Free‐breathing post‐contrast three‐dimensional T₁ mapping: Volumetric assessment of myocardial T₁ values

Abstract

Purpose: To develop a 3D free-breathing myocardial T1 mapping sequence for assessment of left ventricle diffuse fibrosis after contrast administration. Methods: In the proposed sequence, multiple 3D inversion recovery images are acquired in an interleaved manner. A mixed prospective/retrospective navigator scheme is used to obtain the 3D Cartesian k-space data with fully sampled center and randomly undersampled outer k-space. The resulting undersampled 3D k-space data are then reconstructed using compressed sensing. Subsequently, T1 maps are generated by voxel-wise curve-fitting of the individual interleaved images. In a phantom study, the accuracy of the 3D sequence was evaluated against modified 2D Look-Locker inversion recovery (MOLLI) and spin-echo sequences. In-vivo T1 times of the proposed method were compared to 2D multi-slice MOLLI T1 mapping. Subsequently, the feasibility of high-resolution 3D T1 mapping with spatial resolution of 1.7×1.7×4mm3 was demonstrated. Results: The proposed method shows good agreement with 2D MOLLI and the spin-echo reference in phantom. No significant difference was found in the in-vivo T1 times estimated using the proposed sequence and the 2D MOLLI technique (myocardium: 330 ± 66ms vs. 319 ± 93 ms, blood-pools: 211 ± 68 ms vs. 210 ± 98 ms). However, improved homogeneity, as measured using standard deviation of the T1 signal, was observed in the 3D T1 maps. Conclusion: The proposed sequence enables high-resolution 3D T1 mapping after contrast injection during free-breathing with volumetric LV coverage.

A novel profile/view ordering with a non-convex star shutter for high-resolution 3D volumetric T1 mapping under multiple breath-holds

“…Therefore, the regions near the middle of the excited slab would yield higher signal, which drops slightly in the trophs between the side lobes, and the edge slices suffered from more noticeable SNR loss, which also affects the T 1 map calculation. This phenomena, which was also reported in , agreed with our findings from the homogeneous phantom. In our study, the 3D‐MOLLI sequence was applied in vivo over an 8‐cm slab that covered the entire LV, where the basal, mid, and apical slices were typically sufficiently away from these edge slices.…”

“…For in vivo clinical imaging, we acknowledge that the utility of this sequence would benefit more greatly by integrating both k‐space and image‐domain motion correction to address the variability between each breath‐held diaphragm position, or in patients with limited breath‐hold capabilities and low heart rates. This correction can be achieved by either generating self‐navigation volume from each fan pair for registration, or by employing diaphragmatic , direct image‐based 2D navigators in a prospective manner, or correction methods in the final T 1 map generation steps . These correction methods warrant further investigation for eventual adaptation into a multi‐breath‐held 3D acquisition scheme that can be used clinically.…”

“…Recently, several three‐dimensional (3D) T 1 mapping approaches have been proposed to address this problem of limited coverage using 2D acquisition, and have the additional advantage of being able to recover through‐plane motion that is infeasible with the 2D approach. These 3D strategies employ either free‐breathing or multiple breath‐holds that provide improved anatomical coverage and spatial resolution. These include either a 3D volumetric acquisition in three breath‐holds , or interleaved acquisition method of multiple volumes under free‐breathing and navigator gating .…”

“…These 3D strategies employ either free‐breathing or multiple breath‐holds that provide improved anatomical coverage and spatial resolution. These include either a 3D volumetric acquisition in three breath‐holds , or interleaved acquisition method of multiple volumes under free‐breathing and navigator gating . However, these approaches must exploit significant acceleration by employing parallel imaging with a 32‐channel cardiac array, or employ dedicated undersampled acquisition with tailored and iterative reconstruction algorithms such as compressed sensing, which are not commonly available on typical clinical MRI hardware.…”

Recent Advances in Cardiovascular Magnetic Resonance

“…In patients with shortness of breath, breath holding may be inadequate, resulting in image artifacts. Free-breathing CMR techniques which use navigators to track diaphragmatic motion have been implemented in most MR systems from all major vendors and have been used in many CMR applications, such as noncontrast whole-heart coronary MRA, 56 3D myocardial T1 mapping, 57 and 3D cardiac diffusion-weighted CMR. 58 However, relatively low gating efficiency, typically between 30% and 50%, may result in lengthy and unpredictable imaging times, particularly with whole-heart imaging.…”