Accelerated and navigator-gated look-locker imaging for cardiac T1 estimation (ANGIE): Development and application to T1 mapping of the right ventricle.

PURPOSE: To develop a method for high-resolution cardiac T1 mapping. METHODS: A new method, accelerated and navigator-gated look-locker imaging for cardiac T1 estimation (ANGIE), was developed. An adaptive acquisition algorithm that accounts for the interplay between navigator gating and undersampling patterns well-suited for compressed sensing was used to minimize scan time. Computer simulations, phantom experiments, and imaging of the left ventricle (LV) were used to optimize and evaluate ANGIE. ANGIE's high spatial resolution was demonstrated by T1 mapping of the right ventricle (RV). Comparisons were made to modified Look-Locker imaging (MOLLI). RESULTS: Retrospective reconstruction of fully sampled datasets demonstrated the advantages of the adaptive algorithm. For the LV, ANGIE measurements of T1 were in good agreement with MOLLI. For the RV, ANGIE achieved a spatial resolution of 1.2 × 1.2 mm(2) with a scan time of 157 ± 53 s per slice, and measured RV T1 values of 980 ± 96 ms versus 1076 ± 157 ms for lower-resolution MOLLI. ANGIE provided lower intrascan variation in the RV T1 estimate compared with MOLLI (P < 0.05). CONCLUSION: ANGIE enables high-resolution cardiac T1 mapping in clinically reasonable scan times. ANGIE opens the prospect of quantitative T1 mapping of thin cardiovascular structures such as the RV wall.

Detection of elevated right ventricular extracellular volume in pulmonary hypertension using Accelerated and Navigator-Gated Look-Locker Imaging for Cardiac T1 Estimation (ANGIE) cardiovascular magnetic resonance.

BACKGROUND: Assessment of diffuse right ventricular (RV) fibrosis is of particular interest in pulmonary hypertension (PH) and heart failure (HF). Current cardiovascular magnetic resonance (CMR) T1 mapping techniques such as Modified Look-Locker inversion recovery (MOLLI) imaging have limited resolution, but accelerated and navigator-gated Look-Locker imaging for cardiac T1 estimation (ANGIE) is a novel CMR sequence with spatial resolution suitable for T1 mapping of the RV. We tested the hypothesis that patients with PH would have significantly more RV fibrosis detected with MRI ANGIE compared with normal volunteers and patients having HF with reduced (LV) ejection fraction (HFrEF) without co-existing PH, independent of RV dilitation and dysfunction. METHODS: Patients with World Health Organization group 1 or group 4 PH, patients with HFrEF without PH, and normal volunteers were recruited to undergo contrast-enhanced CMR. RV and LV extracellular volume fractions (RV-ECV and LV-ECV) were determined using pre-contrast and post-contrast T1 mapping using ANGIE (RV and LV) and MOLLI (LV only). RESULTS: Thirty-two participants (53.1% female, median age 52 years, IQR 26-65 years) were enrolled, including n = 12 with PH, n = 10 having HFrEF without co-existing PH, and n = 10 normal volunteers. ANGIE ECV imaging was of high quality, and ANGIE measurements of LV-ECV were highly correlated with those of MOLLI (r = 0.91; p < 0.001). The RV-ECV in PH patients was 27.2% greater than the RV-ECV in normal volunteers (0.341 v. 0.268; p < 0.0001) and 18.9% greater than the RV-ECV in HFrEF patients without PH (0.341 v. 0.287; p < 0.0001). RV-ECV was greater than LV-ECV in PH (RV-LV difference = 0.04), but RV-ECV was nearly equivalent to LV-ECV in normal volunteers (RV-LV difference = 0.002) (p < 0.0001 for RV-LV difference in PH versus normal volunteers). RV-ECV was linearly associated with both increasing RVEDVI (p = 0.049) and decreasing RVEF (p = 0.04) in a multivariable linear model, but PH was still associated with greater RV-ECV even after adjustment for RVEDVI and RVEF. CONCLUSIONS: Pre- and post-contrast ANGIE imaging provides high-resolution ECV determination for the RV. PH is independently associated with increased RV-ECV even after adjustment for RV dilatation and dysfunction, consistent with an independent effect of PH on fibrosis. ANGIE RV imaging merits further clinical evaluation in PH.

Magnetic Resonance Fingerprinting-An Overview.

Magnetic Resonance Fingerprinting (MRF) is a new approach to quantitative magnetic resonance imaging that allows simultaneous measurement of multiple tissue properties in a single, time-efficient acquisition. The ability to reproducibly and quantitatively measure tissue properties could enable more objective tissue diagnosis, comparisons of scans acquired at different locations and time points, longitudinal follow-up of individual patients and development of imaging biomarkers. This review provides a general overview of MRF technology, current preclinical and clinical applications and potential future directions. MRF has been initially evaluated in brain, prostate, liver, cardiac, musculoskeletal imaging, and measurement of perfusion and microvascular properties through MR vascular fingerprinting.