  In recent years, several works have adopted the convolutional neural network
(CNN) to diagnose the avascular necrosis of the femoral head (AVNFH) based on
X-ray images or magnetic resonance imaging (MRI). However, due to the tissue
overlap, X-ray images are difficult to provide fine-grained features for early
diagnosis. MRI, on the other hand, has a long imaging time, is more expensive,
making it impractical in mass screening. Computed tomography (CT) shows
layer-wise tissues, is faster to image, and is less costly than MRI. However,
to our knowledge, there is no work on CT-based automated diagnosis of AVNFH. In
this work, we collected and labeled a large-scale dataset for AVNFH ranking. In
addition, existing end-to-end CNNs only yields the classification result and
are difficult to provide more information for doctors in diagnosis. To address
this issue, we propose the structure regularized attentive network (SRANet),
which is able to highlight the necrotic regions during classification based on
patch attention. SRANet extracts features in chunks of images, obtains weight
via the attention mechanism to aggregate the features, and constrains them by a
structural regularizer with prior knowledge to improve the generalization.
SRANet was evaluated on our AVNFH-CT dataset. Experimental results show that
SRANet is superior to CNNs for AVNFH classification, moreover, it can localize
lesions and provide more information to assist doctors in diagnosis. Our codes
are made public at https://github.com/tomas-lilingfeng/SRANet.
