Magnetic resonance k-space ($\mathbf{k}(t)=\gamma {\int }^t\mathbf{G}(t^{\prime })d{t}^{\prime }/(2\pi )$)

The spatial Fourier-frequency coordinates sampled by a magnetic-resonance acquisition. With gyromagnetic ratio in radians per time per field, the displayed expression is in cycles per length. Signal phase, gradient history and sequence refocusing determine the trajectory; the samples require reconstruction to form a spatial image.