Fig. 2.

Mnemonic representation of the way we collect the elements of the Bθ matrix for various CW imaging modalities. The diagonal double-headed arrows (1–5, 2–6, 3–7, 4–8, 5–1, 6–2, 7–3, 8–4) represent conventional projection data collection, with 8 sweeps (B1–B8) each with constant gradient orientation from θ1 to θ8. The concentric dotted circles represent the stepped-field-rotating-gradient modality (Ohno et al. [25] and Deng et al. Ref. [12]), and the Kaleidoscopic pattern (continuous lines) represent the simultaneous rapid scan and rotating gradient strategy.