A Quantitative Comparison of Synthetic Mammograms with Images from Conventional Mammography

Sammanfattning: Breast cancer is the most common cancer among women in Sweden. To be able to treat the disease it is important that it is detected at an early stage. In Sweden, women between 40 and 74 years are regularly offered screening with mammography to detect abnormalities in their breasts. The mammograms give the radiologist a good image of the breasts’ appearances, but it is difficult to detect structures that are covered by overlaying breast tissue, which are thus not seen in the image. To visualize structures hidden within the tissue and to see structures at different depths in the breast, breast tomosynthesis can be used. Breast tomosynthesis gives a three-dimensional image of the breast. In order to obtain the three-dimensional image, the breast is scanned in an angle of for example 50° and 25 projections of the breast are acquired. This can be reconstructed into a 3D image stack of the breast. To give an overview of what is shown in the corresponding tomosynthesis stack, the data can be reconstructed into a single synthetic mammogram. In this project, a quantitative comparison has been done between synthetic mammograms and conventional mammograms to investigate similarities and differences. The ultimate goal was to examine if it could be possible to use synthetic mammograms to compare to prior synthetic mammograms in order to track changes in the breast over time, when screening for breast cancer, just as conventional mammograms are used today. If that would be possible, the synthetic mammograms can provide a good overview of the breast, additionally the image stack acquired from breast tomosynthesis would give the radiologist the possibility to examine the breast in detail. The results showed that the synthetic mammograms were similar to conventional mammograms in one out of three aspects, the breast area density. Another comparison of the three was to use Transpara, an AI software, to examine the mammograms. This indicated similarities but there is still not enough evidence to draw conclusions. The last method of the three indicated significant differences in the frequency content, thus different structures were visible in the two types of mammograms. To conclude, synthetic mammograms and conventional mammograms are quite similar, but there are still improvements to be done before being able to state that they are equivalent.