Exploring the Limits of Super-Resolution MRI with Phaseless Encoding

The recently proposed method of Super-resolution (SR) MRI with phaseless subpixel encoding simultaneously samples three neighboring k-space bands and provides resolution enhancement factor up to 3.0. We now demonstrate an almost five-fold resolution enhancement by applying additional encoding steps of higher modulation frequency, which allows five bands to be acquired without compromising the methods’ immunity to phase fluctuations. Since the signal-to-noise ratio at high resolution becomes critical, we derived and experimentally verified the optimum flip angle of the encoding (tagging) sequence. A possibility to correct artefacts caused by flip angle inhomogeneity is also shown based on simulation.