Target detection is one of the most important research directions in computer vision. Recently, a variety of target detection algorithms have been proposed. Since the targets have varying sizes in a scene, it is essential to be able to detect the targets at different scales. To improve the detection performance of targets with different sizes, a multi-scale target detection algorithm was proposed involving improved YOLO (You Only Look Once) V3. The main contributions of our work include: (1) a mathematical derivation method based on Intersection over Union (IOU) was proposed to select the number and the aspect ratio dimensions of the candidate anchor boxes for each scale of the improved YOLO V3; (2) To further improve the detection performance of the network, the detection scales of YOLO V3 have been extended from 3 to 4 and the feature fusion target detection layer downsampled by 4× is established to detect the small targets; (3) To avoid gradient fading and enhance the reuse of the features, the six convolutional layers in front of the output detection layer are transformed into two residual units. The experimental results upon PASCAL VOC dataset and KITTI dataset show that the proposed method has obtained better performance than other state-of-the-art target detection algorithms.

The accurate segmentation of the paraspinal muscle in Magnetic Resonance (MR) images is a critical step in the automated analysis of lumbar diseases such as chronic low back pain, disc herniation and lumbar spinal stenosis. However, the automatic segmentation of multifidus and erector spinae has not yet been achieved due to three unusual challenges: (1) the muscle boundary is unclear; (2) the gray histogram distribution of the target overlaps with the background; (3) the intra- and inter-patient shape is variable. We propose to tackle the problem of the automatic segmentation of paravertebral muscles using a deformed U-net consisting of two main modules: the residual module and the feature pyramid attention (FPA) module. The residual module can directly return the gradient while preserving the details of the image to make the model easier to train. The FPA module fuses different scales of context information and provides useful salient features for high-level feature maps. In this paper, 120 cases were used for experiments, which were provided and labeled by the spine surgery department of Shengjing Hospital of China Medical University. The experimental results show that the model can achieve higher predictive capability. The dice coefficient of the multifidus is as high as 0.949, and the Hausdorff distance is 4.62 mm. The dice coefficient of the erector spinae is 0.913 and the Hausdorff distance is 7.89 mm. The work of this paper will contribute to the development of an automatic measurement system for paraspinal muscles, which is of great significance for the treatment of spinal diseases.

In crowded scenes, one of the most important issues is that heavily overlapped objects are hardly distinguished from each other since most of their pixels are shared and the visible pixels of the occluded objects, which are used to represent their features, are limited. In this paper, a spatial pyramid convolutional shuffle (SPCS) module is proposed to extract refined information from the limited visible pixels of the occluded objects and generate distinguishable representations for the heavily overlapped objects. We adopt four convolutional kernels with different sizes and dilation rates at each location in the pyramid features and adjacently recombine their fused outputs spatially using a pixel shuffle module. In this way, four distinguishable instance predictions corresponding different convolutional kernels can be produced for each location in the pyramid feature. In addition, multiple convolutional operations with different kernel sizes and dilation rates at the same location can generate refined information for the corresponding regions, which is helpful to extract features for the occluded objects from their limited visible pixels. Extensive experimental results demonstrate that SPCS module can effectively boost the performance in crowded human detection. YOLO detector with SPCS module achieves 94.11% AP, 41.75% MR, 97.75% Recall on CrowdHuman, 93.04% AP, and 98.45% Recall on WiderPerson, which are the best compared with previous state-of-the-art models.