Abstract: This system comprises means (9) for determining a position of a first portion of a medical instrument in the body of a subject at a determination time, and means (11) for displaying an image of the first portion in the determined position. The determination means (9) comprise an imaging module (15) that is capable of acquiring, at an acquisition time that precedes said determination time, a position of the first portion, a detection module (17) for detecting a movement of a second portion of the medical instrument between said acquisition and determination times, and a determination module (19) for determining the position of the first portion (3d) at said determination time, from said position of the first portion at said acquisition time and from said movement of the second portion.