  Image registration is an essential but challenging task in medical image
computing, especially for echocardiography, where the anatomical structures are
relatively noisy compared to other imaging modalities. Traditional
(non-learning) registration approaches rely on the iterative optimization of a
similarity metric which is usually costly in time complexity. In recent years,
convolutional neural network (CNN) based image registration methods have shown
good effectiveness. In the meantime, recent studies show that the
attention-based model (e.g., Transformer) can bring superior performance in
pattern recognition tasks. In contrast, whether the superior performance of the
Transformer comes from the long-winded architecture or is attributed to the use
of patches for dividing the inputs is unclear yet. This work introduces three
patch-based frameworks for image registration using MLPs and transformers. We
provide experiments on 2D-echocardiography registration to answer the former
question partially and provide a benchmark solution. Our results on a large
public 2D echocardiography dataset show that the patch-based MLP/Transformer
model can be effectively used for unsupervised echocardiography registration.
They demonstrate comparable and even better registration performance than a
popular CNN registration model. In particular, patch-based models better
preserve volume changes in terms of Jacobian determinants, thus generating
robust registration fields with less unrealistic deformation. Our results
demonstrate that patch-based learning methods, whether with attention or not,
can perform high-performance unsupervised registration tasks with adequate time
and space complexity. Our codes are available
https://gitlab.inria.fr/epione/mlp\_transformer\_registration
