• Hiba Chougrad, Hamid Zouaki, and Omar Alheyane.
• Laboratory of Computer Science and Mathematics and their Applications (LIMA), Faculty of science, University Chouaib Doukkali, El Jadida 24000, Morocco. Electronic address: chougrad.h@ucd.ac.ma.
• Comput Methods Programs Biomed. 2018 Apr 1; 157: 19-30.

Background And ObjectiveRadiologists often have a hard time classifying mammography mass lesions which leads to unnecessary breast biopsies to remove suspicions and this ends up adding exorbitant expenses to an already burdened patient and health care system.MethodsIn this paper we developed a Computer-aided Diagnosis (CAD) system based on deep Convolutional Neural Networks (CNN) that aims to help the radiologist classify mammography mass lesions. Deep learning usually requires large datasets to train networks of a certain depth from scratch. Transfer learning is an effective method to deal with relatively small datasets as in the case of medical images, although it can be tricky as we can easily start overfitting.ResultsIn this work, we explore the importance of transfer learning and we experimentally determine the best fine-tuning strategy to adopt when training a CNN model. We were able to successfully fine-tune some of the recent, most powerful CNNs and achieved better results compared to other state-of-the-art methods which classified the same public datasets. For instance we achieved 97.35% accuracy and 0.98 AUC on the DDSM database, 95.50% accuracy and 0.97 AUC on the INbreast database and 96.67% accuracy and 0.96 AUC on the BCDR database. Furthermore, after pre-processing and normalizing all the extracted Regions of Interest (ROIs) from the full mammograms, we merged all the datasets to build one large set of images and used it to fine-tune our CNNs. The CNN model which achieved the best results, a 98.94% accuracy, was used as a baseline to build the Breast Cancer Screening Framework. To evaluate the proposed CAD system and its efficiency to classify new images, we tested it on an independent database (MIAS) and got 98.23% accuracy and 0.99 AUC.ConclusionThe results obtained demonstrate that the proposed framework is performant and can indeed be used to predict if the mass lesions are benign or malignant.Copyright © 2018 Elsevier B.V. All rights reserved.

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