Joshua D. Robinson

Advanced flow MRI: emerging techniques and applications.

Magnetic resonance imaging (MRI) techniques provide non-invasive and non-ionising methods for the highly accurate anatomical depiction of the heart and vessels throughout the cardiac cycle. In addition, the intrinsic sensitivity of MRI to motion offers the unique ability to acquire spatially registered blood flow simultaneously with the morphological data, within a single measurement. In clinical routine, flow MRI is typically accomplished using methods that resolve two spatial dimensions in individual planes and encode the time-resolved velocity in one principal direction, typically oriented perpendicular to the two-dimensional (2D) section. This review describes recently developed advanced MRI flow techniques, which allow for more comprehensive evaluation of blood flow characteristics, such as real-time flow imaging, 2D multiple-venc phase contrast MRI, four-dimensional (4D) flow MRI, quantification of complex haemodynamic properties, and highly accelerated flow imaging. Emerging techniques and novel applications are explored. In addition, applications of these new techniques for the improved evaluation of cardiovascular (aorta, pulmonary arteries, congenital heart disease, atrial fibrillation, coronary arteries) as well as cerebrovascular disease (intra-cranial arteries and veins) are presented.

Thoracic Aorta 3D Hemodynamics in Pediatric and Young Adult Patients With Bicuspid Aortic Valve

To evaluate the 3D hemodynamics in the thoracic aorta of pediatric and young adult bicuspid aortic valve (BAV) patients.

Distribution of blood flow velocity in the normal aorta: Effect of age and gender

To apply flow distribution analysis in the entire aorta across a wide age range from pediatric to adult subjects.

Assessment of myocardial motion in children and young adults using High-temporal resolution MR tissue phase mapping

Background MR Tissue phase mapping (TPM) is a non-invasive tool to detect regional and global myocardial wall motion. Evaluation of myocardial velocity in radial and longitudinal direction throughout the cardiac cycle may help us better understand myocardial mechanics. Our goal is to investigate regional and global left ventricular myocardial motion using respiratory-gated high temporal resolution TPM in children and young adults. Methods

Comparison of 4D flow and 2D PC MRI blood flow quantification in children and young adults with congenital heart disease

Background Echocardiography (echo) is the primary imaging modality for assessment of aortic and pulmonary blood flow velocities. 2D phase contrast (PC) MRI provides better access to all segments of the aortic and pulmonary system and is considered the standard for evaluating blood flow. Both techniques are limited by velocity analysis in 2D planes and by single-direction velocity measurement which may be inadequate to characterize the complex 3D hemodynamics in congenital heart disease (CHD). 4D flow MRI provides simultaneous assessment of 3D blood flow characteristics of all vessels within a 3D volume and offers the ability to retrospectively quantify blood flow parameters at selectable regions of interest. The aim of this study is to test the potential of 4D flow for accuracy of quantification of aortic and pulmonary flow parameters compared to the reference standards echo and 2D PC MRI in children and young adults with CHD. Methods 32 patients with CHD who underwent simultaneous 4D flow and 2D PC MRI and echo within 9 months of MRI were retrospectively included. 2D PC MRI flow quantification in the aortic root (Ao), pulmonary trunk (PT), and right and left pulmonary arteries (RPA, LPA) was analyzed using Medis (Medis, Leiden, The Netherlands). 4D flow data analysis included calculation of a 3D-PC-angiogram which was used to position analysis planes in the Ao, PT, LPA and RPA (EnSight, CEI, Apex, NC) for quantification of net flow, regurgitant fraction, Qp:Qs, and peak velocities. Ao peak velocities were assessed by echo. Linear regression analysis was performed. Pearson’ sc orrelation coefficient (r) was calculated. A correlation with p<0.05 was considered significant. Results

Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently ‘Have-A-Heart’ campaign

Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently “Have-A-Heart” campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.

4D flow MRI demonstrates changes in cardiovascular haemodynamics in complex congenital heart disease

An 8-month-old female with heterotaxy syndrome, single ventricle physiology, double outlet right ventricle, mitral atresia, total anomalous pulmonary venous connection to the coronary sinus, an interrupted inferior vena cava with azygous continuation to the superior vena cava, and post pulmonary artery banding underwent a Kawashima palliative procedure. Seven months …

Evaluating the disease progression of pediatric bicuspid aortic valve patients using 4D flow MRI data

Background Understanding the natural history of bicuspid aortic valve (BAV) disease from childhood through adulthood may aid in determining if and when these patients are at risk for disease progression. 4D flow MRI can be used to visualize blood flow patterns in BAV patients and can be used to assess valvular function. In this study, we track the progression of pediatric BAV disease by assessing flow pattern and velocity changes over the course of two 4D flow MRI exams separated by at least 7 months between baseline and follow-up scan.

Enhanced segmentation improves 4D blood flow quantification in patients with tetralogy of Fallot and pulmonary regurgitation

Background 2D phase contrast (PC) MRI provides reliable quantification of blood flow in pts with tetralogy of Fallot (TOF). While 2D PC is the standard for evaluating pulmonary regurgitant fraction, it is limited by single direction velocity measurement and may be inadequate to characterize 3D hemodynamics. Multiple planar acquisitions are often required. While 4D flow MRI provides simultaneous assessment of 3D flow characteristics of all vessels within a volume and offers the ability to retrospectively quantify blood flow parameters at selectable regions of interest, these exams require substantial postprocessing and adjacent structures may be difficult to analyze. We compared traditional 2D PC and 4D flow quantification in patients with TOF using both traditional and enhanced segmentation techniques.

Aortic coarctation augments changes in thoracic aortic hemodynamics in pediatric and young adult patients with bicuspid aortic valve

Background Bicuspid aortic valve (BAV) is a congenital abnormality that is often associated with aortic coarctation. Evidence suggests this combination may increase the risk of secondary aortic complications compared to patients with BAV alone.[1] Altered aortic hemodynamics likely induce vascular remodeling[2] and may contribute to these complications. No study has investigated the impact of aortic coarctation on aortic hemodynamics in pediatric and young adult patients with BAV using time-resolved three-dimensional phase contrast (4D flow) MRI. The aim of this study is to utilize 4D flow MRI to compare thoracic aorta flow patterns in pediatric and young adult patients with BAV with and without aortic coarctation or coarctation repair. Methods In accordance with an IRB-approved protocol, 17 patients with BAV (age = 11.9 +/- 5.3 years) who underwent cardiovascular MRI including 4D flow as part of follow-up care were included. Seven patients had aortic coarctation including 5 patients with coarctation repairs. Images were processed using in-house software for noise reduction, anti-aliasing, and eddy current correction. Flow visualization and quantification were performed in EnSight (CEI, Apex, NC). Aortic root z-scores were calculated from MRI measurements and height and weight at time of scan in EchoIMS (Merge, Chicago, IL). Flow jet pattern and helicity were assessed in the ascending aorta, aortic arch, and descending aorta. Flow jet pattern was determined by the region of peak velocity in systole corresponding to anatomically designated quadrants of