Joseph Y. Cheng

Fast pediatric 3D free-breathing abdominal dynamic contrast enhanced MRI with high spatiotemporal resolution.

To develop a method for fast pediatric 3D free‐breathing abdominal dynamic contrast enhanced (DCE) magnetic resonance imaging (MRI) and investigate its clinical feasibility.

Free‐breathing pediatric MRI with nonrigid motion correction and acceleration

To develop and assess motion correction techniques for high‐resolution pediatric abdominal volumetric magnetic resonance images acquired free‐breathing with high scan efficiency.

Nonrigid motion correction in 3d using autofocusing with localized linear translations

MR scans are sensitive to motion effects due to the scan duration. To properly suppress artifacts from nonrigid body motion, complex models with elements such as translation, rotation, shear, and scaling have been incorporated into the reconstruction pipeline. However, these techniques are computationally intensive and difficult to implement for online reconstruction. On a sufficiently small spatial scale, the different types of motion can be well approximated as simple linear translations. This formulation allows for a practical autofocusing algorithm that locally minimizes a given motion metric — more specifically, the proposed localized gradient‐entropy metric. To reduce the vast search space for an optimal solution, possible motion paths are limited to the motion measured from multichannel navigator data. The novel navigation strategy is based on the so‐called “Butterfly” navigators, which are modifications of the spin‐warp sequence that provides intrinsic translational motion information with negligible overhead. With a 32‐channel abdominal coil, sufficient number of motion measurements were found to approximate possible linear motion paths for every image voxel. The correction scheme was applied to free‐breathing abdominal patient studies. In these scans, a reduction in artifacts from complex, nonrigid motion was observed. Magn Reson Med, 2012.

Comprehensive motion‐compensated highly accelerated 4D flow MRI with ferumoxytol enhancement for pediatric congenital heart disease

To develop and evaluate motion‐compensation and compressed‐sensing techniques in 4D flow MRI for anatomical assessment in a comprehensive ferumoxytol‐enhanced congenital heart disease (CHD) exam.

Nonrigid Autofocus Motion Correction for Coronary MR Angiography with a 3D Cones Trajectory

To implement a nonrigid autofocus motion correction technique to improve respiratory motion correction of free‐breathing whole‐heart coronary magnetic resonance angiography acquisitions using an image‐navigated 3D cones sequence.

Assessment of the precision and reproducibility of ventricular volume, function, and mass measurements with ferumoxytol-enhanced 4D flow MRI.

To compare the precision and interobserver agreement of ventricular volume, function, and mass quantification by 3D time‐resolved (4D) flow MRI relative to cine steady‐state free precession (SSFP).

Fast concomitant gradient field and field inhomogeneity correction for spiral cardiac imaging.

Non‐Cartesian imaging provides many advantages in terms of flexibility, functionality, and speed. However, a major drawback to these imaging methods is off‐resonance distortion artifacts. These artifacts manifest as blurring in spiral imaging. Common techniques that remove the off‐resonance field inhomogeneity distortion effects are not sufficient, because the high order concomitant gradient fields are nontrivial for common imaging conditions, such as imaging 5 cm off isocenter in an 1.5 T scanner. Previous correction algorithms are either slow or do not take into account the known effects of concomitant gradient fields along with the field inhomogeneities. To ease the correction, the distortion effects are modeled as a non‐stationary convolution problem. In this work, two fast and accurate postgridding algorithms are presented and analyzed. These methods account for both the concomitant field effects and the field inhomogeneities. One algorithm operates in the frequency domain and the other in the spatial domain. To take advantage of their speed and accuracy, the algorithms are applied to a real‐time cardiac study and a high‐resolution cardiac study. Both of the presented algorithms provide for a practical solution to the off‐resonance problem in spiral imaging. Magn Reson Med, 2011.

Nonrigid motion correction with 3D image-based navigators for coronary MR angiography

To develop a retrospective nonrigid motion‐correction method based on 3D image‐based navigators (iNAVs) for free‐breathing whole‐heart coronary magnetic resonance angiography (MRA).

Robust self-navigated body MRI using dense coil arrays.

To develop a robust motion estimation method for free‐breathing body MRI using dense coil arrays.

A semiflexible 64-channel receive-only phased array for pediatric body MRI at 3T.

To design, construct, and validate a semiflexible 64‐channel receive‐only phased array for pediatric body MRI at 3T.