So on a CT scan, subdural hematomas follow the contour of the brain and form a crescent shape and cross suture lines.

所以在CT上，硬膜下血肿的轮廓和大脑轮廓一，月形，过颅。

Since the outer layer of the dura mater adheres tightly to the skull at sutures, epidural hematoma don't cross suture lines, and they push on the brain, forming a bi-convex shape.

由于硬脑膜外层与颅骨在颅处紧紧相贴，硬膜外出血不会过颅，且血肿会压迫大脑，形成双凸镜形。

Subdural hematomas cross suture lines and follow the contour of the brain forming a crescent shape, unlike epidural hematomas which don't cross suture lines and push on the brain and form a bi-convex shape.

硬膜下血肿可过颅，与大脑轮廓一，月形；相形之下，硬膜外血肿不过颅，而且压迫大脑双凸镜形。