This procedure allows the treatment of large veins in an outpatient setting. It consists in inserting a catheter into the vein, guided by ultrasound. The catheter delivers thermal energy to the vein wall, causing it to heat, collapse and seal shut. This procedure is less invasive then the other methods, avoids the formation of large hematomas and reduces the number of incisions. It is performed with local anaesthesia and has a short recovery period.