The invention relates to an introducer for inserting a tubular element into the body of a mammal, in which the tubular element is a catheter, a guide cable, a probe or similar that is inserted until it reaches a suitable position in a tissue or duct, such as a blood vessel or a bile duct. According to the invention, the read means are housed at least partially inside the introducer body and disposed perpendicularly to the direction of movement of the tubular element through the introducer and at least one connection between the read means and the transmission means for transmission to the external unit is external to the introducer body. Advantageously, the read means housed inside the introducer device provide information allowing the distance covered by the catheter to be viewed on an external display. The introducer device can be made from plastic materials compatible with NMR equipment.Dispositivo introductor para introducción de un elemento tubular en el cuerpo de un mamífero, donde dicho elemento tubular es un catéter, cable guía, sonda o similar hasta una posición adecuada de un tejido o de un conducto corporal tal como un vaso sanguíneo o un conducto biliar, donde los medios de lectura están alojados al menos parcialmente en el cuerpo introductor y dispuestos perpendicularmente a la dirección de desplazamiento de dicho elemento tubular a través y donde al menos una conexión entre los medios de lectura y los medios transmisores a la unidad externa es externa al cuerpo introductor.
