Photon Counting Detector Improves Low Contrast CT Resolution

Achieving the limits of resolution in nanofocus X-ray inspection requires finding the most appropriate combination of X-ray detector and X-ray source. A joint project to explore the capabilities of their components was initiated by ADVACAM s.r.o from Czech Republic and X-RAY WorX GmbH from Germany. The combination of ADVACAM’s photon counting WidePIX detectors with the nanofocus tube XWT-190-TCNF yielded a performance even below the tube’s nominal resolution of 0.5 microns.

ADVACAM develops the WidePIX line of high-resolution detector arrays with 55 microns pixel size using Si or CdTe sensors. By specifying energy bins, a very high sensitivity and low noise, especially for low contrast material, can be achieved. During the experiments, Si sensors of 500 microns thickness were used to image resolution test charts.

X-RAY WorX has designed the product line TCNF of nanofocus X-ray sources for highest resolution CT applications. Special diamond-based transmission targets and an internal cooling of the electron optics allow for various applications in semiconductor industry and material science.

For the experiments, the tube and detector were set up on a granite base. The resolution test charts were mounted on a micro-manipulator. Different exposure times were evaluated. At 50 seconds exposure, the 0.4 microns line patterns of JIMA RT RC-02b and NTT-AT X-Reso-100 were clearly resolved at voltages of 150kV and 190kV. At 100kV the 0.5 microns pattern of JIMA RT RC-02b was resolved. These results undercut the nominal values specified by X-RAY WorX for the product line TCNF by 20% (at 150kV and 190kV).

The joint experiments of ADVACAM and X-RAY WorX showed an amazing improvement of low contrast resolution when working with a photon counting detector. By excluding parts of the X-ray spectrum from the image, the WidePIX detector offers better contrast and unveils structures otherwise covered by quantum noise.

For more information: www.x-ray-worx.com


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