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Inter-site Reproducibility of Cardiac Magnetic Resonance Fingerprinting T1 and T2 Quantification in the ISMRM/NIST MRI System Phantom and Human Heart
Yuchi Liu1, Luuk H.G.A. Hopman2, Jesse Hamilton1, Elizabeth Hillier2, Matthias Friedrich2, and Nicole Seiberlich1,3

1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Research Institute of the McGill University Health Center, Montreal, QC, Canada, 3Department of Radiology, University Hospitals Cleveland Medical Center, Cleveland, OH, United States

Synopsis

Cardiac Magnetic Resonance Fingerprinting (cMRF) is a novel technique for simultaneous T1 and T2 quantification in the myocardium. Because cMRF has the potential to take heart rate variations and any variable system properties into account, it is hypothesized that cMRF will enable more reproducible measurements of T1 and T2. The purpose of this study is to evaluate the inter-site reproducibility of cMRF. Excellent agreement of cMRF measurements between two sites (University Hospitals Cleveland Medical Center, Cleveland, US and McGill University Health Center, Montreal, CA) was achieved in the ISMRM/NIST phantom and in the hearts of healthy subjects.

Introduction

A significant challenge to clinical myocardial T1 and T2 mapping has been the lack of reproducibility in these measurements across MRI scanners. Experts agree that T1 values must be interpreted in the context of normative T1 values for the specific MRI scanner; different sequence versions, vendors, and software platforms can lead to non-physiological variations in the measured T1 values1. Cardiac Magnetic Resonance Fingerprinting (cMRF) is a novel technique for simultaneous T1 and T2 quantification in the myocardium in a single scan2. Because cMRF has the potential to take heart rate variations and any variable system properties into account3, it is hypothesized that cMRF will enable more reproducible measurements of T1 and T2 in the heart. In order to evaluate the reproducibility of cMRF across different scanners at different sites, the ISMRM/NIST MRI system phantom and healthy subjects were scanned at University Hospitals Cleveland Medical Center (UHCMC), Cleveland, US and McGill University Health Center (MUHC), Montreal, CA in this study.

Methods

A 15-heartbeat cMRF sequence using a 5-segment scheme4 was applied to the ISMRM/NIST MRI system phantom5 and healthy subjects at both sites. In this 15-heartbeat, 5-segment scheme, an inversion pulse was employed in the first heartbeat; T2-preparation pulses were employed in the third, fourth, and fifth heartbeats in each segment with echo times of 30ms, 50ms, and 80ms. No magnetization preparation pulse was used in the second heartbeat. This scheme was repeated three times resulting in an acquisition with a total of 15-heartbeats during a breath-hold (Figure 1). A constant TR of 5.1ms and ramped flip angles between 4° to 25° were used. 50 excitations were collected at end-diastole with ECG triggering, leading to an acquisition window of ~255ms. Other acquisition parameters are: FOV 300×300 mm2; matrix size 192×192; slice thickness 8mm.

Nine healthy subjects (age 26.7±5.5; 7 female, 2 male) were recruited in this IRB-approved study at UHCMC in Cleveland. The protocol involved collecting cMRF scans as well as scans from conventional T1 and T2 mapping methods (MOLLI and T2-prepared FLASH) in mid-ventricular level short axis slice at 3T (Siemens Skyra, Erlangen, Germany). Nine healthy subjects (age 38.1±13.3; 5 female, 4 male) were scanned at MUHC in Montreal using the same cMRF sequence and conventional T1 and T2 mapping methods (MOLLI and T2-prepared bSSFP) at 3T (Siemens Skyra, Erlangen, Germany). The ISMRM/NIST MRI system phantom was also scanned at both sites using the cMRF sequence. All cMRF data were reconstructed using a low rank method6 with a dictionary including slice profile and preparation pulses efficiency corrections3.

Results

Figure 2 shows cMRF T1 and T2 measurements in the ISMRM/NIST MRI system phantom acquired at UHCMC, Cleveland and MUHC, Montreal compared with reference values. Excellent agreement was observed between cMRF measurements and reference values (Fig2.B,C) as well as between cMRF measurements at the two sites (Fig2.D). cMRF also shows excellent reproducibility in myocardial T1 (1353.9±40.4 ms in Montreal vs. 1346.4±36.7 ms in Cleveland) and T2 (29.7±2.8 ms in Montreal vs. 29.6±4.2 ms in Cleveland) quantification in healthy subjects. Conventional parametric mapping methods yield similar T1 measurements (1220.8±39.1 ms in Montreal vs. 1207.7±26 ms in Cleveland) but significantly different T2 measurements (41.6±1.6 ms in Montreal vs. 38±2.1 ms in Cleveland, p<0.05). T1 values obtained by cMRF are significantly higher than those generated by MOLLI (p<0.05); while T2 values are significantly lower than conventional mapping results (p<0.05) (Figure 3). Representative T1 and T2 maps in healthy subjects obtained by cMRF and conventional parametric mapping methods are shown in Figure 4.

Discussion

While reproducibility of MRF has been shown for brain and prostate MRF implementations7-9, this work is the first demonstration of inter-site reproducibility of cMRF in the heart. Note that imperfect slice profile and preparation pulses efficiency are taken into account in the cMRF mapping in the current study; other confounding factors not modeled in the dictionary such as flow and magnetization transfer may still affect the accuracy of cMRF measurements in vivo. Conventional T2 mapping results are significantly different at the two sites possibly due to different readout schemes of the sequence employed (bSSFP vs. FLASH).

Conclusion

This study shows excellent inter-site reproducibility of cMRF in quantifying T1 and T2 in the ISMRM/NIST MRI system phantom and in the human heart. Because variations in heart rate and confounding effects of the system properties on tissue characterization can be modeled in the dictionary, cMRF has the potential to provide unbiased measurements that are reproducible on all MRI scanners, regardless of institutions, vendors, and installations.

Acknowledgements

R01HL094557, R01DK098503, CBET 1553441, C06 RR12463-01, Siemens Healthineers (Erlangen, Germany).

References

1. Messroghli DR, Moon JC, Ferreira VM, et al. Clinical recommendations for cardiovascular magnetic resonance mapping of T1, T2, T2* and extracellular volume: A consensus statement by the Society for Cardiovascular Magnetic Resonance (SCMR) endorsed by the European Association for Cardiovascular Imagin. J. Cardiovasc. Magn. Reson. 2017;19:1–24.

2. Hamilton JI, Jiang Y, Chen Y, Ma D, Lo WC, Griswold M, Seiberlich N. MR fingerprinting for rapid quantification of myocardial T1, T2, and proton spin density. Magn. Reson. Med. 2017;77:1446–1458.

3. Hamilton JI, Jiang Y, Ma D, Lo W-C, Gulani V, Griswold M, Seiberlich N. Investigating and reducing the effects of confounding factors for robust T1 and T2 mapping with cardiac MR fingerprinting. Magn. Reson. Imaging 2018;53:40–51.

4. Hamilton JI, Jiang Y, Ma D, Pahwa S, Chen Y, Lo W-C, Griswold MA, Seiberlich N. A Comparison of 5-Heartbeat vs. 15-Heartbeat Cardiac MR Fingerprinting Sequences in Normal Volunteers. ISMRM Work. MRF 2017.

5. Russek SE, Boss M, Jackson EF, Jennings DL, Eveloch JL, Gunter JL, et al. Characterization of NIST/ISMRM MRI System Phantom. Proc. 20th Annu. Meet. ISMRM 2012:2456.

6. Hamilton JI, Jiang Y, Chen Y, Pawha S, Lo W, Batesole J, Seiberlich N. Low Rank Compressed Sensing Reconstruction for More Precise Cardiac MRF Measurements. Proc. 25th Annu. Meet. ISMRM 2017:554.

7. Jiang Y, Ma D, Keenan KE, Stupic KF, Gulani V, Griswold MA. Repeatability of magnetic resonance fingerprinting T1 and T2 estimates assessed using the ISMRM/NIST MRI system phantom. Magn. Reson. Med. 2017;78:1452–1457.

8. Lo WC, Jiang Y, Bittencourt LK, et al. Multicenter repeatability and reproducibility of MR Fingerprinting. Proc. 26th Annu. Meet. ISMRM 2018:5236.

9. Körzdörfer G, Kirsch R, Liu K, Pfeuffer J, Hensel B, Jiang Y, Ma D, Griswold M, Gulani V, Nittka M. Multicenter and multiscanner reproducibility of Magnetic Resonance Fingerprinting relaxometry in the brain. Proc. 26th Annu. Meet. ISMRM 2018:798.

Figures

Figure 1. Diagram of the 15-heartbeat cMRF sequence. Acq: acquisition; Inv: inversion pulse; T2-prep: T2-preparation pulse.

Figure 2. T1 and T2 measurements in the ISMRM/NIST MRI system phantom using the 15-heartbeat cMRF sequence at UHCMC in Cleveland and MUHC in Montreal.

Figure 3. Myocardial T1 and T2 in the mid-ventricular level short axis slice measured in 9 healthy subjects at each site using cMRF and conventional parametric mapping methods.

Figure 4. Representative T1 and T2 maps generated by cMRF and conventional parametric mapping methods in the mid-ventricular slice acquired at MUHC, Montreal (top row) and UHCMC, Cleveland (bottom row).

Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)
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