1. A system ( 300 ) for repeated determination of a first vector between: a reference structure ( 120 ) comprised in an anatomical volume ( 100 ), and a medical imaging transducer ( 360 ) configured to provide imaging data of the anatomical volume ( 100 ); the system comprising: a user input ( 350 ) configured to specify the reference structure ( 120 ); an imager ( 310 ) configured to receive the imaging data; a model input ( 320 ) configured to provide a model of the reference structure ( 120 ); a segmenter ( 330 ) configured to receive the model and to segment the imaging data, using the model, whereby the imaging data associated with the reference structure ( 120 ) is at least partially annotated, and a determiner ( 370 ) configured to receive the annotated imaging data of the reference structure ( 120 ) and to determine the first vector between the transducer ( 360 ) and the reference structure ( 120 ) based on the annotated imaging data.