1. A method for metal artifact elimination in a medical image, operable in a medical imaging device, the method comprising: obtaining a medical image; determining a metal region in the medial image; determining a metal density value of the metal region; and performing an artifact elimination processing to the medical image when the metal density value of the metal region is greater than or equal to a preset density value, said artifact elimination processing comprising: determining a boundary region of the metal region as: forming a circular detecting area for determining a boundary region with each of the pixel points in the metal region being as a center of a circle, and presetting an initial radius; determining the circular detection area is the boundary region when a ratio between the metal region and the non-metal region within the circular detecting area is greater than or equal to a preset value, and reducing the initial radius gradually when the ratio between the metal region and the non-metal region within the circular detecting area is smaller than the preset value until the ratio between the metal region and non-metal region within the formed circular detecting area is greater than the preset value; and performing boundary smoothing processing to the boundary region.