Additive Manufacturing techniques such as Selective laser melting (SLM) are increasingly used in the fabrication of hip, knee and other orthopaedic implants. This is due to the ability of these techniques to print geometrically complex parts with osteoconductive features, resulting in a decreased chance of aseptic loosening. To facilitate wider adoption of SLM, in-situ process monitoring is required. This paper examines the robustness of a novel monitoring systems ability to detect voids within the bulk of a component with varying part density. This work reports the results of a printing study carried out with Ti6Al4V parts using a production scale Renishaw system. This system is equipped with the recently developed in-situ monitoring system, called InfiniAM Spectral. InfiniAM measures the level of optical emissions emitted during the build process. The Spectral software creates a 3D representation of the part, in near real time, based on the level of emissions detected. In this work, Spectral 3D images are compared with those generated after printing using a micro CT scanner. The latter creates a virtual 3D representation of the part and has the ability to detect part defects and voids, as well as quantify part density, within the body of a component. In this work, parts were designed with voids of diameters in the range 200 to 600 μm. The sensitivity of the in-situ monitoring system was correlated with post process analysis of the void dimensions. Additionally, the detection of part density variation due to a variation of input energy, was also evaluated.