Rapid assessment of regional and global left ventricular function using three-dimensional k-t BLAST imaging

Clinical evaluation of left ventricular function and morphology using an accelerated k-t sensitivity encoding method in cardiovascular magnetic resonance

Objectives

To provide clinical validation of a recent 2D SENSE-based accelerated cardiovascular magnetic resonance (CMR) sequence (accelerated k-t SENSE), investigating whether this technique accurately quantifies left ventricle (LV) volumes, function, and mass as compared to 2D cine steady-state free precession (2D-SSFP).

Methods

Healthy volunteers (n = 16) and consecutive heart failure patients (n = 26) were scanned using a 1.5 T MRI system. Two LV short axis (SA) stacks were acquired: (1) accelerated k-t SENSE (5–6 breath-holds; temporal/spatial resolution: 37 ms/1.82 × 1.87 mm; acceleration factor = 4) and (2) standard 2D-SSFP (10–12 breath-holds; temporal/spatial resolution: 49 ms/1.67 × 1.87 mm, parallel imaging). Ascending aorta phase-contrast was performed on all volunteers as a reference to compare LV stroke volumes (LVSV) and validate the sequences. An image quality score for SA images was used, with lower scores indicating better quality (from 0 to 18).

Results

There was a high agreement between accelerated k-t SENSE and 2D-SSFP for LV measurements: bias (limits of agreement) of 2.4% (− 5.4% to 10.1%), 6.9 mL/m² (− 4.7 to 18.6 mL/m²), − 1.5 (− 8.3 to 5.2 mL/m²), and − 0.2 g/m² (− 11.9 to 12.3 g/m²) for LV ejection fraction, end-diastolic volume index, end-systolic volume index, and mass index, respectively. LVSV by accelerated k-t SENSE presented good agreement with aortic flow. Interobserver and intraobserver variabilities for all LV parameters were also high.

Conclusion

The accelerated k-t SENSE CMR sequence is clinically feasible and accurately quantifies LV volumes, function, and mass, with short acquisition time and good image quality.

2D phase contrast blood flow velocity measurements of the thoracic vasculature: comparison of the effect of gadofosveset trisodium and gadopentetate dimeglumine

The aim of this prospective study is to compare the performance of 2D time-resolved phase-contrast (PC) MRI prior to and after the administration of an intravascular (gadofosveset-trisodium) and extravascular (gadopentetate-dimeglumine) contrast agent in the same patient in the cardiovascular system. This study was approved by the ethics committee (Study-Number-07/Q0704/2) and registered with the MedicinesAndHealthcareProductsRegulatoryAgency (MHRA-Study-Number-28482/0002/001-0001, EudraCT-Number-2006-007042). All patients signed an informed consent. 20 patients were examined using a 1.5T MR-scanner and 32-channel-coil-technology. Gadopentetate-dimeglumine (GdD) and gadofosveset-trisodium (GdT) were administered in the same patient on consecutive days. Image quality, velocity-to-noise-ratios (VNRs) and standard-deviation of blood-flow-velocities (phase-noise) were compared between GdT, GdD and non-contrast-enhanced imaging. On both days pre- and post-contrast-scans were performed. The administration of GdT significantly improved the delineation of the perfused lumen and the VNR compared to GdD and non-contrast-enhanced imaging. Standard deviations of through-plane and in-plane velocity-measurements (phase-noise) were significantly reduced after GdT administration (p < 0.05). No significant differences (p > 0.05) were measured regarding absolute flow values prior to and after the administration of GdD and GdT. PC flow imaging benefits from the administration of an intravascular contrast agent by improving the delineation of the perfused lumen and reducing phase noise in flow measurements.

Quantification of left ventricular functional parameter values using 3D spiral bSSFP and through-time non-Cartesian GRAPPA

BACKGROUND

The standard clinical acquisition for left ventricular functional parameter analysis with cardiovascular magnetic resonance (CMR) uses a multi-breathhold multi-slice segmented balanced SSFP sequence. Performing multiple long breathholds in quick succession for ventricular coverage in the short-axis orientation can lead to fatigue and is challenging in patients with severe cardiac or respiratory disorders. This study combines the encoding efficiency of a six-fold undersampled 3D stack of spirals balanced SSFP sequence with 3D through-time spiral GRAPPA parallel imaging reconstruction. This 3D spiral method requires only one breathhold to collect the dynamic data.

METHODS

Ten healthy volunteers were recruited for imaging at 3 T. The 3D spiral technique was compared against 2D imaging in terms of systolic left ventricular functional parameter values (Bland-Altman plots), total scan time (Welch's t-test) and qualitative image rating scores (Wilcoxon signed-rank test).

RESULTS

Systolic left ventricular functional values were not significantly different (i.e. 3D-2D) between the methods. The 95% confidence interval for ejection fraction was -0.1 ± 1.6% (mean ± 1.96*SD). The total scan time for the 3D spiral technique was 48 s, which included one breathhold with an average duration of 14 s for the dynamic scan, plus 34 s to collect the calibration data under free-breathing conditions. The 2D method required an average of 5 min 40s for the same coverage of the left ventricle. The difference between 3D and 2D image rating scores was significantly different from zero (Wilcoxon signed-rank test, p < 0.05); however, the scores were at least 3 (i.e. average) or higher for 3D spiral imaging.

CONCLUSION

The 3D through-time spiral GRAPPA method demonstrated equivalent systolic left ventricular functional parameter values, required significantly less total scan time and yielded acceptable image quality with respect to the 2D segmented multi-breathhold standard in this study. Moreover, the 3D spiral technique used just one breathhold for dynamic imaging, which is anticipated to reduce patient fatigue as part of the complete cardiac examination in future studies that include patients.

Three-dimensional magnetic resonance imaging using single breath-hold k-t BLAST for assessment of global left ventricular functional parameters

OBJECTIVES

To determine the accuracy of three-dimensional k-t broad-use linear acquisition speed-up technique (k-t BLAST) accelerated magnetic resonance imaging (MRI) for the assessment of left ventricular (LV) parameters compared to segmented multiple breath-hold cine imaging.

METHODS

A multislice cine (steady state free precession [SSFP]) sequence was performed with complete ventricular coverage during multiple breath-holds (temporal resolution 47 ms, voxel size 1.25 × 1.25 × 8 mm(3)). In addition, two k-t BLAST sequences with complete coverage were acquired, KT1 (temporal resolution 57 ms, voxel size 1.25 × 1.25 × 4 mm(3)) and k-t2 (temporal resolution 57 ms, voxel size 1.25 × 1.25 × 8 mm(3)), during a single breath-hold. For comparison of SSFP and k-t BLAST, LV parameters were determined: ejection fraction (EF), end-diastolic volume, end-systolic volume, and LV mass.

RESULTS

EF was underestimated by KT1 (47%) and KT2 (48%) compared to the SSFP sequence (53%). All parameters showed high correlation with the k-t BLAST sequences and the SSFP sequence (r = 0.88-0.98, P < .001). The mean relative difference for KT1/KT2 compared to the SSFP sequence was -0.11/-0.09 for the EF, -0.073/-0.086 for the EDV, 0.044/0.051 for the ESV, and 0.085/0.12 for the LV mass.

CONCLUSIONS

The use of three-dimensional k-t BLAST enabled a determination of the LV parameters with high correlation compared to the SSFP sequence. EF was slightly underestimated, and LV mass was slightly overestimated.

Single breath-hold assessment of cardiac function using an accelerated 3D single breath-hold acquisition technique--comparison of an intravascular and extravascular contrast agent

BACKGROUND

Cardiovascular magnetic resonance (CMR) is the current gold standard for the assessment of left ventricular (LV) function. Repeated breath-holds are needed for standard multi-slice 2D cine steady-state free precession sequences (M2D-SSFP). Accelerated single breath-hold techniques suffer from low contrast between blood pool and myocardium. In this study an intravascular contrast agent was prospectively compared to an extravascular contrast agent for the assessment of LV function using a single-breath-hold 3D-whole-heart cine SSFP sequence (3D-SSFP).

METHODS

LV function was assessed in fourteen patients on a 1.5 T MR-scanner (Philips Healthcare) using 32-channel coil technology. Patients were investigated twice using a 3D-SSFP sequence (acquisition time 18-25 s) after Gadopentetate dimeglumine (GdD, day 1) and Gadofosveset trisodium (GdT, day 2) administration. Image acquisition was accelerated using sensitivity encoding in both phase encoding directions (4xSENSE). CNR and BMC were both measured between blood and myocardium. The CNR incorporated noise measurements, while the BMC represented the coeffiancy between the signal from blood and myocardium [1]. Contrast to noise ratio (CNR), blood to myocardium contrast (BMC), image quality, LV functional parameters and intra-/interobserver variability were compared. A M2D-SSFP sequence was used as a reference standard on both days.

RESULTS

All 3D-SSFP sequences were successfully acquired within one breath-hold after GdD and GdT administration. CNR and BMC were significantly (p < 0.05) higher using GdT compared to GdD, resulting in an improved endocardial definition. Using 3D-SSFP with GdT, Bland-Altman plots showed a smaller bias (95% confidence interval LVEF: 9.0 vs. 23.7) and regression analysis showed a stronger correlation to the reference standard (R2 = 0.92 vs. R2 = 0.71), compared to 3D-SSFP with GdD.

CONCLUSIONS

A single-breath-hold 3D-whole-heart cine SSFP sequence in combination with 32-channel technology and an intravascular contrast agent allows for the accurate and fast assessment of LV function.

Single breathhold cardiac CINE imaging with multi-echo three-dimensional hybrid radial SSFP acquisition

PURPOSE

To achieve single breathhold whole heart cardiac CINE imaging with improved spatial resolution and temporal resolution by using a multi-echo three-dimensional (3D) hybrid radial SSFP acquisition.

MATERIALS AND METHODS

Multi-echo 3D hybrid radial SSFP acquisitions were used to acquire cardiac CINE imaging within a single breathhold. An optimized interleaving scheme was developed for view ordering throughout the cardiac cycle.

RESULTS

Whole heart short axis views were acquired with a spatial resolution of 1.3 x 1.3 x 8.0 mm(3) and temporal resolution of 45 ms, within a single 17 s breathhold. The technique was validated on eight healthy volunteers by measuring the left ventricular volume throughout the cardiac cycle and comparing with the conventional 2D multiple breathhold technique. The left ventricle functional measurement bias of our proposed 3D technique from the conventional 2D technique: end diastolic volume -3.3 mL +/- 13.7 mL, end systolic volume 1.4 mL +/- 6.1 mL, and ejection fraction -1.7% +/- 4.3%, with high correlations 0.94, 0.97, and 0.91, accordingly.

CONCLUSION

A multi-echo 3D hybrid radial SSFP acquisition was developed to allow for a whole heart cardiac CINE exam in a single breathhold. Cardiac function measurements in volunteers compared favorably with the standard multiple breathhold exams.