1. A system for repeated determination of a first vector between: a reference structure comprised in an anatomical volume, and a medical imaging transducer configured to provide imaging data of the anatomical volume; the system comprising: a user input configured to specify the reference structure; an imager configured to receive the imaging data; a model input configured to provide a model of the reference structure; a segmenter configured to receive the model and to segment the imaging data, using the model, whereby the imaging data associated with the reference structure is at least partially annotated, and a determiner configured to receive the annotated imaging data of the reference structure and to determine the first vector between the transducer and the reference structure based on the annotated imaging data.