**Dual Energy Imaging**

In x-ray imaging, pixel values represent effective attenuation measurements of an object in the beam and can be expressed by the following equation:

N = N0e-*u*t

Where N is the number of detected photons, N0 is the number of photons incident on the object, u is the attenuation coefficient and is material specific and a function of energy, tis the object thickness. When imaging two distinct materials, the equation becomes:

N = N0e-(*u*jtj+*u*ata)

Only in limited situations with specific* a priori* knowledge can information about the thickness of both materials be discerned from a single measurement.