a radially expandable intravascular medical device is disclosed . the device typically includes two members . the first member is an outer tube - shaped sheath which is radially expandable by being formed from elastic material or other means and having relatively low column strength . the second member is an inner portion extending throughout the outer tube . this inner portion includes a slit to allow it to expand radially as well . using the structure diagnostic , therapeutic , or other desired objects may be conveyed through the device yet still enable the device to have a smaller cross - sectional area throughout most of its length than the object conveyed therethrough .