  Diffeomorphic registration has become a powerful approach for seeking a
smooth and invertible spatial transformation between two coordinate systems
which have been measured via the template and reference images. While the
pointwise volume-preserving constraint is effective for some problems, it is
too stringent for many other problems especially when the local deformations
are relatively large, because it may lead to a poor large-deformation for
enforcing local matching.In this paper, we propose a novel bi-variant
diffeomorphic image registration model with the soft constraint of Jacobian
equation, which allows local deformations to shrink and grow in a flexible
range.The Jacobian determinant of the transformation is explicitly controlled
by optimizing the relaxation function. To prevent deformation folding and
enhance the smoothness of deformation, we not only impose a positivity
constraint in optimizing the relaxation function, but also employ a regularizer
to ensure the smoothness of the relaxation function.Furthermore, the positivity
constraint ensures that is as close to one as possible, which helps to obtain a
volume-preserving transformation on average.We further analyze the existence of
the minimizer for the variational model and propose a penalty splitting method
with a multilevel strategy to solve this model. Numerical experiments show that
the proposed algorithm is convergent, and the positivity constraint can control
the range of relative volume and not compromise registration accuracy.
Moreover, the proposed model produces diffeomorphic maps for large deformation,
and achieves better performance compared to the several existing registration
models.

Computer Vision and Pattern Recognition