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Author : Sven Petersson
Publisher :
ISBN 13 : 9789175195063
Total Pages : pages
Book Rating : 4.1/5 (95 download)
Download or read book Fast and Accurate 4D Flow MRI for Cardiovascular Blood Flow Assessment written by Sven Petersson and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Mariana Bustamante
Publisher : Linköping University Electronic Press
ISBN 13 : 9176853462
Total Pages : 77 pages
Book Rating : 4.1/5 (768 download)
Download or read book Automated Assessment of Blood Flow in the Cardiovascular System Using 4D Flow MRI written by Mariana Bustamante and published by Linköping University Electronic Press. This book was released on 2018-03-23 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Medical image analysis focuses on the extraction of meaningful information from medical images in order to facilitate clinical assessment, diagnostics and treatment. Image processing techniques have gradually become an essential part of the modern health care system, a consequence of the continuous technological improvements and the availability of a variety of medical imaging techniques. Magnetic Resonance Imaging (MRI) is an imaging technique that stands out as non-invasive, highly versatile, and capable of generating high quality images without the use of ionizing radiation. MRI is frequently performed in the clinical setting to assess the morphology and function of the heart and vessels. When focusing on the cardiovascular system, blood flow visualization and quantification is essential in order to fully understand and identify related pathologies. Among the variety of MR techniques available for cardiac imaging, 4D Flow MRI allows for full three-dimensional spatial coverage over time, also including three-directional velocity information. It is a very powerful technique that can be used for retrospective analysis of blood flow dynamics at any location in the acquired volume. In the clinical routine, however, flow analysis is typically done using two-dimensional imaging methods. This can be explained by their shorter acquisition times, higher in-plane spatial resolution and signal-to-noise ratio, and their relatively simpler post-processing requirements when compared to 4D Flow MRI. The extraction of useful knowledge from 4D Flow MR data is especially challenging due to the large amount of information included in these images, and typically requires substantial user interaction. This thesis aims to develop and evaluate techniques that facilitate the post-processing of thoracic 4D Flow MRI by automating the steps necessary to obtain hemodynamic parameters of interest from the data. The proposed methods require little to no user interaction, are fairly quick, make effective use of the information available in the four-dimensional images, and can easily be applied to sizable groups of data.The addition of the proposed techniques to the current pipeline of 4D Flow MRI analysis simplifies and expedites the assessment of these images, thus bringing them closer to the clinical routine. Medicinsk bildanalys fokuserar på extrahering av meningsfull information från medicinska bilder för att underlätta klinisk bedömning, diagnostik, och behandling. Bildbehandlingsteknik har gradvis blivit en viktig del av det moderna sjukvårdsystemet, en följd av de kontinuerliga tekniska förbättringarna och tillgången till en mängd olika medicinska bildtekniker. Magnetic resonanstomografi (MRT) är en bildteknik som är ickeinvasiv, flexibel och kan generera bilder av hög kvalitet utan joniserande strålning. MRT utförs ofta i klinisk miljö för att bedöma anatomi och funktion av hjärtat och blodkärlen. När man fokuserar på hjärt-kärlsystemet är bedömning av blodflödet viktigt för att kunna förstå och identifiera sjukdomar fullt ut. Bland de olika MRT-teknikerna som är tillgängliga för avbildning av hjärtat möjliggör 4D flödes-MRT komplett täckning av hjärtat i tre dimensioner över tid, och med hastighetsinformation i tre riktningar. 4D flödes-MRT är en mycket effektiv metod som kan användas för retrospektiv analys av blodflödesdynamik på vilken position som helst i den avbildade volymen. Till vardags görs dock blodflödesanalysen vanligtvis på bilder tagna med tvådimensionella avbildningsmetoder. Detta kan förklaras av deras kortare insamlingstider, högre spatiella upplösning, bättre signal-brusförhållandet, och att de är relativt enklare att efterbehandla jämfört med 4D flödes-MRT. Utvinningen av användbar information från 4D flödes-MRT-data är väldigt utmanande på grund av den stora mängden information som dessa bilder innehåller och kräver vanligtvis väsentlig användarinteraktion. Denna avhandling syftar till att utveckla och utvärdera metoder som underlättar efterbehandlingen av 4D flödes-MRT genom att automatisera de steg som är nödvändiga för att härleda hemodynamiska parametrarna av intresse från dessa data. De föreslagna metoderna kräver liten eller ingen användarinteraktion, är relativt snabba, använder all information som finns i de fyrdimensionella bilderna, och kan enkelt appliceras på stora datamängder. Tillägget av de i avhandlingen beskrivna metoderna till den nuvarande analysen av 4D flödes-MRT medger en avsevärd förenkling och uppsnabbad utvärdering, vilket gör att den avancerade 4D flödes MRT-tekniken kommer närmare att kunna användas i kliniskt rutinarbete.
Author : Belén Casas Garcia
Publisher : Linköping University Electronic Press
ISBN 13 : 9176852172
Total Pages : 71 pages
Book Rating : 4.1/5 (768 download)
Download or read book Towards Personalized Models of the Cardiovascular System Using 4D Flow MRI written by Belén Casas Garcia and published by Linköping University Electronic Press. This book was released on 2019-02-15 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: Current diagnostic tools for assessing cardiovascular disease mostly focus on measuring a given biomarker at a specific spatial location where an abnormality is suspected. However, as a result of the dynamic and complex nature of the cardiovascular system, the analysis of isolated biomarkers is generally not sufficient to characterize the pathological mechanisms behind a disease. Model-based approaches that integrate the mechanisms through which different components interact, and present possibilities for system-level analyses, give us a better picture of a patient’s overall health status. One of the main goals of cardiovascular modelling is the development of personalized models based on clinical measurements. Recent years have seen remarkable advances in medical imaging and the use of personalized models is slowly becoming a reality. Modern imaging techniques can provide an unprecedented amount of anatomical and functional information about the heart and vessels. In this context, three-dimensional, three-directional, cine phase-contrast (PC) magnetic resonance imaging (MRI), commonly referred to as 4D Flow MRI, arises as a powerful tool for creating personalized models. 4D Flow MRI enables the measurement of time-resolved velocity information with volumetric coverage. Besides providing a rich dataset within a single acquisition, the technique permits retrospective analysis of the data at any location within the acquired volume. This thesis focuses on improving subject-specific assessment of cardiovascular function through model-based analysis of 4D Flow MRI data. By using computational models, we aimed to provide mechanistic explanations of the underlying physiological processes, derive novel or improved hemodynamic markers, and estimate quantities that typically require invasive measurements. Paper I presents an evaluation of current markers of stenosis severity using advanced models to simulate flow through a stenosis. Paper II presents a framework to personalize a reduced-order, mechanistic model of the cardiovascular system using exclusively non-invasive measurements, including 4D Flow MRI data. The modelling approach can unravel a number of clinically relevant parameters from the input data, including those representing the contraction and relaxation patterns of the left ventricle, and provide estimations of the pressure-volume loop. In Paper III, this framework is applied to study cardiovascular function at rest and during stress conditions, and the capability of the model to infer load-independent measures of heart function based on the imaging data is demonstrated. Paper IV focuses on evaluating the reliability of the model parameters as a step towards translation of the model to the clinic.
Author : Alexandru Grigorescu Fredriksson
Publisher : Linköping University Electronic Press
ISBN 13 : 9176854159
Total Pages : 95 pages
Book Rating : 4.1/5 (768 download)
Download or read book Blood flow specific assessment of ventricular function written by Alexandru Grigorescu Fredriksson and published by Linköping University Electronic Press. This book was released on 2017-12-06 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The spectrum of cardiovascular diseases is the leading cause of morbidity and mortality globally. Early assessment and treatment of these conditions, acquired as well as congenital, is therefore of paramount importance. The human heart has a great ability to adapt to various hemodynamic conditions by cardiac remodeling. Pathologic cardiac remodeling can occur as a result of cardiovascular disease in an effort to maintain satisfactory cardiac function. With time, cardiac function diminishes leading to disease progression and subsequent heart failure, the end-point of many heart diseases, associated with very poor prognosis. Within the normal cardiac ventricles blood flows in highly organized patterns, and changes in cardiac configuration or function will affect these flow patterns. Conversely, altered flows and pressures can bring about cardiac remodeling. In congenital heart disease, even after corrective surgery, cardiac anatomy and thereby intracardiac blood flow patterns are inherently altered. The clinically most available imaging technique, ultrasound with Doppler, allows only for one-directional flow assessment and is limited by the need of clear examination windows, thus failing to fully assess the complex three-dimensional blood flow within the beating heart. Cardiovascular magnetic resonance imaging (CMR) with phase-contrast has the ability to acquire three-dimensional (3D), three-directional time resolved velocity data (3D + time = 4D flow data) from which visualization and quantification of blood flow patterns over the complete cardiac cycle can be performed. Four functional blood flow components have previously been defined based on the blood route and distribution through the ventricle, where the inflowing blood that passes directly to the outflow is called Direct flow. From these components, various quantitative measures can be derived, such as component volumes and kinetic energy (KE) throughout the cardiac cycle. In addition, the 4D flow technique has the ability to quantify and visualize turbulent flow with increased velocity fluctuations in the heart and vessels, turbulent kinetic energy (TKE). The technique has been developed and evaluated for assessment of left ventricular (LV) blood flow in healthy subjects and in patients with dilated dysfunctional left ventricles, showing significant changes in blood flow patterns and energetics with disease. There is however still no study addressing the gap in the spectrum from the healthy cohorts to patients with moderate to severe left ventricular remodeling. In Paper III, 4D flow CMR was utilized to assess LV blood flow in patients with subtle LV dysfunction, and a shift in blood flow component volumes and KE was seen from the Direct flow to the non-ejecting blood flow components. In patients with both left- and right-sided acquired and congenital heart disease, right ventricular (RV) function is of great prognostic significance, however this ventricle has historically been somewhat overseen. With its complex geometry, advanced physiology and retrosternal location, assessment of the RV is still challenging and the right ventricular blood flow is still incompletely described. In Paper I, the RV blood flow in healthy subjects was assessed, and the proportionally larger Direct flow component was located in the most basal region of the ventricle and possessed higher levels of KE at end-diastole than the other flow components suggesting that this portion of blood was prepared for efficient systolic ejection. In Paper II, the blood flow was assessed in the RV of patients with subtle primary LV disease, and even if conventional echocardiographic or CMR RV parameters did not show any RV dysfunction, alterations of flow patterns suggestive of RV impairment were found in the patients with the more remodeled LVs. With improvements of the cardiovascular health care, including the surgical techniques, the number of adult patients with surgically corrected complex congenital heart diseases increases, one of which is tetralogy of Fallot (ToF). Surgical repair of ToF involves widening of the pulmonary stenosis, which postoperatively may cause pulmonary insufficiency and regurgitation (PR). Disturbed or turbulent flow patterns are rare in the healthy cardiovascular system. With pathological changes, such as valvular insufficiency, increased amounts of TKE have been demonstrated. Turbulence is known to be harmful to organic tissues and could be significant in the development of ventricular remodeling, such as dilation and other complications seen in Fallot patients. In Paper IV, the RV intraventricular TKE levels were assessed in relation to conventional measures of PR. Results showed that RV TKE was increased in ToF patients with PR compared to healthy controls, and that these 4D flow-specific measures related slightly stronger to indices of RV remodeling than the conventional measures of PR. 4D flow CMR analysis of the intracardiac blood flow has the potential of adding to pathophysiological understanding, and thereby provide useful diagnostic information and contribute to optimization of treatment of heart disease at earlier stages before irreversible and clinically noticeable changes occur. The flow specific measures used in this thesis could be utilized to detect these alterations of intracardiac blood flow and could thus act as potential markers of progressing ventricular dysfunction, pathological remodeling or used for risk stratification in adults with early repair tetralogy of Fallot. Visualizations of intracardiac flow patterns could provide useful information to cardiac/thoracic surgeons pre- and post-operatively.
Author : Philip Corrado (Ph.D.)
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)
Download or read book Cardiac 4D Flow MRI written by Philip Corrado (Ph.D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) is a medical imaging modality with the ability to acquire images sensitized to several different contrast mechanisms. One of the many mechanisms that can generate contrast in MR images is blood flow. "4D flow MRI", a method for quantifying time-resolved velocity fields in 3-dimensional regions, is employed in the context of comprehensive flow assessment within the heart and major blood vessels but requires long acquisition and post-processing times. The aims of the work presented in this dissertation are to accelerate the acquisition and processing of cardiac 4D flow MRI images, and to apply 4D flow MRI to quantify intracardiac hemodynamics in two disease population: survivors of myocardial infarction and young adults born very-to-extremely premature. This work is divided into six research chapters. The technical innovations introduced and evaluated in my work (Chapters 2-4) relate to the validation of accelerated 4D flow acquisitions and the development of fast, automated pipelines for 4D flow image analysis. In Chapter 2, I describe the construction of a model of the left ventricle of the heart and use it to compare acceleration acquisition techniques for 4D flow MRI. Using an optical imaging-based reference standard, I show lower error in velocity estimations at short scan times for one technique over the other, supporting the use of this technique in scan-time-limited scenarios and demonstrating a generalizable workflow for head-to-head comparison of image acquisition or reconstruction techniques which can be adopted in other applications in order to minimize acquisition time. In Chapters 3 and 4, I use deep learning to automate image processing tasks for quantitative flow assessment in 4D flow MRI of the chest. In particular, I automate the segmentation of the myocardial ventricles (Chapter 3), necessary for the measurement of ventricular kinetic energy or the analysis of ventricular flow components, and the placement of measurement planes (Chapter 4), necessary for the measurement of flow and peak velocity in the great vessels of the heart. Both methods are thoroughly evaluated, finding similar performance to manual segmentation/plane placement. This enables 4D flow MR images of the chest to be processed in an automated fashion, vastly reducing the processing time required for users of 4D flow MRI and enabling large and longitudinal studies without biases between observers. The applications of cardiac 4D flow MRI explored in my work are myocardial infarction (Chapter 5) and cardiac development after preterm birth (Chapters 6-7). In Chapter 5, I apply cardiac 4D flow MRI to study hemodynamics in the left ventricle after acute myocardial infarction. 4D flow data is compared region-by-region between myocardial infarction patients and controls, finding reduced flow in several left ventricular regions in patients relative to controls, perhaps providing indications of risk of post-infarction sequelae. In Chapters 6 and 7, I apply cardiac 4D flow MRI to study intracardiac hemodynamics in another at-risk population: young adults born very-to-extremely premature. I first compare intraventricular flow in young adults born premature to those born at term (Chapter 6), finding decreased right ventricular early-to-late diastolic kinetic energy ratios and increased viscous energy dissipation in preterm subjects relative to term subjects, suggesting altered right ventricular filling which may be relevant to the elevated early heart failure risk in this population. I then use acute pharmacological interventions to assess the effects of hemodynamic manipulations on cardiac hemodynamics measured by 4D flow MRI in young adults born premature (Chapter 7). Acute pharmacological reduction of pulmonary blood pressure increases cardiac function, suggesting that pulmonary hypertension may play a role in this group's heart failure risk. Recommendations for future work include assembling large multicenter databases aimed at using 4D flow to predict cardiovascular outcomes in the general population, a longitudinal 4D flow study of the developing preterm heart throughout childhood, and a prospective 4D flow study to predict post-myocardial infarction thrombus formation.
Author : Philip Corrado (Ph.D.)
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)
Download or read book Cardiac 4D Flow MRI written by Philip Corrado (Ph.D.) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic resonance imaging (MRI) is a medical imaging modality with the ability to acquire images sensitized to several different contrast mechanisms. One of the many mechanisms that can generate contrast in MR images is blood flow. "4D flow MRI", a method for quantifying time-resolved velocity fields in 3-dimensional regions, is employed in the context of comprehensive flow assessment within the heart and major blood vessels but requires long acquisition and post-processing times. The aims of the work presented in this dissertation are to accelerate the acquisition and processing of cardiac 4D flow MRI images, and to apply 4D flow MRI to quantify intracardiac hemodynamics in two disease population: survivors of myocardial infarction and young adults born very-to-extremely premature. This work is divided into six research chapters. The technical innovations introduced and evaluated in my work (Chapters 2-4) relate to the validation of accelerated 4D flow acquisitions and the development of fast, automated pipelines for 4D flow image analysis. In Chapter 2, I describe the construction of a model of the left ventricle of the heart and use it to compare acceleration acquisition techniques for 4D flow MRI. Using an optical imaging-based reference standard, I show lower error in velocity estimations at short scan times for one technique over the other, supporting the use of this technique in scan-time-limited scenarios and demonstrating a generalizable workflow for head-to-head comparison of image acquisition or reconstruction techniques which can be adopted in other applications in order to minimize acquisition time. In Chapters 3 and 4, I use deep learning to automate image processing tasks for quantitative flow assessment in 4D flow MRI of the chest. In particular, I automate the segmentation of the myocardial ventricles (Chapter 3), necessary for the measurement of ventricular kinetic energy or the analysis of ventricular flow components, and the placement of measurement planes (Chapter 4), necessary for the measurement of flow and peak velocity in the great vessels of the heart. Both methods are thoroughly evaluated, finding similar performance to manual segmentation/plane placement. This enables 4D flow MR images of the chest to be processed in an automated fashion, vastly reducing the processing time required for users of 4D flow MRI and enabling large and longitudinal studies without biases between observers. The applications of cardiac 4D flow MRI explored in my work are myocardial infarction (Chapter 5) and cardiac development after preterm birth (Chapters 6-7). In Chapter 5, I apply cardiac 4D flow MRI to study hemodynamics in the left ventricle after acute myocardial infarction. 4D flow data is compared region-by-region between myocardial infarction patients and controls, finding reduced flow in several left ventricular regions in patients relative to controls, perhaps providing indications of risk of post-infarction sequelae. In Chapters 6 and 7, I apply cardiac 4D flow MRI to study intracardiac hemodynamics in another at-risk population: young adults born very-to-extremely premature. I first compare intraventricular flow in young adults born premature to those born at term (Chapter 6), finding decreased right ventricular early-to-late diastolic kinetic energy ratios and increased viscous energy dissipation in preterm subjects relative to term subjects, suggesting altered right ventricular filling which may be relevant to the elevated early heart failure risk in this population. I then use acute pharmacological interventions to assess the effects of hemodynamic manipulations on cardiac hemodynamics measured by 4D flow MRI in young adults born premature (Chapter 7). Acute pharmacological reduction of pulmonary blood pressure increases cardiac function, suggesting that pulmonary hypertension may play a role in this group's heart failure risk. Recommendations for future work include assembling large multicenter databases aimed at using 4D flow to predict cardiovascular outcomes in the general population, a longitudinal 4D flow study of the developing preterm heart throughout childhood, and a prospective 4D flow study to predict post-myocardial infarction thrombus formation.
Author : Mohammadjavad Negahdar
Publisher :
ISBN 13 :
Total Pages : 158 pages
Book Rating : 4.:/5 (938 download)
Download or read book 4D Reduced TE (RTE) Spiral Phase Contrast NRI for Rapid Quantification and Visualization of Blood Flow and Hemodynamics written by Mohammadjavad Negahdar and published by . This book was released on 2015 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: 4D flow Phase Contrast MRI is a relatively new technique in MRI which is capable of deriving time-resolved three-dimensional velocity fields in a 3D volume noninvasively. 4D flow imaging is a 3D k-space acquisition where for the third dimension, an additional phase-encoding step is required. The velocity field can then be used to obtain flow waveform, wall shear stress, vascular compliance, blood pressure, and other hemodynamic information. A significant limitation of 4D flow methods has been the requisite long scan times, requiring the patient to remain motionless at times on the order of 10-20 minutes, depending on scan parameters. The scan times may become more prohibitive in case of 4D cardiovascular studies where respiratory gating with navigator echoes is required. In this thesis the feasibility of using a reduced TE stack of spirals k-space acquisition for 4D flow imaging are investigated. Starting with fundamentals of MRI, the basics of Phase contrast and 4D flow MRI are thoroughly discussed in Chapter 1-3 and subsequently experimental phantom results are reported in Chapter 4, pointing to the feasibility of performing highly accurate 4D velocity and flow measurement with the proposed pulse sequence under a variety of flow conditions and with substantial reductions in scan time when compared to conventional 4D flow. In phantom studies, results based on the root mean square error criterion indicate that 4D Reduced TE (RTE) Spiral PC MRI is capable of providing the same level of accuracy as conventional 4D conventional PC MRI but in a much shorter scan time (30% reduction in scan time when imaging an FOV of 100*100*60 mm3 and spatial resolution of 1.5*1.5*3 mm3). Moreover, the proposed method has the added advantage of achieving the shorter echo time of 2 ms versus 3.6 ms for conventional 4D flow at Q=50ml/s and 1.57 ms versus 3.2 ms at the higher flow rate of Q=150 ml/s leading to more accurate assessment of flow distal to narrowings. Statistical results indicate that at low flow rates performance of both methods are similar. At higher flow rates, however, 4D RTE spiral flow achieves better accuracy. Qualitative results in phantom studies also revealed that at higher flow rates, better flow visualization was achieved with4D RTE spiral flow compared with conventional 4D flow. In the second part of Chapter 4, we also report on application of the proposed sequence, in-vivo, to 5 healthy volunteers and 5 subjects with mild to moderate Aortic Stenosis (AS) disease. Results from the proposed method were statistically correlated with velocity profiles derived from conventional 4D flow and Doppler Ultrasound. Results indicate that 4D RTE Spiral is capable of providing the same level of accuracy in flow measurement as Conventional 4D flow MRI for imaging of the aortic valve, but on average resulted in a 30% reduction in scan time and 45% reduction in echo time. 4D RTE Spiral was also able to achieve an echo time of 1.68 ms versus 2.9 ms for that of conventional 4D flow MRI, permitting less signal dephasing in the presence of jet flows distal to occlusions. With Doppler Ultrasound adopted as the reference method, 4D RTE Spiral flow measured peak velocity and maximum pressure gradient with a higher level of accuracy when compared to Conventional 4D flow MRI. Both methods measured left-ventricular out flow tract (LVOT) diameter, Aortic Valve (AV) eject time and time to AV peak with same accuracy. It is concluded that 4D RTE Spiral flow MRI is an excellent technique for flow measurement in cardiac patients who are unable to tolerate longer scan times, currently required by conventional 4D flow methods.
Author : Hadley L. Conn
Publisher :
ISBN 13 :
Total Pages : 976 pages
Book Rating : 4.3/5 (91 download)
Download or read book Cardiac and Vascular Diseases written by Hadley L. Conn and published by . This book was released on 1971 with total page 976 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Institute of Medicine
Publisher : National Academies Press
ISBN 13 : 030915698X
Total Pages : 304 pages
Book Rating : 4.3/5 (91 download)
Download or read book Cardiovascular Disability written by Institute of Medicine and published by National Academies Press. This book was released on 2010-12-04 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Social Security Administration (SSA) uses a screening tool called the Listing of Impairments to identify claimants who are so severely impaired that they cannot work at all and thus immediately qualify for benefits. In this report, the IOM makes several recommendations for improving SSA's capacity to determine disability benefits more quickly and efficiently using the Listings.
Author : Ali Nahardani
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (142 download)
Download or read book Novel Fast 4D Phase Contrast Velocity Mapping MRI Sequences and Their Application on Cardiovascular Hemodynamics written by Ali Nahardani and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 4D-flow velocity mapping is a technique in magnetic resonance imaging (MRI) to quantify blood flow velocity in 3D space and over time. To increase accuracy, novel sequences have been developed to overcome its technical limitations, including the low signal-to-noise ratio (SNR), low velocity-to-noise ratio (VNR), background velocity fluctuations due to concomitant fields, and flow-related intra-voxel dephasing. However, for a long time, this field was almost untouched in preclinical imaging until Krämer et al. (2017) developed the self-gated ultra-short-echo 4D-flow (UTE-4D-flow) technique. Although UTE-4D-flow showed superior SNR and VNR compared to the conventional prospectively-gated Cartesian-4D-flow method, its total scan time was too long to be applied in routine practice, especially in bigger animals than mice. To shorten the total scan time and preserve SNR and VNR, we combined the concepts of UTE-4D-flow and Cartesian-4D-flow techniques, which resulted in a Stack-of-Stars 4D-flow (SoS-4D-flow) sequence. The in-vitro evaluations of the sequence proved that it benefited from an improved SNR, VNR, and background velocity bias compared to the Cartesian counterpart. Thereafter, we applied the sequence on rats by integrating it into a prospective-gating system. The initial results prompted us to quantify the pulmonary and vena-cava venous blood flow in addition to arterial hemodynamics. The later study resulted in a novel diagnostic marker - “the pulmonary arteriovenous pressure gradient” - to diagnose pulmonary arterial hypertension non-invasively by MRI. Finally, by refining the sequence and replacing the prospective-gating system with a retrospective k0-navigator and compressed sensing (CS) reconstruction, we could shorten the scan time to almost half the measurement time in the UTE-4D-flow sequence. Finally, we tested the sequence on phantoms and mice, and could confirm the expected advantages which the previous study on rats revealed.
Author : Julio Garcia
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)
Download or read book Four-Dimensional Flow Magnetic Resonance Imaging and Applications in Cardiology written by Julio Garcia and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Blood flow through the heart and great vessels moves in three dimensions (3D) throughout time. However, the assessment of its 3D nature has been limited in the human body. Recent advances in magnetic resonance imaging (MRI) allow for the comprehensive visualization and quantification of in-vivo flow dynamics using four-dimensional (4D) flow MRI. In addition, this technique provides the opportunity to obtain advanced hemodynamic biomarkers such as vorticity, helicity, wall shear stress (WSS), pressure gradients, viscous energy loss (EL), and turbulent kinetic energy (TKE). This chapter will introduce 4D flow MRI which is currently used for blood flow visualization and advanced quantification of cardiac hemodynamic biomarkers. We will discuss its advantages relative to other in-vivo flow imaging techniques and describe its potential clinical applications in cardiology.
Author : Mark A. Fogel
Publisher : John Wiley & Sons
ISBN 13 : 1444317040
Total Pages : 480 pages
Book Rating : 4.4/5 (443 download)
Download or read book Principles and Practice of Cardiac Magnetic Resonance in Congenital Heart Disease written by Mark A. Fogel and published by John Wiley & Sons. This book was released on 2010-03-02 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: CMR is a powerful tool in the armamentarium of pediatric cardiology and health care workers caring for patients with congenital heart disease (CHD), but a successful study still presents major technical and clinical challenges. This text was created to give trainees, practitioners, allied professionals, and researchers a repository of dependable information and images to base their use of CMR on. Because CHD presents an intricate web of connections and associations that need to be deciphered, the imager performing CMR needs to understand not only anatomy, physiology, function, and surgery for CHD, but also the technical aspects of imaging. Written by experts from the world’s leading institutions, many of whom pioneered the techniques and strategies described, the text is organized in a logical way to provide a complete understanding of the issues involved. It is divided into three main parts: The Basics of CMR - familiarizes the reader with the minimum tools needed to understand the basics, such as evaluating morphology, ventricular function, and utilizing contrast agents CMR of Congenital and Acquired Pediatric Heart Disease - discusses broad categories of CHD and the use of CMR in specific disease states Special Topics in Pediatric Cardiac MR - covers other important areas such as the complementary role of CT scanning, interventional CMR, the role of the technologist in performing a CMR exam, and more With the ever increasing sophistication of technology, more can be done with CMR in a high quality manner in a shorter period of time than had been imagined as recently as just a few years ago. Principles and Practice of Cardiac Magnetic Resonance in Congenital Heart Disease: Form, Function, and Flow makes a major contribution to applying these techniques to improved patient care. An ideal introduction for the novice or just the curious, this reference will be equally useful to the seasoned practitioner who wants to keep pace with developments in the field and would like a repository of information and images readily availalble.
Author : Andre J. Duerinckx
Publisher : Springer Science & Business Media
ISBN 13 : 0387949593
Total Pages : 355 pages
Book Rating : 4.3/5 (879 download)
Download or read book Coronary Magnetic Resonance Angiography written by Andre J. Duerinckx and published by Springer Science & Business Media. This book was released on 2002 with total page 355 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, there has been increasing interest in the clinical applications of coronary angiography techniques. Coronary MRA can be instrumental in the evaluation of congenital coronary artery anomalies, however, the complexity of advanced MR pulse sequences and strategies may be overwhelming to many. Coronary MR Angiography demystifies the art of coronary MRA by providing a text in plain language with clearly illustrated imaging steps and protocols. Designed to bridge the gap between radiology and cardiology, it is written for physicians and scientists planning to incorporate this technique into their research or practice.
Author : Benjamin Köhler
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (96 download)
Download or read book Guided Qualitative and Quantitative Analysis of Cardiac 4D PC-MRI Blood Flow Data written by Benjamin Köhler and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Hideyuki Hasegawa
Publisher : MDPI
ISBN 13 : 3038971278
Total Pages : 185 pages
Book Rating : 4.0/5 (389 download)
Download or read book Ultrafast Ultrasound Imaging written by Hideyuki Hasegawa and published by MDPI. This book was released on 2018-09-21 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Ultrafast Ultrasound Imaging" that was published in Applied Sciences
Author : Mo Kadbi
Publisher :
ISBN 13 :
Total Pages : 161 pages
Book Rating : 4.:/5 (89 download)
Download or read book 4D Ultra-short TE (UTE) Phase-contrast MRI for Assessing Stenotic Flow and Hemodynamics written by Mo Kadbi and published by . This book was released on 2013 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase-contrast (PC) MRI is a non-invasive technique to assess cardiovascular blood flow. However, this technique is not accurate in the case of atherosclerotic disease and vascular and valvular stenosis due to intravoxel dephasing secondary to disturbed blood flow, flow recirculation, and turbulence distal to the narrowing, resulting in flow-related artifacts. Previous studies have shown that reducing the echo time (TE) decreases the errors associated with phase incoherence due to random motions as observed in unsteady and turbulent flows. As part of this dissertation, a novel 3-D cine Ultra-Short (UTE)-PC imaging method has been developed, and implemented to measure the blood velocity using a UTE center-out radial k-space trajectory with short TE time compared to standard PC MRI sequences. 3D UTE characterizes flow in one direction in a 3D volume, resulting in a single component of the flow velocities. In order to obtain a comprehensive flow assessment in three directions, the 3D UTE sequence needs to be repeated three times, which can be inefficient and time consuming. 4-D flow MRI has been recently used for quantitative flow assessment and visualization of complex flow patterns resulting in more anatomical information and comprehensive assessment of blood flow. With 4D flow MRI method, all the flow information in three direction in a 3D volume though the time can be achieved as part of a single scan. In this dissertation, a novel 4D UTE flow MRI technique has also been designed and implemented which is capable of deriving the three orthogonal components of the velocity field in the flow in a single scan, while achieving very short echo times. In flow phantom studies, comprehensive investigation of several different flow rates revealed significant improvement in flow quantification and reduction of flow artifacts when compared to conventional 4D flow. Furthermore, a reduced TE 4D Spiral flow MRI method has also been implemented which reduces scan times when compared to conventional 4D flow MRI (as well as 4D UTE flow). Despite reduction of scan time as well as TE relative to conventional 4D flow, the achieved TE with the 4D spiral technique is indeed longer than 4D UTE flow. In order to assess clinical feasibility and in order to perform further validation of 4D UTE flow, in an IRB-approved study, twelve aortic stenosis (AS) patients underwent Doppler Ultrasound, conventional 4D flow, and 4D UTE flow scans for a 3 way comparison. 4D UTE flow displayed good correlation with Doppler Ultrasound in patients with moderately severe aortic stenosis, though with the added benefit of not having confounding factors encountered in Doppler Ultrasound (e.g., angle dependence, 2D measurement, and difficulty in locating a proper acoustic window). The proposed 4D UTE flow permits 4D visualization of flow and true 3D measurement of all flow quantities, not possible with Doppler. Further investigations will be required to test the technique in patients with severe or critical aortic stenosis wherein conventional 4D flow will be less accurate due to intravoxel dephasing and spin incoherence.
Author : Donald W. McRobbie
Publisher : Cambridge University Press
ISBN 13 : 1316688259
Total Pages : 405 pages
Book Rating : 4.3/5 (166 download)
Download or read book MRI from Picture to Proton written by Donald W. McRobbie and published by Cambridge University Press. This book was released on 2017-04-13 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt: MR is a powerful modality. At its most advanced, it can be used not just to image anatomy and pathology, but to investigate organ function, to probe in vivo chemistry, and even to visualise the brain thinking. However, clinicians, technologists and scientists struggle with the study of the subject. The result is sometimes an obscurity of understanding, or a dilution of scientific truth, resulting in misconceptions. This is why MRI from Picture to Proton has achieved its reputation for practical clarity. MR is introduced as a tool, with coverage starting from the images, equipment and scanning protocols and traced back towards the underlying physics theory. With new content on quantitative MRI, MR safety, multi-band excitation, Dixon imaging, MR elastography and advanced pulse sequences, and with additional supportive materials available on the book's website, this new edition is completely revised and updated to reflect the best use of modern MR technology.
