Catheter apparatus for positioning a wire

Abstract

A method and apparatus for positioning a radioactive portion of a wire at one or more positions within the lumen of a guide catheter, such as for intravascular radiotherapy, are disclosed. The method and the apparatus provide for better positioning the radioactive portion in light of bunching of the wire within the lumen during insertion. A computerized controller uses a monitoring device to control an afterloader's insertion and withdrawal of the wire into the guide catheter. The guide catheter includes a sensor at its distal end, the sensor being an electrical contact having conductive surfaces exposed within the lumen and outside the guide catheter. The wire is electrically conductive, and is configured to come into contact with the sensor's conductive surface within the lumen when the wire is fully inserted into the lumen. The monitoring device includes one lead connected to the wire and a second lead connected to the subject's body. The monitoring device is configured to use an alternating current signal to sense a closed circuit extending sequentially through a signal path including the wire, the sensor, and the subject's body, when the wire comes into contact with the sensor. The computer controller directs the afterloader to insert the wire into the lumen until a closed circuit is sensed. The controller then directs the afterloader to controllably withdraw the wire until the circuit is broken, thus removing any bunching from the wire. The wire then can be maintained in position at the end of the lumen to irradiate the subject. The wire also may be withdrawn by prescribed amounts to other positions within the lumen, to treat the subject at these locations.