The Sentinel system consists of a scanner unit, containing the laser and the camera, and
surface-matching registration software. For the registration procedure, both a computed tomogra-
phy (CT) and a Sentinel image can be used as a reference. Tests were performed on phantoms using
an Elekta Synergy V
R
beam modulator Linac equipped with a cone beam CT (CBCT), a HexaPOD
RT couch top, and an iViewGT portal imaging system. Experiments conducted in this study tested
reproducibility of the Sentinel surface acquisition and of set-up procedure, accuracy in quantifying
known phantom mispositioning, and compared Sentinel, CBCT, and portal imaging system
performance.