Fig. 1.

Elements of the Bθ matrix that represents the projections obtained at a constant gradient as a function of the orientation of the gradient vector. Elements are collected row-wise in conventional EPR imaging and column-wise in rotating-gradient stepped-field data collection. The large horizontal arrow represents the conventional way of collection projections at constant gradient vector at a given orientation, and then changing the orientation sequentially. The big vertical arrow represents the stepped-gradient-rotating-gradient approach of Ohno and Watanabe [11] and Deng et al. [12]. The big slanted arrow represents the present method that corresponds to the simultaneous application of the field sweep field and rotating gradients.