Optimizing 3D Noncartesian Gridding Reconstruction for Hyperpolarized 129 Xe MRI—Focus on Preclinical Applications SCOTT H. ROBERTSON, 1,2 ROHAN S. VIRGINCAR, 1,3 MU HE, 1,4 MATTHEW S. FREEMAN, 1,2 SURYANARAYANAN S. KAUSHIK, 1,3 BASTIAAN DRIEHUYS 1,2,3,5 1 Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA 2 Medical Physics Graduate Program, Duke University, Durham, NC, USA 3 Department of Biomedical Engineering, Duke University, Durham, NC, USA 4 Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA 5 Department of Radiology, Duke University Medical Center, Durham, NC, USA ABSTRACT: The goal of this work is to characterize and optimize gridding reconstruc- tion of 3D radial hyperpolarized (HP) 129 Xe MRI. In support of this objective, we devel- oped a flexible, open source reconstruction software package in MATLAB to optimally reconstruct radially acquired, undersampled HP 129 Xe MRI. Using this framework, we demonstrate the effects of 5 key reconstruction parameters: overgridding, gridding kernel function, kernel sharpness, kernel extent, and the density compensation algorithm. We further demonstrate how each parameter can be tuned to optimize a high-resolution 3D radially acquired HP 129 Xe image of a ventilated mouse. Specifically, wrap-around arti- fact, caused by non-selective RF excitation of signal in the trachea, was eliminated by overgridding onto a finely spaced k-space grid; high-frequency aliasing was reduced using iterative density compensation; image SNR and sharpness were optimized by tun- ing kernel sharpness; and computational burden was minimized by defining an appropri- ate kernel extent. Compared to our previous reconstruction methods, this optimized method extended visualization from the 5th to 6th generation of mouse airway, while maintaining comparable SNR. Although optimized here for preclinical mouse MRI, this work suggests that 3D radial acquisition offers many broader advantages to under- Received 10 July 2015; revised 15 October 2015; accepted 21 October 2015 Correspondence to: Bastiaan Driehuys; E-mail: Bastiaan.Driehuys@duke.edu Concepts in Magnetic Resonance Part A, Vol. 44A(4) 190–202 (2015) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/cmr.a.21352 Ó 2015 Wiley Periodicals, Inc. 190