Purpose To perform B1+$$ {B}_1^{+} $$‐selective excitation using the Bloch–Siegert shift for spatial localization. Theory and Methods A B1+$$ {B}_1^{+} $$‐selective excitation is produced by an radiofrequency (RF) pulse consisting of two summed component pulses: an off‐resonant pulse that induces a B1+$$ {B}_1^{+} $$‐dependent Bloch–Siegert frequency shift and a frequency‐selective excitation pulse. The passband of the pulse can be tailored by adjusting the frequency content of the frequency‐selective pulse, as in conventional B0$$ {B}_0 $$ gradient‐localized excitation. Fine magnetization profile control is achieved by using the Shinnar–Le Roux algorithm to design the frequency‐selective excitation pulse. Simulations analyzed the pulses' robustness to off‐resonance, their suitability for multi‐echo spin echo pulse sequences, and how their performance compares to that of rotating‐frame selective excitation pulses. The pulses were evaluated experimentally on a 47.5 mT MRI scanner using an RF gradient transmit coil. Multiphoton resonances produced by the pulses were characterized and their distribution across B1+$$ {B}_1^{+} $$ predicted. Results With correction for varying B1+$$ {B}_1^{+} $$ across the desired profile, the proposed pulses produced selective excitation with the specified profile characteristics. The pulses were robust against off‐resonance and RF amplifier distortion, and suitable for multi‐echo pulse sequences. Experimental profiles closely matched simulated patterns. Conclusion The Bloch–Siegert shift can be used to perform B0$$ {B}_0 $$‐gradient‐free selective excitation, enabling the excitation of slices or slabs in RF gradient‐encoded MRI.
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