We present the prototype of an image-guided robotic system for accurate, consistent placement of percutaneous needles in soft-tissue targets under CT guidance inside the gantry of a CT scanner The couch-mounted system consists of a seven-degrees-of-freedom passive mounting arm, a remote center-of-motion robot, and a motorized needle-insertion device Single-image-based coregistration of the robot, image space is achieved by stereotactic localization using a miniature version of the BRW head frame built into the radiolucent needle driver The surgeon plans, controls the intervention in the scanner room on a desktop computer that receives DICOM images from the scanner The system does not need calibration, employs pure image-based registration, and does not utilize any vendor-specific hardware or software features In the open air, where there is no needle-tissue interaction, we systematically achieved an accuracy better than 1 mm in hitting targets at 5-8 cm from the fulcrum point In the phantom, the orientation accuracy was 0 6 degrees, and the distance between the needle tip, the target was 1 04 mm Experiments indicated that this robotic system is suitable for a variety of percutaneous clinical applications