Free‐running 3D whole heart myocardial T₁ mapping with isotropic spatial resolution

Abstract

Purpose To develop a free‐running (free‐breathing, retrospective cardiac gating) 3D myocardial T1 mapping with isotropic spatial resolution. Methods The free‐running sequence is inversion recovery (IR)‐prepared followed by continuous 3D golden angle radial data acquisition. 1D respiratory motion signal is extracted from the k‐space center of all spokes and used to bin the k‐space data into different respiratory states, enabling estimation and correction of 3D translational respiratory motion, whereas cardiac motion is recorded using electrocardiography and synchronized with data acquisition. 3D translational respiratory motion compensated T1 maps at diastole and systole were generated with 1.5 mm isotropic spatial resolution with low‐rank inversion and high‐dimensionality patch‐based undersampled reconstruction. The technique was validated against conventional methods in phantom and 9 healthy subjects. Results Phantom results demonstrated good agreement (R2 = 0.99) of T1 estimation with reference method. Homogeneous systolic and diastolic 3D T1 maps were reconstructed from the proposed technique. Diastolic septal T1 estimated with the proposed method (1140 ± 36 ms) was comparable to the saturation recovery single‐shot acquisition (SASHA) sequence (1153 ± 49 ms), but was higher than the modified Look‐Locker inversion recovery (MOLLI) sequence (1037 ± 33 ms). Precision of the proposed method (42 ± 8 ms) was comparable to MOLLI (41 ± 7 ms) and improved with respect to SASHA (87 ± 19 ms). Conclusions The proposed free‐running whole heart T1 mapping method allows for reconstruction of isotropic resolution 3D T1 maps at different cardiac phases, serving as a promising tool for whole heart myocardial tissue characterization.

Prospective correction of patient‐specific respiratory motion in myocardial T1 and T2 mapping

“…Another solution is a freerunning 3D acquisition with respiratory self-navigation. 35 This technique has several advantages over traditional single-shot 2D mapping acquisitions, including total heart coverage, ease of acquisition, multiple cardiac phases, and high-resolution reconstruction. However, scan and reconstruction times are 2 limiting factors for such techniques, which are reported as 9.5 minutes and 174.5 minutes, respectively.…”

Fully self‐gated free‐running 3D Cartesian cardiac CINE with isotropic whole‐heart coverage in less than 2 min

“…To address the above limitations, free-breathing 3D CINE, [17][18][19][20][21][22][23][24][25][26][27][28] so called free-running methods, with non-Cartesian (spiral phyllotaxis, 19,24 radial stack of stars, [25][26][27]29 3D radial koosh-ball 17,18,22,30 ) or Cartesian trajectories (MUSIC, 28 centric reordering, 23 CASPR 21 ), have been proposed to provide isotropic resolution with whole-heart (WH) coverage. Non-Cartesian approaches have shown promising image quality in scan times of about 10-15 min for high spatial isotropic resolutions ($1.05 to 1.5mm 3 ) or shorter scan times of about 5-8 min for anisotropic resolutions (1-2 mm in plane, 3-8 mm through plane).…”

“…For sufficient contrast, some methods apply an interruption with T 2 preparation pulses 17,19,24 or rely on the administration of contrast agents. 18,[21][22][23]25,28 In free-breathing CINE, fat-related artifacts can arise from high signal intensities of the subcutaneous fat that becomes aliased within the field of view (FOV) due to motion and undersampling. Fat suppression techniques such as interleaved spectral selective fat saturation pulses, 19,24 multi-echo balanced steady-state free precession (bSSFP), 27 fast interrupted steady state (FISS) [31][32][33] or lipid insensitive binomial off-resonance excitation (LIBRE) 34 have been proposed to counteract these.…”

“…In the reconstruction, data is usually binned into cardiac and respiratory phases based on ECG, [17][18][19][20][21][22][23][24][26][27][28] self-gated cardiac 25,35 or respiratory [17][18][19][20][21][22][23][24][25][26][27]35 signals. Motion-resolved/corrected images are then reconstructed exploiting temporal redundancy in both cardiac and respiratory directions, using primarily regularized CS-based reconstructions.…”

“…For Cartesian sampling, scan times of about 4‐8 min for about 2 mm 3 isotropic resolution have been achieved. For sufficient contrast, some methods apply an interruption with T 2 preparation pulses 17,19,24 or rely on the administration of contrast agents 18,21–23,25,28 . In free‐breathing CINE, fat‐related artifacts can arise from high signal intensities of the subcutaneous fat that becomes aliased within the field of view (FOV) due to motion and undersampling.…”