Convex optimized diffusion encoding (CODE) gradient waveforms for minimum echo time and bulk motion–compensated diffusion‐weighted MRI

Abstract

CODE significantly improved SNR for ADC mapping in the brain, liver and heart, and significantly improved DWI bulk motion robustness in the liver and heart. Magn Reson Med 77:717-729, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Microstructurally Anchored Cardiac Kinematics by Combining In Vivo DENSE MRI and cDTI

“…DENSE: balanced 4-point encoding, 2.5×2.5×8mm, TE/TR=1.04/15ms, k e =0.06cycles/mm, N avg =3, spiral interleaves=10, T scan =5 min. CODE [3] cDTI: 2×2×5mm, TE/TR= 74/4000ms, b-value=0,350s/mm 2 , N avg =10, N dir =12, T scan =4 min.…”

“…Recent advances in cDTI [3, 14] enable in vivo measurements of local myofiber orientation and microstructural rearrangement during the cardiac cycle [9]. Combining cDTI with DENSE displacement data permits computing microstructurally anchored myofiber deformation to characterize myocyte performance in vivo.…”

Eddy current–nulled convex optimized diffusion encoding (EN‐CODE) for distortion‐free diffusion tensor imaging with short echo times

“…The previously reported CODE framework uses convex optimization to design diffusion‐encoding gradient waveforms that minimize TE in SE‐EPI DWI for a given b‐value with no explicit constraint on gradient waveform shape or symmetry . Minimum TE waveforms are achieved by first maximizing the b‐value for any particular sequence timing, which is given by where b is the b‐value; γ is the gyromagnetic ratio of 1 H; T Diff is the time corresponding to the end of diffusion encoding, and where the time t = 0 corresponds with the center of the excitation pulse.…”

“…The time‐optimal EN‐CODE gradient waveforms are determined by finding the minimum TE for which a gradient waveform exists that is consistent with all constraints and reaches the desired b‐value. This is efficiently accomplished using a binary search through a TE search space with each iteration of Equation [] (Fig. ).…”

Magnetic Resonance Diffusion Tensor Imaging Provides New Insights Into the Microstructural Alterations in Dilated Cardiomyopathy

“…Alternative techniques to address patient comfort and arrhythmia would be motion compensated spin echo diffusion CMR techniques 3,5,7,8 that diffusion encode in a single heart beat allowing for free breathing and more robustness to arrhythmia. Future improvements to the STEAM DTI CMR technique are needed to reduce the burden to patients.…”