Showing papers by "James C. Carr published in 2013"

Intracranial 4D flow MRI: toward individualized assessment of arteriovenous malformation hemodynamics and treatment-induced changes.

Abstract: BACKGROUND AND PURPOSE: Arteriovenous malformations are an important etiology of hemorrhagic stroke. However, current imaging modalities and risk do not provide insights into individual AVM hemodynamics and its role in pathophysiology. The aims of this study are to determine whether intracranial 4D flow MR imaging can provide insights into arteriovenous malformation hemodynamics independent of the Spetzler-Martin grade and to report the changes in flow observed during staged embolization. MATERIALS AND METHODS: Intracranial 3D blood flow was assessed in 20 patients with AVM (age = 39 ± 15 years, Spetzler-Martin grade ranging from 1–4) with the use of 4D flow MR imaging (temporal resolution = 45 ms, spatial resolution = [1.2–1.6mm]3). AVM hemodynamics were visualized by means of time-integrated 3D pathlines depicting the AVM arterial feeding and venous draining patterns over the cardiac cycle. Analysis included the grading of feeding and draining velocities on a 3-point scale (0 = low 50 cm/s). For 4 of 20 patients undergoing 4D flow MR imaging follow-up after staged embolization, peak velocities were quantified in arterial feeders, draining veins, the sagittal sinus, and contralateral arteries. RESULTS: In 50% of the cases with Spetzler-Martin grade >2, heterogeneous flow (velocity grade differences >1) was found across arteries and veins. Velocities in draining veins increased from Spetzler-Martin grade = 1 (grading = 0.5 ± 0.6) to Spetzler-Martin grade ≥3 (1.1 ± 0.6), whereas arterial velocities were similar (1.7 ± 0.6 versus 1.5 ± 0.6). In the postembolization subgroup of 4 patients, 4D flow MR imaging demonstrated successively more compact AVM and redistribution of velocities. Changes in arterial and venous velocities during treatment were highly different among individuals. CONCLUSIONS: Spetzler-Martin grade does not reflect differences in 3D AVM arterial and venous hemodynamics, and an individual assessment of AVM hemodynamics may be needed for improved lesion characterization. Four-dimensional flow MR imaging may have the potential to monitor and guide embolization treatment planning.

Proximal Superficial Femoral Artery Occlusion, Collateral Vessels, and Walking Performance in Peripheral Artery Disease

Abstract: Objectives We studied associations of magnetic resonance imaging (MRI)-measured superficial femoral artery (SFA) occlusions with functional performance, leg symptoms, and collateral vessel number in peripheral artery disease (PAD). We studied associations of collateral vessel number with functional performance in PAD. Background Associations of MRI-detected SFA occlusion and collateral vessel number with functional performance among individuals with PAD have not been reported. Methods A total of 457 participants with an ankle brachial index (ABI) Results Adjusting for age, sex, race, comorbidities, and other confounders, the presence of an SFA occlusion was associated with poorer 6-min walk performance (1,031 vs. 1,169 feet, p = 0.006), slower fast-paced walking velocity (1.15 vs. 1.22 m/s, p = 0.042), and lower SPPB score (9.07 vs. 9.75, p = 0.038) compared with the absence of an SFA occlusion. More numerous collateral vessels were associated with better 6-min walk performance (0 to 3 collaterals—1,064 feet, 4 to 7 collaterals—1,165 feet, ≥8 collaterals—1,246 feet, p trend = 0.007), faster usual-paced walking speed (0 to 3 collaterals—0.84 m/s, 4 to 7 collaterals—0.88 m/s, ≥8 collaterals—0.91 m/s, p trend = 0.029), and faster rapid-paced walking speed (0 to 3 collaterals—1.17 m/s, 4 to 7 collaterals—1.22 m/s, ≥8 collaterals—1.29 m/s, p trend = 0.002), adjusting for age, sex, race, comorbidities, ABI, and other confounders. Conclusions Among PAD participants, MRI-visualized occlusions in the proximal SFA are associated with poorer functional performance, whereas more numerous collaterals are associated with better functional performance. (Magnetic Resonance Imaging to Identify Characteristics of Plaque Build-Up in People With Peripheral Arterial Disease; NCT00520312 )

Myocardial T2-mapping and velocity mapping: changes in regional left ventricular structure and function after heart transplantation.

Abstract: Monitoring post cardiac transplant (TX) status relies on frequent invasive techniques such as endomyocardial biopsies and right heart cardiac catheterization. The aim of this study was to noninvasively evaluate regional myocardial structure, function, and dyssynchrony in TX patients. Myocardial T2-mapping and myocardial velocity mapping of the left ventricle (basal, midventricular, and apical short-axis locations) was applied in 10 patients after cardiac transplantation (49 ± 13years, n = 2 with signs of mild rejection, time between TX and MRI = 1–64 months) and compared to healthy controls (n = 20 for myocardial velocity mapping and n = 14 for T2). Segmental analysis based on the 16-segment American Heart Association model revealed increased T2 (P = 0.0003) and significant (P < 0.0001) reductions in systolic and diastolic radial and long-axis peak myocardial velocities in TX patients without signs of rejection compared to controls. Multiple comparisons of individual left ventricular segments demonstrated reductions of long-axis peak velocities in 50% of segments (P < 0.001) while segmental T2 values were not significantly different. Systolic radial as well as diastolic radial and long-axis dyssynchrony were significantly (P < 0.04) increased in TX patients indicating less coordinated contraction, expansion, and lengthening. Correlation analysis revealed moderate but significant (P < 0.010) inverse relationships between myocardial T2 and long-axis peak velocities suggesting a structure–function relationship between altered T2 and myocardial function. Magn Reson Med 70:517–526, 2013. © 2012 Wiley Periodicals, Inc.

Cerebral arteriovenous malformation: complex 3D hemodynamics and 3D blood flow alterations during staged embolization.

Abstract: Complex hemodynamics in cerebral arteriovenous malformations (AVM) are thought to play a key role in their pathophysiology. We applied 4D flow magnetic resonance imaging (MRI) for the detailed evaluation of AVM function at baseline and to investigate the impact of staged embolization on AVM hemodynamics in a patient with a Spetzler-Martin grade III AVM. The patient underwent three embolization procedures resulting in >50% nidal casting and obliteration of several arteriovenous fistulae. 4D flow MRI demonstrated highly complex 3D hemodynamics at baseline and revealed intricate arterial feeding, a large vascularized nidus with high variability in regional blood flow velocities, and clearly visible venous drainage with high flow velocities above 50 cm/s. 3D blood flow visualization and quantification during follow-up illustrated the systemic impact of focal embolization on cerebral hemodynamics resulting in compaction of the AVM, redistribution of blood flow velocities, and altered peak flow velocities and blood flow in multiple vascular territories. 4D flow MRI may offer a useful noninvasive tool to help to identify subtleties and nuances of the quantitative hemodynamic alterations in AVM vascular architecture as a supplement to established imaging modalities.

Cardiac computed tomographic imaging to evaluate myocardial scarring/fibrosis in patients with hypertrophic cardiomyopathy: a comparison with cardiac magnetic resonance imaging

Abstract: Contrast enhanced magnetic resonance imaging (CeMRI) reliably identifies myocardial fibrosis in patients with hypertrophic cardiomyopathy (HCM). However, many patients have contraindications to ceMRI. Previous studies have shown that contrast enhanced multi-detector computed tomography (ceMDCT) can visualize focal scars following myocardial infarction in experimental animals and patients. The purpose of this manuscript is to assess the ability of ceMDCT to detect focal myocardial scars in patients with HCM. Twelve HCM patients underwent ceMRI and ceMDCT. Fibrotic areas of myocardium were defined as focal or diffuse areas of fibrosis. The mean signal intensity in ceMRI and attenuation values in ceMDCT of the fibrotic regions, normal myocardium and left ventricle blood pool contrast were measured using qualitative and quantitative analysis. Focal scar mass was calculated using both techniques. Focal scars were detected in 9 patients and diffuse fibrosis was visualized in all patients by ceMRI. Differences between normalized SI of normal myocardium and focal scars, normal and diffuse areas of fibrosis, and diffuse fibrosis and focal scars were significant for both ceMRI and ceMDCT (p < 0.05). Diffuse fibrosis was poorly visualized by ceMDCT but was detectable using quantitative measurements. CeMDCT has potential to detect focal myocardial scars in patients with HCM who have contraindications to ceMRI study. However, ceMDCT does not enable adequate visualization of diffuse myocardial fibrosis, and thus is less well suited than ceMRI for assessment of total burden of fibrosis. This limitation may be overcome using quantitative methodology.

Time-resolved MR venography of the pulmonary veins precatheter-based ablation for atrial fibrillation.

Abstract: Purpose: To evaluate time-resolved magnetic resonance angiography (TR-MRA) of the pulmonary venous circulation using the time-resolved angiography with interleaved stochastic trajectories (TWIST) method and compare it with the more commonly used conventional contrast-enhanced magnetic resonance angiography (CE-MRA) approach in atrial fibrillation patients referred for preablation pulmonary vein mapping. Materials and Methods: This study was approved by the Institutional Review Board. Twenty-six patients (15 males; age 59.6 ± 12.7 years) referred for preablation pulmonary vein mapping underwent both conventional CE-MRA and TR-MRA with TWIST. Imaging was performed on a 1.5 T (Magnetom Avanto, Siemens Healthcare, Erlangen, Germany) MRI scanner. Source partition and maximum intensity projection (MIP) images were evaluated retrospectively. For quantitative analysis, pulmonary vein ostium orthogonal dimensions were measured using double oblique multiplanar reformatting. The results were analyzed using paired t-tests, Lin's concordance correlation coefficient, and Bland–Altman plots. For qualitative analysis, both source partition images and MIP images were assessed by two observers (A.P. and M.G.). The presence of common ostiums or accessory veins was recorded and analyzed using unweighted Cohen's kappa. Pulmonary vein conspicuity was scored on a scale of 1–4 (1 = poor, 2 = fair, 3 = good, 4 = excellent) and analyzed using paired t-tests, intraclass correlation coefficients, and quadratic weighted kappa statistics. Results: Orthogonal venous diameters were comparable for both TR-MRA and conventional CE-MRA (1.34 ± 0.37 vs. 1.38 cm ± 0.36, respectively). Results of paired t-tests, Lin's concordance correlation coefficient, and Bland–Altman analysis revealed relatively close comparison between methods. The magnitude of the mean difference for any of the statistical comparisons did not exceed 0.10 cm. The visualization of variant pulmonary vein anatomy was very similar for both techniques. Agreement between techniques was determined to be “good” to “very good” (κ = 0.78–0.85). Conspicuity scores for each pulmonary vein were also very close. Paired t-tests, intraclass correlation coefficients, and quadratic weighted kappa statistics all revealed strong agreement between methods. Conclusion: TR-MRA using TWIST produces comparable anatomic images and pulmonary venous dimensions to the more widely used CE-MRA technique. Additionally, the TWIST technique improves arterio-venous separation, does not need exact bolus timing, requires less gadolinium, and gives additional information on vein perfusion. J. Magn. Reson. Imaging 2013;37:127–137. © 2012 Wiley Periodicals, Inc.

Time-resolved three-dimensional phase contrast MRI evaluation of bicuspid aortic valve and coarctation of the aorta.

Abstract: A 41-year-old man with a bicuspid aortic valve (BAV) and coarctation of the aorta, as visualized by 2D phase contrast cardiovascular magnetic resonance imaging (CMR) ( Figure 1D , Supplementary data online, Videos S1 ) and contrast enhanced MR angiography ( Figure 1A ), was referred for evaluation by time-resolved 3D phase contrast (4D flow) CMR to assess the flow velocity through the coarctation and provide aortic flow characterization. Findings of the comprehensive examination demonstrate the complex haemodynamic patterns that emerge throughout the aorta secondary …

Impact of Aneurysm Repair on Thoracic Aorta Hemodynamics

Abstract: We present pre- and postoperative imaging findings in a 29-year-old man with a bicuspid aortic valve (BAV) with fusion of the right and left coronary leaflets and a 6.1 cm × 6.3 cm ascending aorta aneurysm (Figure 1). The patient underwent a valve-sparing aortic root replacement with a 34-mm Dacron graft and BAV repair with resection of the raphe of the fused leaflet and leaflet shortening of the noncoronary cusp. Figure 1. Sagital ( A ) and axial ( B ) preoperative MRI demonstrating a 6.1×6.3 cm ascending aorta (AAo) aneurysm. To better understand the preoperative flow characteristics in the large aneurysm and the impact of surgical repair and reconstruction on thoracic aorta hemodynamics, time-resolved 3-dimensional phase contrast (4D flow) MRI was performed before and after surgery. The MRI examinations (pre: 3.0 T Skyra, post: 1.5 T Avanto, Siemens, Germany) included both 4D flow MRI (velocity sensitivity pre:150 cm/s, post: 250 cm/s, spatial/temporal resolution pre: 3.14×2.13×3.2 mm3/39 ms, post: 2.88×2.13×2.15 mm3/38ms) and dynamic 2-D cine imaging of the heart (steady-state free precession, spatial/temporal resolution pre: 1.25×1.25×6 mm3/29 ms post:1.8×1.8×6 mm3/39 ms). The study was approved by the local institutional review board, and informed consent was obtained from the patient. Blood flow patterns within the thoracic aorta were visualized using time-resolved 3D pathlines to illustrate complex blood flow dynamics over the entire cardiac cycle (EnSight, CEI). In addition, 3D velocity streamlines drawn tangent to the time-resolved velocity field were used to illustrate instantaneous flow dynamics in the thoracic aorta. Forward and …

Effects of respiratory motion on coronary wall MR imaging: a quantitative study of older adults.

Abstract: The aim of the present study is to assess the effects of respiratory motion on the image quality of two-dimensional (2D), free-breathing, black-blood coronary wall magnetic resonance (MR) imaging. This study was compliance with the HIPPA. With the approval of the institution review board, 230 asymptomatic participants, including 164 male patients (72.9 ± 4.4 years) and 66 female patients (72.4 ± 5.1 years), were recruited. Written informed consent was obtained. A 2D navigator (NAV)-gated, black-blood coronary wall MR imaging sequence was run on the left main artery, the left anterior descending artery and the right coronary artery. The drift of the location of the NAV and scan efficiency were compared between good (scored 2 or 3) and poor images (scored 1). Age, body weight, body weight index, heart rate, length of the rest period of cardiac motion, diaphragm excursion and breathing frequency were compared using a t test between the “successful” (having 2 or 3 good images) and “unsuccessful” cases (having 1 or 0 good images). A logistic regression model was applied to identify the contributors to good image quality. The drift of the NAV location and the scan efficiency were higher in the 411 good images compared with the 279 poor images. Minimal drift of the NAV location and low body weight were identified as independent predictors of good images after using a logistic regression model to adjust for multiple physiological and technical factors. The stability of respiratory motion significantly influences the image quality of 2D, free-breathing, black-blood coronary wall MR imaging.

4D flow jet shear layer detection method for the measurement of effective orifice area and assessment of aortic stenosis severity

Abstract: Background Aortic stenosis (AS) is the most common cause of valve replacement and its severity is mainly assessed by transthoracic Doppler echocardiography (TTE) to quantify valve effective orifice area (EOA) as determined by the continuity equation. In a previous study we demonstrated that EOA can be directly determined with 2D flow MRI downstream of the AS using the jet shear layer detection (JSLD) method and the acoustical source term (AST) concept. However, both TTE and 2D flow MRI rely on the measurement of local and single-directional velocities and thus incomplete assessment of the complex post-valve flow dynamics in a significant proportion of patients. 3D CINE phase contrast MRI with 3-directional velocity encoding (4D flow MRI) may improve EOA estimation by the JSLD method coupled with full volumetric coverage of ascending aortic 3D blood flow. The objective of this study was to validate 4D flow MRI based EOA estimation using an in-vitro stenosis phantom and to apply the technique for the in-vivo measurement of the valve EOA compared to the reference standard 2D flow MRI. Methods

Quantification of left atrial flow velocity distribution in atrial fibrillation using 4D flow MRI

Abstract: Background Atrial fibrillation (AF) is an arrhythmia characterized by irregular electrical activity in the left atrium (LA). Thromboembolism is the most serious complication of AF, usually manifesting as stroke or systemic embolism (1). This is thought to be linked to the increased risk of thrombus formation in the LA due to a decrease in blood velocity (stasis) or flow abnormalities. A better appreciation of the underlying mechanisms and risk factors for thrombus formation in the individual patient are needed to improve risk stratification and therapy planning. Using 4D-flow MRI, time resolved blood velocity measurements can be made in patients with AF. The aim of this study was to compare LA velocity distributions in different groups of AF patients. We hypothesize that persistent AF results in more deranged LA flow patterns with reduced velocities which may be related to an increased risk of thrombus formation and thus stroke. Methods MRI data were acquired from 31 AF patients (mean age 63+/-10.5) from two groups (n=21 post-treatment, in sinus rhythm, n=10 in persistent AF). Each subject underwent gated 4D-Flow MRI on 1.5T and 3T MR systems (Siemens, Erlangen, Germany). After noise filtering, Maxwell, and eddy current correction, time resolved pathlines were emitted from planes placed manually over the pulmonary veins at the junction with the LA (Fig 1). The LA was segmented and the distribution of velocities was quantified by histogram analysis. Mean velocities were calculated for each subject group. In addition number of voxels with velocities greater than 0.2m/s was calculated. The selection of the velocity threshold was based on previous TEE results which found that systolic LA velocities less than 0.2m/s constitute a risk factor for stroke (2). Results Qualitative observation of the blood flow patterns in patients showed very different patterns between those subjects imaged in sinus rhythm and those in persistent AF. Fig 1 displays clear differences in blood flow at end systole (A,D), early diastole (B,E), and mid diastole (C,F) for a post-intervention AF patient in sinus rhythm and in persistent AF. The quantitative results from all subjects are summarized in fig 2. Patients with persistent AF had a mean blood flow of 0.14±0.03m/s, lower than AF patients in sinus rhythm (0.19±0.04m/s, p=0.006). 14% of the velocity values for patients in AF were greater than 0.2m/s, lower than patients in sinus (35%, p=0.004).

From unicuspid to quadricuspid: the impact of aortic valve morphology on 3D hemodynamics

Abstract: Background The purpose of this study was to assess the impact of aortic valve morphology on aortic 3D blood flow dynamics and wall shear stress (WSS) in normal and a wide range of congenitally altered aortic valves ranging from unicuspid to quadricuspid morphology. Methods In-vivo aortic 3D hemodynamics were evaluated by MRI in 17 patients with unicuspid (n=3), bicuspid (n=9, 3 true bicuspid, 3 right-left (RL) coronary leaflet fusion, and 3 right-non (RN) coronary leaflet fusion), trileaflet (n=3), and quadricuspid aortic valves (n=2). Valve morphology and dynamics were assessed using 2D CINE MRI. Aortic blood flow was measured using ECG and respiration synchronized 4D flow MRI with full volumetric coverage of the aorta. Data analysis included co-registered visualization of aortic valve morphology with systolic 3D blood flow and grading of valve-specific aortic out-flow patterns. The influence of valve geometry on aortic hemodynamics was quantified by calculation of valve flow angle and segmental distribution of ascending aorta WSS. Results All congenitally altered valves showed marked flow derangement, elevated velocity jets along the aortic wall and distinct flow impingement locations. While all RLBAV valves were associated with flow jets directed towards the right anterior aortic wall, RN-fusion and unicuspid valves showed jet patterns towards the right-posterior wall. Quantitative analysis revealed higher flow angles for unicuspid, true BAV, RN-BAV, RL-BAV, and quadricuspid

Abstract 17900: Analysis of Left Atrial Flow Velocity Distribution by 4D Flow MRI in Patients With Atrial Fibrillation

Abstract: Background: To identify atrial fibrillation (AF) patients with high stroke risk, clinicians use risk scores with mediocre predictive values (C statistic 0.55-0.64). Because blood stasis is a key factor responsible for thrombus formation in the left atrium (LA), evaluating LA 3D flow patterns may improve understanding of stroke risk in AF patients. Objective: To assess differences in LA flow velocity distribution in AF patients and controls by 4D flow MRI Methods: We performed 4D flow MRI in 21 AF patients in sinus rhythm during imaging (AF-sinus), 10 AF patients in AF (AF-afib), and 9 controls. Manual segmentation of LA volume enabled analysis of all LA voxel velocities over all phases of the cardiac cycle. LA flow was quantified by mean LA velocity and the percentage of LA velocities > 0.2 m/s (incidence). To evaluate the highest velocities in each voxel, varying proportions of the velocity profiles (top 5%, 25%, 50%, 65%, 100%) were analyzed. Results: Patient ages (years) in the groups were control (59±...

Quantitative cardiac MR assessment of left ventricular diastology

Abstract: Background Cardiac MR (CMR) is the accepted gold standard for the assessment of myocardial scar and biventricular systolic function. Bright blood cine imaging with phase-contrast mitral inflow assessment has shown promise for the evaluation of left ventricular (LV) diastology. The purpose of this study is to evaluate the accuracy of LV diastolic function grading by CMR, using Doppler echocardiography as the reference standard. We hypothesize that quantitative CMR analysis of diastolic function coupled with left atrial volume (LAV) assessment is accurate in characterizing LV diastology. Methods 83 patients without mitral valve disease (47 men, average age 53 years) underwent CMR imaging on a 1.5T scanner for evaluation of myocardial viability or infiltrative heart disease. All patients underwent 2-D phase-contrast (PC) imaging of the mitral valve (TR/TE 48/2.2, FA 30 degrees, VENC 80 cm/s, 20 phases, bw 554). Brightblood (BB) 4- and 2-chamber cine imaging was performed (TR/TE 13/1.1, FA 69 degrees, 40 to 50 phases, BW 933) for lateral mitral annular and left atrial volume (LAV) assessment. Peak E and A velocities were obtained from PC data. 4-chamber BB cine images were analyzed using prototype software evaluating deformation fields to automatically identify and track the mitral base plane at the lateral and septal insertions, extracting lateral e’ values (Siemens Corp., Corporate Technology, Princeton, New Jersey). LAV was obtained using the lengtharea method. LV diastolic function was graded using established echocardiographic criteria. Differences in means were assessed using the student’ st -test. Results

A pilot study of leakage and compartmentalization of the contrast agent Ablavar

Abstract: Methods Simulation study: In vitro studies have shown Ablavar to be 80-90% bound to albumin, with up to 10 fold relaxivity difference between bound and free fractions. We performed simulations to assess the effect of extravasation of the free fraction on signal. Vascular fraction measurements were simulated assuming slow two-compartment exchange for different contrast agent injection concentrations, binding fractions, bound and free relaxivity, and true vascular fractions. Volunteer study: five healthy volunteers (4 males, average age 33) underwent T1 measurement pre and 2 minutes post administration of five injections of 0.006 mmol/kg (a fifth of a single dose) Ablavar. Steady-state T1 was mapped using a cardiac gated Modified Look Locker Inversion Recovery (MOLLI) pulse sequence (slice thickness 8 mm, FOV 300 x 400 mm, matrix 256 x 172, effective TI 100 ms). Image Processing: Maps of vascular fraction were calculated from signal difference maps, according to a slow water exchange model. Fv was measured in the myocardium, dome of the liver, and skeletal muscle visible on the short axis MOLLI images, and was corrected for Ablavar extravasation based on the leakage study. The true fv and exchange rate of water protons was determined by chi square minimization between data and simulations of the effect of water exchange on fv according to the two compartment water exchange model presented by Donahue et al. (1996).

4D flow MRI of the aorta becomes practical: performance and observer variability for a new semi-automated workflow for 3D visualization and quantification of aortic hemodynamics

Abstract: Background To systematically investigate the performance and interobserver variability of a new standardized workflow for the analysis of aortic hemodynamics based on 4D-flow MRI in a study with 30 subjects. The semi-automated workflow was developed to ensure faster and standardized data analysis including systematic placement of analysis planes, 3D-flow visualization, and quantification of standard clinical flow parameters.

Viscous Energy Loss in Aortic Valve Disease Patients

Abstract: Purpose: Aortic valve disease (AVD) in the form of stenosis, insufficiency, or congenital defect will disrupt normal function beyond the valve itself. This includes an increase in cardiac afterload and a drastic alteration in post-valvular 3D blood flow patterns1, 2. The current AHA/ACC standard-of-care guidelines, however, assess disease severity based on simplified measurements local to the valve, such as: peak velocity, effective orifice area, regurgitation, aortic diameter and transvalvular pressure gradient3. Paradoxically, it is known that similarly classified AVD patients under these guideline metrics can exhibit radically divergent outcomes — implying an incomplete characterization of the disease4. For this reason, functional assessment and risk-stratification may benefit from a robust methodology capable of quantifying the energetic load placed on the left ventricle (LV) due to the presence of AVD. The measurement of viscous energy loss, a parameter which is directly responsible for increased cardiac afterload and is independent of pressure recovery effects, is a promising candidate to quantify LV loading. With this in mind, the 4D flow technique (time-resolved 3D phase-contrast MRI with all principal velocity directions encoded) provides the necessary information to calculate this parameter. Therefore, we present a theoretical basis for the use of 4D flow MRI to characterize in-vivo energy loss and apply the technique in a pilot study of patients with aortic valve stenosis (n = 13) or aortic dilation (n = 17) as compared to normal controls (n = 12).© 2013 ASME

In vivo quantification of blood mixing in single ventricle patients with Fontan circulation using 4D flow MRI

Abstract: Background Single ventricle physiology (SVP) is one of the most severe forms of complex congenital heart disease (CHD). Patients undergo multiple surgical interventions including the Fontan procedure (caval venous return is routed directly to the pulmonary arteries). Despite the apparent success of the procedure, it is unclear why some patients develop ‘failing Fontan physiology’ while others remain asymptomatic. However, there is growing evidence that underlying hemodynamics in the Fontan circulation may

Semi-automatic inline calculation of left ventricular function using cardiac MRI (CMR)

Abstract: Background Cardiac Magnetic Resonance (CMR) imaging is increasingly recognized as the gold standard for evaluating left ventricular function (LVF). Measurement of LVF is typically done manually by tracing endocardial and epicardial borders on a stack of short axis (SA) cine images of the heart and is based on the modified Simpson assumption that the left ventricle approximates a spherical shape. A drawback of this method is that it is laborious and timeconsuming. The recent introduction of computer-based inline VF software that allows for automatic assessment raised the prospect for significant reductions in CMR post processing times. Initial results have found that fully automatic analysis is unreliable as compared to manual calculations. However, usually only 1 or 2 contours are inaccurate using the automatic software suggesting that, if these are corrected manually, a semi-automatic approach may be helpful. This study sought to compare fully automatic inline VF tracking to this semi-automatic method using the manual technique as gold standard.

4D flow MRI demonstrates altered aortic hemodynamics in patients with right-left and right-noncoronary bicuspid aortic valve fusion patterns

Abstract: Background Altered aortic hemodynamics associated with bicuspid aortic valve (BAV) have been implicated in the development of aortopathy in patients with congenitally altered valves[1]. Most studies have focused on the most common “right-left” bicuspid aortic valve (RL-BAV) fusion pattern [2]. This study assessed the effects of valve morphology on aortic 3D blood flow in cohorts with the most common RL-BAV fusion, less common right-noncoronary (RNC-BAV), and normal trileaflet valves.

High acceleration quiescent-interval single shot magnetic resonance angiography at 3T in patients with peripheral artery disease

Abstract: Background Quiescent-Interval Single Shot (QISS) non-contrast MR angiography (QISS-MRA) is an emerging technique with growing evidence for its use in the evaluation of peripheral artery disease (PAD) at 1.5T [1,2]. The use of 3 Tesla MRI scans is becoming more common in clinical practice and offers the main advantage of roughly double the signal-to-noise ratio (SNR) than that of 1.5 Tesla MRI. Improvements in B1 field inhomogeneity along with fast (parallel) imaging make QISS-MRA a viable technique on state-of-the-art 3T scanners. A prior study from this group investigated the potential to accelerate imaging at 3T using higher parallel imaging acceleration (PAT) factors on healthy volunteers [3]. With this technique optimized, we report preliminary results in clinical patients. The objective of this study is to evaluate the diagnostic quality of QISS at 3T in patients with PAD using contrast-enhanced MR angiography (CE-MRA) as the reference standard. Methods With IRB approval, eight patients (5 males, age 58-78 yrs; 3 females age 37-82) with symptoms of chronic lower extremity PAD were recruited prospectively and underwent imaging on a 3T scanner (MAGNETOM Skyra; Siemens Healthcare, Germany) using an ECG-gated QISSMRA sequence (PAT factor of 3); CE-MRA was acquired at 3T for each patient at the time of visit. The degree of stenosis was evaluated using a 5-point scale for 31 predefined arterial segments (from infra-renal aorta through to bilateral run-off vessels) on both QISS- and CE-MRA. The sensitivity and specificity of QISS-MRA at 3T for the determination of clinically significant (≥50%) versus nonsignificant (<50%) stenosis were calculated with CE-MRA as the reference standard; time-resolved acquisitions were included in the analysis.

Assessment of diastolic dysfunction in the transplanted heart with analysis of pixel-based deformation fields on CMR

Abstract: Background Diastolic dysfunction is often used as a marker for allograft rejection and may even precede systolic abnormalities. However, diastolic indices provided by echocardiography can be of inconsistent quality with low sensitivities. Cardiac magnetic resonance (CMR) with high temporal resolution cine imaging offers an alternate noninvasive method for evaluating ventricular function. The purpose of this study is to describe CMR LV diastology indices in a cohort of heart transplant patients, comparing CMR results to echocardiography. Methods

Effect of cold ischemic times and time after transplantation on regional myocardial motion after heart transplantation

Abstract: Background Transplant rejection affects the course and survival after heart transplantation (HTx). As a non-invasive alternative to myocardial biopsy, which is the gold standard used for screening and for the diagnosis of rejection, regional left ventricular (LV) myocardial motion analysis has been suggested. But myocardial biopsy is invasive and its diagnostic value is restricted by high sample errors due to the patchy distribution of early rejection. Alterations of regional wall motion [1], especially in diastole, might be sensitive for the diagnosis. However, evaluation by echocardiography is limited in this context and LV motion after HTx differs from the motion of native hearts. We assessed the influence of cold ischemic time (CIT) and time after HTx on myocardial velocities in stable HTx patients.