Abstract
OBJECTIVE
1) Verify the method of inline phase contrast imaging of soft tissue within closed cochleae. 2) Optimize phase contrast computed tomography (PCCT) image reconstruction of soft tissue within closed cochleae.
METHOD
This is an experimental animal study. Image acquisition was conducted from 7/2008-11/2008 at the Advanced Photon Source of Argonne National Laboratory, where phase contrast images of mice and gerbil cochleae were captured using hard X-rays. Parameters included: photon energy 15-31.5keV, full width half maximum 630 m × 28 m, monochromatic flux 1013 photons/second, and beam size 1-2 mm2 at a distance 70 m from the source. The experimental image processing was conducted from 11/2008-2/2010. Qualitative analysis was compared for data sets from 12 cochleae, to determine processing parameters for optimal spatial resolution and anatomical identification. A rendered and segmented three-dimensional model of the decalcified mouse cochlea was created. Three-dimensional tomographic reconstructions were produced by the weighted back projection algorithm. The spatial resolution was determined by taking the lowest Full-Width Half-Maximum of the line spread function, measured using a sharp edge on Reissners membrane for the optimally oriented, decalcified mouse cochlea.
RESULTS
Optimized PCCT reconstruction of a decalcified mouse cochlea revealed outer pillar cells, inner pillar cells, inner spiral sulcus, outer hair cells, tectorial membrane, basilar membrane pectinate zone, and Reissners membrane. The spatial resolution was determined to be 1.9 m.
CONCLUSION
The results demonstrate the ability of PCCT to image cochlear structures at an unprecedented cellular level through the decalcified bony capsule. Future experiments will continue to refine imaging and reconstruction parameters to optimize imaging results.