Native T1 value in the remote myocardium is independently associated with left ventricular dysfunction in patients with prior myocardial infarction.

PURPOSE: To compare remote myocardium native T1 in patients with chronic myocardial infarction (MI) and controls without MI and to elucidate the relationship of infarct size and native T1 in the remote myocardium for the prediction of left ventricular (LV) systolic dysfunction after MI. MATERIALS AND METHODS: A total of 41 chronic MI (18 anterior MI) patients and 15 age-matched volunteers with normal LV systolic function and no history of MI underwent cardiac magnetic resonance imaging (MRI) at 1.5T. Native T1 map was performed using a slice interleaved T1 mapping and late gadolinium enhancement (LGE) imaging. Cine MR was acquired to assess LV function and mass. RESULTS: The remote myocardium native T1 time was significantly elevated in patients with prior MI, compared to controls, for both anterior MI and nonanterior MI (anterior MI: 1099 ± 30, nonanterior MI: 1097 ± 39, controls: 1068 ± 25 msec, P < 0.05). Remote myocardium native T1 moderately correlated with LV volume, mass index, and ejection fraction (r = 0.38, 0.50, -0.49, respectively, all P < 0.05). LGE infarct size had a moderate correlation with reduced LV ejection fraction (r = -0.33, P < 0.05), but there was no significant association between native T1 and infarct size. Native T1 time in the remote myocardium was independently associated with reduced LV ejection fraction, after adjusting for age, gender, infarct size, and comorbidity (ß = -0.34, P = 0.03). CONCLUSION: In chronic MI, the severity of LV systolic dysfunction after MI is independently associated with native T1 in the remote myocardium. Diffuse myocardial fibrosis in the remote myocardium may play an important pathophysiological role of post-MI LV dysfunction. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017;46:1073-1081.

Joint myocardial T1 and T2 mapping using a combination of saturation recovery and T2 -preparation.

PURPOSE: To develop a heart-rate independent breath-held joint T1 -T2 mapping sequence for accurate simultaneous estimation of coregistered myocardial T1 and T2 maps. METHODS: A novel preparation scheme combining both a saturation pulse and T2 -preparation in a single R-R interval is introduced. The time between these two pulses, as well as the duration of the T2 -preparation is varied in each heartbeat, acquiring images with different T1 and T2 weightings, and no magnetization dependence on previous images. Inherently coregistered T1 and T2 maps are calculated from these images. Phantom imaging is performed to compare the proposed maps with spin echo references. In vivo imaging is performed in ten subjects, comparing the accuracy and precision of the proposed technique to existing myocardial T1 and T2 mapping sequences of the same duration. RESULTS: Phantom experiments show that the proposed technique provides accurate quantification of T1 and T2 values over a wide-range (T1 : 260 ms to 1460 ms, T2 : 40 ms to 200 ms). In vivo imaging shows that the proposed sequence quantifies T1 and T2 values similar to a saturation-based T1 mapping and a conventional breath-hold T2 mapping sequence, respectively. CONCLUSION: The proposed sequence allows joint estimation of accurate and coregistered quantitative myocardial T1 and T2 maps in a single breath-hold. Magn Reson Med 76:888-896, 2016. © 2015 Wiley Periodicals, Inc.

Free-breathing slice-interleaved myocardial T2 mapping with slice-selective T2 magnetization preparation.

PURPOSE: To develop and evaluate a free-breathing slice-interleaved T2 mapping sequence by proposing a new slice-selective T2 magnetization preparation (T2 prep) sequence that allows interleaved data acquisition for different slices in subsequent heartbeats. METHODS: We developed a slice-selective T2 prep for myocardial T2 mapping by adding slice-selective gradients to a conventional single-slice T2 prep sequence. In this sequence, five slices are acquired during five consecutive heartbeats, each using a slice-selective T2 prep. The scheme was repeated four times using different T2 prep echo times. We compared the performance of the proposed slice-interleaved T2 mapping sequence and the conventional single-slice T2 mapping sequence in term of accuracy, precision, and reproducibility using phantom experiments and in vivo imaging in 10 healthy subjects. We also evaluated the feasibility of the proposed sequence in 28 patients with cardiovascular disease, and the quality of the maps was scored subjectively. Furthermore, we investigated the impact of through-plane motion by comparing T2 measurements acquired during end-systole versus mid-diastole. RESULTS: T2 measurements using a slice-interleaved T2 mapping sequence were correlated with a spin echo (r(2) = 0.88) and single-slice T2 mapping sequence (r(2) = 0.98). The mean myocardial T2 values were correlated between slice-interleaved (48 ms) and single-slice (51 ms) T2 mapping sequences. Subjective scores of T2 map quality were good to excellent in 81% of the maps in patients. There was no difference in T2 measurements between end-systole versus mid-diastole. CONCLUSIONS: The proposed free-breathing slice-interleaved T2 mapping sequence allows T2 measurements of five left ventricular slices in 20 heartbeats with similar reproducibility and precision as the single-slice T2 mapping sequence but with a four-fold reduction in acquisition time. Magn Reson Med 76:555-565, 2016. © 2015 Wiley Periodicals, Inc.

Comparison of spoiled gradient echo and steady-state free-precession imaging for native myocardial T1 mapping using the slice-interleaved T1 mapping (STONE) sequence.

Cardiac T1 mapping allows non-invasive imaging of interstitial diffuse fibrosis. Myocardial T1 is commonly calculated by voxel-wise fitting of the images acquired using balanced steady-state free precession (SSFP) after an inversion pulse. However, SSFP imaging is sensitive to B1 and B0 imperfection, which may result in additional artifacts. A gradient echo (GRE) imaging sequence has been used for myocardial T1 mapping; however, its use has been limited to higher magnetic field to compensate for the lower signal-to-noise ratio (SNR) of GRE versus SSFP imaging. A slice-interleaved T1 mapping (STONE) sequence with SSFP readout (STONE-SSFP) has been recently proposed for native myocardial T1 mapping, which allows longer recovery of magnetization (>8 R-R) after each inversion pulse. In this study, we hypothesize that a longer recovery allows higher SNR and enables native myocardial T1 mapping using STONE with GRE imaging readout (STONE-GRE) at 1.5T. Numerical simulations and phantom and in vivo imaging were performed to compare the performance of STONE-GRE and STONE-SSFP for native myocardial T1 mapping at 1.5T. In numerical simulations, STONE-SSFP shows sensitivity to both T2 and off resonance. Despite the insensitivity of GRE imaging to T2 , STONE-GRE remains sensitive to T2 due to the dependence of the inversion pulse performance on T2 . In the phantom study, STONE-GRE had inferior accuracy and precision and similar repeatability as compared with STONE-SSFP. In in vivo studies, STONE-GRE and STONE-SSFP had similar myocardial native T1 times, precisions, repeatabilities and subjective T1 map qualities. Despite the lower SNR of the GRE imaging readout compared with SSFP, STONE-GRE provides similar native myocardial T1 measurements, precision, repeatability, and subjective image quality when compared with STONE-SSFP at 1.5T.

Reproducibility of myocardial T1 and T2 relaxation time measurement using slice-interleaved T1 and T2 mapping sequences.

PURPOSE: To assess measurement reproducibility and image quality of myocardial T1 and T2 maps using free-breathing slice-interleaved T1 and T2 mapping sequences at 1.5 Tesla (T). MATERIALS AND METHODS: Eleven healthy subjects (33 ± 16 years; 6 males) underwent a slice-interleaved T1 and T2 mapping test/retest cardiac MR study at 1.5T on 2 days. For each day, subjects were imaged in two sessions with removal out of the magnet and repositioning before the subsequent session. We studied measurement reproducibility as well as the required sample size for sufficient statistical power to detect a predefined change in T1 and T2 . In a separate prospective study, we assessed T1 and T2 map image quality in 241 patients (54 ± 15 years; 73 women) with known/suspected cardiovascular disease referred for clinical cardiac MR. A subjective quality score was used to assess a segment-based image quality. RESULTS: In the healthy cohort, the slice-interleaved T1 measurements were highly reproducible, with global coefficients of variation (CVs) of 2.4% between subjects, 2.1% between days, and 1.7% between sessions. Slice-interleaved T2 mapping sequences provided similar reproducibility with global CVs of 7.2% between subjects, 6.3% between days, and 5.0 between sessions. A lower variability resulted in a reduction of the required number of subjects to achieve a certain statistical power when compared with other T1 mapping sequences. In the subjective image quality assessment, >80% of myocardial segments had interpretable data. CONCLUSION: Slice-interleaved T1 and T2 mapping sequences yield highly reproducible T1 and T2 measurements with >80% of interpretable myocardial segments. J. Magn. Reson. Imaging 2016;44:1159-1167.

Myocardial Native T1 Time in Patients With Hypertrophic Cardiomyopathy.

In hypertrophic cardiomyopathy (HC), there are significant variations in left ventricular (LV) wall thickness and fibrosis, which necessitates a volumetric coverage. Slice-interleaved T1 (STONE) mapping sequence allows for the assessment of native T1 time with complete coverage of LV myocardium. The aims of this study were to evaluate spatial heterogeneity of native T1 time in patients with HC. Twenty-nine patients with HC (55 ± 16 years) and 15 healthy adult control subjects (46 ± 19 years) were studied. Native T1 mapping was performed using STONE sequence which enables acquisition of 5 slices in the short-axis plane within a 90 seconds free-breathing scan. We measured LV native T1 time and maximum LV wall thickness in each 16 segments from 3 slices (basal, midventricular and apical slice). Late gadolinium enhanced (LGE) magnetic resonance imaging was acquired to assess the presence of myocardial enhancement. In patients with HC, LV native T1 time was significantly elevated compared with healthy controls, regardless of the presence or absence of LGE (mean native T1 time; LGE positive segments from HC, 1,141 ± 46 ms; LGE negative segments from HC, 1,114 ± 56 ms; segments from healthy controls, 1,065 ± 35 ms, p <0.001). Elevation of native T1 time was defined as >1,135 ms, which was +2SD of native T1 time by STONE sequence in healthy controls. A total of 120 of 405 (30%) LGE negative segments from patients with HC showed elevated native T1 time. Prevalence of segments with elevated native T1 time for basal, midventricular, and apical slice was 29%, 25%, 38%, respectively. Significant correlation was found between LV wall thickness and LV native T1 time (y = 0.029 × -22.6, p <0.001 by Spearman's correlation coefficient). In conclusion, substantial number of segments without LGE showed elevation of native T1 time, and whole-heart T1 mapping revealed heterogeneity of myocardial native T1 time in patients with HC.

Native Myocardial T1 as a Biomarker of Cardiac Structure in Non-Ischemic Cardiomyopathy.

Diffuse myocardial fibrosis is involved in the pathology of nonischemic cardiomyopathy (NIC). Recently, the application of native (noncontrast) myocardial T1 measurement has been proposed as a method for characterizing diffuse interstitial fibrosis. To determine the association of native T1 with myocardial structure and function, we prospectively studied 39 patients with NIC (defined as left ventricular ejection fraction (LVEF) ≤ 50% without cardiac magnetic resonance (CMR) evidence of previous infarction) and 27 subjects with normal LVEF without known overt cardiovascular disease. T1, T2, and extracellular volume fraction (ECV) were determined over 16 segments across the base, mid, and apical left ventricular (LV). NIC participants (57 ± 15 years) were predominantly men (74%), with a mean LVEF 34 ± 10%. Subjects with NIC had a greater native T1 (1,131 ± 51 vs 1,069 ± 29 ms; p <0.0001), a greater ECV (0.28 ± 0.04 vs 0.25 ± 0.02, p = 0.002), and a longer myocardial T2 (52 ± 8 vs 47 ± 5 ms; p = 0.02). After multivariate adjustment, a lower global native T1 time in NIC was associated with a greater LVEF (ß = -0.59, p = 0.0003), greater right ventricular ejection fraction (ß = -0.47, p = 0.006), and smaller left atrial volume index (ß = 0.51, p = 0.001). The regional distribution of native myocardial T1 was similar in patients with and without NIC. In NIC, native myocardial T1 is elevated in all myocardial segments, suggesting a global (not regional) abnormality of myocardial tissue composition. In conclusion, native T1 may represent a rapid, noncontrast alternative to ECV for delineating myocardial tissue remodeling in NIC.

Epicardial adipose tissue assessed by cardiac magnetic resonance imaging in patients with heart failure due to dilated cardiomyopathy.

OBJECTIVE: We sought to investigate the association of the EAT with CMR parameters of ventricular remodelling and left ventricular (LV) dysfunction in patients with non-ischemic dilated cardiomyopathy (DCM). DESIGN AND METHODS: One hundred and fifty subjects (112 consecutive patients with DCM and 48 healthy controls) underwent CMR examination. Function, volumes, dimensions, the LV remodelling index (LVRI), the presence of late gadolinium enhancement (LGE) and the amount of EAT were assessed. RESULTS: Compared to healthy controls, patients with DCM revealed a significantly reduced indexed EAT mass (31.7 ± 5.6 g/m(2) vs 24.0 ± 7.5 g/m(2) , p<0.0001). There was no difference in the EAT mass between DCM patients with moderate and severe LV dysfunction (23.5 ± 9.8 g/m(2) vs 24.2 ± 6.6 g/m(2) , P = 0.7). Linear regression analysis in DCM patients showed that with increasing LV end-diastolic mass index (LV-EDMI) (r = 0.417, P < 0.0001), increasing LV end-diastolic volume index (r = 0.251, P = 0.01) and increasing LV end-diastolic diameter (r = 0.220, P = 0.02), there was also a significantly increased amount of EAT mass. However, there was no correlation between the EAT and the LV ejection fraction (r = 0.0085, P = 0.37), right ventricular ejection fraction (r = 0.049, P = 0.6), LVRI (r = 0.116, P = 0.2) and the extent of LGE % (r = 0.189, P = 0.1). Among the healthy controls, the amount of EAT only correlated with increasing age (r = 0.461, P = 0.001), BMI (r = 0.426, P = 0.003) and LV-EDMI (r = 0.346, P = 0.02). CONCLUSION: In patients with DCM the amount of EAT is decreased compared to healthy controls irrespective of LV function impairment. However, an increase in LV mass and volumes is associated with a significantly increase in EAT in patients with DCM.