Purpose Parallel imaging allows the reconstruction of images from undersampled multicoil data. The two main approaches are: SENSE, which explicitly uses coil sensitivities, and GRAPPA, makes use learned correlations in k‐space. purpose this work is to clarify their relationship develop evaluate an improved algorithm. Theory Methods A theoretical analysis shows: (1) k‐space are encoded null space a calibration matrix. (2) Both restrict solution subspace spanned by sensitivities. (3)...

Abstract The reconstruction of artifact‐free images from radially encoded MRI acquisitions poses a difficult task for undersampled data sets, that is much lower number spokes in k‐space than samples per spoke. Here, we developed an iterative method radial which (i) based on nonlinear optimization, (ii) allows the incorporation prior knowledge with use penalty functions, and (iii) deals multiple coils. procedure arises as two‐step mechanism first estimates coil profiles then renders final...

Abstract The desire to visualize noninvasively physiological processes at high temporal resolution has been a driving force for the development of MRI since its inception in 1973. In this article, we describe unique method real‐time that reduces image acquisition times only 20 ms. Although approaching ultimate limit technology, yields quality terms spatial resolution, signal‐to‐noise ratio and absence artifacts. As proposed previously, fast low‐angle shot (FLASH) gradient‐echo technique...

A new acquisition and reconstruction method called T

The use of parallel imaging for scan time reduction in MRI faces problems with image degradation when using GRAPPA or SENSE high acceleration factors. Although an inherent loss SNR is inevitable due to the reduced measurement time, sensitivity artifacts that result from severe undersampling can be ameliorated by alternative reconstruction methods. While introduction and extended reconstructions a simple unitary transformation (Fourier transform) inversion ill-conditioned linear system, next...

Abstract Purpose: To develop a model‐based reconstruction technique for T2 mapping based on multi‐echo spin‐echo MRI sequences with highly undersampled Cartesian data encoding. Materials and Methods: The proposed relies nonlinear inverse algorithm which directly estimates spin‐density map from train of spin echoes. method is applicable to acquisitions single receiver coils but benefits multi‐element coil arrays. validated trains 16 echoes spacing 10 12 ms using numerical simulations as well...

Purpose To develop and assess motion correction techniques for high-resolution pediatric abdominal volumetric magnetic resonance images acquired free-breathing with high scan efficiency. Materials Methods First, variable-density sampling radial-like phase-encode ordering were incorporated into the 3D Cartesian acquisition. Second, intrinsic multichannel butterfly navigators used to measure respiratory motion. Lastly, these estimates are applied both motion-weighted data-consistency in a...

In radial fast spin-echo magnetic resonance imaging (MRI), a set of overlapping spokes with an inconsistent T2 weighting is acquired, which results in averaged image contrast when employing conventional reconstruction techniques. This work demonstrates that the problem may be overcome use dedicated method further allows for quantification by extracting embedded relaxation information. Thus, proposed directly yields spin-density and relaxivity map from only single data set. The based on...

Dynamic MRI studies of the upper airway during speaking, singing or swallowing are complicated by need for high temporal resolution and presence air-tissue interfaces that may give rise to image artifacts such as signal void geometric distortions. This work exploits a recently developed real-time technique address these challenges monitoring speech production at 3 T. The method combines short-echo time radial FLASH sequence (pulse repetition time/echo = 2.22/1.44 ms; flip angle 5°) with...

Purpose To develop and evaluate motion‐compensation compressed‐sensing techniques in 4D flow MRI for anatomical assessment a comprehensive ferumoxytol‐enhanced congenital heart disease (CHD) exam. Materials Methods A Cartesian sequence was developed to enable intrinsic navigation two variable‐density sampling schemes: VDPoisson VDRad. Four methods were developed: A) scan reconstructed using spatial wavelets; B) added temporal total variation A; C) VDRad the same reconstruction as B; D)...

Right heart catheterization using exercise stress is the reference standard for diagnosis of failure with preserved ejection fraction (HFpEF) but carries risk invasive procedure. We hypothesized that real-time cardiac magnetic resonance (RT-CMR) imaging pathophysiologic data at excellent temporal and spatial resolution may represent a contemporary noninvasive alternative diagnosing HFpEF.The HFpEF-Stress trial (CMR Exercise Stress Testing in HFpEF; URL: https://www.clinicaltrials.gov; Unique...

Purpose We introduce a framework that enables efficient sampling from learned probability distributions for MRI reconstruction. Method Samples are drawn the posterior distribution given measured k‐space using Markov chain Monte Carlo (MCMC) method, different conventional deep learning‐based reconstruction techniques. In addition to maximum posteriori estimate image, which can be obtained by maximizing log‐likelihood indirectly or directly, minimum mean square error and uncertainty maps also...

Functional assessments of the heart by dynamic cardiovascular magnetic resonance (CMR) commonly rely on (i) electrocardiographic (ECG) gating yielding pseudo real-time cine representations, (ii) balanced gradient-echo sequences referred to as steady-state free precession (SSFP), and (iii) breath holding or respiratory gating. Problems may therefore be due need for a robust ECG signal, occurrence arrhythmia beat variations, technical instabilities (e.g., SSFP "banding" artefacts), limited...

The finite sampling of k-space in MRI causes spurious image artifacts, known as Gibbs ringing, which result from signal truncation at the border k-space. effect is especially visible for acquisitions low resolution and commonly reduced by filtering expense blurring. present work demonstrates that simple assumption a piecewise-constant object can be exploited to extrapolate data beyond measured part. method allows significant reduction artifacts without compromising resolution. translates...

A previously proposed nonlinear inverse reconstruction for autocalibrated parallel imaging simultaneously estimates coil sensitivities and image content. This work exploits this property real-time MRI, where need to be dynamically adapted the conditions generated by moving objects. The development comprises (i) an extension of algorithm non-Cartesian k-space encodings, (ii) its implementation on a graphical processing unit reduce times, (iii) use convolution-based iteration, which...

Abstract A new approach based on nonlinear inversion for autocalibrated parallel imaging with arbitrary sampling patterns is presented. By extending the iteratively regularized Gauss–Newton method variational penalties, improved reconstruction quality obtained from joint estimation of image and coil sensitivities combined superior noise suppression total variation generalized regularization. In addition, proposed can lead to enhanced removal artifacts arising pseudorandom radial patterns....

Purpose To develop a method for fast pediatric 3D free‐breathing abdominal dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) and investigate its clinical feasibility. Materials Methods A combined locally low rank parallel with soft gating is proposed DCE MRI acquisition. With Institutional Review Board (IRB) approval informed consent/assent, 23 consecutive patients were recruited this study. Free‐breathing ∼1 mm 3 spatial resolution 6.5‐sec frame rate was acquired on 3T...

Velocity-encoded phase-contrast MRI of cardiovascular blood flow commonly relies on electrocardiogram-synchronized cine acquisitions multiple heartbeats to quantitatively determine the an averaged cardiac cycle. Here, we present a new method for real-time that combines flow-encoding gradients with highly undersampled radial fast low-angle shot and phase-sensitive image reconstructions by regularized nonlinear inversion. Apart from calibration studies using steady pulsatile flow, preliminary...

Purpose To develop a model‐based reconstruction technique for single‐shot T 1 mapping with high spatial resolution, accuracy, and precision using an inversion‐recovery (IR) fast low‐angle shot (FLASH) acquisition radial encoding. Methods The proposed jointly estimates all model parameters, that is, the equilibrium magnetization, steady‐state 1/ , coil sensitivities from data of IR FLASH small golden‐angle trajectory. Joint sparsity constraints on parameter maps are exploited to improve...

Endomyocardial biopsies (EMB) are an important diagnostic tool for myocarditis and other infiltrative cardiac diseases. Routinely, obtained under fluoroscopic guidance with a substantial radiation burden. Despite procedural success, there is large sampling error caused by missing the affected myocardium. Therefore, multiple (>6) taken in clinical setting. In cardiovascular magnetic resonance (CMR), late gadolinium enhancement (LGE) depicts areas of myocardium or cardiomyopathies. Thus,...

To investigate four-dimensional flow denoising using the divergence-free wavelet (DFW) transform and compare its performance with existing techniques.DFW is a vector-wavelet that provides sparse representation of in generally field can be used to enforce "soft" conditions when discretization partial voluming result numerical nondivergence-free components. Efficient achieved by appropriate shrinkage coefficients. SureShrink cycle spinning are investigated further improve performance.DFW was...

Diagnostic testing often assesses the cardiovascular or respiratory systems in isolation, ignoring major pathophysiologic interactions between many diseases. When both are assessed currently, multiple modalities utilized costly fashion with burdensome logistics and decreased accessibility. Thus, we have developed a new acquisition reconstruction paradigm using flexibility of MRI to enable comprehensive exam from single 5-15 min scan. We constructed compressive-sensing approach...

ABSTRACT Aims The REDUCE‐LAP II trial demonstrated adverse outcomes after interatrial shunt device (IASD) placement in heart failure with preserved ejection fraction (HFpEF) attributed to latent pulmonary vascular disease (PVD). We hypothesized that exercise stress cardiovascular magnetic resonance (CMR) imaging could provide non‐invasive characterization of cardiac and physiology for improved patient selection. Methods results HFpEF‐Stress prospectively enrolled 75 patients exertional...

Recent advances in real-time MRI result high-quality images with acquisition times of only approximately 30 ms. The technique employs a fast low-angle shot sequence proton density, T1 or T2/T1 contrast and radial data encoding for motion robustness. High temporal resolution is achieved by an up to 20-fold undersampling the data. An iterative reconstruction algorithm estimates image as solution nonlinear inverse problem ensures fidelity regularization, which exploits continuity successive...