A number of substances have been used as positive contrast agents: silver, bismuth, caesium, thorium, tin, zirconium, tantalum, tungsten and lanthanide compounds have been used as contrast agents.
许多物质已被用来作为阳性造影剂：银，铋，铯，钍，锡，锆，钽，钨和稀土化合物已被使用造影剂。
2
The zirconium-tungsten electrode boasts a fine performance in welding under the condition of AC.