This chapter focuses on the MARS extremity imaging system, which is a small footprint shielded system, designed to bring advanced spectral photon-counting CT (SPCCT) to the point of care. MARS SPCCT provides high spatial resolution and excellent spectral fidelity. High resolution imaging of cortical and trabecular bone is key for orthopaedic applications where accurate assessment of fracture healing is significant for clinical decision-making. For patients with metal implants, resolution at the bone–metal interface is critical for early detection of complications in an area that is traditionally affected by beam hardening artefact. The technology provides charge summing capability and high energy resolution which, together with proprietary algorithms, enables highly accurate measurements for fat, water, and calcium. Metrics have many applications including, for example, the evaluation of avascular necrosis, osteoporosis, and monitoring response to treatment. Important vascular applications include the identification and characterization of carotid plaques. Results from clinical and pre-clinical research are provided as evidence of the recent advances in SPCCT.