(Sunday, 7/14/2019) 3:30 PM - 4:00 PM
Room: Exhibit Hall | Forum 8
Purpose: To investigate the effect of incident x-ray spectrum on the CT image quality of an ex vivo mouse scanned with an experimental dual mode benchtop CT and x-ray fluorescence CT (XFCT) system.
Methods: Cone-beam CT scans of a euthanized mouse were performed using the current CT/XFCT system. The mouse was placed 39-cm away from the x-ray source and the flat panel detector was placed 5.5-cm away from the rotation axis. The CT image quality was tested using three different incident beams: i) a beam with x-ray spectrum suitable for small animal CT imaging (Cu & Al-filtered 40 kVp, 10 mA, 1-mm focal spot size), ii) a beam with x-ray spectrum optimized for XFCT imaging (Sn-filtered 125 kVp, 24 mA, 5.5-mm focal spot size), and iii) a beam with x-ray spectrum optimized for XFCT imaging but with different tube current and focal spot size (Sn-filtered 125 kVp, 5.1 mA, 1-mm focal spot size).
Results: The key internal and external anatomical structures of the mouse were visible with sufficient CT contrast when scanned using the 40 kVp beam, whereas the internal structures were not distinguishable when scanned using the 125 kVp beams involving considerably hardened x-ray spectra. Between the two 125 kVp beam spectra tested, the 24 mA beam resulted in > 2x better CT contrast than the 5.1 mA beam, primarily because of larger imaging dose delivered with the 24 mA beam.
Conclusion: The current results show the difficulty in obtaining the attenuation map required for the XFCT image reconstruction using the beam optimized for XFCT imaging. While it is worth investigating the possibility of improving the CT image quality using the 125 kVp beams, an immediate solution for the currently shown difficulty can be found by performing CT and XFCT sequentially using 40 kVp and 125 kVp beam, respectively.
Funding Support, Disclosures, and Conflict of Interest: Supported by NIH/NIBIB R01EB020658
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