Groupwise Multimodal Image Registration using Joint Total Variation

In medical imaging it is common practice to acquire a wide range of modalities (MRI, CT, PET, etc.), to highlight different structures or pathologies. As patient movement between scans or scanning session is unavoidable, registration is often an essential step before any subsequent image analysis. In this paper, we introduce a cost function based on joint total variation for such multimodal image registration. This cost function has the advantage of enabling principled, groupwise alignment of multiple images, whilst being insensitive to strong intensity non-uniformities. We evaluate our algorithm on rigidly aligning both simulated and real 3D brain scans. This validation shows robustness to strong intensity non-uniformities and low registration errors for CT/PET to MRI alignment. Our implementation is publicly available at https://github.com/brudfors/coregistration-njtv

Multimodal MRI template creation in the ring-tailed lemur and rhesus macaque

We present a multimodal registration algorithm for simultaneous alignment of datasets with both scalar and tensor MRI images. We employ a volumetric, cubic B-spline parametrised transformation model. Regularisation is based on the logarithm of the singular values of the local Jacobian and ensures diffeomorphic warps. Tensor registration takes reorientation into account during optimisation, through a finite-strain approximation of rotation due to the warp. The combination of scalar, tensor and regularisation cost functions allows us to optimise the deformations in terms of tissue matching, orientation matching and distortion minimisation simultaneously. We apply our method to creating multimodal T2 and DTI MRI brain templates of two small primates (the ring-tailed lemur and rhesus macaque) from high-quality, ex vivo, 0.5/0.6 mm isotropic data. The resulting templates are of very high quality across both modalities and species. Tissue contrast in the T2 channel is high indicating excellent tissue-boundary alignment. The DTI channel displays strong anisotropy in white matter, as well as consistent left/right orientation information even in relatively isotropic grey matter regions. Finally, we demonstrate where the multimodal templating approach overcomes anatomical inconsistencies introduced by unimodal only methods