Efficient microcancer detection in the small intestine can be realised by infrared fluorescence endoscopy (IRFE). The affected areas can be visualised through that technique in conjunction with an infrared fluorescent-labeling contrast agent, which is selectively uptaken by cancerous cells. In this paper we present a screening capsule prototype that is able to measure IR fluorescence levels emitted by fluorophore indocyanine green (ICG) of different concentrations. The mixed-signal system presented has small area footprint, and very little power requirements. In-vitro experiments have shown that the system is able to detect and discriminate low concentrations of ICG in the micromolar region, which is required to detect early cancer in the small intestine.