This paper presents a novel Augmented Reality
(AR) probe and method for use with image-guided surgical
navigation systems. Its purpose is to enhance existing systems
by providing a video image of the therapeutic site augmented
with relevant structures preoperatively defined by the user. The
AR probe consists of a video camera and a tracked reference
plate mounted on a lightweight ergonomic casing. It directly
connects to the navigation tracking system, and can be handheld
or fixed. The method automatically updates the displayed
augmented images to match the AR probe viewpoint without
additional on-site calibration or registration. The advantages of
the AR probe are its ease of use close to the clinical practice,
its adaptability to changing viewpoints, and its low cost. Our
in-vitro experiments show that the accuracy of targeting under
AR probe guidance is 1.9 mm on average.