Non-destructive X-ray imaging with Talbot interferometry
X-ray images you can obtain
Using X-ray Talbot interferometer, differential phase contrast images and visibility contrast (dark field or small-angle scattering contrast) images can be obtained in addition to ordinary X-ray absorption images on one set-up, which allows you to get far more information of the inside and surface of the sample than the conventional X-ray absorption imaging method.
In the example images below, you will find the difference of the obtained information between the different modalities (absorption contrast and differential phase contrast) of the same sample taken at the same time.
Absorption contrast image |
Differential phase contrast |
In the example pictures below you find a differential phase contrast image and small-angle scattering image (dark field image) of a piece of old rubber tube. The dark field imaging is highly sensitive to structural change and density changes of tissues like lungs and can identify lung diseases where conventional X-ray imaging cannot do. Now, intensive efforts are geared at the realisation of medical equipments using the Talbot-Lau interferometry for imaging breast and lung diseases.
Differential phase contrast image |
Small angle scattering image (dark field image) |
Talbot Interferometer: Multi modal X-ray imaging method using X-ray gratings
By adding a source grating (absorption grating) G0 to a Talbot interferometer set-up, coherent X-ray can be obtained from a standard X-ray tube (Talbot-Lau interferometer).
Talbot-Lau interferometry system (TALINT) set-up example
Talbot Lau set-up exmple Microworks suggests
| Talint-EDU | Option 1 | Option 2 |
|---|---|---|
| Design energy | 40 keV | 21 keV |
| Talbot order | 1 | 3 |
| FOV | 70 mm round | 70 mm round |
| Phase stepping visibility | > 20% | > 20% |
| Total length | 600 mm | 600 mm |
| G0-G1 distance | 290 mm | 290 mm |
| G1-G2 distance | 290 mm | 290 mm |
| G0，G2 gold thickness | > 120 µm | > 40 µm |
| p0 (G0 period)，p2 (G2 period) | 6.0 µm | 4.8 µm |
| p1 (G1 period) | 6.0 µm | 4.8 µm |
| Angular sensitivity (p2/(G1-G2)) | 21 µrad | 17 µrad |
| G0 and G2 substrate | Graphite 400 µm | Graphite 400 µm |
| G1 substrate | Silicon 200 µm | Silicon 200 µm |
X-ray gratings from Karlsruhe, Germany
Karlsruhe Institute of Technology (KIT)/IMT and its spin-off company Microworks GmbH have a long experience in the fabrication of micro structures by X-ray lithography and electroplating (LIGA process) and they supply worldwide high aspect ratio X-ray gratings necessary for Talbot interferometer.
High aspect ratio absorption grating |
Bent absorption grating to avoid shadow effects |
Grating structure examples
X-ray gratings are made by copying the precision structure of an X-ray mask onto the resist on the substrate, followed by electroplating done between the gaps of the X-ray exposed resist lamellae. Grating layout designs can either be chosen from existing masks or be newly made for your special set-up.
| Absorption grating | Phase grating | |
|---|---|---|
| Metal height (examples) | 250 μm | 4.0 μm |
| Period (metal + space) | 4.8 μm | 3.57 μm |
| Material | Au | Ni |
Grating standard specifications
Here are some examples of grating specifications and some options which do not require special development.
| Absorber / Phase shift material | Au, Ni or polymer resist |
|---|---|
| Substrate |
Standard: Si wafer (200 or 550 µm) Optional: Low X-ray absorption materials like graphite and polyimide |
| Structured area |
Standard: 70 mm diameter Optionald: 100-140 mm diameter, 100 mm x 90 mm Further larger area by stitching some plates. See also bleow, "Development 1: Large area gratings". |
Development 1: Large area X-ray gratings
Microworks has realised large area X-ray gratings with increased FOV for dark-field imaging of lung and breast diseases.
Large FOV absorption gratings for Talbot-Lau interferometry, fabricated by Microworks. Gratings have a chest size, 350 mm x 30 mm (top), 400 mm x 30 mm (bottom), for clinical testing of X-ray dark field radiography of the lung. Much improved radiographic diagnostic of lung pathologies, including COVID-19, with radiation dose comparable to conventional chest X-ray is expected.
Large area gratings: Spec examples
| Single grating | Tiled gratings | |
|---|---|---|
| Structured area | 200 mm x 100 mm | e.g. 400 mm x 30 mm |
| Grating period | 7.0-10.0 μm | Ask us |
| Gold thickness | Up to 200-250 μm | Up to 200-250 μm |
| Substrate material | Si | Si |
Development 2: Very narrow period gratings for hard X-ray
Gratings for hard X-ray with very narrow periods of 1.0 to 2.0 µm are realised in some limited structure areas.
Grating structure with a line width of 0.5 µm |
Ring-shape structure, line width 1.0 µm |
| Phase grating 18 keV, π/2 |
Phase grating 26 keV, π/2 |
Absorption grating | |
|---|---|---|---|
| Period | 2.0 μm | 1.0 μm | 1.4 μm |
| Metal material | Ni | Au | Au |
| Structure height | 3.2 μm | Up to 5 μm | > 20 μm |
| Structured area | 10 mm x 10 mm | 5 mm x 5 mm | 20 mm x 20 mm |
| Substrate material | Polyimide | Si 200 µm | Polyimide and others |
| Structure design | Continuous line | Bridge | Bridge |
Manufacturers and recent results
Manufacturers
Karlsruhe Institute of Technology (KIT)/IMT and its spin-off company Microworks GmbH supply X-ray gratings for Talbot and Talbot-Lau interferometers not only with standard specifications described above but also with ones based on the customers' special requirements. ASICON Tokyo Ltd. serves as their local distributor and as technical partner of customers in Japan, South Korea and Taiwan.
KIT/IMT and Microworks GmbH are two of the world's top authorities in the fabrication of high aspect ratio polymer and metal structures using X-ray lithography and electroplating techniques. With these techniques (LIGA Process), X-ray gratings with both a narrow period and high aspect ratio have been realised.
Imaging examples
■ Internal link (Japanese): X-ray images of some samples taken with X-ray gratings fabricated by Microworks GmbH
[KIT/IMT and Microworks GmbH]