Stents are generally known, and by way of example reference is made to US-A-5628787, US-A-5630840 and EP-A-0873734.

Up till now a number of metals or metal alloys have been used and/or proposed as basic material for the stent.

In a first type of stent stainless steel has been used especially stainless steel 316 (L, LVM).

One of the problems with this alloy is that it contains nickel, which can lead to unwanted reactions with patients sensitive to this metal, because of the so-called nickel-allergy.

Otherwise a stent must be clearly visible in a radiography and clearly discernible from its surrounding while being implanted.

This is especially important because the stent must be positioned in the optimal way in order to have the optimal result. Stainless steel does not give a good reflection to X-ray radiation implying that its visibility while being implanted is low and far from optimal.

In view of these problems with stainless steel it has been proposed to use stainless steel coated with other metals, especially with gold. This has resulted in a better visibility of the stent during implantation, and from that point of view such a stent will have good results.

Gold-coated stainless steel stent are difficult to make and are relatively expensive. Moreover there might be a problem that the gold layer is not sufficiently adhered to the supporting base material so that locally the coating cracks or flakes off the stent during expansion. Such local removal of the gold coating can result into adverse corrosion effects and free floating of gold particles in the visculature. Moreover the use of two different metals or metal alloys contacting each other may imply galvanic reactions of which long term clinical effects are unknown, but of which it is suspected that they negatively affect restenosis rates.

In another stent use is made of tantalum as constructive material for the stent. This has resulted in a reliable stent, but tantalum has the disadvantage that it is too visible in radiographic imaging, to such an extend that it obstructs the imaging of the result of the implantation of such stent.

It is therefore an object of the invention to provide a stent avoiding the above mentioned problems.

This object has been obtained in that the stent is made of an alloy comprising at least 90 % by weight of niobium.

It has been found that niobium is a metal offering the combination of required characteristics especially with respect to the mechanical and chemical properties and in view of the radiographic imaging.

In a preferred embodiment of the invention the alloy comprise at least 95 % by weight niobium and more preferably at least 98 %.

Niobium can be combined with a number of other metals in order to obtain the required characteristics.

According to the invention it is preferred that the niobium alloy contains further one or more elements selected from the group of Zr, Ti, V, Hf, W, Ta and Mo.

Most of these elements, or combinations thereof, improve the mechanical characteristics of the alloy without negatively influencing the biocompatibility with blood or blood vessel systems nor the visibility in radiography.

In the most preferred embodiment of the invention the alloy consists of 98,5-99,5 % by weight of niobium and 0,1-1,5 % by weight of zirconium.