A well integrity inspection system configured to inspect a well structure including multiple concentric layers. The well integrity inspection system includes an inspection probe positioned in the well structure. The inspection probe includes a plurality of excitation assemblies for transmitting a plurality of radiation emissions into the well structure. The plurality of excitation assemblies includes at least a neutron excitation assembly and an X-ray excitation assembly. The inspection probe also includes a plurality of detection assemblies configured to receive a plurality of backscatter radiation returns from the well structure. The plurality of detection assemblies includes at least a neutron detection assembly and an X-ray detection assembly. The well integrity inspection system further including a processor operatively coupled to the inspection probe. The processor is configured to determine a well integrity parameter of the well structure based on at least one of the plurality of backscatter radiation returns.