Recently, Convolutional Neural Networks (CNNs) have been successfully used to detect microcalcifications in mammograms. An important step in CNN-based detection is image preprocessing that, in raw mammograms, is usually employed to equalize or remove the intensity-dependent quantum noise. In this work, we show how removing the noise can significantly improve the microcalcification detection performance of a CNN. To this end, we describe the quantum noise with a uniform square-root model. Under this assumption, the generalized Anscombe transformation is applied to the raw mammograms by estimating the noise characteristics from the image at hand. In the Anscombe domain, noise is filtered through an adaptive Wiener filter. The denoised images are recovered with an appropriate inverse transformation and are then used to train the CNN-based detector. Experiments were performed on 1,066 mammograms acquired with GE Senographe systems. MC detection performance of a CNN on noise-free mammograms was statistically significantly higher than on unprocessed mammograms. Results were also superior in comparison with a nonparametric noise-equalizing transformation previously proposed for digital mammograms.
The aim of this paper is to propose a deep learning framework for micro-calcification detection in 2D mammography and in 2D synthetic mammography (C-view) from digital breast tomosynthesis (DBT). The dataset analyzed for 2D mammograms is the INbreast dataset that consists of 410 digital images and we used 360 images with annotated micro-calcifications. For the synthetic views in DBT, we used a private dataset of 245 images, where micro-calcifications were validated by an experienced radiologist. The network is trained in a patch-based fashion, where micro-calcifications are considered positive samples, while patches containing other breast tissues are considered negative. For evaluating the entire dataset, a 2-fold cross validation was performed. In addition, a sliding window method was used to classify new patches within an image with those from the trained model. Considering 5,656 positive samples and 18,000,000 of negative samples, results for the 2D mammography, on the entire dataset, showed an area under the curve (AUC) of 0.9998 and a logarithmic partial area under the curve (logPAUC), in the interval (10<sup>−6</sup> , 1), of 0.8252. Results for the C-View, considering 3,420 positive samples and 11,395,939 of negative samples, showed an AUC, on the entire dataset, of 0.9997 and a logPAUC, in the interval (10<sup>−6</sup> , 1), of 0.8178. In this paper, we illustrate the applied methodologies, the network architecture used for training and test, and the results obtained.
Recently, both Deep Cascade classifiers and Convolutional Neural Networks (CNNs) have achieved state-ofthe-art microcalcification (MC) detection performance in digital mammography. Deep Cascades consist in long sequences of weak classifiers designed to effectively learn from heavily unbalanced data as in the case of MCs (∼ 1 MC every 10, 000 non-MC samples). CNNs are powerful models that achieve impressive results for image classification thanks to the ability to automatically extract general-purpose features from the data, but require balanced classes. In this work, we introduce a two-stage classification scheme that combines the benefits of both systems. Firstly, Deep Cascades are trained by requiring a very high sensitivity (99.5%) throughout the sequence of classifiers. As a result, while the number of MC samples remains practically unchanged, the number of non-MC samples is greatly reduced. The remaining data, approximately balanced, are used to train an additional stage of classification with a CNN. We evaluated the proposed approach on a database of 1, 066 digital mammograms. MC detection results of the combined classification were statistically significantly higher than Deep Cascade and CNN alone, yielding an average improvement in mean sensitivity of 3.19% and 2.45%, respectively. Remarkably, the proposed system also yielded a faster per-mammogram processing time (2.0s) compared to Deep Cascade (2.5s) and CNN (5.7s).