Figure 4.

Polychromatic spectrum of our tabletop CT system. (a) Spectrum from our x-ray tube after 4 mm of Al filtrations at 120 kVp; (b) energy deposition efficiency of our CsI scintillator with 270 mg∕cm² of thickness; (c) spectrum of the x-ray system χ(E) in Eq. 13; it is the product of (a) and (b). When simulating the spectrum from the x-ray tube, a tungsten target with a 12° target angle was used, and three electron interactions (multiple scattering, ionization, and bremsstrahlung) and two photon interactions (photoelectric absorption and Compton scattering) were included in the physical process. The energy deposition efficiency of the scintillator was simulated by calculating the deposited energy in the scintillator, where photoelectric absorption and Compton scattering were involved.