Using gratings to boost contrast – The Nano Argovia project “NANOCREATE” aids the optimization of diagnostic imagesJuly 2018
In the Nano-Argovia project “NANOCREATE”, scientists from the Paul Scherrer Institute (PSI), in collaboration with the University of Applied Sciences (FHNW) and GratXray AG (Villigen, AG), are developing a cost-effective fabrication method for optical X-ray gratings. These gratings are used in a computed tomography (CT) scanner developed by GratXray that allows for high-resolution, high-contrast imaging of low absorbing tissues, such as the female breast.
In classic X-ray imaging, contrast between different tissue types get better the lower the X-ray energy. However, the lower the X-ray energy, the higher the radiation dose that is deposited in the patient. Therefore, classical X-ray imaging is physically limited by the image contrast that can be reached. This limitation can partially be overcome with grating interferometry, where not only the absorption, but also the refraction and scatter of X-ray can be measured. These additional signals are much stronger in soft tissue and thus, allow to significantly improve image contrast under dose control. Integrated in a dedicated breast CT, this technique allows for retrieving unprecedented image quality in 3D, ultimately leading to a more accurate diagnosis of breast cancer.
New fabrication method
Grating interferometry for medical diagnostics has been developed extensively in recent years, but the high production costs of specialized gratings remains a limiting factor for the technique’s broad application. The team behind the Nano Argovia project “NANOCREATE”, led by Dr. Konstantins Jefimovs (PSI), is therefore focusing on the development of alternative manufacturing method, to lower fabrication cost so that gratings can be produced on larger area and in higher volumes.
The scientists at PSI are developing a method based on metal assisted chemical etching to produce silicon structures of high aspect ratio, larger area and lower costs. These structures, which have low X-ray absorbance, are then filled with gold, strongly absorbing X-ray. They want to produce and test the grating performance manufactured by this new method on a lab CT-system. On the other hand, the team at FHNW is testing laser ablation as an alternative method to directly make the gratings from a metal foil. These techniques are now being examined in greater detail as part of the Nano Argovia project.
In addition to the project leader, Dr. Konstantins Jefimovs (PSI), the team consists of Professor Lucia Romano (PSI), Professor Ronald Holtz (FHNW), Dr. Bojan Resan (FHNW), as well as Dr. Martin Stauber and Dr. Zhentian Wang (both of GratXray AG). “The Nano Argovia project “NANOCREATE” will help us in our efforts to make grating interferometry available for a broad range of applications,” says Dr. Martin Stauber of GratXray, a spin-off company of PSI.