Correction of B₀ eddy current effects in spiral MRI

Abstract

Purpose B0 eddy currents are a subtle but important source of artifacts in spiral MRI. This study illustrates the importance of addressing these artifacts and presents a system response‐based eddy current correction strategy using B0 eddy current phase measurements on a phantom. Methods B0 and linear eddy current system response measurements were estimated from phantom‐based measurement and used to predict residual eddy current effects in spiral acquisitions. The measurements were evaluated across multiple systems and gradient sets. The corresponding eddy current corrections were studied in both axial spiral‐in/out TSE and sagittal spiral‐out MPRAGE volunteer data. Results Correction of B0 eddy currents using the proposed method mitigated blurriness in the axial spiral‐in/out images and artifacts in the sagittal spiral‐out images. The system response measurement was found to yield repeatable results over time with some variation in the B0 eddy current responses measured between different systems. Conclusions The proposed eddy current correction framework was effective in mitigating the effects of residual B0 and linear eddy currents. Any spiral acquisition should take residual eddy currents into account. This is particularly important in spiral‐in/out acquisitions.

Rapid acquisition of the 3D MRI gradient impulse response function using a simple phantom measurement

“…It demonstrates improved image quality by applying the direct 1st order terms of the measured 3D GMTF instead of the standard model for compensating the gradient chain filtering effect on the trajectory. Similar results based on the measured 1D GMTF have been shown by others . Supporting Information Figure shows the spectral properties of the relevant GMTF terms, whereas Supporting Information Figure compares the image reconstruction results.…”

“…Similar results based on the measured 1D GMTF have been shown by others. 19,20 Supporting Information Figure S1 shows the spectral properties of the relevant GMTF terms, whereas Supporting Information Figure S2 compares the image reconstruction results.…”

“…A reference measurement with zero or inverse gradient allows removal of effects not related to the test gradient pulse under investigation . Using 2 thin slices on all gradient axes, the 0th and 1st order field responses can be determined and the respective uniform (“B 0 response”) and linear (“gradient response”) GMTFs can be calculated for each gradient channel and applied for correction . As the thin‐slice approach only provides spatial information in the single dimension along which the slices are positioned, it is not suitable for measurement of cross terms and higher order terms.…”

“…18 Using 2 thin slices on all gradient axes, the 0th and 1st order field responses can be determined and the respective uniform ("B 0 response") and linear ("gradient response") GMTFs can be calculated for each gradient channel and applied for correction. 19,20 As the thin-slice approach only provides spatial information in the single dimension along which the slices are positioned, it is not suitable for measurement of cross terms and higher order terms. For obtaining the 3D spatial profile, non-selective excitation with subsequent 3D phase encoding has been suggested.…”

The effect of spiral trajectory correction on pseudo‐continuous arterial spin labeling with high‐performance gradients on a compact 3T scanner

“…As other possibilities, the B0 term of the eddy current is known as a source of artifact with spiral trajectory . The 0th‐order dynamic field was measured by the field camera, and the B0 deviation on spiral readout data can be corrected by complex multiplication with the 0th‐order dynamic field before a gridding procedure in reconstruction . Note that it differs from the B0 concomitant field correction, which was corrected in real time with frequency tracking .…”