557849 DOI: 10.1002/jmri.21790] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To assess the distribution and regional differences of flow and vessel wall parameters such as wall shear stress (WSS) and oscillatory shear index (OSI) in the entire thoracic aorta. MATERIALS AND METHODS Thirty-one healthy volunteers (mean age = 23.7 +/- 3.3 years) were examined by flow-sensitive four-dimensional (4D)-MRI at 3T. For eight retrospectively positioned 2D analysis planes distributed along the thoracic aorta, flow parameters and vectorial WSS and OSI were assessed in 12 segments along the vascular circumference. RESULTS Mean absolute time-averaged WSS ranged between 0.25 +/- 0.04 N/m(2) and 0.33 +/- 0.07 N/m(2) and incorporated a substantial circumferential component (-0.05 +/- 0.04 to 0.07 +/- 0.02 N/m(2)). For each analysis plane, a segment with lowest absolute WSS and highest OSI was identified which differed significantly from mean values within the plane (P < 0.05). The distribution of atherogenic low WSS and high OSI closely resembled typical locations of atherosclerotic lesions at the inner aortic curvature and supraaortic branches. CONCLUSION The normal distribution of vectorial WSS and OSI in the entire thoracic aorta derived from flow-sensitive 4D-MRI data provides a reference constituting an important perquisite for the examination of patients with aortic disease. Marked regional differences in absolute WSS and OSI may help explaining why atherosclerotic lesions predominantly develop and progress at specific locations in the aorta.
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Affiliation(s)
- Alex Frydrychowicz
- Department of Diagnostic Radiology and Medical Physics, University Hospital Freiburg, Freiburg, Germany
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27
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Katzberg RW, Buonocore MH, Low R, Hu B, Jain K, Castillo M, Troxel S, Nguyen MM. MR determination of glomerular filtration rate in subjects with solitary kidneys in comparison to clinical standards of renal function: feasibility and preliminary report. CONTRAST MEDIA & MOLECULAR IMAGING 2009; 4:51-65. [PMID: 19274681 DOI: 10.1002/cmmi.270] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
This study was conducted to demonstrate the feasibility of quantifying single kidney glomerular filtration rate (skGFR) by magnetic resonance (MR) by comparison to the clinical estimates of GFR in volunteer subjects with a single kidney. Seven IRB-approved subjects with a solitary kidney, stable serum creatinine (SCr) and a 24 h creatinine clearance (CrCl) volunteered to undergo an MR examination that determined renal extraction fraction (EF) with a breathhold inversion recovery echo planar pulse sequence and renal blood flow with a velocity encoded phase imaging sequence. The product of EF and blood flow determines GFR. These values were compared with the 24 h CrCl, estimated GFR by the modification of diet in renal disease (MDRD) regression analysis and the Cockroft-Gault (CG) determination of CrCl. The mean and standard deviation of differences between the MR GFR, MDRD and CG vs the 24 h CrCl were 12.3+/-35.7, -8.9+/-18.5 and 1.2+/-19.6, respectively. The Student t-test showed that none of the mean differences were statistically significant between techniques. This clinical investigation shows that MR can be used for skGFR determination in human subjects with comparable values to those derived from clinically used serum-based GFR estimation techniques.
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Affiliation(s)
- Richard W Katzberg
- Department of Radiology, University of California Davis Medical Center, Sacramento, California 95817, USA.
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28
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Liu X, Pu F, Fan Y, Deng X, Li D, Li S. A numerical study on the flow of blood and the transport of LDL in the human aorta: the physiological significance of the helical flow in the aortic arch. Am J Physiol Heart Circ Physiol 2009; 297:H163-70. [PMID: 19429823 DOI: 10.1152/ajpheart.00266.2009] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been proposed that a mass transfer phenomenon called concentration polarization of low-density lipoproteins (LDLs) may occur in the arterial system and is likely involved in the localization of atherogenesis. To test the hypothesis that concentration polarization of LDL may be suppressed by the helical flow pattern in the human aorta, hence sparing the ascending aorta from atherosclerosis, the effects of aortic torsion, branching, curvature, and taper on blood flow and LDL transport in the lumen were simulated numerically under steady-state flow conditions using four aorta models constructed based on in vivo MRI slices. The results showed that it was the aortic torsion that induced the helical flow in the aortic arch, stabilizing the flow of blood in the aorta, and compensated the adverse effects of the aortic curvature on blood flow and LDL transport. The helical flow reduced the luminal surface LDL concentration in the aortic arch and probably played a role in suppressing severe polarization of LDL at the entrances of the three branches on the arch, hence, protecting them from atherogenesis. The taper of the aorta was another important feature of the aorta that further stabilized the flow of blood and delayed the attenuation of the helical flow, making it move beyond the arch and into the beginning part of the descending aorta. The results therefore may account for why the ascending aorta and the arch are relatively free of atherosclerosis.
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Affiliation(s)
- Xiao Liu
- School of Biological Science and Medical Engineering, Beihang University, Beijing, China
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29
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Harloff A, Strecker C, Dudler P, Nuβbaumer A, Frydrychowicz A, Olschewski M, Bock J, Stalder AF, Stroh AL, Weiller C, Hennig J, Markl M. Retrograde Embolism From the Descending Aorta. Stroke 2009; 40:1505-8. [DOI: 10.1161/strokeaha.108.530030] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Andreas Harloff
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Christoph Strecker
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Patrick Dudler
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Andrea Nuβbaumer
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Alex Frydrychowicz
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Manfred Olschewski
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Jelena Bock
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Aurelien F. Stalder
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Anna L. Stroh
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Cornelius Weiller
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Jürgen Hennig
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
| | - Michael Markl
- From the Departments of Neurology and Clinical Neurophysiology (A.H., C.S., P.D., A.N., C.W.), Diagnostic Radiology, Medical Physics (A.F., J.B., A.F.S., J.H., M.M.), Cardiology and Angiology (A.L.S.), and the Institute of Medical Biometrics and Statistics (M.O.), University of Freiburg, Germany
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30
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Svedlund S, Wetterholm R, Volkmann R, Caidahl K. Retrograde blood flow in the aortic arch determined by transesophageal Doppler ultrasound. Cerebrovasc Dis 2008; 27:22-8. [PMID: 19018134 DOI: 10.1159/000172630] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Accepted: 07/22/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Aortic arch atheromas may be important sources of cerebral embolism. Aortic plaques are frequently found somewhat distal to the origin of the cerebral arteries, implying that cerebral embolization from such plaques depends on local retrograde blood flow components in this area. Therefore, we investigated the occurrence of blood flow reversal in this part of the aorta. Furthermore, since the presence and magnitude of retrograde flow might be influenced by aortic wall properties, we also studied the relationship between plaque size and distribution, aortic strain and degree of retrograde flow. METHODS We evaluated aortic arch ante- and retrograde blood flow velocities in 56 patients by transesophageal echocardiography using color-Doppler-guided pulsed-Doppler techniques. The velocity-time integrals (VTI) were measured and the diastolic/systolic VTI ratio was calculated. RESULTS Retrograde diastolic blood flow was noted in all subjects, and diastolic/systolic VTI ratios were higher (p < 0.05) in patients with plaque >or=4 mm (n = 17) compared to those (n = 39) without. Patients exhibiting plaques exclusively in the aortic arch showed the highest VTI ratios (p < 0.01) and tended to have the lowest strain values. Aortic strain was also reduced in patients >50 years of age (p < 0.01). CONCLUSIONS Our findings demonstrate retrograde aortic flow in all subjects and its proportion increases in subjects with atherosclerosis, particularly in the aortic arch. Aortic plaques situated distally to the origin of the cerebral arteries are therefore possible sources of cerebral emboli.
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Affiliation(s)
- S Svedlund
- Department of Clinical Physiology, Sahlgrenska University Hospital and Goteborg University, Goteborg, Sweden
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31
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Guo G. The Quantification of Cerebral Blood Flow by Phase Contrast MRA: Basics and Applications. Neuroradiol J 2008; 21:11-21. [PMID: 24256745 DOI: 10.1177/197140090802100102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2007] [Accepted: 12/02/2007] [Indexed: 11/16/2022] Open
Abstract
Phase-contrast magnetic resonance (PCMRA) flow quantification can determine vascular velocities and volumetric flow rate (VFR) non-invasively for in vitro and in vivo studies. Recently, the increasing power of MR imaging units and the reduced time for data acquisition and post-processing have led to an increasing number of investigations on the use of phase-contrast flow measurements as an additional source of quantitative functional information in MR imaging. In addition, PCMRA can be added to morphologic MRI sequences, offering the option to correlate flow to morphology based on data generated during one examination. This review discusses the basics of phase-contrast imaging, describing the errors and avoiding methods associated with PCMRA, providing guidelines for flow measurement and data analysis, and presenting the current clinical cerebral applications.
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Affiliation(s)
- Gang Guo
- Department of Radiology, No.2 Hospital Xiamen; Xiamen, Fujian, China -
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32
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Doyle A, Mark PB, Johnston N, Foster J, Connell JM, Dargie H, Jardine A, Padmanabhan N. Aortic Stiffness and Diastolic Flow Abnormalities in End-Stage Renal Disease Assessed by Magnetic Resonance Imaging. ACTA ACUST UNITED AC 2008; 109:c1-8. [DOI: 10.1159/000130170] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Accepted: 02/12/2008] [Indexed: 11/19/2022]
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33
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Michaely HJ, Kramer H, Attenberger U, Sourbron SP, Weckbach S, Reiser MF, Schoenberg SO. Renal magnetic resonance angiography at 3.0 T: technical feasibility and clinical perspectives. Top Magn Reson Imaging 2007; 18:117-25. [PMID: 17621225 DOI: 10.1097/rmr.0b013e3180f6128e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The increased signal-to-noise ratio at 3.0 T holds promise for high-spatial resolution renal magnetic resonance angiography (MRA). Today, state-of-the-art renal MRA is feasible with submillimeter isotropic spatial resolution in less than 20 seconds acquisition time with sufficient signal-to-noise ratio. This article explains the fundamentals of 3.0-T imaging that are essential for renal MRA, with a focus on the clinical implications. Protocol and imaging recommendations are given based on the physical principles of 3.0-T imaging and underlined by current clinical cases. Apart from pure morphological imaging, the value of functional renal imaging such as renal flow measurements and renal perfusion measurements for a comprehensive 3.0-T renal MRA protocol is discussed.
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Affiliation(s)
- Henrik J Michaely
- University Hospitals-Grosshadern, Ludwig-Maximilians-University Munich, Munich, Germany.
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34
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Venkatachari AK, Halliburton SS, Setser RM, White RD, Chatzimavroudis GP. Noninvasive quantification of fluid mechanical energy losses in the total cavopulmonary connection with magnetic resonance phase velocity mapping. Magn Reson Imaging 2006; 25:101-9. [PMID: 17222721 DOI: 10.1016/j.mri.2006.09.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2006] [Accepted: 09/09/2006] [Indexed: 11/29/2022]
Abstract
A major determinant of the success of surgical vascular modifications, such as the total cavopulmonary connection (TCPC), is the energetic efficiency that is assessed by calculating the mechanical energy loss of blood flow through the new connection. Currently, however, to determine the energy loss, invasive pressure measurements are necessary. Therefore, this study evaluated the feasibility of the viscous dissipation (VD) method, which has the potential to provide the energy loss without the need for invasive pressure measurements. Two experimental phantoms, a U-shaped tube and a glass TCPC, were scanned in a magnetic resonance (MR) imaging scanner and the images were used to construct computational models of both geometries. MR phase velocity mapping (PVM) acquisitions of all three spatial components of the fluid velocity were made in both phantoms and the VD was calculated. VD results from MR PVM experiments were compared with VD results from computational fluid dynamics (CFD) simulations on the image-based computational models. The results showed an overall agreement between MR PVM and CFD. There was a similar ascending tendency in the VD values as the image spatial resolution increased. The most accurate computations of the energy loss were achieved for a CFD grid density that was too high for MR to achieve under current MR system capabilities (in-plane pixel size of less than 0.4 mm). Nevertheless, the agreement between the MR PVM and the CFD VD results under the same resolution settings suggests that the VD method implemented with a clinical imaging modality such as MR has good potential to quantify the energy loss in vascular geometries such as the TCPC.
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Affiliation(s)
- Anand K Venkatachari
- Laboratory of Biofluid Mechanics and Cardiovascular Imaging, Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH 44115-2425, USA
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35
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Didier D, Saint-Martin C, Lapierre C, Trindade PT, Lahlaidi N, Vallee JP, Kalangos A, Friedli B, Beghetti M. Coarctation of the aorta: pre and postoperative evaluation with MRI and MR angiography; correlation with echocardiography and surgery. Int J Cardiovasc Imaging 2005; 22:457-75. [PMID: 16267620 DOI: 10.1007/s10554-005-9037-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Accepted: 09/08/2005] [Indexed: 10/25/2022]
Abstract
AIMS To compare MRI and MRA with Doppler-echocardiography (DE) in native and postoperative aortic coarctation, define the best MR protocol for its evaluation, compare MR with surgical findings in native coarctation. MATERIALS AND METHODS 136 MR studies were performed in 121 patients divided in two groups: Group I, 55 preoperative; group II, 81 postoperative. In group I, all had DE and surgery was performed in 35 cases. In group II, DE was available for comparison in 71 cases. MR study comprised: spin-echo, cine, velocity-encoded cine (VEC) sequences and 3D contrast-enhanced MRA. RESULTS In group I, diagnosis of coarctation was made by DE in 33 cases and suspicion of coarctation and/or aortic arch hypoplasia in 18 cases. Aortic arch was not well demonstrated in 3 cases and DE missed one case. There was a close correlation between VEC MRI and Doppler gradient estimates across the coarctation, between MRI aortic arch diameters and surgery but a poor correlation in isthmic measurements. In group II, DE detected a normal isthmic region in 31 out of 35 cases. Postoperative anomalies (recoarctation, aortic arch hypoplasia, kinking, pseudoaneurysm) were not demonstrated with DE in 50% of cases. CONCLUSIONS MRI is superior to DE for pre and post-treatment evaluation of aortic coarctation. An optimal MR protocol is proposed. Internal measurement of the narrowing does not correspond to the external aspect of the surgical narrowing.
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Affiliation(s)
- D Didier
- Department of Radiology, University Hospital of Geneva, Geneva, Switzerland.
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36
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Buonocore MH, Katzberg RW. Estimation of extraction fraction (EF) and glomerular filtration rate (GFR) using MRI: considerations derived from a new Gd-chelate biodistribution model simulation. IEEE TRANSACTIONS ON MEDICAL IMAGING 2005; 24:651-66. [PMID: 15889552 DOI: 10.1109/tmi.2005.845331] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Previous reports have described the use of magnetic resonance imaging (MRI) to estimate single-kidney extraction fraction (EF) and glomerular filtration rate (GFR), by measuring the concentration difference of intravenously injected Gd-chelate ([Gd]) in the renal artery and renal vein from measurements of blood T1. Problematic is the fact that [Gd] measurements in the renal artery are often inaccurate due to the small size, tortuousness and motion of the vessel. Consequently, the [Gd] in the inferior vena cava (IVC) below the renal vein ostia (i.e., the infrarenal IVC) has been used instead of the renal artery [Gd], based on the assumption that the [Gd] in the infrarenal IVC is the same as it is in the renal artery. However, this assumption has neither been theoretically nor experimentally investigated. Herein, we describe new difference and differential equation pharmacological models that can predict the biodistribution of Gd-chelate throughout the extracellular space. Assuming known average normal blood flows and GFR, our models predict that the infrarenal IVC [Gd] is 3.2% to 4.7% greater than the renal artery [Gd], and that the EF estimate using this IVC measurement is overestimated by 14.2%-20.0%. To support these predictions, algebraic equations are derived which show that the infrarenal IVC must develop a relatively high [Gd] in order to satisfy Gd flux constraints within the vascular system. These results suggest that the infrarenal IVC [Gd] is not a valid substitute for the renal artery [Gd].
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Affiliation(s)
- Michael H Buonocore
- Department of Radiology, University of California Davis Medical Center, UC Davis Imaging Research Center, 4701 X Street, Sacramento, CA 95817, USA.
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37
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Michaely HJ, Schoenberg SO, Rieger JR, Reiser MF. MR Angiography in Patients with Renal Disease. Magn Reson Imaging Clin N Am 2005; 13:131-51, vi. [PMID: 15760760 DOI: 10.1016/j.mric.2004.12.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Henrik J Michaely
- Department of Clinical Radiology, University Hospitals, Ludwig Maximilians University-Munich, Grosshadern Marchioninistrasse 15, Munich 81377, Germany.
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38
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Volodos SM, Sayers RD, Gostelow JP, Sir Bell PRF. An Investigation Into the Cause of Distal Endoleaks: Role of Displacement Force on the Distal End of a Stent-Graft. J Endovasc Ther 2005; 12:115-20. [PMID: 15683261 DOI: 10.1583/04-1315mr.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE To investigate if the forces developed by pulsatile flow on a stent-graft and dimensional changes of the graft material might contribute to distal endoleak and stent-graft kinking. METHODS An in vitro experimental model was used to measure the peak displacement force developed by pulsatile flow pressure on the distal end of a stent-graft. Polytetrafluoroethylene (PTFE) graft material (110 mm long, 22 mm in diameter) was evaluated in a flow circuit, with water as the circulating liquid. In addition, the effect of internal pressure on PTFE graft dimensions was measured under nonpulsatile conditions in 3 configurations (1 bifurcated and 2 straight). RESULTS Pressure in the PTFE graft did not cause a change in graft diameter but did increase the length of the graft. The mean load required to prevent retrograde displacement was 208.5+/-2.5 g. Peak retrograde displacement force developed on the distal end of the stent-graft by the pressure of pulsatile flow was strongly associated with the systolic phase of the cardiac cycle. CONCLUSIONS The distal end of the stent-graft is subject to a retrograde displacement force by the pressure of pulsatile arterial flow. In addition, pressure inside the PTFE graft causes its length to increase. Both of these factors may be important in the development of late complications of stent-grafting.
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39
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Zhang H, Halliburton SS, White RD, Chatzimavroudis GP. Fast Measurements of Flow through Mitral Regurgitant Orifices with Magnetic Resonance Phase Velocity Mapping. Ann Biomed Eng 2004; 32:1618-27. [PMID: 15675675 DOI: 10.1007/s10439-004-7815-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Magnetic-resonance (MR) phase velocity mapping (PVM) shows promise in measuring the mitral regurgitant volume. However, in its conventional nonsegmented form, MR-PVM is slow and impractical for clinical use. The aim of this study was to evaluate the accuracy of rapid, segmented k-space MR-PVM in quantifying the mitral regurgitant flow through a control volume (CV) method. Two segmented MR-PVM schemes, one with seven (seg-7) and one with nine (seg-9) lines per segment, were evaluated in acrylic regurgitant mitral valve models under steady and pulsatile flow. A nonsegmented (nonseg) MR-PVM acquisition was also performed for reference. The segmented acquisitions were considerably faster (<10 min) than the nonsegmented (>45 min). The regurgitant flow rates and volumes measured with segmented MR-PVM agreed closely with those measured with nonsegmented MR-PVM (differences <5%, p > 0.05), when the CV was large enough to exclude the region of flow acceleration and aliasing from its boundaries. The regurgitant orifice shape (circular vs. slit-like) and the presence of aortic outflow did not significantly affect the accuracy of the results under both steady and pulsatile flow (p > 0.05). This study shows that segmented k-space MR-PVM can accurately quantify the flow through regurgitant orifices using the CV method and demonstrates great clinical potential.
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Affiliation(s)
- Haosen Zhang
- Laboratory of Biofluid Mechanics and Cardiovascular Imaging, Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, OH 44115-2425, USA
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40
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Abstract
Color Doppler echocardiography has limitations, particularly in the assessment of valvular regurgitation and pericardial diseases. MRI, with the help of three dimensional morphologic data, dynamic acquisitions with cine techniques and functional evaluation with flow sensitive techniques can be envisioned as a complementary noninvasive procedure able to provide the complete information required for planning therapeutic options. Qualitative as well as accurate and reproducible quantitative information (volume measurements, cardiac function and flow velocity profiles) are unique for the evaluation of the severity of valve or pericardial diseases. Multislice CT is unique in precisely demonstrating valvular and pericardial calcifications. This article reviews both imaging techniques used in assessing valvular and pericardial disease and discusses the advantages and limitations of these techniques in current clinical applications.
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Affiliation(s)
- D Didier
- Département de Radiologie, Hôpital Cantonal Universitaire de Genève, 24 rue Micheli du Crest, 1211 Genève 14 Suisse.
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41
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Bogren HG, Buonocore MH, Valente RJ. Four-dimensional magnetic resonance velocity mapping of blood flow patterns in the aorta in patients with atherosclerotic coronary artery disease compared to age-matched normal subjects. J Magn Reson Imaging 2004; 19:417-27. [PMID: 15065165 DOI: 10.1002/jmri.20018] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To test the hypothesis that age and atherosclerotic coronary artery disease (CAD) may influence aortic blood flow patterns. MATERIALS AND METHODS A total of 21 patients with CAD, 37-86 years old, were studied, together with 20 age-matched normal subjects. Time-resolved, three-direction velocity data over an entire volume were obtained with sequential single-slice two-dimensional cardiac-gated magnetic resonance (MR) velocity-encoded phase-contrast sequences. RESULTS In both normal subjects and CAD patients, the time it took for particles to travel from aortic valve to descending aorta was significantly longer in the elderly age group than in the younger (37-46 years old). This time was significantly longer in patients than in normal subjects. Systolic velocities were significantly higher in young normal subjects than in elderly normal subjects, and significantly lower in CAD patients than in age-matched normal subjects. Retrograde velocity was higher in CAD patients than in normal subjects, and higher in elderly CAD patients than in young. CONCLUSION CAD patients have abnormal blood flow patterns in the aorta compared with age-matched normal subjects, especially young patients ages 37-46. The aging process has a similar effect on blood flow patterns as atherosclerosis. Ascending aorta flow is chaotic in some very elderly normal subjects and in CAD patients of all ages. Chaotic aortic flow may result in reduced blood flow into the coronary arteries.
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Affiliation(s)
- Hugo G Bogren
- Department of Radiology, University of California-Davis, Sacramento, California, USA.
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42
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Abstract
Evaluation of valve disease has changed significantly with the development of color Doppler echocardiography. Nevertheless, this technique has limitations, particularly in the assessment of valvular regurgitation. MR imaging, with its ability to provide three-dimensional morphologic data, dynamic cine information, and functional evaluation with flow-sensitive techniques, can be envisioned as a complementary noninvasive modality, able to provide the complete information required for planning therapeutic options. With MR imaging, qualitative as well as accurate and reproducible quantitative information such as volume measurements, cardiac function, and flow velocity profiles are unique for the evaluation of the severity of valve disease. This article reviews the different MR imaging techniques used in assessing valvular heart disease and discusses the advantages and limitations of these techniques in current clinical applications in comparison with classical imaging methods.
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Affiliation(s)
- Dominique Didier
- Department of Radiology, Hôpital Cantonal Universitaire de Genève, 24 rue Micheli du Crest, 1211 Geneva 14, Switzerland.
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43
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Chatzimavroudis GP, Zhang H, Halliburton SS, Moore JR, Simonetti OP, Schvartzman PR, Stillman AE, White RD. Clinical blood flow quantification with segmented k-space magnetic resonance phase velocity mapping. J Magn Reson Imaging 2003; 17:65-71. [PMID: 12500275 DOI: 10.1002/jmri.10231] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To evaluate the accuracy of segmented k-space magnetic resonance phase velocity mapping (PVM) in quantifying aortic blood flow from through-plane velocity measurements. MATERIALS AND METHODS Two segmented PVM schemes were evaluated, one with seven lines per segment (seg-7) and one with nine lines per segment (seg-9), in twenty patients with cardiovascular disease. A non-segmented (non-seg) PVM acquisition was also performed to provide the reference data. RESULTS There was agreement between the aortic flow curves acquired with segmented and non-segmented PVM. The calculated systolic and total flow volume per cycle from the seg-7 and the seg-9 scans correlated and agreed with the flow volumes from the non-seg scans (differences < 5%). Sign tests showed that there were no statistically significant differences (P-values > 0.05) between the segmented and the non-segmented PVM measurements [corrected]. Seg-9, which was the fastest among the three sequences, provided adequate spatial and temporal resolution (> 10 phases per cycle). CONCLUSION Segmented k-space PVM shows great clinical potential in blood flow quantification.
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Affiliation(s)
- George P Chatzimavroudis
- Section of Cardiovascular Imaging, Division of Radiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.
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44
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Washiyama N, Kazui T, Takinami M, Yamashita K, Fujita S, Terada H, Suzuki K, Muhammad BAH, Ukawa J. A newly developed cerebral perfusion catheter for aortic arch operation. J Artif Organs 2001. [DOI: 10.1007/bf02479896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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45
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Stevanov M, Baruthio J, Musse O, Gounot D, Armspach JP. Determination of vessel cross section for flow rate quantification. Magn Reson Imaging 2001; 19:891-7. [PMID: 11551731 DOI: 10.1016/s0730-725x(01)00407-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
This study was motivated by the interest of measuring different cardiac parameters for which changes in the flow rate during a cardiac cycle needs to be determined at different positions along a vessel segment. These measurements result in a great number of images for which automatic contour detection is very helpful. A model-based algorithm for intraluminal contour detection has been developed in order to allow an accurate quantitative image analysis. The algorithm permits to select contours automatically on all the frames and slices of an imaging study. Images obtained on a flow phantom simulating the effects of blood circulation in large arteries have been used to validate the method. They were acquired with a specially designed interleaved multi slice and phase sequence, using a standard whole-body 2 Tesla NMR scanner. A potential in vivo application of the algorithm has been demonstrated on abdominal aorta images.
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Affiliation(s)
- M Stevanov
- Université Louis Pasteur, Faculté de Médecine, Institut de Physique Biologique, UPRES-A-7004 (ULP-CNRS), 4, rue Kirschleger, 67085, Strasbourg Cedex, France.
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46
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Balédent O, Henry-Feugeas MC, Idy-Peretti I. Cerebrospinal fluid dynamics and relation with blood flow: a magnetic resonance study with semiautomated cerebrospinal fluid segmentation. Invest Radiol 2001; 36:368-77. [PMID: 11496092 DOI: 10.1097/00004424-200107000-00003] [Citation(s) in RCA: 161] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES To investigate and measure temporal and amplitude aspects of blood and cerebrospinal fluid (CSF) flow waveform relations. METHODS A cine phase-contrast magnetic resonance imaging pulse sequence was used to measure blood and CSF flow in 16 healthy subjects aged 27 +/- 4 years. A semiautomated segmentation algorithm was developed to study CSF flow. RESULTS Standard deviations of the aqueductal and cervical flow measurements carried out by five observers were 1% and 4%, respectively. The peak systolic arterial flow was 1087 +/- 169 mL/min, and the peak cervical CSF flush (173 +/- 59 mL/min) occurred at 5% +/- 3% of the cardiac cycle after the internal carotid systolic peak flow. Peak aqueductal flush flow (13 +/- 5 mL/min) occurred at 21% +/- 7% of the cardiac cycle after the internal carotid systolic peak flow. CONCLUSIONS The CSF segmentation algorithm is reproducible. Brain expansion was quickly regulated by a major extracerebral CSF flush flow, whereas ventricular CSF made only a very small contribution.
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Affiliation(s)
- O Balédent
- Service de biophysique et traitement de l'image médicale, UMR 6600 CNRS, CHU Amiens, Université Picardie Jules Verne, Amiens, France
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47
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Abstract
MR angiography has become a realistic diagnostic option for patients with neurovascular disease. MR angiography is not a single imaging sequence, but a collection of related methods for obtaining angiographic data. As a guide for practice, we review the literature on MR angiography in a spectrum of neurovascular indications with particular attention paid to choice of technique. The principles underlying the different techniques available are also presented. Summers, P. E.et al.
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Affiliation(s)
- P E Summers
- Clinical Neurosciences, Guy's, King's and St. Thomas's Medical and Dental School, U.K.
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48
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Wood NB, Weston SJ, Kilner PJ, Gosman AD, Firmin DN. Combined MR imaging and CFD simulation of flow in the human descending aorta. J Magn Reson Imaging 2001; 13:699-713. [PMID: 11329191 DOI: 10.1002/jmri.1098] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A combined MR and computational fluid dynamics (CFD) study is made of flow in the upper descending thoracic aorta. The aim was to investigate further the potential of CFD simulations linked to in vivo MRI scans. The three-dimensional (3D) geometrical images of the aorta and the 3D time-resolved velocity images at the entry to the domain studied were used as boundary conditions for the CFD simulations of the flow. Despite some measurement uncertainties, comparisons between simulated and measured flow structures at the exit from the domain demonstrated encouraging levels of agreement. Moreover, the CFD simulation allowed the flow structure throughout the domain to be examined in more detail, in particular the flow separation region in the distal aortic arch and its influence on the downstream flow during late systole. Additional information such as relative pressure and wall shear stress, which could not be measured via MRI, were also extracted from the simulation. The results have encouraged further applications of the methods described. J. Magn. Reson. Imaging 2001;13:699-713.
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Affiliation(s)
- N B Wood
- Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2BX, UK.
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49
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Didier D, Ratib O, Lerch R, Friedli B. Detection and quantification of valvular heart disease with dynamic cardiac MR imaging. Radiographics 2000; 20:1279-99; discussion 1299-301. [PMID: 10992018 DOI: 10.1148/radiographics.20.5.g00jl111279] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Magnetic resonance (MR) imaging is rapidly gaining acceptance as an accurate, reproducible, noninvasive method for optimal assessment of structural and functional parameters in patients with valvular heart disease. The severity of valvular regurgitation can be evaluated with cine gradient-echo MR imaging, which allows measurement of the area of the signal void corresponding to the abnormal flow jet. Alternatively, this modality can be used to obtain ventricular volumetric measurements and calculate the regurgitant fraction, or velocity-encoded cine (VEC) MR imaging can be used to quantify regurgitant blood flow. The severity of valvular stenosis can be determined by evaluating the flow jet and associated findings with either modality or by using VEC MR imaging to calculate the transvalvular pressure gradient and valve area. Dynamic MR imaging allows accurate assessment of ventricular function and comprehensive evaluation of pathophysiologic changes. In addition, good interstudy reproducibility suggests a role for VEC MR imaging in assessing the effects of therapeutic intervention and monitoring regurgitant fraction, thereby helping in surgical planning and the prevention of ventricular dysfunction. With greater cost-effectiveness and the increasing availability of new hardware and more advanced techniques, MR imaging will become a routine procedure in valvular heart disease.
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Affiliation(s)
- D Didier
- Department of Radiology, Hôpital Cantonal Universitaire de Genève, 24 rue Micheli du Crest, 1211 Geneva 14, Switzerland.
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50
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Engellau L, Olsrud J, Brockstedt S, Albrechtsson U, Norgren L, Ståhlberg F, Larsson EM. MR evaluation ex vivo and in vivo of a covered stent-graft for abdominal aortic aneurysms: ferromagnetism, heating, artifacts, and velocity mapping. J Magn Reson Imaging 2000; 12:112-21. [PMID: 10931571 DOI: 10.1002/1522-2586(200007)12:1<112::aid-jmri13>3.0.co;2-g] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Magnetic resonance imaging (MRI) safety was evaluated at 1.5 T in a covered nickel titanium stent-graft (Vanguard) used for endovascular treatment of abdominal aortic aneurysms (AAAs). Imaging artifacts were assessed on MRI with contrast-enhanced (CE) three-dimensional (3D) MR angiography (MRA) and spiral computed tomography (CT) in 10 patients as well as ex vivo. Velocity mapping was performed in the suprarenal aorta and femoral arteries in 14 patients before and after stent-graft placement. For comparison it was also performed in six healthy volunteers. No ferromagnetism or heating was detected. Metal artifacts caused minimal image distortion on MRI/MRA. The artifacts disturbed image evaluation on CT at the graft bifurcation and graft limb junction. No significant differences in mean flow were found in patients before and after stent-graft placement. Our study indicates that MRI at 1.5 T may be performed safely in patients with the (Vanguard) stent-graft. MRI/MRA provides diagnostic image information. Velocity mapping is not included in our routine protocol.
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Affiliation(s)
- L Engellau
- Department of Radiology, University Hospital Lund, Sweden.
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