Weakly Supervised Pediatric Bone Age Assessment Using Ultrasonic Images via Automatic Anatomical RoI Detection

Abstract

Bone age assessment (BAA) is vital in pediatric clinical diagnosis. Existing deep learning methods predict bone age based on Regions of Interest (RoIs) detection or segmentation of hand radiograph, which requires expensive annotations. Limitations of radiographic technique on imaging and cost hinder their clinical application as well. Compared to X-ray images, ultrasonic images are rather clean, cheap and flexible, but the deep learning research on ultrasonic BAA is still a white space. For this purpose, we propose a weakly supervised interpretable framework entitled USB-Net, utilizing ultrasonic pelvis images and only image-level age annotations. USB-Net consists of automatic anatomical RoI detection stage and age assessment stage. In the detection stage, USB-Net locates the discriminative anatomical RoIs of pelvis through attention heatmap without any extra RoI supervision. In the assessment stage, the cropped anatomical RoI patch is fed as fine-grained input to estimate age. In addition, we provide the first ultrasonic BAA dataset composed of 1644 ultrasonic hip joint images with image-level labels of age and gender. The experimental results verify that our model keeps consistent attention with human knowledge and achieves 16.24 days mean absolute error (MAE) on USBAA dataset.