ABSTRACT
Objective · To investigate the feasibility of four-dimensional flow MRI (4D flow MRI) in evaluating the hemodynamics of forearm autologous arteriovenous fistula (AVF) in renal dialysis patients. Methods · Forty-five patients from Renal Division of Renji Hospital, Shanghai Jiao Tong University School of Medicine were included. Patients with forearm AVF underwent ultrasonography and MRI. The consistency of 4D flow MRI hemodynamic parameters measured by two radiologists and hemodynamic parameters at the same plane of AVF by 4D flow MRI and ultrasonography were analyzed by paired t test. The morphological parameters of AVF were acquired from black blood sequence, and they were used for Pearson correlation analysis with the hemodynamic parameters obtained from 4D flow MRI. Results · Forty-two patients completed the forearm AVF ultrasonography and MRI successfully.Paired t test showed that the consistency of 4D flow MRI hemodynamic parameters by two radiologists was good (all P=0.000), and all hemodynamic parameters measured by 4D flow MRI and ultrasonography were in good agreement (r=0.292-0.569, all P＜0.05) except for the peak flow velocity at anastomosis (r=-0.078, P＞0.05). Pearson correlation analysis showed that the cephalic venous flow volume of AVF was correlated with the diameter ratio of the cephalic venous to radial artery and the anastomosis area (r=-0.671, r=0.482, both P＜0.05), and the wall shear stress (WSS) near the anastomosis was correlated with the anastomosis angle and wall thickness (r=0.530, r=0.462, both P＜0.05). Conclusion · 4D flow MRI can be used to evaluate the hemodynamic parameters of forearm AVF in renal dialysis patients, which can provide a reference for further study of AVF dysfunction.
ABSTRACT
Objective • To investigate the feasibility of four-dimensional flow MRI (4D flow MRI) in evaluating the hemodynamics of forearm autologous arteriovenous fistula (AVF) in renal dialysis patients. Methods • Forty-five patients from Renal Division of Renji Hospital, Shanghai Jiao Tong University School of Medicine were included. Patients with forearm AVF underwent ultrasonography and MRI. The consistency of 4D flow MRI hemodynamic parameters measured by two radiologists and hemodynamic parameters at the same plane of AVF by 4D flow MRI and ultrasonography were analyzed by paired t test. The morphological parameters of AVF were acquired from black blood sequence, and they were used for Pearson correlation analysis with the hemodynamic parameters obtained from 4D flow MRI. Results • Forty-two patients completed the forearm AVF ultrasonography and MRI successfully. Paired t test showed that the consistency of 4D flow MRI hemodynamic parameters by two radiologists was good (all P=0.000), and all hemodynamic parameters measured by 4D flow MRI and ultrasonography were in good agreement (r=0.292-0.569, all P0.05). Pearson correlation analysis showed that the cephalic venous flow volume of AVF was correlated with the diameter ratio of the cephalic venous to radial artery and the anastomosis area ( r=-0.671, r=0.482, both P<0.05), and the wall shear stress (WSS) near the anastomosis was correlated with the anastomosis angle and wall thickness (r=0.530, r=0.462, both P<0.05). Conclusion • 4D flow MRI can be used to evaluate the hemodynamic parameters of forearm AVF in renal dialysis patients, which can provide a reference for further study of AVF dysfunction.
ABSTRACT
Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions.
Subject(s)
Biomarkers , Hemodynamics , Hydrodynamics , Magnetic Resonance ImagingABSTRACT
Objective: Hemodynamic parameters are critical to perform a proper diagnosis. However, due to the large number of variables that can be obtained, overall analysis may represent a complex task. To facilitate this, we propose to create a model for classifying different hemodynamic variables between those belonging to a healthy individual and to a pathological patient. For this purpose, we employed data mining techniques to identify relationships among various aortic hemodynamic parameters obtained through multi-dimensional (4D flow) MR imaging. Method: A 4D flow sequence of whole heart and great vessels was acquired using MRI in 19 healthy volunteers and 2 patients (one with aortic coarctation and one with repaired coarctation of the aorta). Retrospectively, data were reformatted along the aorta; three MRI acquisitions were performed for volunteers and 30 sequences for each patient. In each slice the aorta was segmented and various parameters were quantified: area, maximum velocity, minimum velocity, flow and volumen, with following values being calculated for last four parameters: maximum, average, standard deviation, kurtosis, skewness, proportion of time to reach the maximum value, among others. A total of 26 variables for each acquisition were obtained. In order to classify data, the CART Technique (Classification and Regression Trees) was applied. To validate the model, two extra projections were generated per each volunteer and 20 slice per each patient. Results: By using only 7 variables, the CART Technique allows discrimination between images performed either on volunteers or patients with an error rate of 14.1 percent, a sensitivity of 82.5 percent, and a specificity of 89.4 percent. Conclusions: 4D flow MR imaging provides a wealth of hemodynamic data that can be difficult to analyze. In this paper we demonstrate that by using data mining techniques it is possible to classify images from relevant hemodynamic parameters and their relationships in order...
Objetivo: Los parámetros hemodinámicos son de gran utilidad para realizar un adecuado diagnóstico. Sin embargo, debido a la gran cantidad de variables que pueden obtenerse, el análisis global de todas ellas puede ser complejo. Para facilitar esta tarea, nosotros proponemos crear un modelo que permita clasificar distintas variables hemodinámicas entre las pertenecientes a un individuo sano o a uno patológico. Para ello, usaremos técnicas de minería de datos que permitan identificar y encontrar relaciones entre distintos parámetros hemodinámicos de la aorta obtenidos a través de flujo multidimensional (4D flow) por resonancia magnética. Método: Una secuencia 4D flow de todo el corazón y los grandes vasos fue adquirida utilizando resonancia magnética en 19 voluntarios sanos y 2 pacientes (uno con una coartación aórtica y otro con una coartación aórtica reparada). Retrospectivamente, los datos fueron reformateados a lo largo de la aorta, originándose 3 cortes en los voluntarios y 30 cortes en cada paciente. En cada corte la aorta fue segmentada y distintos parámetros fueron cuantificados: área, velocidad máxima, velocidad mínima, flujo y volumen, calculándose en los cuatro últimos su valor máximo, promedio, desviación estándar, curtosis, sesgo, proporción de tiempo en alcanzar el valor máximo, entre otros. Teniendo un total de 26 variables por cada corte. Se aplicó la técnica de árboles de decisión tipo CART (por sus siglas en inglés) para clasificar los datos. Para validar el modelo, 2 cortes extras fueron generados por cada voluntario y 20 cortes por cada paciente. Resultados: La técnica CART, mediante la utilización de sólo 7 variables, puede clasificar las imágenes de los voluntarios y pacientes con una tasa de error del 14,1 por ciento, una sensibilidad de 82,5 por ciento y una especificidad de 89.4 por ciento. Conclusiones: 4D flow provee una gran cantidad de datos hemodinámicos que son difíciles de analizar. En este trabajo demostramos que al utilizar...
Subject(s)
Humans , Aorta/physiopathology , Cardiac Imaging Techniques , Imaging, Three-Dimensional/methods , Magnetic Resonance Imaging/methods , Blood Flow Velocity/physiology , Image Enhancement/methods , Data Mining , Decision Trees , Cardiovascular Diseases/diagnosis , Hemodynamics , Regional Blood Flow , Regression Analysis , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Objective. To validate the utility of 4D Blood Flow and Navier-Stokes equations to create relative pressure (RP) maps in the aorta and pulmonary artery (PA) in healthy volunteers and patients with repaired tetralogy of Fallot (TOF). Methods. A 4D flow sequence of whole heart and its major vessels was acquired in 10 healthy volunteers and 6 patients with repaired TOF. The root of the ascending aorta was used as the reference point to calculate RP along five different points of this area. In addition, relative pressure of both right and left PA was measured as correlated to absolute pressure. Results. Patients with repaired TOF showed greater pulmonary artery (PA) relative pressure differences between maximum and minimum values when compared to volunteers (p <0.05). Additionally, aortic relative pressures had an excellent correlation with published data, whether using 4D flow or by catheterization. Conclusions. 4D Flow MRI may represent a new non-invasive and non operator-dependent diagnostic tool in CV disease management.
Objetivo. Utilizar 4D Flow y las ecuaciones de Navier-Stokes para obtener mapas de presiones relativas (PR) en la Aorta y Arteria Pulmonar (AP) de voluntarios y pacientes con Tetralogía de Fallot reparada (TOFr). Métodos. En 10 voluntarios y 6 pacientes con TOFr se adquirió la secuencia 4D flow del corazón y sus principales vasos. La raíz de la Aorta Ascendente se utilizó como referencia para calcular las PR a esta zona en cinco puntos distintos. Además, se midió la PR de la AP derecha e izquierda respecto a la AP. Resultados. Los pacientes con TOFr tuvieron diferencias de PR entre los valores máximos y mínimos más grandes que los voluntarios en la AP (p<0,05). Adicionalmente, las PR de la aorta tuvieron una excelente correlación con datos publicados utilizando 4D flow y mediante cateterización. Conclusiones. 4D Flow podría constituir una nueva herramienta diagnóstica, no invasiva, ni operador dependiente, en el manejo de patologías CV.
Subject(s)
Middle Aged , Aorta, Thoracic/physiopathology , Pulmonary Artery/physiopathology , Magnetic Resonance Imaging , Tetralogy of Fallot/physiopathology , Blood Flow Velocity , PressureABSTRACT
Purpose. To demonstrate the utility of 4D flow MR imaging for analyzing blood flow patterns and flow distribution in patients with congenital heart diseases. Methods: Six patients with congenital heart diseases were scanned using a standard cardiac MRI protocol, according to their condition. Additionally, 2D flow sequences of the great vessels, and a 4D flow sequence covering the entire heart were acquired. Flow patterns were visualized by using vector fields, streamlines and particle traces. Results: 4D flow technique depicted vortices and helical flow in the pulmonary artery of most patients, as well as in the aorta and superior vena cava of one patient with corrected aortic coarctation and a levoatrial cardinal vein. Conclusion: 4D flow MR imaging enables the identification of flow patterns difficult to detect with other diagnostic modalities. Comprehensive evaluation of flow patterns might help to understand the hemodynamic consequences of congenital heart diseases and their surgical procedures.
Objetivo. Demostrar la utilidad de 4D flow para el análisis de patrones y distribución de flujos en pacientes con cardiopatías congénitas. Métodos: Seis pacientes con cardiopatías congénitas fueron escaneados con un protocolo de resonancia magnética cardíaca estándar. Además se incluyeron secuencias de flujo 2D en los principales vasos del tórax y una secuencia 4D flow que cubría todo el corazón. Para la visualización de los patrones de flujo se emplearon vectores de velocidad, líneas de flujo y trazadores de partículas. Resultados: 4D flow reveló vórtices y hélices en la arteria pulmonar de la mayoría de los pacientes, y en la aorta y vena cava superior de un paciente con coartación aórtica reparada y vena cardinal levoatrial. Conclusiones: 4D flow permite identificar patrones de flujo en pacientes con cardiopatías congénitas, difíciles de observar con otros métodos diagnósticos. La evaluación de patrones de flujo podría contribuir a comprender las consecuencias hemodinámicas de diferentes cardiopatías congénitas.