2D cine DENSE with low encoding frequencies accurately quantifies cardiac mechanics with improved image characteristics

Abstract

BackgroundDisplacement Encoding with Stimulated Echoes (DENSE) encodes displacement into the phase of the magnetic resonance signal. The encoding frequency (ke) maps the measured phase to tissue displacement while the strength of the encoding gradients affects image quality. 2D cine DENSE studies have used a ke of 0.10 cycles/mm, which is high enough to remove an artifact-generating echo from k-space, provide high sensitivity to tissue displacements, and dephase the blood pool. However, through-plane dephasing can remove the unwanted echo and dephase the blood pool without relying on high ke. Additionally, the high sensitivity comes with the costs of increased phase wrapping and intra-voxel dephasing. We hypothesized that ke below 0.10 cycles/mm can be used to improve image characteristics and provide accurate measures of cardiac mechanics.MethodsSpiral cine DENSE images were obtained for 10 healthy subjects and 10 patients with a history of heart disease on a 3 T Siemens Trio. A mid-ventricular short-axis image was acquired with different ke: 0.02, 0.04, 0.06, 0.08, and 0.10 cycles/mm. Peak twist, circumferential strain, and radial strain were compared between acquisitions employing different ke using Bland-Altman analyses and coefficients of variation. The percentage of wrapped pixels in the phase images at end-systole was calculated for each ke. The dephasing of the blood signal and signal to noise ratio (SNR) were also calculated and compared.ResultsNegligible differences were seen in strains and twist for all ke between 0.04 and 0.10 cycles/mm. These differences were of the same magnitude as inter-test differences. Specifically, the acquisitions with 0.04 cycles/mm accurately quantified cardiac mechanics and had zero phase wrapping. Compared to 0.10 cycles/mm, the acquisitions with 0.04 cycles/mm had 9 % greater SNR and negligible differences in blood pool dephasing.ConclusionsFor 2D cine DENSE with through-plane dephasing, the encoding frequency can be lowered to 0.04 cycles/mm without compromising the quantification of twist or strain. The amount of wrapping can be reduced with this lower value to greatly simplify the input to unwrapping algorithms. The strain and twist results from studies using different encoding frequencies can be directly compared.

Right Ventricular Strain, Torsion, and Dyssynchrony in Healthy Subjects Using 3D Spiral Cine DENSE Magnetic Resonance Imaging

“…Spiral cine DENSE was acquired at each of the image locations with balanced 3D displacement encoding (Figure 1) [15]. DENSE parameters included: 12 spirals, 1 average, 360×360 mm 2 FOV, 180×180 image matrix, 8 mm slice thickness, ramped 20° flip angle, 17 ms repetition time, 1.8 ms echo time, 0.04 cyc/mm encoding frequency [16], two spirals per heartbeat (34 ms temporal resolution), and 3–point phase cycling for artifact suppression [11], [17]. Based on typical values of off-resonance and T2* decay, the estimated net spatial resolution from full width at half maximum analysis of the point spread function was 3.7 mm [18].…”

An interactive videogame designed to improve respiratory navigator efficiency in children undergoing cardiovascular magnetic resonance

“…There was, however, no difference in longitudinal strain. While these findings warrant further study and consideration, the clinical relevance of such small differences (1 % for circumferential strain, 4 % for radial strain) is likely minimal as they are smaller than previously observed inter-test (±2.0 % for circumferential, ±13 % for radial) and inter-observer (±1.4 % for circumferential, ±14 % for radial) 95 % limits of agreement for DENSE [11, 12]. …”

“…1) and measured myocardial signal ( M in Eq. 2) to compute the true SNR [11, 12, 18]. The SNR was defined as the ratio of the true myocardial signal to the true standard deviation.…”

Optimal configuration of respiratory navigator gating for the quantification of left ventricular strain using spiral cine displacement encoding with stimulated echoes (DENSE) MRI

“…Prospective ECG gating was used and the number of cardiac phases was selected to allow 100–150 ms at the end of the cardiac cycle for heart rate variability. Acquisition parameters for all scans were: spiral type = uniform density, interleaves = 6, interleaves per beat = 2, field of view (FOV) = 360 × 360 mm 2 , pixel spacing = 2.8 × 2.8 mm 2 , slice thickness = 8 mm, echo time (TE) = 1.1 ms, repetition time (TR) = 17 ms, variable flip angle = 20, displacement encoding = 0.06 cyc/mm, through‐plane dephasing = 0.08 cyc/mm, CSPAMM echo suppression, and view sharing. The temporal resolution was 34 ms, however, sliding window view sharing yielded a 17‐ms temporal resolution between reconstructed cardiac frames.…”