Research On The Performance Of Dual-energy CT System

Compared with conventional CT from which we can only get effective linearattenuation coefficients, dual energy CT can be used to obtain atomic number andelectron density in order to discriminate different materials. As a result, dual energy CTis widely used in both security field and medical treatment field. However, thereconstruction error of dual energy CT is relatively large, especially in atomic number.There are many possible factors leading to the big error including the approximation ofdual energy decomposition, discretization error, statistical noise, etc. No systematicanalysis of error and noise propagation on dual energy CT has been put forward up tonow. We have not got a clear understanding of the contribution to final results of eachstep in dual energy CT.Our main task is to give a systematic analysis of error and noise propagation ondual energy CT, aiming at providing advices for the designing of dual energy CTsystems. We have derived related theoretical formulas and given experiment results.In error analysis, we firstly studied on influences on reconstruction results of X-rayenergy discretization, detector number discretization, projection angle numberdiscretization and approximation of dual energy decomposition. Discretization error canbe limited to a negligible level by increasing the degree of discretization. The mainsource of results error comes from the approximation of dual energy decomposition.Besides, we studied on X-ray energy spectrum estimation error. We obtained someformulas on error propagation of spectrum estimation, proposed the definition ofequivalent spectrum and gave parameter optimization methods on spectrum estimation.In noise analysis, we modeled the noise of the projection data. Considering FBPreconstruction method, we analyzed the noise propagation in dual energy decomposition,CT reconstruction, solving atomic number and electron density. Theoretical calculationmethods are derived and formulas are put forward. We give experiment results forverification. This study is significant for noise estimation in dual energy CT.