Exploring local rotation invariance in 3D CNNs with steerable filters

Andrearczyk, Vincent (University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis)) ; Fageot, Julien (Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland) ; Oreiller, Valentin (University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis); Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland) ; Montet, Xavier (Hopitaux Universitaires de Geneve (HUG), Geneva, Switzerland) ; Depeursinge, Adrien (University of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis))

Locally Rotation Invariant (LRI) image analysis was shown to be fundamental in many applications and in particular in medical imaging where local structures of tissues occur at arbitrary rotations. LRI constituted the cornerstone of several breakthroughs in texture analysis, including Local Binary Patterns (LBP), Maximum Response 8 (MR8) and steerable lterbanks. Whereas globally rotation invariant Convolutional Neural Networks (CNN) were recently proposed, LRI was very little investigated in the context of deep learning. We use trainable 3D steerable lters in CNNs in order to obtain LRI with directional sensitivity, i.e. non-isotropic. Pooling across orientation channels after the rst convolution layer releases the constraint on nite rotation groups as assumed in several recent works. Steerable lters are used to achieve a ne and ecient sampling of 3D rotations. We only convolve the input volume with a set of Spherical Harmonics (SHs) modulated by trainable radial supports and directly steer the responses, resulting in a drastic reduction of trainable parameters and of convolution operations, as well as avoiding approximations due to interpolation of rotated kernels. The proposed method is evaluated and compared to standard CNNs on 3D texture datasets including synthetic volumes with rotated patterns and pulmonary nodule classication in CT. The results show the importance of LRI in CNNs and the need for a ne rotation sampling.

Conference Type:
full paper
Economie et Services
Institut Informatique de gestion
London, UK, 8-10 July 2019
London, UK
8-10 July 2019
11 p.
Published in:
Proceedings of the International Conference on Medical Imaging with Deep Learning (MIDL) 2019
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 Record created 2019-10-21, last modified 2020-10-27

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