Visualization of Reissner membrane and the spiral ganglion in human fetal cochlea by micro-computed tomography.

PURPOSE: Although visualization of fine structures in the cochlea such as Reissner membrane (vestibular membrane) is important for elucidation of the mechanism and the establishment of therapy for inner ear diseases, they cannot be visualized by even the most advanced high-resolution medical computed tomography (CT) and magnetic resonance imaging. Visualization of Reissner membrane in dissected animals by micro-magnetic resonance imaging has been reported, but bone could not be visualized. We attempted to visualize human fetal Reissner membrane and the spiral ganglion by micro-focus x-ray CT (micro-CT), which has a spatial resolution several hundred times greater than the conventional medical CT. MATERIALS AND METHODS: Serial tomograms of a dissected pyramis, including the cochlea of human fetuses (stillborn specimens), were obtained by micro-CT, and 3-dimensional reconstruction was performed by a volume-rendering method. RESULTS: Clear tomograms (theoretical spatial resolution, 12.2 x 12.2 microm; slice thickness 77.5 microm) and 3-dimensional reconstructed images (theoretical spatial resolution, 6.8 x 6.8 microm; slice thickness, 40.0 microm) of Reissner membrane and the spiral ganglion with a bony labyrinth (cochlear bone) were successfully obtained for the first time. The thickness of Reissner membrane obtained by the tomogram was 12 microm, which corresponds to the optical macroscopic value from resin-embedded histologic sections. CONCLUSIONS: This study showed that micro-CT enables us to visualize the internal fine structure of the human cochlea. As the success rate of the visualization of Reissner membrane is not high, it is necessary to improve the image quality and contrast resolution of micro-CT to enable stable visualization of fine structures. The development of imaging equipment such as micro-CT for medical use should play an important role in the elucidation of the mechanism and the establishment of therapy for inner ear diseases.

Micro-focus X-ray computed tomography images of the 3D structure of the cranium of a fetus with asymmetric double malformation.

Reconstructed micro computed tomography (Micro-CT, micro-CT) images have revealed the detailed three-dimensional structure of the cranium of human fetal congenital anomalies for the first time. The objects were a head and a cervix of female autosite and a parasite consisting of only a head conjoined to the scapular region of the autosite of an asymmetric double malformation (asymmetric conjoined twins, heteropagus twinning) at a gestational age of 8 months. The cranium of the autosite was normal, but that of the parasite was characterized by otocephaly (agnathia, synotia, and monorhina) and almost all the cranial bones were of an abnormal shape. It is suggested that a part of occipital bone (the basioccipital and exoccipital bones), the vomer and cribriform plate were absent and this resulted in the fusion and overlapping of bilateral temporal and craniofacial bones that should have been adjacent to them. This resulted in a reformation and relocation of most of the cranial bones. Micro-CT is a useful tool to visualize the detailed bone structure which has not been clarified by the conventional dissection methods and other imaging technologies and is a powerful instrument for studying congenital anomalies.