The indexing process occurs over a 593 GBytes (Institution A) and 1362 GBytes (Institution B) information volume, and took about 93 hours at Institution A and 212 hours at Institution B.

As a result of the indexing process we collected, data relating to 351.248 images, from 210.582 Computed Radiography studies and belonging to 69.041 patients (Table 1).

After indexing we performed the query and retrieval process where we assembled 8087 images, from 2047 mammographic studies belonging to 1757 patients.

The statistical analysis (Table 2) highlights the following issues:

• High standard deviation for the Sensitivity values (much influenced by Minimum and Maximum Sensitivity values identified in the sample);
• Very low Sensitivity values reflecting a hyper-exposed radiation detector;
• Very high Sensitivity values reflecting a hypo-exposed radiation detector.

The results suggest a higher radiation exposure at Institution A, namely considering the 25 and 75 percentiles values analysis.

From the analysis of the mammographic projections performed with Sensitivity values above and below the median exposure values (Table 3) we found that:​

• At Institution A a sharp radiation exposure increase (decreasing Sensitivity values) was identified during 2009 and 2010 (high number of images with S value lower than the median) and a decrease during 2011;
• At Institution B the Sensitivity values analysis exhibited a reduction of the detector radiation exposure over time. 

The Kruskal-Wallis statistical test allows us to reject H0 in all the analysis and it demonstrates the Sensitivity values inhomogeneity at Institution A and Institution B. At Table 4 we can see:

• A discrepancy between Sensitivity median values obtained in different years in the same mammographic projection;
• The Sensitivity median values variation is statistically significant (p <0.001);
• Disparity between SD values belonging to the same type of projection performed over time.

There are differences between the Sensitivity median values over the study period, under the same mammographic projection and performed in each institution.