This document relates to a medical application of augmented reality in which areal image shows a medical device, or at least a part thereof. In an exemplary application, the real image further shows at least a part of a patient's body which is (to be) treated using the medical device. A part of the medical device might not be visible in the real image, for example because it extends into or behind the patient's body. In this case, the virtual image can comprise an augmentation of the medical device, which, for example, represents at least the part of the medical device which is invisible in the real image. This document in particular addresses a correct alignment of the augmentation with the medical device.