Imaging a microfocus X-ray focal spot with a thin coded aperture.

Area of Science:

• Medical Imaging
• X-ray Microscopy
• Materials Science

Background:

• Imaging microfocus X-ray generator focal spots requires thin, highly attenuating materials like gold.
• Low attenuation in thin gold pinholes (e.g., 5 µm) results in poor signal-to-noise ratio (SNR < 1).
• Existing coded aperture techniques primarily reduce exposure time, not enhance SNR in low-attenuation scenarios.

Purpose of the Study:

• To develop and validate a coded aperture imaging method for enhancing SNR in microfocus X-ray focal spot characterization.
• To adapt coded aperture technology for low-attenuation imaging conditions.
• To improve the visualization and quantification of micro-X-ray focal spots.

Main Methods:

• Utilized a no-two-holes-touching variation of a modified uniformly redundant array (MURA) coded aperture.
• Employed a prototype with 5 µm gold featuring 2.75 µm holes.
• Applied the technique to image the focal spot of a microfocus X-ray generator used in a micro-CT system.

Main Results:

• Successfully visualized and quantified the focal spot of a microfocus X-ray generator.
• Achieved clear imaging despite very low attenuation (11% with 5 µm gold).
• Observed directionality in aberrations, aiding intuitive focusing and reducing optimization time.

Conclusions:

• The MURA coded aperture technique effectively enhances SNR for imaging small X-ray focal spots in low-attenuation materials.
• This method offers a viable solution for accurate focal spot characterization in micro-CT systems.
• Improved focusing intuitiveness and reduced optimization time contribute to more efficient X-ray generator performance analysis.