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

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 78:950–962, 2017. © 2016 International Society for Magnetic Resonance in Medicine