Ghost artifacts occur in EPI reconstruction because odd and even lines of k-space are acquired with opposite polarity

and experimental imperfections such as gradient eddy current

B_0 field inhomogeneity

susceptibility

and chemical shift result in different phase offset between the even and odd echos.The method for removing ghost artifacts is based on the phase retrieval.First

a ROS(region of support) is specified using morphological method and ghost artifacts outside ROS are set to zero.Then a model image can be obtained.According to the criterion of entropy in the imaging field

the algorithm for several iterations is applied to obtain an acceptable image.It is shown that applying this method will reduce the ghost artifact evidently.The method has been tested using computer simulation and successfully removed most of ghost artifacts.The experimental results show the effectiveness of the method.