Apparatus for determining a position of an interventional device respective an image plane of an ultrasound field defined by a plurality of beams (B 1..k) emitted by an ultrasound transducer array of a beamforming ultrasound imaging system in which the position is determined based on ultrasound signals emitted by the ultrasound transducer array that have been detected by an ultrasound detector attached to the interventional device; the apparatus comprising: an image reconstruction unit configured to provide a reconstructed ultrasound image corresponding to the image plane based on the ultrasound signals detected by the ultrasound transducer array; and a position determination unit configured to identify, based on a correlation of the ultrasound signals emitted by the ultrasound transducer array with the ultrasound signals detected by the ultrasound detector, the position of the interventional device respective the image plane; and wherein the position includes an out-of-plane distance (Dop) corresponding to the shortest distance between the ultrasound detector and the image plane; and a geometry-providing unit comprising a plurality of transducer-to-distal-end lengths (Ltde 1..n), wherein each length corresponds to a predetermined distance (Ltde) between a distal end (17, 47) of an interventional device (11, 41) and an ultrasound detector (16, 46) attached to the interventional device, for each of a plurality of interventional device types (Ti..n); and an image fusion unit configured to: receive data indicative of the type of the interventional device within the ultrasound field; and based on the type to: select from the geometry-providing unit, a corresponding transducer-to-distal-end length (Ltde); and to indicate in the reconstructed ultrasound image both the out-of-plane distance (Dop) and the transducer-to-distal-end length (Ltde) for the interventional device within the ultrasound field; wherein the out-of-plane distance (Dop) is indicated in the reconstructed ultrasound image as a first shape (Cop) having a first size corresponding to the out-of-plane distance (Dop); and wherein the transducer-to-distal-end length (Ltde) is indicated in the reconstructed ultrasound image as a second shape (Cde) having a second size corresponding to the transducer-to-distal-end length (Ltde). an image reconstruction unit configured to provide a reconstructed ultrasound image corresponding to the image plane based on the ultrasound signals detected by the ultrasound transducer array; and a position determination unit configured to identify, based on a correlation of the ultrasound signals emitted by the ultrasound transducer array with the ultrasound signals detected by the ultrasound detector, the position of the interventional device respective the image plane; and wherein the position includes an out-of-plane distance (Dop) corresponding to the shortest distance between the ultrasound detector and the image plane; and a geometry-providing unit comprising a plurality of transducer-to-distal-end lengths (Ltde 1..n), wherein each length corresponds to a predetermined distance (Ltde) between a distal end (17, 47) of an interventional device (11, 41) and an ultrasound detector (16, 46) attached to the interventional device, for each of a plurality of interventional device types (Ti..n); and an image fusion unit configured to: receive data indicative of the type of the interventional device within the ultrasound field; and based on the type to: select from the geometry-providing unit, a corresponding transducer-to-distal-end length (Ltde); and to indicate in the reconstructed ultrasound image both the out-of-plane distance (Dop) and the transducer-to-distal-end length (Ltde) for the interventional device within the ultrasound field; select from the geometry-providing unit, a corresponding transducer-to-distal-end length (Ltde); and to indicate in the reconstructed ultrasound image both the out-of-plane distance (Dop) and the transducer-to-distal-end length (Ltde) for the interventional device within the ultrasound field; wherein the out-of-plane distance (Dop) is indicated in the reconstructed ultrasound image as a first shape (Cop) having a first size corresponding to the out-of-plane distance (Dop); and wherein the transducer-to-distal-end length (Ltde) is indicated in the reconstructed ultrasound image as a second shape (Cde) having a second size corresponding to the transducer-to-distal-end length (Ltde).