A novel imaging techonolgy, referred to as phase contrast x-ray imaging has allowed researchers from TH Zurich, the Paul Scherrer Institute (PSI) and the Kantonsspital Baden to conduct mammographic imaging that leads to higher accuracy in the evaluation of breast cancer and its symptoms. The imaging technology could greatly enhance biopsy diagnostics and follow-up.
The researchers have achieved in furthering an emerging imaging technique for breast investigations: the X-ray phase-contrast mammography. The latest developments allow researchers to make a solid distinction between the various kinds of microcalcifications noted in breast tissue and help assigning them to malignant lesions.
The study has gone on to be published in the journal, Nature Communications.
One of the benefits of the phase contrast method is its unique ability to provide images of high contrast. For future practices, this method can significantly help physicians to determine in a non-invasive manner in which premalignant and malignant breast lesions are mostly located. The prime objective of any breast cancer screening is to detect (groups of) microcalcifications in the breast, because they may be linked with early stages of breast cancer since they usually occur in asscociation with cancer cell death. Mammographic screening does usually lead to definitive conclusions in regards to the underlining conditions that cause calcifications. Only tissue biopsies that are investigated under the microscope by pathologists can ultimately determine which lesions have caused the calcareous deposits and which haven't.
At the PSI, the use of phase contrast for medical X-ray imaging has been a topic of investigation for several years now. X-ray radiation as applied in traditional mammography was long considered unsuitable for phase contrast procedures due to its incoherence and blend of several wavelengths.
"The fact that we have now managed to use these X-ray sources for the phase contrast method in order to develop a new and improved imaging method is a considerable step towards application in daily clinical practice," said Professor at the Institute for Biomedical Engineering at ETH Zurich and Head of the X-ray Tomography Group at the PSI, Marco Stampanoni.
Stampanoni received an ERC Consolidator Grant in 2012 to advance the clinical use of X-ray phase contrast.
In X-ray phase contrast, the degree to which tissue absorbs x-rays is not the only factor that is being measured but also how tissue repels radiation laterally (refraction) and subsequently how it impacts the series of oscillation peaks and valleys of X-ray waves, the so-called phase.
Depending on the tissue type, the overall scattering also differs. In order to measure the phase shift, researchers use three different grids. The first one is situated directly at the source. It guarantees that the object is lit with the needed coherence. Another grid is situated behind the object and produces an interference signal that is then analyzed by a third grid downstream. Using appropriate algorithms, the researchers determine the absorption, phase, and scattering properties of the object from the interference signal. This information can then be used to produce sharp and high-contrast images that reveal very detailed soft tissue properties.
"During my trials with the phase contrast method, I noticed that there are microcalcifications with different absorption and scattering signals. That indicated that the new method might identify different types of calcifications. I was persuaded that my observation could be very interesting for breast cancer diagnosis, since it could distinguish between the different types of microcalcifications," said researcher Zhentian Wang.
The relevance of the new discovery also encouraged physicians who took part in the study.
"We are hopeful that the new technique, in comparison to standard mammography, will help to better indicate where a biopsy must be carried out in the breast. Still, it is not ready for clinical use as it needs to be validated in a larger number of cases," said Head of the Institute of Radiology at the Kantonsspital Baden, Rachel Kubik.
"It is very encouraging that the new method enables a distinction between the different well-known microscopic types of calcifications," concurs Head of the Institute of Pathology at the Kantonsspital Baden, Gad Singer.
Now what remains to be seen is whether the technology will be employed in clinical practice or not depends on its radiation dose.
"The aim will be to significantly improve quality, resolution and diagnosis with the same radiation dose as for a standard mammography so that breasts can be better examined. If we can significantly improve imaging, this would enable better assessments of tumor extent prior to surgery. Then the new method will quickly become important," said Head of Gynaecology and of the Interdisciplinary Breast Center at the Kantonsspital Baden, Nik Hauser.
