Abstract
It is difficult to evaluate human soft tissues in detail using conventional X-ray absorption imaging due to the small density differences. By analyzing the phase shifts based on the inherent characteristics of X-ray waves, it is possible to obtain images of soft tissues with approximately 1000 times higher sensitivity as compared to the conventional method employing X-ray absorption. Using a phase-contrast X-ray CT system with an X-ray interferometer, we obtained images of rat hearts fixed in either formalin or ethanol. After each rat was anesthetized, it was perfused with physiological saline solution and fixed with either formalin or ethanol. The heart was surgically resected and replaced in each solution, and phase-contrast X-ray CT imaging was then performed at KEK. Formalin fixation has traditionally been used to prepare tissue samples, but we employed ethanol fixation to further enhance image contrast. In phase-contrast X-ray CT images, three myocardial layers (the endocardium, midcardium, and epicardium) were clearly depicted in the ethanol-fixed hearts, but these myocardial structures were not visible in the formalin-fixed hearts. Observation of this myocardial layer structure makes it possible to analyze abnormalities such as injury to specific myocardial layers, which previously could not be visualized.
