Dataset Information

Hybrid T2 - and T1 -weighted radial acquisition for free-breathing abdominal examination.

ABSTRACT: PURPOSE:Most clinical MR examinations require acquisition of different image contrasts. For abdominal exams, the scans are conventionally performed as separate acquisitions using respiratory gating or repeated breath holding, which can be time-inefficient and challenging for patients. Here, a hybrid imaging approach is described that creates T2 - and T1 -weighted images from a single scan and allows for free-breathing acquisition. THEORY AND METHODS:T2 -weighted data is collected using 3D fast spin-echo (FSE) acquisition with motion-robust radial stack-of-stars sampling. The wait time between the FSE trains is used to acquire T1 -weighted gradient-echo (GRE) data. Improved robustness is achieved by extracting a respiratory signal from the GRE data and using it for motion-weighted reconstruction. RESULTS:As validated in simulations and phantom scans, GRE acquisition in the wait time has minor effect on the signal strength and contrast. Volunteer scans at 1.5T showed that T2 - and T1 -weighted hybrid imaging is feasible during free-breathing. Furthermore, it has been demonstrated in a patient that hybrid imaging with T1 -weighted Dixon acquisition is possible. CONCLUSION:The described hybrid sequence enables comprehensive T2 - and T1 -weighted imaging in a single scan. In addition to free-breathing abdominal examination, it promises value for clinical applications that are frequently affected by motion artifacts.

SUBMITTER: Benkert T

PROVIDER: S-EPMC6107373 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Hybrid T<sub>2</sub> - and T<sub>1</sub> -weighted radial acquisition for free-breathing abdominal examination.

Benkert Thomas T Mugler John P JP Rigie David S DS Sodickson Daniel K DK Chandarana Hersh H Block Kai Tobias KT

Magnetic resonance in medicine 20180415 5

<h4>Purpose</h4>Most clinical MR examinations require acquisition of different image contrasts. For abdominal exams, the scans are conventionally performed as separate acquisitions using respiratory gating or repeated breath holding, which can be time-inefficient and challenging for patients. Here, a hybrid imaging approach is described that creates T<sub>2</sub> - and T<sub>1</sub> -weighted images from a single scan and allows for free-breathing acquisition.<h4>Theory and methods</h4>T<sub>2</ ...[more]

PMID: 29656522

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Project description:PURPOSE:To develop an accelerated motion corrected 3D whole-heart imaging approach (qBOOST-T2) for simultaneous high-resolution bright- and black-blood cardiac MR imaging and quantitative myocardial T2 characterization. METHODS:Three undersampled interleaved balanced steady-state free precession cardiac MR volumes were acquired with a variable density Cartesian trajectory and different magnetization preparations: (1) T2-prepared inversion recovery (T2prep-IR), (2) T2-preparation, and (3) no preparation. Image navigators were acquired prior the acquisition to correct for 2D translational respiratory motion. Each 3D volume was reconstructed with a low-rank patch-based reconstruction. The T2prep-IR volume provides bright-blood anatomy visualization, the black-blood volume is obtained by means of phase sensitive reconstruction between first and third datasets, and T2 maps are generated by matching the signal evolution to a simulated dictionary. The proposed sequence has been evaluated in simulations, phantom experiments, 11 healthy subjects and compared with 3D bright-blood cardiac MR and standard 2D breath-hold balanced steady-state free precession T2 mapping. The feasibility of the proposed approach was tested on 4 patients with suspected cardiovascular disease. RESULTS:High linear correlation (y = 1.09 × -0.83, R2 = 0.99) was found between the proposed qBOOST-T2 and T2 spin echo measurements in phantom experiment. Good image quality was observed in vivo with the proposed 4x undersampled qBOOST-T2. Mean T2 values of 53.1 ± 2.1 ms and 55.8 ± 2.7 ms were measured in vivo for 2D balanced steady-state free precession T2 mapping and qBOOST-T2, respectively, with linear correlation of y = 1.02x+1.46 (R2 = 0.61) and T2 bias = 2.7 ms. CONCLUSION:The proposed qBOOST-T2 sequence allows the acquisition of 3D high-resolution co-registered bright- and black-blood volumes and T2 maps in a single scan of ~11 min, showing promising results in terms of T2 quantification.

Project description:PurposeTo 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.MethodsWe 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.ResultsT2 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.ConclusionsThe 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.

Project description:BackgroundConventional liver T1 mapping techniques are typically performed under breath-holding conditions; they have limited slice coverage and often rely on multiple acquisitions. Furthermore, liver fat affects the accuracy of T1 quantification. Therefore, we aim to propose a free-breathing technique for simultaneous water-fat separation and T1 mapping of the whole liver (SWALI) in a single scan.MethodsThe proposed SWALI sequence included an inversion recovery (IR) preparation pulse followed by a series of multiecho three-dimensional (3D) golden-angle radial acquisitions. For each echo time (TE), a series of images containing a mix of water and fat were reconstructed using a sliding window method. For each inversion time (TI), water and fat were separated, and then water and fat T1 estimation was conducted. The fat fraction (FF) was calculated based on the last TI image. The FF and water T1 quantification accuracy were compared with the gold standard sequences in the phantom. The in vivo feasibility was tested in 9 healthy volunteers, 2 patients with fatty liver, and 3 patients with hepatocellular carcinoma (HCC). The reproducibility was evaluated in the patients with fatty liver and in the healthy volunteers.ResultsThe mean FF and the mean water T1 values obtained by the SWALI sequence showed good agreements with chemical shift-encoded magnetic resonance imaging (CSE-MRI; r=0.998; P<0.001) and fat-suppressed (FS) IR-spin echo (SE; r=0.997; P<0.001) in the phantom. For the patients with fatty liver and the healthy volunteers, the SWALI sequence showed no significant difference with CSE-MRI in FF quantification (P=0.53). In T1 quantification, comparable T1 values were obtained with the SWALI sequence and modified Look-Locker inversion recovery (MOLLI; P=0.10) in healthy volunteers, while the water T1 estimated by the SWALI sequence was significantly lower than the water-fat compound T1 estimated by MOLLI (P<0.001) in patients with fatty liver. In the reproducibility study, the intraclass correlation coefficients (ICCs) for the estimated FF and water T1 were 0.997 and 0.943, respectively. Water T1 of the patients with HCC calculated using the SWALI sequence showed a significant reduction after the contrast administration (P<0.001).ConclusionsFree-breathing water-fat separation and T1 mapping of the whole liver with 2.5 mm isotropic spatial resolution were achieved simultaneously using the SWALI sequence in a 5-min scan.

Dataset Information

Hybrid T2 - and T1 -weighted radial acquisition for free-breathing abdominal examination.

Publications

Hybrid T<sub>2</sub> - and T<sub>1</sub> -weighted radial acquisition for free-breathing abdominal examination.

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