Abstract
Purpose: To investigate the effect of the asymmetric gradient concomitant fields (CF) with zeroth and first-order spatial dependence on fast/turbo spin-echo acquisitions, and to demonstrate the effectiveness of their real-time compensation. Methods: After briefly reviewing the CF produced by asymmetric gradients, the effects of the additional zeroth and first-order CFs on these systems are investigated using extended-phase graph simulations. Phantom and in vivo experiments are performed to corroborate the simulation. Experiments are performed before and after the real-time compensations using frequency tracking and gradient pre-emphasis to demonstrate their effectiveness in correcting the additional CFs. The interaction between the CFs and prescan-based correction to compensate for eddy currents is also investigated. Results: It is demonstrated that, unlike the second-order CFs on conventional gradients, the additional zeroth/first-order CFs on asymmetric gradients cause substantial signal loss and dark banding in fast spin-echo acquisitions within a typical brain-scan field of view. They can confound the prescan correction for eddy currents and degrade image quality. Performing real-time compensation successfully eliminates the artifacts. Conclusions: We demonstrate that the zeroth/first-order CFs specific to asymmetric gradients can cause substantial artifacts, including signal loss and dark bands for brain imaging. These effects can be corrected using real-time compensation. Magn Reson Med 79:1354–1364, 2018.
Original language | English (US) |
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Pages (from-to) | 1354-1364 |
Number of pages | 11 |
Journal | Magnetic Resonance in Medicine |
Volume | 79 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2018 |
Keywords
- EPG
- FSE
- TSE
- asymmetric gradient
- concomitant field
- extended phase graph
- fast spin echo
- turbo spin echo
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging