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Hyperpolarized xenon MRI suffers from heterogeneous coil bias and magnetization decay that obscure pulmonary abnormalities. Non‐physiological signal variability can be mitigated by measuring and mapping the nominal flip angle, and by rescaling the images to correct for signal bias and decay. While flip angle maps can be calculated from sequentially acquired images, scan time and breath‐hold duration are doubled. Here, we exploit the low‐frequency oversampling of 2D‐spiral and keyhole reconstruction to measure flip angle maps from a single acquisition.

Flip angle maps were calculated from two images generated from a single dataset using keyhole reconstructions and a Bloch‐equation–based model suitable for hyperpolarized substances. Artifacts resulting from acquisition and reconstruction schemes (e.g., keyhole reconstruction radius, slice‐selection profile, spiral‐ordering, and …