An endovascular sheath device for use with a thermal treatment apparatus is provided. The device includes a longitudinal tube which is designed to receive a thermal treatment device and is designed to be inserted into a blood vessel. An ultrasonically visible reinforcement element is disposed along the length of the longitudinal tube. The reinforcement element such as a braided wire provides several functions including increased visibility under ultrasound, clearer identification of sheath tip, and increased durability to protect the fiber from needle punctures during tumescent injections into the perivenous space. The wire reinforcement also increases shaft torquability and kink resistance during sheath insertion and withdrawal.