Magnetic resonance tissue phase mapping: analysis of age-related and pathologically altered left ventricular radial and long-axis dyssynchrony

Purpose:

To employ magnetic resonance tissue phase mapping (TPM) for the assessment of age‐related left ventricular (LV) synchrony of radial and long‐axis motion in healthy volunteers and in hypertensive heart disease, dilated cardiomyopathy (DCM), and left bundle branch block (LBBB).

Materials and Methods:

TPM (spatial/temporal resolution = 1.3 × 2.6 mm²/13.8 msec) was employed to measure radial and long‐axis myocardial velocities in 58 healthy volunteers of three age groups and 37 patients (hypertensive, n = 18; DCM, n = 12; DCM and LBBB n = 7). Regional times‐to‐peak velocities (TTP) in systole and diastole were derived for all LV segments. Four measures of dyssynchrony were defined as the standard deviation of systolic and diastolic TTP for radial and long‐axis motion.

Results:

Systolic radial and diastolic long‐axis dyssynchrony was increased (P < 0.01) in all patient groups compared to controls. Multiple regressions revealed a significant relationship of dyssynchrony with LV ejection fraction and mass for systolic radial (P < 0.001 resp. P = 0.02), diastolic radial (P < 0.001 resp. P < 0.05), and long‐axis (P < 0.001 resp. P = 0.001) motion. Diastolic dyssynchrony correlated with the LV remodeling index (P < 0.05) and increased with age (P < 0.03). Systolic long‐axis dyssynchrony was not influenced by disease or LV function.

Conclusion:

Radial systolic and long‐axis diastolic dyssynchrony were the most sensitive markers for altered dyssynchrony in hypertensive heart disease or DCM. Future studies are needed to evaluate the diagnostic value of TPM‐derived dyssynchrony parameters. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Segmental myocardial velocities in dilated cardiomyopathy with and without left bundle branch block

Purpose:

To quantify three‐directional left ventricular (LV) myocardial velocities and intraventricular synchrony in dilated cardiomyopathy (DCM) with and without left bundle branch block (LBBB) using MR tissue phase mapping (TPM).

Materials and Methods:

Regional velocities were assessed by TPM (spatial/temporal resolution = 1.3 × 1.3 mm² × 8 mm/14 ms) in DCM patients with (n = 12) and without LBBB (n = 7) compared with age‐matched volunteers (n = 20). For the evaluation the AHA 16‐segment and an extended LV visualization model was used.

Results:

Radial velocities in DCM patients were reduced in 75% (systole) and in 94% (diastole) (P = 0.0001 – P = 0.0360), long‐axis velocities in 31% (systole) and in 75% (diastole) of the 16 segments compared with controls (P = 0.0001 – P = 0.0310). LBBB resulted in inferolaterally delayed diastolic long‐axis velocities (P = 0.0012 – P = 0.0464) and shortened TTP for septal systolic radial velocities (P = 0.0002). Intra‐ventricular radial systolic TTP differed up to 150 ms between segments in patients with LBBB (89 ms without LBBB, 34 ms in volunteers) reflecting an increased dyssynchrony. LV twist was altered in all patients with reduced and delayed systolic and diastolic peak velocities.

Conclusion:

TPM identified previously not described alterations of the spatial distribution and timing of all myocardial velocities in patients with DCM and LBBB. This may help to optimize therapy management in future. J. Magn. Reson. Imaging 2013;37:119–126. © 2012 Wiley Periodicals, Inc.     

Artifact‐reduced two‐dimensional cine steady state free precession for myocardial blood‐ oxygen‐level‐dependent imaging

Purpose:

To minimize image artifacts in long TR cardiac phase‐resolved steady state free precession (SSFP) based blood‐oxygen‐level‐dependent (BOLD) imaging.

Materials and Methods:

Nine healthy dogs (four male, five female, 20–25 kg) were studied in a clinical 1.5 Tesla MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long repetition time (TR) SSFP images. Breath‐held 2D SSFP cine sequences with various temporal resolutions (10–204 ms), bandwidths (239–930 Hz/pixel), with and without first‐order motion compensation were prescribed in the basal, mid‐ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact‐reduction strategies.

Results:

Shortening the readout time by means of increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of first‐order motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle.

Conclusion:

Artifact‐reduction methods used in this study provide significant improvement in image quality compared with conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial oxygenation changes throughout the cardiac cycle with long TR SSFP‐based myocardial BOLD MRI. J. Magn. Reson. Imaging 2010;31:863–871. ©2010 Wiley‐Liss, Inc.     

Correction of left ventricular wall thickening from short-axis cine MRI for basal-descent through-plane motion

Purpose

To solve the problem of the basal descent movement in quantification of the regional left ventricular (LV) myocardial wall thickness (WTh) and wall thickening (%WT) in short‐axis (SA) cine MRI for effectively assessing the regional wall motion of LV myocardium.

Materials and Methods

LV long‐axis tagged MRI and SA cine MRI were performed to calculate the longitudinal translation and circumferential WTh of LV myocardium in eight normal volunteers. The new SA end‐systolic thickness (EST) data were reconstructed from the original EST data, based on the quantified longitudinal translation of LV myocardium.

Results

The mean %WT of six segments in the basal section after correction was significantly different from that before correction in both intra‐ and inter‐operator experiments. The polar map also showed the significant improvement of the variability of regional %WT and lack of quantification of %WT in the most basal SA slices after correction.

Conclusion

The proposed technique demonstrated an important advantage to calculate the %WT in the most basal SA myocardial tissue, which was considered difficult to be achieved using cine MRI. J. Magn. Reson. Imaging 2011;33:464–473. © 2011 Wiley‐Liss, Inc.     

Hypertensive heart disease: MR tissue phase mapping reveals altered left ventricular rotation and regional myocardial long-axis velocities

Objectives

The aim of this study was the evaluation of left ventricular (LV) segmental 3D velocities in patients with hypertensive heart disease using magnetic resonance (MR) tissue phase mapping (TPM).

Methods

LV radial, long-axis and rotational myocardial velocities were assessed by TPM in patients with LV hypertrophy and preserved EF (n?=?18, age = 53?±?12 years) and volunteers (n?=?20, age = 51?±?4 years). Systolic and diastolic peak and time-to-peak velocities were mapped onto a 16-segment LV model. 3D myocardial motion was displayed on an extended visualisation model. Correlation coefficients were calculated to investigate differences in regional dynamics.

Results

Patients revealed diastolic dysfunction as expressed by decreased peak long-axis velocities in all (except apical) segments (basal, P?≤?0.01; two midventricular segments, P?=?0.02, P?=?0.03). During systole, hypertrophy was associated with heterogeneous behaviour for long-axis velocities including an increase in anteroseptal apical and midventricular regions (P?=?0.001), a reduction in mid-inferior segments (P?=?0.03) and enhanced septal velocities (P?<?0.05). Segmental correlation analysis revealed altered dynamics of LV base rotation and increased dyssynchrony of lateral long-axis motion.

Conclusions

Patients with hypertensive heart disease demonstrated alterations in systolic long-axis motion, basal rotation and dyssynchrony. Longitudinal studies are needed to investigate the value of regional wall motion abnormalities regarding disease progression and outcome.

Key Points

? Magnetic resonance tissue phase mapping enables segmental evaluation of 3D myocardial velocities. ? Patients with hypertensive heart disease demonstrated new alterations in systolic long-axis motion. ? Correlation analysis revealed left ventricular long-axis dyssynchrony and an altered rotation. ? MR may provide new, sensitive diagnostic markers concerning hypertensive heart disease.     

Strain‐encoded MRI to evaluate normal left ventricular function and timing of contraction at 3.0 Tesla

Purpose

To define the reproducibility of strain‐encoded (SENC) magnetic resonance imaging (MRI) for assessment of regional left ventricular myocardial strain and timing of contraction in a 3T MRI system.

Materials and Methods

The study population consisted of 16 healthy subjects. SENC measurements were performed in three short‐axis (SA) slices (apical, mid, and basal) and three long‐axis (LA) views (two‐, three‐, and four‐chamber) for assessment of maximal transmural systolic strain and time to peak strain. To assess the interobserver and interstudy reproducibility, analysis of SENC MRI was performed by two independent observers who were blinded to each other's results and four studies were repeated on a different day.

Results

Maximal longitudinal strain was highest at the apex, as was maximal circumferential strain. Peak longitudinal strain occurred earliest at the base, as did peak circumferential strain. Interclass correlation coefficient between observers and repeated studies ranged from 0.92 to 0.98 (P < 0.001 for all).

Conclusion

The present study demonstrates the ability of SENC MRI to define regional left ventricular strain and the time sequence of regional strain. SENC MRI may represent a highly objective method for quantifying regional left ventricular function. J. Magn. Reson. Imaging 2009;29:799–808. © 2009 Wiley‐Liss, Inc.     

Left ventricular regional myocardial motion and twist function in repaired tetralogy of Fallot evaluated by magnetic resonance tissue phase mapping

Objectives

We aimed to characterise regional myocardial motion and twist function in the left ventricles (LV) in patients with repaired tetralogy of Fallot (rTOF) and preserved LV global function.

Methods

We recruited 47 rTOF patients and 38 age-matched normal volunteers. Tissue phase mapping (TPM) was performed for evaluating the LV myocardial velocity in longitudinal, radial, and circumferential (Vz, Vr, and VØ) directions in basal, middle, and apical slices. The VØ peak-to-peak (PTP) during systolic phases, the rotation angle of each slice, and VØ inconsistency were computed for evaluating LV twist function and VØ dyssynchrony.

Results

As compared to the controls, the rTOF patients presented decreased RV ejection fraction (RVEF) (p?=?0.002) and preserved global LV ejection fraction (LVEF). They also demonstrated decreased systolic and diastolic Vz in several LV segments and higher diastolic Vr in the septum (all p?<?0.05). A lower VØ PTP, higher VØ inconsistency, and reduced peak net rotation angle (all p?<?0.05) were observed. The aforementioned indices demonstrated an altered LV twist function in rTOF patients in an early disease stage.

Conclusions

MR TPM could provide information about early abnormalities of LV regional motion and twist function in rTOF patients with preserved LV global function.

Key points

? Patients with rTOF presented significantly reduced systolic and diastolic Vz in the LV.? rTOF patients demonstrated significantly increased diastolic Vr in the septum.? Abnormal characteristics of the segmental dynamic velocity evolution were shown in rTOF.? rTOF patients presented altered circumferential rotation and velocity inconsistency in early stage.

     

Details of left ventricular radial wall motion supporting the ventricular theory of the third heart sound obtained by cardiac MR

Objective:

Obtaining new details of radial motion of left ventricular (LV) segments using velocity-encoding cardiac MRI.

Methods:

Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Cine images for navigator-gated phase contrast velocity mapping were acquired using a black blood segmented κ-space spoiled gradient echo sequence with a temporal resolution of 13.8 ms. Peak systolic and diastolic radial velocities as well as radial velocity curves were obtained for 16 ventricular segments.

Results:

Significant differences among peak radial velocities of basal and mid-ventricular segments have been recorded. Particular patterns of segmental radial velocity curves were also noted. An additional wave of outward radial movement during the phase of rapid ventricular filling, corresponding to the expected timing of the third heart sound, appeared of particular interest.

Conclusion:

The technique has allowed visualization of new details of LV radial wall motion. In particular, higher peak systolic radial velocities of anterior and inferior segments are suggestive of a relatively higher dynamics of anteroposterior vs lateral radial motion in systole. Specific patterns of radial motion of other LV segments may provide additional insights into LV mechanics.

Advances in knowledge:

The outward radial movement of LV segments impacted by the blood flow during rapid ventricular filling provides a potential substrate for the third heart sound. A biphasic radial expansion of the basal anteroseptal segment in early diastole is likely to be related to the simultaneous longitudinal LV displacement by the stretched great vessels following repolarization and their close apposition to this segment.Advances in cardiac imaging techniques have allowed evaluation of new details of the complex pattern of left ventricular (LV) motion. Using high temporal resolution cardiovascular MR with myocardial velocity-encoding techniques, we previously performed a detailed analysis of rotational and longitudinal motions of the left ventricle, correlating them with the orientation or cardiomyocyte aggregates within the LV wall.^1,2 However, accurate evaluation of radial motion is equally important. For example, radial wall motion abnormalities have been detected in patients with diabetes³ and hypertrophic cardiomyopathy,⁴ whereas radial dyssynchrony is almost universal in patients with heart failure.⁵ The purpose of this study was to obtain new details of global and regional radial wall motion of the left ventricle using the cardiac MR high temporal resolution myocardial velocity-encoding technique.^6,7 Considering recent interest in myocardial multilayer measurements, which provide more layer-specific information about the functional state of the myocardium at different levels,^8–13 separate calculations of all myocardial velocities and their corresponding peak times for the inner (endocardial), middle (transmural) and outer (epicardial) layers of the LV wall were performed.     

Three‐directional acceleration phase mapping of myocardial function

An optimized acceleration encoded phase contrast method termed “acceleration phase mapping” for the assessment of regional myocardial function is presented. Based on an efficient gradient waveform design using two‐sided encoding for in vivo three‐directional acceleration mapping, echo and repetition times TE = 12–14 ms and TR = 15–17 ms for low accelerations sensitivity aenc = 5–8 m/s² were achieved. In addition to phantom validation, the technique was applied in a study with 10 healthy volunteers at 1.5T and 3T to evaluate its feasibility to assess regional myocardial acceleration at 1.5T and 3T. Results of the acceleration measurements were compared with the temporal derivative of myocardial velocities from three‐directional velocity encoded standard phase contrast MRI in the same volunteers. The feasibility to assess myocardial acceleration along the radial, circumferential, and longitudinal direction of the left ventricle was demonstrated. Despite improved signal‐to‐noise‐ratio at 3T (34% increase compared with 1.5T), image quality with respect to susceptibility artifacts was better 1.5T compared with 3T. Analysis of global and regional left ventricular acceleration showed characteristic patterns of systolic and diastolic acceleration and deceleration. Comparisons of directly measured and derived myocardial acceleration dynamics over the cardiac cycle revealed good correlation (r = 0.45–0.68, P < 0.01) between both methods. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Strain‐encoded (SENC) magnetic resonance imaging to evaluate regional heterogeneity of myocardial strain in healthy volunteers: Comparison with conventional tagging

Purpose

To evaluate the ability of strain‐encoded (SENC) magnetic resonance imaging (MRI) for regional systolic and diastolic strain analysis of the myocardium in healthy volunteers.

Materials and Methods

Circumferential and longitudinal peak systolic strain values of 75 healthy volunteers (35 women and 40 men, mean age 44 ± 12 years) were measured using SENC at 1.5T. MR tagging was used as the reference standard for measuring regional function. Diastolic function was assessed in the 10 youngest (24 ± 8 years) and 10 oldest (62 ± 5 years) subjects.

Results

Peak strain values assessed with SENC were comparable to those obtained by MR tagging, showing narrow limits of agreement (limits of agreement ?5.6% to 8.1%). Regional heterogeneity was observed between different segments of the left ventricle (LV) by both techniques (P < 0.001). Longitudinal strain obtained by SENC was also heterogenous (P < 0.001). Interestingly, no age‐ or gender‐specific differences in peak systolic strain were observed, whereas the peak rate of relaxation of circumferential strain rate was decreased in the older group.

Conclusion

SENC is a reliable tool for accurate and objective quantification of regional myocardial systolic as well as diastolic function. In agreement with tagged MRI, SENC detected slightly heterogeneous myocardial strain within LV segments. J. Magn. Reson. Imaging 2009;29:99–105. © 2008 Wiley‐Liss, Inc.

     

3D velocity quantification in the heart: Improvements by 3D PC‐SSFP

Purpose:

To test whether a 3D imaging sequence with phase contrast (PC) velocity encoding based on steady‐state free precession (SSFP) improves 3D velocity quantification in the heart compared to the currently available gradient echo (GE) approach.

Materials and Methods:

The 3D PC‐SSFP sequence with 1D velocity encoding was compared at the mitral valve in 12 healthy subjects with 3D PC‐GE at 1.5T. Velocity measurements, velocity‐to‐noise‐ratio efficiency (VNR_eff), intra‐ and interobserver variability of area and velocity measurements, contrast‐to‐noise‐ratio (CNR), and artifact sensitivity were evaluated in both long‐ and short‐axis orientation.

Results:

Descending aorta mean and peak velocities correlated well (r² = 0.79 and 0.93) between 3D PC‐SSFP and 3D PC‐GE. At the mitral valve, mean velocity correlation was moderate (r² = 0.70 short axis, 0.56 long axis) and peak velocity showed good correlation (r² = 0.94 short axis, 0.81 long axis). In some cases VNR_eff was higher, in others lesser, depending on slab orientation and cardiac phase. Intra‐ and interobserver variability was generally better for 3D PC‐SSFP. CNR improved significantly, especially at end systole. Artifact levels did not increase.

Conclusion:

3D SSFP velocity quantification was successfully tested in the heart. Blood‐myocardium contrast improved significantly, resulting in more reproducible velocity measurements for 3D PC‐SSFP at 1.5T. J. Magn. Reson. Imaging 2009;30:947–955. © 2009 Wiley‐Liss, Inc.     

Quantification of left ventricular indices from SSFP cine imaging: Impact of real‐world variability in analysis methodology and utility of geometric modeling

Purpose:

To assess the impact of “real‐world” practice variation in the process of quantifying left ventricular (LV) mass, volume indices, and ejection fraction (EF) from steady‐state free precession cardiovascular magnetic resonance (CMR) images. The utility of LV geometric modeling techniques was also assessed.

Materials and Methods:

The effect of short‐axis‐ versus long‐axis‐derived LV base identification, simplified versus detailed endocardial contouring, and visual versus automated identification of end‐systole were evaluated using CMR images from 50 consecutive, prospectively recruited patients. Additionally, the performance of six geometric models was assessed. Repeated measurements were performed on 25 scans (50%) in order to assess observer variability.

Results:

Simplified endocardial contouring significantly overestimated volumes and underestimated EF (–6 ± 4%, P < 0.0005) compared to detailed contouring. A mean difference of –34g (P < 0.0005) was observed between mass measurements made using short‐axis‐ versus long‐axis‐derived LV base positioning. A technique involving long‐axis LV base identification, signal threshold‐based detailed endocardial contouring, and automated identification of end‐systole had significantly higher observer agreement. Geometric models showed poor agreement with conventional analysis and high variability.

Conclusion:

Real‐world variability in CMR image analysis leads to significant differences in LV mass, volume and EF measurements, and observer variability. Appropriate reference ranges should be applied. Use of geometric models should be discouraged. J. Magn. Reson. Imaging 2013;37:1213–1222. © 2012 Wiley Periodicals, Inc.     

Effects of ventricular insertion sites on rotational motion of left ventricular segments studied by cardiac MR

Objective:

Obtaining new details for rotational motion of left ventricular (LV) segments using velocity encoding cardiac MR and correlating the regional motion patterns to LV insertion sites.

Methods:

Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Peak rotational velocities and circumferential velocity curves were obtained for 16 ventricular segments.

Results:

Reduced peak clockwise velocities of anteroseptal segments (i.e. Segments 2 and 8) and peak counterclockwise velocities of inferoseptal segments (i.e. Segments 3 and 9) were the most prominent findings. The observations can be attributed to the LV insertion sites into the right ventricle, limiting the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments as viewed from the apex. Relatively lower clockwise velocities of Segment 5 and counterclockwise velocities of Segment 6 were also noted, suggesting a cardiac fixation point between these two segments, which is in close proximity to the lateral LV wall.

Conclusion:

Apart from showing different rotational patterns of LV base, mid ventricle and apex, the study showed significant differences in the rotational velocities of individual LV segments. Correlating regional wall motion with known orientation of myocardial aggregates has also provided new insights into the mechanisms of LV rotational motions during a cardiac cycle.

Advances in knowledge:

LV insertion into the right ventricle limits the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments adjacent to the ventricular insertion sites. The pattern should be differentiated from wall motion abnormalities in cardiac pathology.Assessment of regional rotation patterns of the left ventricular (LV) wall improves the understanding of the systolic and diastolic ventricular function [1]. Cardiac echocardiography with speckle tracking performed in healthy individuals demonstrated large regional differences in the rotation of individual LV segments. For example, significant rotational differences of inferoseptal segments compared with anterolateral segments were reported at the LV base and papillary level [1]. Small regional differences were also recorded at the apical level [1]. Recent developments in cardiac imaging techniques have helped in assessing rotational patterns of LV segments in patients with cardiac pathology. Thus, patients with an atrial septal defect and pulmonary hypertension demonstrated higher average counterclockwise peak rotation of basal LV segments, lower peak rotations of posterior, inferior and posteroseptal walls at the LV base and delayed average interval time of rotational motion [2]. In patients with hypertrophic cardiomyopathy, a reduced cardiac rotation of the posterior region and a reduced radial displacement of the inferior septal zone were recorded [3]. In dog models, occlusion of left anterior descending or left circumflex arteries had a pronounced effect on apex rotation [4]. Under controlled pre-ischaemic conditions, a linear relationship between the apex rotation and the segment length was recorded during ejection and a different steeper relationship during the isovolumic relaxation. In regionally ischaemic segments, this relationship became non-linear for both ejection and isovolumic relaxation [4]. Because the affected myocardial segments may vary depending on the occluded coronary vessel, knowledge about the normal pattern of rotational motion of individual segments becomes increasingly important.The cause of regional differences in rotational pattern of ventricular segments is likely to be multifactorial and determined by regional ventricular anatomy and dynamics. For example, in a study assessing regional rotational patterns of individual LV segments using speckle tracking echocardiography, Gustafsson et al [1] reported that the diastolic untwist matches the phases of both the E-wave and the A-wave and seems to be related to the intraventricular pressure differences. We hypothesise that the insertion sites of the left ventricle and the cardiac fixation points tethering the heart to the mediastinum in close proximity with the left ventricle may particularly influence the rotational pattern of adjacent LV segments. In the present study, we aimed to correlate the potential differences in rotational velocities of individual LV segments with ventricular insertion sites or major heart vessels located in close proximity with the left ventricle. Considering recent interest in myocardial multilayer measurements, which provide more layer-specific information about the functional state of myocardium at different levels [5–10], separate measurements of rotational myocardial velocities for the inner (endocardial), middle (transmural) and outer (epicardial) layers of the LV wall were performed for 16 ventricular segments.     

Improved method for quantification of regional cardiac function in mice using phase‐contrast MRI

Phase‐contrast magnetic resonance imaging is a technique that allows for characterization of regional cardiac function and for measuring transmural myocardial velocities in human hearts with high temporal and spatial resolution. The application of this technique (also known as tissue phase mapping) to murine hearts has been very limited so far. The aim of our study was to implement and to optimize tissue phase mapping for a comprehensive assessment of murine transmural wall motion. Baseline values for regional motion patterns in mouse hearts, based on the clinically used American Heart Association's 17‐segment model, were established, and a detailed motion analysis of mouse heart for the entire cardiac cycle (including epicardial and endocardial motion patterns) is provided. Black‐blood contrast was found to be essential to obtain reproducible velocity encoding. Tissue phase mapping of the mouse heart permits the detailed assessment of regional myocardial velocities. While a proof‐of‐principle application in a murine ischemia–reperfusion model was performed, future studies are warranted to assess its potential for the investigation of systolic and diastolic functions in genetically and surgically manipulated mouse models of human heart disease. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Imaging three‐dimensional myocardial mechanics using navigator‐gated volumetric spiral cine DENSE MRI

A navigator‐gated 3D spiral cine displacement encoding with stimulated echoes (DENSE) pulse sequence for imaging 3D myocardial mechanics was developed. In addition, previously described 2D postprocessing algorithms including phase unwrapping, tissue tracking, and strain tensor calculation for the left ventricle (LV) were extended to 3D. These 3D methods were evaluated in five healthy volunteers, using 2D cine DENSE and historical 3D myocardial tagging as reference standards. With an average scan time of 20.5 ± 5.7 min, 3D data sets with a matrix size of 128 × 128 × 22, voxel size of 2.8 × 2.8 × 5.0 mm³, and temporal resolution of 32 msec were obtained with displacement encoding in three orthogonal directions. Mean values for end‐systolic mid‐ventricular mid‐wall radial, circumferential, and longitudinal strain were 0.33 ± 0.10, ?0.17 ± 0.02, and ?0.16 ± 0.02, respectively. Transmural strain gradients were detected in the radial and circumferential directions, reflecting high spatial resolution. Good agreement by linear correlation and Bland‐Altman analysis was achieved when comparing normal strains measured by 2D and 3D cine DENSE. Also, the 3D strains, twist, and torsion results obtained by 3D cine DENSE were in good agreement with historical values measured by 3D myocardial tagging. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Flow‐sensitive 4D MRI of the thoracic aorta: Comparison of image quality,quantitative flow,and wall parameters at 1.5 T and 3 T

Purpose:

To evaluate the effect of field strength on flow‐sensitive 4D magnetic resonance imaging (MRI) of the thoracic aorta. A volunteer study at 1.5 T and 3 T was conducted to compare phase‐contrast MR angiography (MRA) and 3D flow visualization quality as well as quantification of aortic hemodynamics.

Materials and Methods:

Ten healthy volunteers were examined by flow‐sensitive 4D MRI at both 1.5 T and 3 T MRI with identical imaging parameters (TE/TR = 6/5.1 msec, spatial/temporal resolution ≈2 mm/40.8 msec). Analysis included assessment of image quality of derived aortic 3D phase contrast (PC) angiography and 3D flow visualization (semiquantitative grading on a 0–2 scale, two blinded observers) and quantification of blood flow velocities, net flow per cardiac cycle, wall shear stress (WSS), and velocity noise.

Results:

Quality of 3D blood flow visualization (average grading = 1.8 ± 0.4 at 3 T vs. 1.1 ± 0.7 at 1.5 T) and the depiction of aortic lumen geometry by 3D PC‐MRA (1.7 ± 0.5 vs. 1.2 ± 0.6) were significantly (P < 0.01) improved at 3 T while velocity noise was significantly higher (P < 0.01) at 1.5 T. Velocity quantification resulted in minimally altered (0.05 m/s, 3 mL/cycle and 0.01 N/m²) but not statistically different (P = 0.40, P = 0.39, and P = 0.82) systolic peak velocities, net flow, and WSS for 1.5 T compared to 3 T.

Conclusion:

Flow‐sensitive 4D MRI at 3 T provided improved image quality without additional artifacts related to higher fields. Imaging at 1.5 T MRI, which is more widely available, was also feasible and provided information on aortic 3D hemodynamics of moderate quality with identical performance regarding quantitative analysis. J. Magn. Reson. Imaging 2012;36:1097–1103. © 2012 Wiley Periodicals, Inc.     

Single‐shot steady‐state free precession can detect myocardial edema in patients: A feasibility study

Purpose

To demonstrate the ability of single‐shot, T₂/T₁ weighted steady‐state free precession (SSFP) to detect myocardial edema in patients with an acute myocardial infarction.

Materials and Methods

This study was performed in a series of patients (n = 10) referred for the assessment of acute myocardial infarcts (AMI). Localizers were used to obtain true short axis views of the left ventricle (LV). These views were used to plan and obtain T₂‐weighted STIR (short TI inversion recovery) images of the LV. These slices were then acquired using single‐shot dark blood‐prepared SSFP with a large (31) number of dummy pulses. Lastly, Contrast agent was injected, and late enhancement (LE) images were acquired. Images were analyzed using a multi‐segment model of the heart. SSFP images were compared with STIR images, with STIR images used as the standard of truth for the presence of edema. LE images were used to identify segments which were positive for microvascular obstruction.

Results

All techniques were successful in all patients. A total of 312 segments were analyzed. Excluding segments positive for microvascular obstruction, SSFP had a sensitivity/specificity of 80%/89%. Including segments positive for microvascular obstruction, sensitivity/specificity was 71%/88%. On a patient‐based analysis, no AMI was missed using SSFP (sensitivity = 100%).

Conclusion

Using single‐shot SSFP to detect myocardial edema in patients with AMI is feasible with a moderate sensitivity and high specificity. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

3D left ventricular strain from unwrapped harmonic phase measurements

Purpose:

To validate a method for measuring 3D left ventricular (LV) strain from phase‐unwrapped harmonic phase (HARP) images derived from tagged cardiac magnetic resonance imaging (MRI).

Materials and Methods:

A set of 40 human subjects were imaged with tagged MRI. In each study the HARP phase was computed and unwrapped in each short‐axis and long‐axis image. Inconsistencies in unwrapped phase were resolved using branch cuts manually placed with a graphical user interface. 3D strain maps were computed for all imaged timeframes in each study. The strain from unwrapped phase (SUP) and displacements were compared to those estimated by a feature‐based (FB) technique and a HARP technique.

Results:

3D strain was computed in each timeframe through systole and mid‐diastole in ≈30 minutes per study. The standard deviation of the difference between strains measured by the FB and the SUP methods was less than 5% of the average of the strains from the two methods. The correlation between peak circumferential strain measured using the SUP and HARP techniques was over 83%.

Conclusion:

The SUP technique can reconstruct full 3D strain maps from tagged MR images through the cardiac cycle in a reasonable amount of time and user interaction compared to other 3D analysis methods. J. Magn. Reson. Imaging 2010;31:854–862. ©2010 Wiley‐Liss, Inc.     

Myocardial T2‐mapping and velocity mapping: Changes in regional left ventricular structure and function after heart transplantation

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.     

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional viability MR imaging of the myocardium at 3.0T: A feasibility study

Purpose

To assess the feasibility of free‐breathing high‐spatial‐resolution delayed contrast‐enhanced three‐dimensional (3D) viability magnetic resonance imaging (MRI) at 3.0T for the detection of myocardial damages.

Materials and Methods

Twenty‐five patients with myocardial diseases, including myocardial infarction and cardiomyopathies, were enrolled after informed consent was given. Free‐breathing 3D viability MRI with high spatial resolution (1.5 × 1.25 × 2.5 mm) at 3.0T, for which cardiac and navigator gating techniques were employed, was compared with breath‐hold two‐dimensional (2D) viability imaging (1.77 × 1.18 × 10 mm) for assessment of contrast‐to‐noise ratio (CNR) and myocardial damage.

Results

Free‐breathing 3D viability imaging was achieved successfully in 21 of the 25 patients. This imaging technique depicted 84.6% of hyperenhancing myocardium with a higher CNR between hyperenhancing myocardium and blood and with excellent agreement for the transmural extension of myocardial damage (k = 0.91). In particular, the 3D viability images delineated the myocardial infarction and linear hyperenhancing myocardium, comparable to the 2D viability images.

Conclusion

Free‐breathing high‐spatial‐resolution delayed contrast‐enhanced 3D viability MRI using 3.0T was feasible for the evaluation of hyperenhancing myocardium, as seen with myocardial infarction and cardiomyopathies. J. Magn. Reson. Imaging 2008;28:1361–1367. © 2008 Wiley‐Liss, Inc.