A detector assembly includes scintillators configured to generate a light signal in response to an impinging backscatter signal, where the scintillators are arranged in a first pattern, a plurality of first detectors, where each first detector is coupled to a scintillator and configured to receive a first portion of a light signal from that scintillator, and where the first detectors are arranged in a second pattern aligned with the first pattern, a plurality of second detectors, where each second detector is disposed adjacent a scintillator and configured to receive a second portion of the light signal from that scintillator, and where the plurality of second detectors is arranged in a third pattern, and a scintillator collimator including a plurality of openings and configured to selectively receive the backscatter signal, where the detector assembly is configured to provide depth resolution, azimuthal resolution, a defect type, a defect size, or combinations thereof.