1. A calibration phantom system for use with an imaging system, said calibration phantom comprising: a first phantom element material block having a first surface at a first height, said first phantom element material block at least partially comprising a first material having a first attenuation coefficient; and a second phantom element material block having a second surface at a second height different than said first height, said second phantom element material block at least partially comprising a second material having a second attenuation coefficient different than said first attenuation coefficient, said first phantom element material block and said second phantom element material block co-positioned on a detector.