Apparatus for performing a medical procedure includes an invasive probe having opposite distal and proximal ends. The probe includes a transmitter, which is arranged to transmit an energy field, and a receiver, which is arranged to receive the energy field, wherein the transmitter and the receiver are disposed at the opposite ends of the probe. A control unit is adapted to determine an orientation of the distal end relative to the proximal end responsively to the energy field received by the receiver.