Two way shape memory alloy medical stent

A catheter device for deploying a stent in a tubular organ, such that the stent will support walls of the tubular organ to secure that the tubular organ will have a critical diameter above a critical diameter comprising a catheter tube or rod carrying a stent coiled on an end segment of the tube or rod, the stent comprising:

• a spiral coil or cylinder made of a two-way shape memory alloy;
• having a super-elastic state in which the stent has a first diameter which is at least about the critical diameter but within a physiological range tolerated by said organ;
• and having a soft state in which the stent has a second diameter, after changing to this state from the super-elastic state, which is less than said critical diameter;
• the shape memory alloy has two transition temperatures being within a range that will not damage biological tissue, of which a first transition temperature, being a temperature which is above body temperature, is a temperature in which said alloy changes from said soft state to said super-elastic state and of which a second transition temperature, being a temperature which is below body temperature, is a temperature in which said alloy changes from said super-elastic state to said sort state, so that after changing into one of the two states, the stent remains in that state at body temperature;
• the stent carried on the catheter tube or rod in said soft state.