B1 Self-Calibration for Artifact Removal in Radial Hyperpolarised 3He Lung Imaging

Helen Marshall¹, Salma Ajraoui¹, Martin Deppe¹, James M. Wild¹

In hyperpolarised ³He lung MRI the transverse signal decays with each RF excitation, imposing a k-space filter on the acquired data. For radially acquired data this filter causes streaking, angular shading and loss of spatial resolution in the images. Radial acquisition samples the centre of k-space with every projection, so tracking the signal decay. The inverse of this decay function was used to retrospectively compensate the data leading to improved image quality. The average flip angle per slice was calculated from the radial data and found to correspond well with conventional flip angle maps providing a means of B₁ self-calibration.