Phase-contrast X-ray CT images generated by differences in refractive
indices can be used to visualize the internal structures of soft tissu
es without contrast enhancement. In this study, imaging of human breas
t tumor was performed on formalin-fixed samples. Experiments were carr
ied out at the synchrotron source of the Photon Factory, Tsukuba, Japa
n. The X-ray energy was adjusted to 17.7 keV. Phase-contrast X-ray CT
images revealed various structures of human breast tumor as clearly as
optical images.