Mass detection in mammograms by bilateral analysis using convolution neural network

https://doi.org/10.1016/j.cmpb.2020.105518Get rights and content

Highlight

  • The self-supervised learning network is designed for bilateral mammogram registration. It directly estimates spatial transformation by maximizing an image-wise similarity metric, which solves the problem of corresponding points labeling.

  • A Siamese-Faster-RCNN consisting of RPN and Siamese-FC network is designed and employed for mass detection. It combines single-image mass detection and bilateral comparison into a whole, which solves the problem of separating single-image mass detection and bilateral comparison apart.

Abstract

Background and objective

Automatic detection of the masses in mammograms is a big challenge and plays a crucial role to assist radiologists for accurate diagnosis. In this paper, a bilateral image analysis method based on Convolution Neural Network (CNN) is developed for mass detection in mammograms.

Methods

The proposed bilateral mass detection method consists of two networks: a registration network for registering bilateral mammograms and a Siamese-Faster-RCNN network for mass detection using a pair of registered mammograms. In the first step, self-supervised learning network is built to learn the spatial transformation between bilateral mammograms. This network can directly estimate spatial transformation by maximizing an image-wise similarity metric and corresponding points labeling is not needed. In the second step, an end-to-end network combining the Region Proposal Network (RPN) and a Siamese Fully Connected (Siamese-FC) network is designed. Different from existing methods, the designed network integrates mass detection on single image with registered bilateral images comparison.

Results

The proposed method is evaluated on three datasets (publicly available dataset INbreast and private dataset BCPKUPH and TXMD). For INbreast dataset, the proposed method achieves 0.88 true positive rate (TPR) with 1.12 false positives per image (FPs/I). For BCPKUPH dataset, the proposed method achieves 0.85 TPR with 1.86 FPs/I. For TXMD dataset, the proposed method achieves 0.85 TPR with 2.70 FPs/I.

Conclusions

Registration experimental result shows that the proposed method is suitable for bilateral mass detection. Mass detection experimental results show that the proposed method performs better than unilateral mass detection method, different bilateral connection schemes and image level fusion bilateral schemes.

Introduction

Breast cancer is the leading type of cancer which affects women's health in developed and developing countries. According to statistics, breast cancer accounts for 22.9% of all newly diagnosed cancers, causing 13.7% cancer related deaths all over the world [1]. In spite of that, if breast cancer can be early diagnosed, it has a high chance to be cured [2]. Based on this scenario, world governments together with health professionals have mobilized various campaigns to alert the female population to the risks that cause this disease [3].

Among many imaging techniques, mammography is currently considered to be the most widely used manner [4]. Mass is the most common type of breast cancer. Compared with normal tissues, a mass usually exhibits in the form of a high intensity region in the mammogram. Mass detection is an important step in mammogram interpreting. Due to the low signal-to-noise ratio of mass visualization and the lack of consistent patterns in shape, size, appearance and location [5], it is a difficult task for radiologists to distinguish between normal tissue and mass. For example, glandular tissues are compressed in a mammogram exam, presenting similar features with a mass. In such case, they may be falsely detected as masses with high probability, which are called false positives (FPs). Studies have shown that manual analysis has a specificity of 91% and a sensitivity of 84% by single radiologist in the task of diagnosing breast cancer [6]. The performance can be improved using independent readings by two radiologists [6]. However, the double reading manner increases the burden of radiologists and reduces work efficiency. In the last several decades, computer vision technologies have been developed for the purpose of a second view [7]. Existing researches have shown that detection sensitivity can be improved in clinical practice with the use of computer vision aided diagnosis that acts as a second view.

Region of interests (ROIs) detected on single mammogram may contain several FP regions. It is noteworthy that bilateral breasts of the same patient tend to have a high degree symmetry [8]. Radiologists may remove FPs by comparing the left breast and the right breast with the same view when interpreting mammograms. This practice is commonly known as bilateral analysis. The main idea of bilateral analysis is that the similarity between corresponding regions of a pair of mammograms in the same view is high for normal tissue and low for a mass [8].

In this paper, a bilateral mass detection method is proposed combining self-supervised learning network and Siamese-Faster-RCNN. A bilateral mammogram registration scheme based on self-supervised learning network is designed to make the bilateral mammograms aligned. As breast is compressed during mammogram imaging, it is even hard for a radiologist to find exact corresponding locations in the bilateral mammogram. The designed registration scheme can directly estimate the spatial transformation by maximizing an image-wise similarity metric and no corresponding points labeling is needed. To detect the mass using bilateral analysis, Siamese-Faster-RCNN network is designed by integrating Siamese Fully Connected (Siamese-FC) network into Region Proposal Network (RPN). For existing bilateral based mass detection method, single-image mass detection and bilateral comparison are separated. It is a sub-optimal problem. The designed Siamese-Faster-RCNN network is trained by an end-to-end manner, which might be the first attempt to combine mass detection and bilateral images comparison into one network.

The rest of the paper is organized as follows. Section 2 presents a review of related works. Section 3 describes the proposed method including image registration, mass detection and bilateral comparison. Section 4 shows the experiments and results. Section 5 and 6 give the discussion and conclusion.

Section snippets

Related works

There are two important issues in bilateral mass detection. One is how to register bilateral mammograms. The other is how to analyze a pair of images.

Methods

The proposed mass detection method consists of three stages: breast segmentation, registration between left breast and right breast, mass detection using bilateral comparison. The whole method is shown in Fig. 1. Pair images after breast segmentation pass through the registration network and the deformed image is obtained. Then the right image and the deformed left image are input to the Siamese-Faster-RCNN network to get the mass detection result for the right image. For mass detection of the

Dataset and experiment implementation

Experiments are performed on three datasets: one is public dataset-INbreast [36], and the other two are private dataset-Breast Center of Peking University People's Hospital (BCPKUPH) [20] and TXMD. The INbreast dataset includes 115 cases (410 images). Each case contains one left CC view, one left MLO view, one right CC view and one right MLO view. Image sizes are 3328 × 4084 and 2560 × 3328. The pixel width is 16-bits. The BCPKUPH dataset includes 100 cases and four images like INbreast are

Discussion

Examples of detection results by unilateral analysis and the proposed bilateral analysis are shown in Fig. 13. True label is indicated by the blue rectangle and the detection result is indicated by the red rectangle. The unilateral results are shown in Fig. 13(a)-(c). It can be seen that some glandular tissues are falsely detected as mass. The proposed bilateral analysis results are shown in Fig. 13(d)-(f). All FP regions are removed by bilateral analysis.

There are some shortages in the

Conclusions

In this paper, a bilateral mass detection method is proposed for mammogram combining self-supervised learning network and Siamese-Faster-RCNN. Registration experimental result shows that the proposed method does not distort glandular structure and the computation efficiency is high. It is suitable for bilateral mass detection. For mass detection, four observations can be concluded. Bilateral analysis outperforms mass detection on single mammogram, especially for dense breast. Using single

Declaration of Competing Interest

None Declared.

Acknowledgments

The work was supported in part by the National Nature Science Foundation of China61872030, and Major Science and Technology Innovation Project of Shandong Province2019TSLH0206.

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      For example, MatchNet architecture was introduced in [21], where the deep features and robust feature comparison network were jointly learned for a pair of breast images. Li et al. [8] built a self-supervised learning network to learn the spatial transformation between bilateral mammograms and it is no need to previously label corresponding points. After obtaining the detected ROI and its contralateral region, the similarity level between them need to be analyzed to discriminate the mass-to-normal pairs and normal-to-normal pairs.

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      Recently, multi-view based approaches are attracting an increasing attention. In (Diniz et al., 2018; Li et al., 2020; Liu et al., 2019), bilateral analysis has been incorporated in DNN-based approaches. Some other DNN-based methods consider information of ipsilateral mammograms (Carneiro et al., 2017; Perek et al., 2018; Ren et al., 2019).

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