An apparatus for determining a relation between a surface motion of a location on a surface of a body (BD) and an object motion of an object (OB) within the body (BD), the apparatus comprising: a first element configured to be placed at the location on the surface of the body (BD) with the surface motion; a first sensing unit (SEU1) configured to acquire a first position signal indicative of a position of the first element placed at the location on the surface of the body (BD) with the surface motion; a second element attached to an interventional device and configured to be placed on or in the object (OB); - a second sensing unit (SEU2) configured to acquire a second position signal indicative of a position of the second element attached to the interventional device and placed on or in the object (OB), wherein the first position signal and the second position signal are acquired during a given duration synchronously; and - a third unit for calculating the relation between the surface motion and the object motion based on the first position signal and the second position signal during a modeling stage that builds a surrogate model defining the relation between the body surface motion and the object motion, wherein the second element attached to the interventional device is further configured to track a location of the interventional device, and wherein the apparatus is configured to switch the operation of the second element from object motion measurement to interventional device tracking upon completion of the surrogate model building, and wherein in the interventional device tracking an accurate motion compensation is applied for previously acquired images based on the position of the interventional device and the determined motion relation. a first element configured to be placed at the location on the surface of the body (BD) with the surface motion; a first sensing unit (SEU1) configured to acquire a first position signal indicative of a position of the first element placed at the location on the surface of the body (BD) with the surface motion; a second element attached to an interventional device and configured to be placed on or in the object (OB); - a second sensing unit (SEU2) configured to acquire a second position signal indicative of a position of the second element attached to the interventional device and placed on or in the object (OB), wherein the first position signal and the second position signal are acquired during a given duration synchronously; and - a third unit for calculating the relation between the surface motion and the object motion based on the first position signal and the second position signal during a modeling stage that builds a surrogate model defining the relation between the body surface motion and the object motion, - a second sensing unit (SEU2) configured to acquire a second position signal indicative of a position of the second element attached to the interventional device and placed on or in the object (OB), wherein the first position signal and the second position signal are acquired during a given duration synchronously; and - a third unit for calculating the relation between the surface motion and the object motion based on the first position signal and the second position signal during a modeling stage that builds a surrogate model defining the relation between the body surface motion and the object motion, wherein the second element attached to the interventional device is further configured to track a location of the interventional device, and wherein the apparatus is configured to switch the operation of the second element from object motion measurement to interventional device tracking upon completion of the surrogate model building, and wherein in the interventional device tracking an accurate motion compensation is applied for previously acquired images based on the position of the interventional device and the determined motion relation. <EOS>