Effect of variable gain on computerized texture analysis on digitized mammograms

Computerized texture analysis of mammographic images has emerged as a means to characterize breast parenchyma and estimate breast percentage density, and thus, to ultimately assess the risk of developing breast cancer. However, during the digitization process, mammographic images may be modified and optimized for viewing purposes, or mammograms may be digitized with different scanners. It is important to demonstrate how computerized texture analysis will be affected by differences in the digital image acquisition. In this study, mammograms from 172 subjects, 30 women with the BRCA1/2 gene-mutation and 142 low-risk women, were retrospectively collected and digitized. Gray-level transformations of the image data were performed for two scenarios -- to simulate different digitizers and to simulate varying the gain for different cases. Computerized texture analysis was performed on these transformed images, and the effect of variable gain on computerized texture analysis on mammograms was investigated. Area under the receiver operating characteristic curve (AUC) was used as a figure of merit to assess the individual texture feature performance in the task of distinguishing between the high-risk and the low-risk women for developing breast cancer. For those features based on coarseness measures and fractal measures, the histogram transformation (contrast enhancement) showed little effect on the classification performance of these features. However, as expected, for those features based on gray-scale histogram analysis, such as balance and skewnesss, and contrast measures, large variations were observed in terms of AUC values for those features. Understanding this effect will allow us to better assess breast cancer risk using computerized texture analysis.