A rapid and robust gradient measurement technique using dynamic single-point imaging

Authors

  • Hyungseok Jang,

    1. Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
    2. Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin, USA
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  • Alan B. McMillan

    Corresponding author
    1. Department of Radiology, Wisconsin Institute for Medical Research, University of Wisconsin, Madison, Wisconsin, USA
    • Correspondence to: Alan B McMillan, Associate Scientist, Department of Radiology, University of Wisconsin – Madison, Rm 1111, Wisconsin Institutes for Medical Research, 1111 Highland Avenue, Madison, WI 53705-2275. Email: abmcmillan@wisc.edu.

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Abstract

Purpose

We propose a new gradient measurement technique based on dynamic single-point imaging (SPI), which allows simple, rapid, and robust measurement of k-space trajectory.

Methods

To enable gradient measurement, we utilize the variable field-of-view (FOV) property of dynamic SPI, which is dependent on gradient shape. First, one-dimensional (1D) dynamic SPI data are acquired from a targeted gradient axis, and then relative FOV scaling factors between 1D images or k-spaces at varying encoding times are found. These relative scaling factors are the relative k-space position that can be used for image reconstruction. The gradient measurement technique also can be used to estimate the gradient impulse response function for reproducible gradient estimation as a linear time invariant system.

Results

The proposed measurement technique was used to improve reconstructed image quality in 3D ultrashort echo, 2D spiral, and multi-echo bipolar gradient-echo imaging. In multi-echo bipolar gradient-echo imaging, measurement of the k-space trajectory allowed the use of a ramp-sampled trajectory for improved acquisition speed (approximately 30%) and more accurate quantitative fat and water separation in a phantom.

Conclusion

The proposed dynamic SPI-based method allows fast k-space trajectory measurement with a simple implementation and no additional hardware for improved image quality.Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine

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