Study On Dose And The Effect Of Scattering Photon On Imaging Quality In X-ray Grating-based Phase Contrast Imaging

Because of the disadvantages of the traditional X-ray imaging techniques:high dose rate and poor imaging quality of light elements,X-ray phase contrast imaging method based on X-ray phase change has been developed since the 1990s.A great many of researches have been done since then.The X-ray grating-based phase contrast imaging method has been a research hotspot,because of its advantages:using ordinary X-ray sources.This paper built up a model in MCNP(Monte Carlo Neutron and Photo Transport Code)program,which is on the strength of the X-ray phase contrast CT pro-totype designed by NSRL(National Synchronous Radiation Laboratory),in order to study the problems of absorbed dose changes and scattering photon,which can provide the basis for the separation of scattered and absorbed signals and can also be a reference of X-ray energy and sample selection.In this paper,simulations of POM samples(? 5 mm,? 10 mm),PMMA samples(? 5 mm,? 10 mm)and water tanks with a series of thicknesses after X-ray radiation exposure have been done.The energy range of X-ray is 30-100 keV.The total non-scattering photon counts and scattering photon counts in different areas of a detector surface have been programed.The results show that energy deposition in different samples and water tanks can reach to the lowest when the X-ray energy is 60keV or slightly lower than 60 keV.When the density of sample is higher,and the exposure area is lager,the absorbed dose will be higher.The counts of scatter-ing photon is 1000-10000 times smaller than the counts of non-scattering photon.When the thickness of water tank is between 8 and 12 cm,the ratio of the counts of scattering photons and non-scattering photon are larger than other thicknesses.There are no obvi-ous rules for scattering photon counts of small samples,but the results of non-scattering photon counts can indicate the position of sample.The results of these two type counts represent the similar rules.If current CT imaging reconstruction techniques and irradi-ation protocols were used,the absorbed dose still cannot achieve the target of less than 10%of the current CT dose for phase-contrast CT design,and it needs to be matched with better new technologies.Subsequent studies can use human tissues and organs as irradiated samples for further study.