Research On Phase Retrieval Methods Of In-line Phase-contrast Imaging And Phase-contrast Tomosynthesis

Tomosynthesis is a three-dimensional imaging technique that can remove theeffect of superimposed phenomena in radiography. In general, computed tomography(CT) needs at least hundreds of projections to reconstruct each cross-sections of thesamples accurately, while tomosynthesis just requires dozens of projections toreconstruct a series of tomosynthetic planes approximately, with much fewerradiation doses. Conventional tomosynthesis which is based on the absorptioncontrast shows poor results when imaging weak-absorption objects such as biologicalsamples, which can be obtained higher contract resolution by use of X-rayphase-contrast imaging methods based on significant phase shifts. So, phase contrasttomosynthesis, which combines the advantage of phase-contrast imaging andtomosynthesis, can provide better results for weak absorption objects with fewerradiation doses and avoid superimposed phenomena.Here, we will first give an introduction on in-line phase-contrast imaging, andgive an evaluation correction factor for in-line X-ray phase-contrast ComputedTomography. With a phase-contrast CT experiment on two samples (a polyethylenetube and a mouse cochlear) at Shanghai Synchrotron Radiation Facility (SSRF), thevalidity of correction factor was quantitatively verified, which will help to retrievephase information for phase contrast tomosynthesis.Then, we will give an introduction on the principle of tomosynthesis andtomosynthetic algorithms. In-line phase-contrast tomosynthesis experiment andgrating-based phase-contrast tomosynthesis experiment are presented in this paper.With the mouse cochlear data acquired at SSRF and Paul Scherrer Institut (PSI), aseries of phase-contrast tomosynthetic planes were generated by SAA, MITS, FBPand ART methods. Compared with the results of phase-contrast CT, the results ofphase contrast tomosynthesis are not as good as CT’s, but phase contrasttomosynthesis need much fewer projections, which will radiation doses significantly.It was proved that phase-contrast tomosynthesis could highly enhance the information of detailed structures of weak absorption objects and mostly remove superpositionphenomenon.