Radioactive hotspots reconstruction is a significant challenge when characterising radioelements in environments that have been impacted by radiological or nuclear activity. A thesis proposal aims to address this issue by developing a compact, highly sensitive multimodal instrument for assessing and characterising gamma-ray and neutron contributions. This system will help to meet the encountered challenges, during decommissioning and dismantling (D&D) operations, in nuclear industry sites. To do this, it will incorporate spectro-imaging specifications to ensure the identification and location of present radioelements. The state of art has already demonstrated the advantages and benefits of combining ionising radiations spectrometry and imaging. However, the suggested solutions show difficulties in deploying measurement systems (size, weight), as well as a sensitivity incompatible with the ground constraints. Results obtained in the frame of thesis works, carried out at SIMRI (Service Instrumentation et Métrologie des Rayonnements Ionisants), have led to the development of a gamma and neutron spectro-imager prototype.