A dual-mode ultrasound array (DMUA) imaging system for monitoring and delivery of transcranial focused ultrasound (tFUS) therapy is described. A DMUA prototype operating in the frequency range 2.4 - 4.2 MHz has been shown to generate tFUS beams at therapeutic levels in rat brains in vivo based on two-dimensional image guidance. Furthermore, real-time ultrasound thermography was shown to be feasible using beamformed DMUA imaging data. In this paper, we demonstrate the use of 3D DMUA imaging for guidance of tFUS beam to specific locations within the brain defined with reference to the bregma. The results demonstrate the ability of the DMUA prototype to clearly resolve the lambda, bregma and the medial suture lines, which allows the precise placement of the focal spot at the target location in a repeatable manner within a single experiment session and from one session to another. This has significant impact on tFUS applications requiring multiple treatments of the same target region, e.g. temporal lobe epilepsy.