Comparison of Low-Brilliance X-Ray Phase-Contrast Tomography and Contrast-Enhanced Attenuation-Contrast Micro-Computed Tomography of Rat Kidneys.

KEY POINTS

X-ray phase-contrast imaging provides superior contrast to attenuation-based X-ray imaging with soft-tissue samples. X-ray phase-contrast tomography is a viable alternative to contrast-enhanced attenuation-based micro–computed tomography in laboratory-based kidney imaging. X-ray phase-contrast imaging could be a suitable method for screening and characterization of rodent renal pathologies.

BACKGROUND

Structural analysis of soft biological tissues is conventionally conducted with destructive 2D histology. Three-dimensional information can be accessed with noninvasive imaging methods, such as X-ray micro–computed tomography (micro-CT). Although attenuation-based X-ray imaging alone does not provide reasonable contrast with soft-tissue samples, the combination with contrast-enhancing staining has proven effective. The staining process, however, comes with several disadvantages, such as tissue alterations and laboriousness. A novel X-ray imaging method known as phase-contrast imaging has emerged as an interesting alternative to contrast-enhanced micro-CT. Our objective was to show the feasibility of laboratory-based phase-contrast imaging in (murine) kidney research.

METHODS

X-ray phase-contrast images of male rat kidneys were acquired with a Talbot-Lau interferometer. Moreover, attenuation-based X-ray images of the same unstained kidneys were acquired with a regular micro-CT device. Afterward, the kidneys were stained with phosphotungstic acid for several months. Attenuation-based micro-CT images were reacquired after the staining. Contrast-to-noise ratio was evaluated for all three cases.

RESULTS

For unstained kidneys, the phase-contrast images show significantly improved contrast in comparison with attenuation images. Several key features, including the cortex, inner and outer medulla, papilla, as well as the main blood vessels, can be identified. While the contrast in attenuation images improves significantly after staining, the benefit is deteriorated by sample areas that the contrast agent did not reach properly, even after 206 days.

CONCLUSIONS

Our results indicate that X-ray phase-contrast imaging is a viable option for kidney imaging in a laboratory setting, providing comparable or better results than contrast-enhanced micro-CT. With imaging setups optimized for image resolution and faster imaging times, the advantages of phase-contrast imaging will be even greater.