MAD: Modality Agnostic Distance Measure for Image Registration
Vasiliki Sideri-Lampretsa Veronika A. Zimmer Huaqi Qiu Georgios Kaissis Daniel Rueckert
Multi-modal image registration is a crucial pre-processing step in many
medical applications. However, it is a challenging task due to the complex
intensity relationships between different imaging modalities, which can result
in large discrepancy in image appearance. The success of multi-modal image
registration, whether it is conventional or learning based, is predicated upon
the choice of an appropriate distance (or similarity) measure. Particularly,
deep learning registration algorithms lack in accuracy or even fail completely
when attempting to register data from an "unseen" modality. In this work, we
present Modality Agnostic Distance (MAD), a deep image distance}] measure that
utilises random convolutions to learn the inherent geometry of the images while
being robust to large appearance changes. Random convolutions are
geometry-preserving modules which we use to simulate an infinite number of
synthetic modalities alleviating the need for aligned paired data during
training. We can therefore train MAD on a mono-modal dataset and successfully
apply it to a multi-modal dataset. We demonstrate that not only can MAD
affinely register multi-modal images successfully, but it has also a larger
capture range than traditional measures such as Mutual Information and
Normalised Gradient Fields.