BACKGROUND:
Dual-energy computed tomography (DECT) can reconstruct electron density ρ
e
and effective atomic number Z
eff
distribution for material discrimination. Image-domain basis material decomposition (IBMD) method is a widely used DECT method. However, IBMD method cannot be used for mineral identification directly due to limitations of complex basis material determination, beam hardening artifacts, and inherent errors caused by approximate empirical formulas.
OBJECTIVE:
This study proposes an improved IBMD (IIBMD) method to overcome the above limitations.
METHODS:
In IIBMD method, the composition of basis material is optimized to obtain accurate decomposition coefficients, which enables accurate ρ
e
and Z
eff
distribution. Moreover, the thickness of basis material is optimized to reduce the effect of beam hardening. Furthermore, two formulas in place of empirical formulas are proposed to calculate ρ
e
and Z
eff
. Finally, a threshold technique is applied to separate different mineral phases.
RESULTS:
Numerical simulations and practical experiments using a photon-counting detector CT system are implemented to verify IIBMD method. Results show that the relative errors of ρ
e
and Z
eff
for seven common minerals are down to 5%, lower than most of the existing DECT methods for rocks. Reasonable volume fraction results of mineral phases are thus obtained through threshold segmentation.
CONCLUSIONS:
This study demonstrates that the proposed IIBMD method has high practical value in mineralogical identification.
