Automatic Off-Resonance Correction with Piecewise Linear Autofocus

Travis Smith¹, Krishna Nayak¹

We present a new method to correct off-resonance blurring in spiral and radial images without knowledge of the field map. The image is divided into blocks and linear field map estimation and correction are performed on each block. The local linear coefficients are estimated through a combination of k-space spectral analysis and mapdrift, an image-domain correlation technique. The deblurring performance is comparable to field map-based techniques. The method does not use objective functions, requires only a blurry image (magnitude and phase) and a trajectory time map, and is suitable for low-SNR and fine-resolution images.