1. A binary image reconstruction method to identify metal objects in a computer tomography (CT) image, comprising: a. providing a suitably programmed computer; b. providing a CT image, wherein said CT image comprises intensity data, wherein said suitably programmed computer is used to determine a first range of attenuation coefficient values and a second range of attenuation coefficient values in said intensity data, wherein when a difference between said first range of attenuation coefficient values and said second range of attenuation coefficient values is less than a pre-determined gradient threshold value a boundary of a metal object in said CT image is determined.