InverseSR: 3D Brain MRI Super-Resolution Using a Latent Diffusion Model
Jueqi Wang Jacob Levman Walter Hugo Lopez Pinaya Petru-Daniel Tudosiu M. Jorge Cardoso Razvan Marinescu
High-resolution (HR) MRI scans obtained from research-grade medical centers
provide precise information about imaged tissues. However, routine clinical MRI
scans are typically in low-resolution (LR) and vary greatly in contrast and
spatial resolution due to the adjustments of the scanning parameters to the
local needs of the medical center. End-to-end deep learning methods for MRI
super-resolution (SR) have been proposed, but they require re-training each
time there is a shift in the input distribution. To address this issue, we
propose a novel approach that leverages a state-of-the-art 3D brain generative
model, the latent diffusion model (LDM) trained on UK BioBank, to increase the
resolution of clinical MRI scans. The LDM acts as a generative prior, which has
the ability to capture the prior distribution of 3D T1-weighted brain MRI.
Based on the architecture of the brain LDM, we find that different methods are
suitable for different settings of MRI SR, and thus propose two novel
strategies: 1) for SR with more sparsity, we invert through both the decoder of
the LDM and also through a deterministic Denoising Diffusion Implicit Models
(DDIM), an approach we will call InverseSR(LDM); 2) for SR with less sparsity,
we invert only through the LDM decoder, an approach we will call
InverseSR(Decoder). These two approaches search different latent spaces in the
LDM model to find the optimal latent code to map the given LR MRI into HR. The
training process of the generative model is independent of the MRI
under-sampling process, ensuring the generalization of our method to many MRI
SR problems with different input measurements. We validate our method on over
100 brain T1w MRIs from the IXI dataset. Our method can demonstrate that
powerful priors given by LDM can be used for MRI reconstruction.