Ethanol fixation method for heart and lung imaging in micro-CT

Purpose The soft tissue imaging in micro-CT remains challenging due to its low intrinsic contrast. The aim of this study was to create a simple staining method omitting the usage of contrast agents for ex vivo soft tissue imaging in micro-CT. Materials and methods Hearts and lungs from 30 mice were used. Twenty-seven organs were either fixed in 97% or 50% ethanol solution or in a series of ascending ethanol concentrations. Images were acquired after 72, 168 and 336h on a custom-built micro-CT machine and compared to scans of three native samples. Results Ethanol provided contrast enhancement in all evaluated fixations. Fixation in 97% ethanol resulted in contrast enhancement after 72 h; however, it caused hardening of the samples. Fixation in 50% ethanol provided contrast enhancement after 336 h, with milder hardening, compared to the 97% ethanol fixation, but the visualization of details was worse. The fixation in a series of ascending ethanol concentrations provided the most satisfactory results; all organs were visualized in great detail without tissue damage. Conclusions Simple ethanol fixation improves the tissue contrast enhancement in micro-CT. The best results can be obtained with fixation of the soft tissue samples in a series of ascending ethanol concentrations