A narrowed part of an artery would appear as a bottle neck on an x-ray image.
动脉狭窄的部分在x光片上会显示为瓶颈。
英语百科
Bottleneck
（重定向自Bottle neck）
Bottleneck literally refers to the top narrow part of a bottle. In engineering, it refers to a phenomenon where the performance or capacity of an entire system is limited by a single or small number of components or resources.
Bottleneck may also refer to:
英英词典
bottle neck n.
a narrowing that reduces the flow through a channel