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 mm(2) × 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.

Analysis of complex cardiovascular flow with three-component acceleration-encoded MRI.

Functional information regarding cardiac performance, pressure gradients, and local flow derangement are available from blood acceleration fields. Thus, this study examines a 2D and 3D phase contrast sequence optimized to efficiently encode three-directional, time-resolved acceleration in vitro and in vivo. Stenosis phantom acceleration measurements were compared to acceleration derived from standard velocity encoded phase contrast-magnetic resonance imaging (i.e., "velocity-derived acceleration"). For in vivo analysis, three-directional 2D acceleration maps were compared to velocity-derived acceleration using regions proximal and distal to the aortic valve in six healthy volunteers at 1.5 and 3.0 T (voxel size = 1.4 × 2.1 × 8 mm, temporal resolution = 16-20 ms). In addition, a 4D acceleration sequence was evaluated for feasibility in a healthy volunteer and postrepair biscuspid aortic valve patient with an ascending aortic aneurysm. The phantom magnetic resonance acceleration measurements were more accurate (nonturbulent root mean square error = 2.2 vs. 5.1 m/s(2) for phase contrast-magnetic resonance imaging) and 10 times less noisy (nonturbulent σ = 0.9 vs. 13.6 m/s(2) for phase contrast-magnetic resonance imaging) than velocity-derived acceleration. Acceleration mapping of the left ventricular outflow tract and aortic arch exhibited signal voids colocated with complex flow events such as vortex formation and high order motion. 4D acceleration data, visualized in combination with the velocity data, may provide new insight into complex flow phenomena.

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/s(2) 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.

Magnetic resonance tissue phase mapping of myocardial motion: new insight in age and gender.

BACKGROUND: An exact understanding of normal age- and gender-matched regional myocardial performance is an essential prerequisite for the diagnosis of heart disease. Magnetic resonance phase-contrast imaging (tissue phase mapping) enabling the analysis of segmental, 3-directional myocardial velocities with high temporal resolution (13.8 ms) was used to assess left ventricular motion. METHODS AND RESULTS: Radial, long-axis, and rotational myocardial velocities were acquired in 58 healthy volunteers (3 age groups, 29 women) in left ventricular basal, midventricular, and apical short-axis locations. For increased age, reduced (P<0.003) and prolonged long-axis and radial velocities (P<0.05) during diastole and reduced long-axis velocities (P<0.001) and apical rotation (P<0.005) during systole were found for both genders. Women demonstrated a reduced systolic twist (P=0.009), apical rotation (P=0.01), and systolic radial velocities (P<0.02) compared with men. Segmental analysis of long-axis motion with aging revealed differences in regional reduction of systolic (lateral 52% versus 30%) and diastolic (lateral 57% versus 41%) velocities in women compared with men. In basal segments, young women demonstrated higher long-axis velocities (+11% during diastole) than men, whereas this difference was reversed in older subjects (same segments, -20%). In addition, increased age resulted in a prolonged time to peak diastolic apical rotation (P<0.04) in women compared with men. CONCLUSIONS: Age and gender strongly influence regional myocardial motion. Tissue phase mapping provides a comprehensive quantitative analysis of all myocardial velocities with high temporal and spatial resolution. The knowledge of the detected age- and gender-related differences in myocardial motion is fundamental for further investigations of cardiac disease. Clinical Trial Registration- http://www.zks.uni-freiburg.de/uklreg/php/suchergebnis_all.php. Identifier: UKF001739.

Visualization of multidirectional regional left ventricular dynamics by high-temporal-resolution tissue phase mapping.

PURPOSE: To apply high-temporal-resolution tissue phase mapping (TPM) to derive a detailed representation of normal regional myocardial motion in a large cohort of 58 normal subjects (three age groups) and one patient with dilated cardiomyopathy. MATERIALS AND METHODS: Analysis included transformation of the acquired myocardial velocities into radial, circumferential, and long-axis motion components representing left ventricular (LV) function with a spatiotemporal resolution of 1.3 x 2.6 x 8 mm(3) and 13.8 msec, respectively. To compare multidirectional regional myocardial velocities between groups of subjects, a multisegment and multislice visualization model was employed. Regional myocardial motion was mapped onto the visualization model to display the current status of myocardial motion from base to apex as in-plane velocity vector fields in conjunction with color-coded long-axis plane motion. Moreover, correlation analysis was used to investigate regional differences in myocardial dynamics. RESULTS: Age-related changes in LV myocardial velocities resulted in significant differences of peak and time-to-peak velocities in the radial and long-axis directions. Correlation analysis revealed clearly visible regional differences in the temporal evolution of long-axis and circumferential velocities, particularly between the youngest and oldest age groups. Comparison of pathological LV motion with age-matched volunteers indicated marked regional alterations in myocardial velocities and dynamics. CONCLUSION: High-temporal-resolution TPM in combination with a schematic visualization model and correlation analysis permits the identification of local changes in myocardial velocities associated with different age groups and a common LV pathology.

[Slice profile measurements of half pulse excitation for MR-imaging with ultra-short echo times (UTE)]. / Schichtprofilmessungen bei Anregung mit halben Pulsen für die MR-Bildgebung mit ultrakurzen Echozeiten (UTE).

Half pulse excitation plays an important role in imaging with ultra-short echo times (UTE imaging) of the order of TE < 100 micros. Based on half RF-pulses this method was theoretically modeled and experimentally applied in 1991 for the first time. Following this work, measurements of slice profiles produced by half pulses were performed and results were compared to the slice profiles produced by the original full pulse. Furthermore, the hypothesis was tested that short RF pulses may be of advantage in minimizing the relaxation effects during the pulse. Within the scope of these measurements no dependency of slice profile on the pulse duration could be found.