Proactively identifying and interdicting transport of commodities associated with illicit nuclear materials and nuclear weapons shielded by high Z-number materials, such as lead, can help ensure effective nuclear nonproliferation. In an embodiment, a method for imaging an object on a surface includes exciting a surface with ultrasonic excitation from an ultrasonic transmitter having an ultrasonic transducer in contact with the surface. The method further includes imaging, at a processor, a two-dimensional representation of the object acoustically coupled to the surface based on the ultrasonic reflections received at an ultrasonic receiver via a receiving transducer in contact with the surface. This method can complement existing x-ray screening systems to increase the odds of detecting radiological materials.
