Hyperpolarized (HP) media enable biomedical imaging applications otherwise unachievable using standard MRI contrast agents. However, quantitative analysis of HP images is complicated by spatially varying signal decay due to T1 relaxation and RF excitation. By imaging with center-out trajectories, HP signal intensity is collected with every acquisition, thereby encoding signal decay alongside k-space data. Using keyhole reconstruction, multiple temporally resolved images were reconstructed to generate voxel-by-voxel maps of hyperpolarized signal decay following a simple analytical model. Here these maps are applied to correct spatially varying magnetization decay in HP 129Xe, improving the quantitative accuracy of ventilation images.