A medical probe includes a hollow guidewire, a balloon, and a magnetic position sensor. The hollow guidewire is configured for insertion into a channel of an organ of a patient. The balloon is fixed to a distal end of the hollow guidewire, is configured to be inserted into the channel using the hollow guidewire, and is further configured to be inflated by pumping of fluid through the hollow guidewire. The magnetic position sensor is fitted at the distal end of the hollow guidewire.
