A magnetizer for a tissue-penetrating medical tool such as a needle, cannula, stylet, or catheter consist of a magnetic flux generator which generates a magnetic field in a tool-receiving space. The tool can be passed through or into and out of the space to magnetise it. Optionally the space can be defined by a disposable plastics tube, with a closed end, so that a defined length of the tool is magnetised. The magnetic flux generator can be a permanent magnet or electromagnet. Alternatively a conveyor belt can be used to transport a tissue-penetrating medical tool through a magnetic field generated by an electromagnet with the belt and the electromagnetic being controlled in response to an optical sensor for detecting the position of the tissue-penetrating medical tool. The device is suitable for magnetising tools for use in surgical procedures where the tool is to be magnetically tracked.
