Current international standards restrict the use of the duplex-wire type IQI to evaluating basic spatial resolution， leaving its broader potential underexplored. This study seeks to extend the application scope of the duplex-wire type IQI by proposing novel methods for assessing radiographic system performance. Initially， a theoretical imaging model of the duplex-wire type IQI is developed， facilitating derivation of a formula for calculating the image contrast transfer function （CTF） and comprehensive analysis of the effects of IQI placement， radiation energy， and line spread function （LSF）. Subsequently， the least-squares method is employed to estimate the CTF， enabling calculation of the LSF and modulation transfer function （MTF）. Integration with an improved Akima interpolation method permits more precise measurement of the system's basic spatial resolution. Furthermore， the duplex-wire type IQI is utilized to calibrate the detector and characterize the focal spot shape of the radiation source， as well as to predict the LSF and MTF across varying imaging magnification ratios. The proposed approach has been rigorously validated using a 9 MeV micro-focus petal CT system and a 300 kV micro-focus industrial CT system developed in China. Experimental results demonstrate that the duplex-wire type IQI serves not only in measuring basic spatial resolution but also plays a critical role in quantifying the CTF， LSF， and MTF of radiation sources， detectors， and imaging systems， thereby offering a effective way for comprehensive performance evaluation of radiographic inspection systems.