ABSTRACT
Image-based trackers are a exible and robust solution to the problem of nding an internal target. ey can be used alone or in conjunction with surrogates. ey are usually used as a point localization device but can also be used to nd larger objects or curves. Images can be used to localize implanted objects and natural anatomical landmarks, and they can be processed to track multiple targets. e chief disadvantage of image-based trackers is that they are usually implemented using uoroscopic imaging, which means an extra radiation burden to the patient under treatment. Management of uoroscopic imaging dose can be accomplished by reducing either the imaging technique or the number of images. ese dose management methods, however, make object localization and tracking more dicult. Robust and reliable detection in image-based tracking systems is therefore desirable to achieve accurate real-time localization.
