Multi-Frame SPRITE: a method for resolution enhancement of multiple-point SPRITE data.

The Single Point Ramped Imaging with T1 Enhancement (SPRITE) sequence is well suited for the acquisition of magnetic resonance signals from fast relaxing nuclei and from heterogeneous materials. However, it is time inefficient compared to sequences that are based on frequency encoding because only one single point is acquired per excitation. Multiple-point SPRITE (mSPRITE) mitigates this problem with the acquisition of multiple FID points. mSPRITE images reconstructed from early FID samples suffer from reduced spatial resolution due to the limited extent of its corresponding k-space. In this work we present a new reconstruction algorithm for spatial resolution enhancement that solves this problem without changes to the mSPRITE sequence. The method, called Multi-Frame mSPRITE, substitutes high spatial frequencies from late FID points into k-spaces of limited extent constructed from early FID points. In this way, images of high quality and resolution can be obtained despite a large range of zoom factors used to reconstruct images with the same FOV and resolution.