Purpose: To investigate aspects of the validation of self-supervised algorithms for reconstruction of undersampled MR images: quantitative evaluation of prospective reconstructions, potential differences between prospective and retrospective reconstructions, suitability of commonly used quantitative metrics, and generalizability. Theory and Methods: Two self-supervised algorithms based on self-supervised denoising and neural network image priors were investigated. These methods are compared to a least squares fitting and a compressed sensing reconstruction using in-vivo and phantom data. Their generalizability was tested with prospectively under-sampled data from experimental conditions different to the training. Results: Prospective reconstructions can exhibit significant distortion relative to retrospective reconstructions/ground truth.

Self-supervised learning algorithms for images, speech, text or other modalities function in very different ways, which has limited researchers in applying them more broadly. Because an algorithm designed for understanding images can't be directly applied to reading text, it's difficult to push several modalities ahead at the same rate. With data2vec, we've developed a unified way for models to predict their own representations of the input data, regardless if it's speech, text or audio. By focusing on these representations, a single algorithm can work with completely different types of input.

But while people appear to learn in a similar way regardless of how they get information -- whether they use sight or sound, for example -- there are currently big differences in the way self-supervised learning algorithms learn from images, speech, text, and other modalities. This discrepancy has been a significant barrier to applying advances in self-supervised learning more broadly. Because a powerful algorithm designed for, say, understanding images can't be directly applied to another modality, such as text, it is difficult to push several modalities ahead at the same rate. This is why Meta AI developed and is excited to announce data2vec, the first high-performance self-supervised algorithm that works for multiple modalities. We apply data2vec separately to speech, images and text and it outperformed the previous best single-purpose algorithms for computer vision and speech and it is competitive on NLP tasks.