Gradient Waveform Design

WHAT'S THE PROBLEM? The development and implementation of novel MRI pulse sequences remains challenging and laborious. Conventional gradient waveform design makes use of analytical expressions to construct gradient waveforms using predetermined waveform shapes. This strategy doesn’t always make optimal use of the available gradient hardware and makes coding the pulse sequence complicated and time inefficient. Unfortunately, this results in expensive MRI systems that underperform relative to their inherent hardware capabilities.

WHAT'S OUR SOLUTION? Our Gradient Optimization (GrOpt) toolbox uses very fast computational optimization methods for MRI gradient waveform design on-the-fly and on the scanner. GrOpt uses the gradient hardware limits, the prescribed MRI protocol parameters, and other constraints (e.g. PNS, eddy currents, etc.) to construct arbitrary gradient waveform shapes that are time-optimal. The GrOpt method enables easier pulse sequence gradient waveform design and permits on-the-fly implementation for a range of MRI pulse sequences.

FUTURE WORK: Plans are in the works to extend the functionality of the GrOpt toolbox to account for concomitant field gradients, acoustic noise, and gradient heating.

GrOpt toolbox source code is available on our software page.

PEER-REVIEWED JOURNAL PAPERS:

Loecher M, Middione MJ, Ennis DB. A Gradient Optimization (GrOpt) Toolbox for General Purpose Time-Optimal MRI Gradient Waveform Design. Magn Reson Med. Accepted May 2020. doi: 10.1002/mrm.28384

Middione MJ, Loecher M, Moulin K, Ennis DB. Optimization Methods for Magnetic Resonance Imaging Gradient Waveform Design. NMR Biomed. 2020 Apr 27:e4308. doi: 10.1002/nbm.4308. [Epub ahead of print] PMID: 32342560

Loecher M, Magrath P, Aliotta E, Ennis DB. Time-optimized 4D phase contrast MRI with real-time convex optimization of gradient waveforms and fast excitation methods. Magn Reson Med. 2019;82(1):213-224. PMID: 30859606

Moulin K, Aliotta E, Ennis DB. Effect of flow-encoding strength on intravoxel incoherent motion in the liver. Magn Reson Med. 2019;81(3):1521-1533. PMID: 30276853

Aliotta E, Moulin K, Ennis DB. Eddy current-nulled convex optimized diffusion encoding (EN-CODE) for distortion-free diffusion tensor imaging with short echo times. Magn Reson Med. 2018;79(2):663-672. PMID: 28444802

Aliotta E, Wu HH, Ennis DB. Convex optimized diffusion encoding (CODE) gradient waveforms for minimum echo time and bulk motion-compensated diffusion-weighted MRI. Magn Reson Med. 2017;77(2):717-729. PMID: 26900872

Middione MJ, Wu HH, Ennis DB. Convex Gradient Optimization for Increased Spatiotemporal Resolution and Improved Accuracy in Phase Contrast MRI. Magn Reson Med. 2014; 72 (6): 1552-1564. PMID: 24347040

GRADIENT WAVEFORM DESIGN TEAM: