Phase-Contrast Mammography with Synchrotron Radiation: Dosimetric Results

At the SYRMEP (Synchrotron Radiation for Medical Physics) beamline of Elettra Laboratory, the Italian Synchrotron Radiation (SR) facility in Trieste (Italy), the first clinical study in SR Mammography (SRM) has been carried out since 2006. The Phase-Contrast Imaging technique is applied during SRM at SYRMEP beamline; this technique is especially suited for imaging objects having low contrast due to X-ray absorption, such as glandular tissue and cancer in mammography. The clinical study demonstrated that the image quality and the diagnostic accuracy increase significantly in SRM compared to conventional mammography. In this study the Entrance Skin Exposure (ESE) and the Mean Glandular Doses (MGDs) delivered during mammographic exams at Elettra and at the University Hospital of Trieste are evaluated and compared. In this study the doses delivered to 73 patients that underwent to a clinical mammographic exam performed with Synchrotron Radiation have been compared to the doses delivered to the same patients in clinical mammography exams using DM. The results show a significant decrease of the Mean Glandular Dose of 42% in respect to the one delivered at DM. One reason of such important reduction is that in Synchrotron Radiation Mammography the X-ray beam is monochromatic, thus there is no presence of the low energy components of the conventional X-ray spectrum, that are instead completely absorbed by breast during conventional exams. Another interesting and unexpected result is that, in SRM, the ESE is constant in all the thickness classes, with a very important reduction of the skin dose in the thick breast exams (e.g. starting from 5 cm compressed breast, already 58% lower than DM is observed). Phase Contrast Mammography with Synchrotron Radiation improves the image quality depicting with high resolution and contrast both the normal anatomic structure of the breast and the abnormal findings, as it was noticed in previous study; in addition it is now possible to highlight that the dose is considerably decreased, making thus the SRM a possible second level exam for effectively enhancing breast cancer diagnosis.