Fig. 3From: High mammographic density is associated with an increase in stromal collagen and immune cells within the mammary epitheliumSecond harmonic generation (SHG) analysis of collagen. (a) Collagen was imaged using an SHG technique. White squares indicate analysed regions. Scale bar indicates 100 μm. (b) Grey-level co-occurrence matrix (GLCM) analysis shows the correlation of the intensity of the SHG signal across the analysed region. Samples with a slower decay have a denser collagen structure than samples with a faster decay. For each sample, three regions were imaged. Within each region, three areas were selected for analysis (total N = 9). Mean parameter values are shown as symbols. Dashed lines represent the nonlinear biexponential fit to each data set. Error bars indicate SEM. (c) The mean decay parameter (slope) in a biexponential fit model of correlation decay curve was calculated and plotted for each sample. (d) The ratio of the mean decay of high mammographic density (HMD) to low mammographic density (LMD) was calculated to determine whether HMD samples contained a higher collagen organisation than LMD samples. A ratio above 1 indicates that HMD samples had a higher collagen organisation than LMD samples. Seventy-five percent of HMD samples showed a higher mean decay than LMD samples. Horizontal bar indicates the meanBack to article page