Breast Density Analysis Using an Automatic Density Segmentation Algorithm.

Breast density is a strong risk factor for breast cancer. In this paper, we present an automated approach for breast density segmentation in mammographic images based on a supervised pixel-based classification and using textural and morphological features. The objective of the paper is not only to show the feasibility of an automatic algorithm for breast density segmentation but also to prove its potential application to the study of breast density evolution in longitudinal studies. The database used here contains three complete screening examinations, acquired 2 years apart, of 130 different patients. The approach was validated by comparing manual expert annotations with automatically obtained estimations. Transversal analysis of the breast density analysis of craniocaudal (CC) and mediolateral oblique (MLO) views of both breasts acquired in the same study showed a correlation coefficient of ρ = 0.96 between the mammographic density percentage for left and right breasts, whereas a comparison of both mammographic views showed a correlation of ρ = 0.95. A longitudinal study of breast density confirmed the trend that dense tissue percentage decreases over time, although we noticed that the decrease in the ratio depends on the initial amount of breast density.

Breast peripheral area correction in digital mammograms.

Digital mammograms may present an overexposed area in the peripheral part of the breast, which is visually shown as a darker area with lower contrast. This has a direct impact on image quality and affects image visualisation and assessment. This paper presents an automatic method to enhance the overexposed peripheral breast area providing a more homogeneous and improved view of the whole mammogram. The method automatically restores the overexposed area by equalising the image using information from the intensity of non-overexposed neighbour pixels. The correction is based on a multiplicative model and on the computation of the distance map from the breast boundary. A total of 334 digital mammograms were used for evaluation. Mammograms before and after enhancement were evaluated by an expert using visual comparison. In 90.42% of the cases, the enhancement obtained improved visualisation compared to the original image in terms of contrast and detail. Moreover, results show that lesions found in the peripheral area after enhancement presented a more homogeneous intensity distribution. Hence, peripheral enhancement is shown to improve visualisation and will play a role in further development of CAD systems in mammography.

Improving a CAD system using bilateral information.

Computer Aided Detection (CAD) mammographic systems are used in medicine to assist radiologists in the evaluation of mammographic images. The aim of this work is to compare the results of a developed single-image CAD system with a new one, dual-image CAD, that adds registration information of bilateral mammographic images in the training step of the former system. The evaluation of the different registration methods is performed using similarity measures. Receiver Operating Characteristic (ROC) analysis and Free Receiver Operating Characteristics (FROC) analysis are used to compare the results of both CAD systems. At a sensitivity of 80%, the false positives per image was 1.68 for the single-image CAD system and 0.90 for the dual-image CAD system. The results shows the benefits of integrating bilateral information into the CAD system.