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Fast data-driven learning of parallel MRI sampling patterns for large scale problems

Zibetti, Marcelo V W; Herman, Gabor T; Regatte, Ravinder R
In this study, a fast data-driven optimization approach, named bias-accelerated subset selection (BASS), is proposed for learning efficacious sampling patterns (SPs) with the purpose of reducing scan time in large-dimensional parallel MRI. BASS is applicable when Cartesian fully-sampled k-space measurements of specific anatomy are available for training and the reconstruction method for undersampled measurements is specified; such information is used to define the efficacy of any SP for recovering the values at the non-sampled k-space points. BASS produces a sequence of SPs with the aim of finding one of a specified size with (near) optimal efficacy. BASS was tested with five reconstruction methods for parallel MRI based on low-rankness and sparsity that allow a free choice of the SP. Three datasets were used for testing, two of high-resolution brain images ([Formula: see text]-weighted images and, respectively, [Formula: see text]-weighted images) and another of knee images for quantitative mapping of the cartilage. The proposed approach has low computational cost and fast convergence; in the tested cases it obtained SPs up to 50 times faster than the currently best greedy approach. Reconstruction quality increased by up to 45% over that provided by variable density and Poisson disk SPs, for the same scan time. Optionally, the scan time can be nearly halved without loss of reconstruction quality. Quantitative MRI and prospective accelerated MRI results show improvements. Compared with greedy approaches, BASS rapidly learns effective SPs for various reconstruction methods, using larger SPs and larger datasets; enabling better selection of sampling-reconstruction pairs for specific MRI problems.
PMID: 34588478
ISSN: 2045-2322
CID: 5046782

Measurement of Three-Dimensional Internal Dynamic Strains in the Intervertebral Disc of the Lumbar Spine With Mechanical Loading and Golden-Angle Radial Sparse Parallel-Magnetic Resonance Imaging

Menon, Rajiv G; Zibetti, Marcelo V W; Pendola, Martin; Regatte, Ravinder R
BACKGROUND:Noninvasive measurement of internal dynamic strain can be potentially useful to characterize spine intervertebral disc (IVD) in the setting of injury or degenerative disease. PURPOSE/OBJECTIVE:To develop and demonstrate a noninvasive technique to quantify three-dimensional (3D) internal dynamic strains in the IVD using a combination of static mechanical loading of the IVD using a magnetic resonance imaging (MRI)-compatible ergometer. STUDY TYPE/METHODS:Prospective. SUBJECTS/METHODS:Silicone gel phantom studies were conducted to assess strain variation with load and repeatability. Mechanical testing was done on the phantoms to confirm MR results. Eight healthy human volunteers (four men and four woman, age = 29 ± 5 years) underwent MRI using a rest, static loading, and recovery paradigm. Repeatability tests were conducted in three subjects. FIELD STRENGTH/SEQUENCE/UNASSIGNED:MRI (3 T) with 3D continuous golden-angle radial sparse parallel (GRASP) and compressed sensing (CS) reconstruction. ASSESSMENT/RESULTS:CS reconstruction of the images, motion deformation, and Lagrangian strain maps were calculated for five IVD segments from L1/L2 to L5/S1. STATISTICAL TESTS/UNASSIGNED:Ranges of displacement and strain in each subject and the resulting mean and standard deviation were calculated. Student t-tests were used to calculate changes in strain from loading to recovery. The correlation coefficient (CC) in the repeatability study was calculated. RESULTS:The most compressive strain experienced by the IVD segments under loaded conditions was in the L4/L5 segment (-7.5 ± 2.9%). The change in minimum strain from load to recovery was the most for the L4/L5 segment (-7.5% to -5.0%, P = 0.026) and the least for the L1/L2 segment (-4.4% to -3.9%, P = 0.51). In vivo repeatability in three subjects shows strong correlation between scans in subjects done 6 months apart, with CCs equal to 0.86, 0.94, and 0.94 along principal directions. DATA CONCLUSION/UNASSIGNED:This study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition with CS reconstruction to measure 3D internal dynamic strains in the spine IVD. LEVEL OF EVIDENCE/METHODS:2 TECHNICAL EFFICACY STAGE: 1.
PMID: 33713520
ISSN: 1522-2586
CID: 4819632

Simultaneous T1 , T2 , and T1ρ relaxation mapping of the lower leg muscle with MR fingerprinting

Sharafi, Azadeh; Medina, Katherine; Zibetti, Marcelo W V; Rao, Smita; Cloos, Martijn A; Brown, Ryan; Regatte, Ravinder R
PURPOSE/OBJECTIVE: METHODS:measured using TB-SL MRF in Bloch simulations, model agar phantoms, and in vivo experiments to those with a self-compensated spin-lock preparation module (SC-SL). The TB-SL MRF repeatability was evaluated in maps acquired in the lower leg skeletal muscle of 12 diabetic peripheral neuropathy patients, scanned two times each during visits separated by about 30 days. RESULTS:= 31.7 ± 3.2 ms in skeletal muscle across patients. Bland-Altman analysis demonstrated low bias between TB-SL and SC-SL MRF and between TB-SL MRF maps acquired in two visits. The coefficient of variation was less than 3% for all measurements. CONCLUSION/CONCLUSIONS:
PMID: 33554369
ISSN: 1522-2594
CID: 4799722

Performance Comparison of Compressed Sensing Algorithms for Accelerating T1ρ Mapping of Human Brain [Editorial]

Menon, Rajiv G; Zibetti, Marcelo V W; Jain, Rajan; Ge, Yulin; Regatte, Ravinder R
BACKGROUND:mapping is useful to quantify various neurologic disorders, but data are currently time-consuming to acquire. PURPOSE/OBJECTIVE:mapping of the human brain with acceleration factors (AFs) of 2, 5, and 10. STUDY TYPE/METHODS:Retrospective. SUBJECTS/METHODS:imaging of the whole brain. FIELD STRENGTH/SEQUENCE/UNASSIGNED:preparation module on a clinical 3T scanner. ASSESSMENT/RESULTS:estimation errors were assessed as a function of AF. STATISTICAL TESTS/UNASSIGNED:estimation errors, respectively. Linear regression plots, Bland-Altman plots, and Pearson correlation coefficients (CC) are shown. RESULTS:estimates. DATA CONCLUSION/UNASSIGNED:mapping of the brain. LEVEL OF EVIDENCE/METHODS:2. TECHNICAL EFFICACY STAGE/UNASSIGNED:1.
PMID: 33190362
ISSN: 1522-2586
CID: 4673552

Simultaneous T-1, T-2, and T-1 rho relaxation mapping of the lower leg muscle with MR fingerprinting

Sharafi, Azadeh; Medina, Katherine; Zibetti, Marcelo W. V.; Rao, Smita; Cloos, Martijn A.; Brown, Ryan; Regatte, Ravinder R.
ISSN: 0740-3194
CID: 4821202

Fast Proximal Gradient Methods for Nonsmooth Convex Optimization for Tomographic Image Reconstruction

Helou, Elias S.; Zibetti, Marcelo V.W.; Herman, Gabor T.
The Fast Proximal Gradient Method (FPGM) and the Monotone FPGM (MFPGM) for minimization of nonsmooth convex functions are introduced and applied to tomographic image reconstruction. Convergence properties of the sequence of objective function values are derived, including a O(1 / k2) non-asymptotic bound. The presented theory broadens current knowledge and explains the convergence behavior of certain methods that are known to present good practical performance. Numerical experimentation involving computerized tomography image reconstruction shows the methods to be competitive in practical scenarios. Experimental comparison with Algebraic Reconstruction Techniques are performed uncovering certain behaviors of accelerated Proximal Gradient algorithms that apparently have not yet been noticed when these are applied to tomographic image reconstruction.
ISSN: 1557-2064
CID: 4612592

Rapid mono and biexponential 3D-T1ρ mapping of knee cartilage using variational networks

Zibetti, Marcelo V W; Johnson, Patricia M; Sharafi, Azadeh; Hammernik, Kerstin; Knoll, Florian; Regatte, Ravinder R
In this study we use undersampled MRI acquisition methods to obtain accelerated 3D mono and biexponential spin-lattice relaxation time in the rotating frame (T1ρ) mapping of knee cartilage, reducing the usual long scan time. We compare the accelerated T1ρ maps obtained by deep learning-based variational network (VN) and compressed sensing (CS). Both methods were compared with spatial (S) and spatio-temporal (ST) filters. Complex-valued fitting was used for T1ρ parameters estimation. We tested with seven in vivo and six synthetic datasets, with acceleration factors (AF) from 2 to 10. Median normalized absolute deviation (MNAD), analysis of variance (ANOVA), and coefficient of variation (CV) were used for analysis. The methods CS-ST, VN-S, and VN-ST performed well for accelerating monoexponential T1ρ mapping, with MNAD around 5% for AF = 2, which increases almost linearly with the AF to an MNAD of 13% for AF = 8, with all methods. For biexponential mapping, the VN-ST was the best method starting with MNAD of 7.4% for AF = 2 and reaching MNAD of 13.1% for AF = 8. The VN was able to produce 3D-T1ρ mapping of knee cartilage with lower error than CS. The best results were obtained by VN-ST, improving CS-ST method by nearly 7.5%.
PMID: 33154515
ISSN: 2045-2322
CID: 4662942

MR fingerprinting for rapid simultaneous T1 , T2 , and T1ρ relaxation mapping of the human articular cartilage at 3T

Sharafi, Azadeh; Zibetti, Marcelo V W; Chang, Gregory; Cloos, Martijn; Regatte, Ravinder R
PURPOSE/OBJECTIVE:To implement a novel technique for simultaneous, quantitative multiparametric mapping of the knee articular cartilage. METHODS:relaxation time (P = .02) in medial femoral cartilage. CONCLUSION/CONCLUSIONS:
PMID: 32385949
ISSN: 1522-2594
CID: 4439232

Volumetric multicomponent T1ρ relaxation mapping of the human liver under free breathing at 3T

Sharafi, Azadeh; Baboli, Rahman; Zibetti, Marcelo; Shanbhogue, Krishna; Olsen, Sonja; Block, Tobias; Chandarana, Hersh; Regatte, Ravinder
PURPOSE/OBJECTIVE:-RAVE) and to evaluate the multi relaxation components in the liver of healthy controls and chronic liver disease (CLD) patients. METHODS:components among patients (n = 3) and a control group (n = 10). RESULTS:relaxation time measurement relative to the reference on 2 different scanners. The coefficient of variation for test-retest scans performed on the same scanner was 5.7% and 2.4% for scans performed on 2 scanners. The comparison between healthy controls and CLD patients showed a significant difference (P < .05) in mono relaxation time (P = .002), stretched-exponential relaxation parameter (P = .04). The Akaike information criteria C criterion showed 2.53 ± 0.9% (2.3 ± 0.3% for CLD) of the voxels are bi-exponential while in 65.3 ± 5.8% (81.2 ± 0.06% for CLD) of the liver voxels, the stretched-exponential model was preferred. CONCLUSION/CONCLUSIONS:assessment of the liver during free breathing and can distinguish between healthy volunteers and CLD patients.
PMID: 31724246
ISSN: 1522-2594
CID: 4185622

Fast multicomponent 3D-T1ρ relaxometry

Zibetti, Marcelo V W; Helou, Elias S; Sharafi, Azadeh; Regatte, Ravinder R
NMR relaxometry can provide information about the relaxation of the magnetization in different tissues, increasing our understanding of molecular dynamics and biochemical composition in biological systems. In general, tissues have complex and heterogeneous structures composed of multiple pools. As a result, bulk magnetization returns to its original state with different relaxation times, in a multicomponent relaxation. Recovering the distribution of relaxation times in each voxel is a difficult inverse problem; it is usually unstable and requires long acquisition time, especially on clinical scanners. MRI can also be viewed as an inverse problem, especially when compressed sensing (CS) is used. The solution of these two inverse problems, CS and relaxometry, can be obtained very efficiently in a synergistically combined manner, leading to a more stable multicomponent relaxometry obtained with short scan times. In this paper, we will discuss the details of this technique from the viewpoint of inverse problems.
PMID: 32359000
ISSN: 1099-1492
CID: 4438672