Title: Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T
Purpose
This work aims to develop an approach for simultaneous water–fat separation and myocardial T1and T2quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.
Methods
Two 15‐heartbeat cMRF sequences with different rosette trajectories designed for water–fat separation at 3T and 1.5T were implemented. Water T1and T2maps, water image, and fat image were generated with B0inhomogeneity correction using a B0map derived from the cMRF data themselves. The proposed water–fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.
Results
Water T1and T2values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T1but 2~3 ms higher T2values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.
Conclusion
Rosette cMRF provides fat images along with myocardial T1and T2maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.
Hamilton, Jesse I.; Pahwa, Shivani; Adedigba, Joseph; Frankel, Samuel; O'Connor, Gregory; Thomas, Rahul; Walker, Jonathan R.; Killinc, Ozden; Lo, Wei‐Ching; Batesole, Joshua; et al(
, Journal of Magnetic Resonance Imaging)
Background
Cardiac MR fingerprinting (cMRF) is a novel technique for simultaneous T1and T2mapping.
Purpose
To compare T1/T2measurements, repeatability, and map quality between cMRF and standard mapping techniques in healthy subjects.
Study Type
Prospective.
Population
In all, 58 subjects (ages 18–60).
Field Strength/Sequence
cMRF, modified Look–Locker inversion recovery (MOLLI), and T2‐prepared balanced steady‐state free precession (bSSFP) at 1.5T.
Assessment
T1/T2values were measured in 16 myocardial segments at apical, medial, and basal slice positions. Test–retest and intrareader repeatability were assessed for the medial slice. cMRF and conventional mapping sequences were compared using ordinal and two alternative forced choice (2AFC) ratings.
Statistical Tests
Pairedt‐tests, Bland–Altman analyses, intraclass correlation coefficient (ICC), linear regression, one‐way analysis of variance (ANOVA), and binomial tests.
Results
Average T1measurements were: basal 1007.4±96.5 msec (cMRF), 990.0±45.3 msec (MOLLI); medial 995.0±101.7 msec (cMRF), 995.6±59.7 msec (MOLLI); apical 1006.6±111.2 msec (cMRF); and 981.6±87.6 msec (MOLLI). Average T2measurements were: basal 40.9±7.0 msec (cMRF), 46.1±3.5 msec (bSSFP); medial 41.0±6.4 msec (cMRF), 47.4±4.1 msec (bSSFP); apical 43.5±6.7 msec (cMRF), 48.0±4.0 msec (bSSFP). A statistically significant bias (cMRF T1larger than MOLLI T1) was observed in basal (17.4 msec) and apical (25.0 msec) slices. For T2, a statistically significant bias (cMRF lower than bSSFP) was observed for basal (–5.2 msec), medial (–6.3 msec), and apical (–4.5 msec) slices. Precision was lower for cMRF—the average of the standard deviation measured within each slice was 102 msec for cMRF vs. 61 msec for MOLLI T1, and 6.4 msec for cMRF vs. 4.0 msec for bSSFP T2. cMRF and conventional techniques had similar test–retest repeatability as quantified by ICC (0.87 cMRF vs. 0.84 MOLLI for T1; 0.85 cMRF vs. 0.85 bSSFP for T2). In the ordinal image quality comparison, cMRF maps scored higher than conventional sequences for both T1(all five features) and T2(four features).
Data Conclusion
This work reports on myocardial T1/T2measurements in healthy subjects using cMRF and standard mapping sequences. cMRF had slightly lower precision, similar test–retest and intrareader repeatability, and higher scores for map quality.
Evidence Level
2
Technical Efficacy
Stage 1 J. Magn. Reson. Imaging 2020;52:1044–1052.
This study introduces a technique called cine magnetic resonance fingerprinting (cine‐MRF) for simultaneous T1, T2and ejection fraction (EF) quantification. Data acquired with a free‐running MRF sequence are retrospectively sorted into different cardiac phases using an external electrocardiogram (ECG) signal. A low‐rank reconstruction with a finite difference sparsity constraint along the cardiac motion dimension yields images resolved by cardiac phase. To improve SNR and precision in the parameter maps, these images are nonrigidly registered to the same phase and matched to a dictionary to generate T1and T2maps. Cine images for computing left ventricular volumes and EF are also derived from the same data. Cine‐MRF was tested in simulations using a numerical relaxation phantom. Phantom and in vivo scans of 19 subjects were performed at 3 T during a 10.9 seconds breath‐hold with an in‐plane resolution of 1.6 x 1.6 mm2and 24 cardiac phases. Left ventricular EF values obtained with cine‐MRF agreed with the conventional cine images (mean bias −1.0%). Average myocardial T1times in diastole/systole were 1398/1391 ms with cine‐MRF, 1394/1378 ms with ECG‐triggered cardiac MRF (cMRF) and 1234/1212 ms with MOLLI; and T2values were 30.7/30.3 ms with cine‐MRF, 32.6/32.9 ms with ECG‐triggered cMRF and 37.6/41.0 ms with T2‐prepared FLASH. Cine‐MRF and ECG‐triggered cMRF relaxation times were in good agreement. Cine‐MRF T1values were significantly longer than MOLLI, and cine‐MRF T2values were significantly shorter than T2‐prepared FLASH. In summary, cine‐MRF can potentially streamline cardiac MRI exams by combining left ventricle functional assessment and T1‐T2mapping into one time‐efficient acquisition.
Weingärtner, Sebastian; Demirel, Ömer B.; Gama, Francisco; Pierce, Iain; Treibel, Thomas A.; Schulz-Menger, Jeanette; Akçakaya, Mehmet(
, Frontiers in Cardiovascular Medicine)
Late gadolinium enhancement (LGE) with cardiac magnetic resonance (CMR) imaging is the clinical reference for assessment of myocardial scar and focal fibrosis. However, current LGE techniques are confined to imaging of a single cardiac phase, which hampers assessment of scar motility and does not allow cross-comparison between multiple phases. In this work, we investigate a three step approach to obtain cardiac phase-resolved LGE images: (1) Acquisition of cardiac phase-resolved imaging data with varyingT1weighting. (2) Generation of semi-quantitativemaps for each cardiac phase. (3) Synthetization of LGE contrast to obtain functional LGE images. The proposed method is evaluated in phantom imaging, six healthy subjects at 3T and 20 patients at 1.5T. Phantom imaging at 3T demonstrates consistent contrast throughout the cardiac cycle with a coefficient of variation of 2.55 ± 0.42%.In-vivoresults show reliable LGE contrast with thorough suppression of the myocardial tissue is healthy subjects. The contrast between blood and myocardium showed moderate variation throughout the cardiac cycle in healthy subjects (coefficient of variation 18.2 ± 3.51%). Images were acquired at 40–60 ms and 80 ms temporal resolution, at 3T and 1.5, respectively. Functional LGE images acquired in patients with myocardial scar visualized scar tissue throughout the cardiac cycle, albeit at noticeably lower imaging resolution and noise resilience than the reference technique. The proposed technique bears the promise of integrating the advantages of phase-resolved CMR with LGE imaging, but further improvements in the acquisition quality are warranted for clinical use.
Weingärtner, Sebastian; Shenoy, Chetan; Rieger, Benedikt; Schad, Lothar R.; Schulz‐Menger, Jeanette; Akçakaya, Mehmet(
, Magnetic Resonance in Medicine)
Purpose
To develop and evaluate a cardiac phase‐resolved myocardial T1mapping sequence.
Methods
The proposed method for temporally resolved parametric assessment of Z‐magnetization recovery (TOPAZ) is based on contiguous fast low‐angle shot imaging readout after magnetization inversion from the pulsed steady state. Thereby, segmented k‐space data are acquired over multiple heartbeats, before reaching steady state. This results in sampling of the inversion‐recovery curve for each heart phase at multiple points separated by an R‐R interval. Joint T1andestimation is performed for reconstruction of cardiac phase‐resolved T1andmaps. Sequence parameters are optimized using numerical simulations. Phantom and in vivo imaging are performed to compare the proposed sequence to a spin‐echo reference and saturation pulse prepared heart rate–independent inversion‐recovery (SAPPHIRE) T1mapping sequence in terms of accuracy and precision.
Results
In phantom, TOPAZ T1values with integratedcorrection are in good agreement with spin‐echo T1values (normalized root mean square error = 4.2%) and consistent across the cardiac cycle (coefficient of variation = 1.4 ± 0.78%) and different heart rates (coefficient of variation = 1.2 ± 1.9%). In vivo imaging shows no significant difference in TOPAZ T1times between the cardiac phases (analysis of variance:P = 0.14, coefficient of variation = 3.2 ± 0.8%), but underestimation compared with SAPPHIRE (T1time ± precision: 1431 ± 56 ms versus 1569 ± 65 ms). In vivo precision is comparable to SAPPHIRE T1mapping until middiastole (P > 0.07), but deteriorates in the later phases.
This study introduces a technique for simultaneous multislice (SMS) cardiac magnetic resonance fingerprinting (cMRF), which improves the slice coverage when quantifying myocardialT1,T2, andM0. The single‐slice cMRF pulse sequence was modified to use multiband (MB) RF pulses for SMS imaging. Different RF phase schedules were used to excite each slice, similar to POMP or CAIPIRINHA, which imparts tissues with a distinguishable and slice‐specific magnetization evolution over time. Because of the high net acceleration factor (R = 48 in plane combined with the slice acceleration), images were first reconstructed with a low rank technique before matching data to a dictionary of signal timecourses generated by a Bloch equation simulation. The proposed method was tested in simulations with a numerical relaxation phantom. Phantom and in vivo cardiac scans of 10 healthy volunteers were also performed at 3 T. With single‐slice acquisitions, the mean relaxation times obtained using the low rank cMRF reconstruction agree with reference values. The low rank method improves the precision inT1andT2for both single‐slice and SMS cMRF, and it enables the acquisition of maps with fewer artifacts when using SMS cMRF at higher MB factors. With this technique, in vivo cardiac maps were acquired from three slices simultaneously during a breathhold lasting 16 heartbeats. SMS cMRF improves the efficiency and slice coverage of myocardialT1andT2mapping compared with both single‐slice cMRF and conventional cardiac mapping sequences. Thus, this technique is a first step toward whole‐heart simultaneousT1andT2quantification with cMRF.
Liu, Yuchi, Hamilton, Jesse, Eck, Brendan, Griswold, Mark, and Seiberlich, Nicole. Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T. Magnetic Resonance in Medicine 85.1 Web. doi:10.1002/mrm.28404.
Liu, Yuchi, Hamilton, Jesse, Eck, Brendan, Griswold, Mark, & Seiberlich, Nicole. Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T. Magnetic Resonance in Medicine, 85 (1). https://doi.org/10.1002/mrm.28404
Liu, Yuchi, Hamilton, Jesse, Eck, Brendan, Griswold, Mark, and Seiberlich, Nicole.
"Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T". Magnetic Resonance in Medicine 85 (1). Country unknown/Code not available: Wiley Blackwell (John Wiley & Sons). https://doi.org/10.1002/mrm.28404.https://par.nsf.gov/biblio/10378832.
@article{osti_10378832,
place = {Country unknown/Code not available},
title = {Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T},
url = {https://par.nsf.gov/biblio/10378832},
DOI = {10.1002/mrm.28404},
abstractNote = {PurposeThis work aims to develop an approach for simultaneous water–fat separation and myocardial T1and T2quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T. MethodsTwo 15‐heartbeat cMRF sequences with different rosette trajectories designed for water–fat separation at 3T and 1.5T were implemented. Water T1and T2maps, water image, and fat image were generated with B0inhomogeneity correction using a B0map derived from the cMRF data themselves. The proposed water–fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T. ResultsWater T1and T2values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T1but 2~3 ms higher T2values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images. ConclusionRosette cMRF provides fat images along with myocardial T1and T2maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.},
journal = {Magnetic Resonance in Medicine},
volume = {85},
number = {1},
publisher = {Wiley Blackwell (John Wiley & Sons)},
author = {Liu, Yuchi and Hamilton, Jesse and Eck, Brendan and Griswold, Mark and Seiberlich, Nicole},
}
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