Abstract: The present invention relates to a model based positioning system 10; 90 that comprises a positioning device 11; 31 having at least one transmitter configured to be in a tracking environment, e.g. inserted into a body 1, a receiver 13 having a plurality of receiver elements 14 arranged outside the tracking environment, a control unit 18; 93 configured to measure amplitude and/or phase information of a signal transmitted from the at least one transmitter and received at each receiving element, and a memory unit M; 15 for storing a model for each receiving element. The control unit is also configured to estimate the position P of the positioning device by comparing the model for each receiving element with the measured received signal for each receiving element.

Abstract: The present invention relates to an antenna system (1, 101, 201, 301, 401, 501) for tracking of a position of a target area (33, 133, 233, 333, 433, 533) within a body (5, 105, 205, 305, 405, 505), comprising a first antenna device (3, 103, 203, 303, 403, 503) and a second antenna device (9, 109, 209, 309, 409, 509), at least said second antenna device (9, 109, 209, 309, 409, 509) is to be located outside said body (5, 105, 205, 305, 405, 505), wherein an interface region (13, 113, 213, 313, 413, 513) between said body (5, 105, 205, 305, 405, 505) and at least said second antenna device (9, 109, 209, 309, 409, 509) at least partially consist of a dielectric medium having a relative permittivity closer to the permittivity of material within the body (5, 105, 205, 305, 405, 505) than the permittivity of air.

Abstract: The present invention relates to an implant (115) fixable relative to a target area (117) within a living body (105), comprising a transmitter (7; 107; 207; 307) arranged to emit an electromagnetic signal, wherein said electromagnetic signal is adapted to propagate with a wavelength 2 in said living body (105) so that a phase difference of said electromagnetic signal in at least three positions, preferably four, separated by a known distance (b) is detectable by a receiver (9; 109; 209; 309) for tracking variations of a position (p) of the implant (115) relative to said receiver (9; 109; 209; 309). Further, the present invention relates to an apparatus (1; 101; 201; 301), a system and a method for tracking a position (p) of a transmitter (7; 107; 207; 307). Additionally, the invention relates to the use of such a method for treatment of a target area (117) in a living body (105) by means of a radiation therapy treatment arrangement (100).