Abstract: A computerised boundary estimation technique (using prostate as an example) in medical images (ultrasound in particular), called Radial Bas-Relief. An imaging probe can be carried by a robot and shares the same reference frame as the robot. The prostate is scanned and the ultrasound images are fed into a computer which provides computational images processing. Such a method is employed to allow a quick and robust extract of the boundary of interest from transverse images taken transurethrally or transrectally.