Computer-assisted interventions (CAI) typically require localization (tracking) of surgical instruments and the patient. For ultrasound (US)-guided interventions, a new compact electromagnetic (EM) field generator enables construction of a combined modality which allows for both, EM tracking and US imaging with one handheld device. In this study, we present a research prototype of such a device and conduct accuracy assessments in a clinical US suite. The results show robust US imaging and EM tracking of the combined device, which emerges as a promising component for US-guided CAI systems.