Ultrasound is an increasingly popular imaging modality in image-guided interventions, due to its safety, accessibility, and low cost. But ultrasound imaging has a steep learning curve, and requires significant coordination skills from the operator. It is difficult to interpret cross-sectional anatomy in arbitrary angles, and even more challenging to orient a needle with respect to the ultrasound plane. Position tracking technology is a promising augmentation method to ultrasound imaging. Both the ultrasound transducer and the needle can be tracked, enabling computer-assisted navigation applications in ultrasound-guided spinal interventions. Furthermore, the patient can also be tracked, which enables fusion of other imaging modalities with ultrasound. In this chapter, we first present the technical background of tracked ultrasound. We will review how to build research systems from commercially available components and open-source software. Then we will review some spine-related applications of tracked ultrasound modality, including procedural skills training, needle navigation for anesthesia, surgical navigation, and other potential applications.