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Compressed sensing acceleration of biexponential 3D-T1? relaxation mapping of knee cartilage.

ABSTRACT: PURPOSE:Use compressed sensing (CS) for 3D biexponential spin-lattice relaxation time in the rotating frame (T1? ) mapping of knee cartilage, reducing the total scan time and maintaining the quality of estimated biexponential T1? parameters (short and long relaxation times and corresponding fractions) comparable to fully sampled scans. METHODS:Fully sampled 3D-T1? -weighted data sets were retrospectively undersampled by factors 2-10. CS reconstruction using 12 different sparsifying transforms were compared for biexponential T1? -mapping of knee cartilage, including temporal and spatial wavelets and finite differences, dictionary from principal component analysis (PCA), k-means singular value decomposition (K-SVD), exponential decay models, and also low rank and low rank plus sparse models. Synthetic phantom (N = 6) and in vivo human knee cartilage data sets (N = 7) were included in the experiments. Spatial filtering before biexponential T1? parameter estimation was also tested. RESULTS:Most CS methods performed satisfactorily for an acceleration factor (AF) of 2, with relative median normalized absolute deviation (MNAD) around 10%. Some sparsifying transforms, such as low rank with spatial finite difference (L + S SFD), spatiotemporal finite difference (STFD), and exponential dictionaries (EXP) significantly improved this performance, reaching MNAD below 15% with AF up to 10, when spatial filtering was used. CONCLUSION:Accelerating biexponential 3D-T1? mapping of knee cartilage with CS is feasible. The best results were obtained by STFD, EXP, and L + S SFD regularizers combined with spatial prefiltering. These 3 CS methods performed satisfactorily on synthetic phantom as well as in vivo knee cartilage for AFs up to 10, with median error below 15%.

SUBMITTER: Zibetti MVW

PROVIDER: S-EPMC6289851 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Compressed sensing acceleration of biexponential 3D-T<sub>1ρ</sub> relaxation mapping of knee cartilage.

Zibetti Marceo V W MVW Sharafi Azadeh A Otazo Ricardo R Regatte Ravinder R RR

Magnetic resonance in medicine 20180919 2

<h4>Purpose</h4>Use compressed sensing (CS) for 3D biexponential spin-lattice relaxation time in the rotating frame (T<sub>1ρ</sub> ) mapping of knee cartilage, reducing the total scan time and maintaining the quality of estimated biexponential T<sub>1ρ</sub> parameters (short and long relaxation times and corresponding fractions) comparable to fully sampled scans.<h4>Methods</h4>Fully sampled 3D-T<sub>1ρ</sub> -weighted data sets were retrospectively undersampled by factors 2-10. CS reconstruct ...[more]

PMID: 30230588

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Project description:BACKGROUND:In addition to the articular cartilage, osteoarthritis (OA) affects several other tissues such as tendons, ligaments, and subchondral bone. T1? relaxation study of these short T2 tissues may provide a more comprehensive evaluation of OA. PURPOSE:To develop a 3D spin-lattice relaxation in the rotating frame (T1? ) prepared zero echo time (ZTE)-based pointwise encoding time reduction with radial acquisition (3D-T1? -PETRA) sequence for relaxation mapping of semisolid short-T2 tissues on a clinical 3?T scanner. STUDY TYPE:Prospective. POPULATION:Phantom, two bovine whole knee joint and Achilles tendon specimens, 10 healthy volunteers with no known inflammation, trauma or pain in the knee or ankle. FIELD STRENGTH/SEQUENCE:A customized PETRA sequence to acquire fat-suppressed 3D T1? -weighted images tissues with semisolid short T2 / T2* relaxation times in the knee and ankle joints at 3?T. ASSESSMENT:Mono- and biexponential T1? relaxation components were assessed in the patellar tendon (PT), anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and Achilles tendon (AT). STATISTICAL TESTS:Kruskal-Wallis with post-hoc Dunn's test for multiple pairwise comparisons. RESULTS:Phantom and ex vivo studies showed the feasibility of T1? relaxation mapping using the proposed 3D-T1? -PETRA sequence. The in vivo study demonstrated an averaged mono-T1? relaxation of (median [IQR]) 15.9 [14.5] msec, 23.6 [9.4] msec, 17.4 [7.4] msec, and 5.8 [10.2] msec in the PT, ACL, PCL, and AT, respectively. The bicomponent analysis showed the short and long components (with their relative fractions) of 0.65 [1.0] msec (46.9 [15.3]%) and 37.3 [18.4] msec (53.1 [15.3]%) for PT, 1.7 [2.1] msec (42.5 [12.5]%) and 43.7 [17.8] msec (57.5 [12.5]%) for ACL, and 1.2 [1.9] msec (42.6 [14.0]%) and 27.7 [14.7] msec (57.3 [14.0]%) for PCL and 0.4 [0.02] msec (58.8 [13.3]%/) and 31.3 [10.8] msec (41.2 [13.3]%) for AT. Statistically significant (P???0.05) differences were observed in the mono- and biexponential relaxation between several regions. DATA CONCLUSION:The 3D-T1? -PETRA sequence allows volumetric, isotropic (0.78?×?0.78?×?0.78?mm), biexponential T1? assessment with corresponding fractions of the tissues with semisolid short T2 / T2* . LEVEL OF EVIDENCE:2 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019;50:1207-1218.

Project description:BackgroundEndogenous contrast T1? cardiovascular magnetic resonance (CMR) can detect scar or infiltrative fibrosis in patients with ischemic or non-ischemic cardiomyopathy. Existing 2D T1? techniques have limited spatial coverage or require multiple breath-holds. The purpose of this project was to develop an accelerated, free-breathing 3D T1? mapping sequence with whole left ventricle coverage using a multicoil, compressed sensing (CS) reconstruction technique for rapid reconstruction of undersampled k-space data.MethodsWe developed a cardiac- and respiratory-gated, free-breathing 3D T1? sequence and acquired data using a variable-density k-space sampling pattern (A?=?3). The effect of the transient magnetization trajectory, incomplete recovery of magnetization between T1?-preparations (heart rate dependence), and k-space sampling pattern on T1? relaxation time error and edge blurring was analyzed using Bloch simulations for normal and chronically infarcted myocardium. Sequence accuracy and repeatability was evaluated using MnCl2 phantoms with different T1? relaxation times and compared to 2D measurements. We further assessed accuracy and repeatability in healthy subjects and compared these results to 2D breath-held measurements.ResultsThe error in T1? due to incomplete recovery of magnetization between T1?-preparations was T1?healthy =?6.1% and T1?infarct =?10.8% at 60?bpm and T1?healthy =?13.2% and T1?infarct =?19.6% at 90?bpm. At a heart rate of 60?bpm, error from the combined effects of readout-dependent magnetization transients, k-space undersampling and reordering was T1?healthy =?12.6% and T1?infarct =?5.8%. CS reconstructions had improved edge sharpness (blur metric?=?0.15) compared to inverse Fourier transform reconstructions (blur metric?=?0.48). There was strong agreement between the mean T1? estimated from the 2D and accelerated 3D data (R2 =?0.99; P <?0.05) acquired on the MnCl2 phantoms. The mean R1? estimated from the accelerated 3D sequence was highly correlated with MnCl2 concentration (R2 =?0.99; P?<?0.05). 3D T1? acquisitions were successful in all human subjects. There was no significant bias between undersampled 3D T1? and breath-held 2D T1? (mean bias?=?0.87) and the measurements had good repeatability (COV2D =?6.4% and COV3D =?7.1%).ConclusionsThis is the first report of an accelerated, free-breathing 3D T1? mapping of the left ventricle. This technique may improve non-contrast myocardial tissue characterization in patients with heart disease in a scan time appropriate for patients.

Dataset Information

Compressed sensing acceleration of biexponential 3D-T1? relaxation mapping of knee cartilage.

Publications

Compressed sensing acceleration of biexponential 3D-T<sub>1ρ</sub> relaxation mapping of knee cartilage.

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