Radiological characterisation plays a crucial role in nuclear engineering, providing essential tools for the accurate assessment and management of radioactive materials across diverse sectors, including nuclear decommissioning and CBRN (Chemical, Biological, Radiological, and Nuclear) threat mitigation. Innovations are underway to enable specialists to operate safely from a distance. This thesis conducts a comparative analysis of radionuclide detection and imaging technologies, focusing on two distinct systems. The first is the Tomographic Gamma Scanner (TGS), a stationary device that utilizes a High-Purity Germanium (HPGe) detector for 3D analysis of object matrix density and radionuclide activity. The second is a portable gamma-ray imaging spectrometer, equipped with a Cadmium Zinc Telluride (CZT) detector.