Tracking radioactive sources in 3D can impact homeland security, airport/port surveillance and the military. Unfortunately, the radiological sensors with the highest SNR and the lowest price are unidirectional - i.e. they integrate radiation from a sphere of directions centered at the sensor. We combine such devices with commercially available depth sensors to break this directional ambiguity. We first introduce radiological sensing as an application area for the 3D vision community. Next, we propose a joint calibration algorithm for 3D sensors and unidirectional, or single cell, radiological sensors. Finally, we show applications for tracking people carrying radiological sources.