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.

脑外层与颅骨在颅缝处紧紧相贴，外出血会跨过颅缝，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.

血肿可跨过颅缝，与大脑轮廓一致，呈新月形；相形之，外血肿跨过颅缝，而且压迫大脑呈双凸镜形。

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，血肿的轮廓和大脑轮廓一致，呈新月形，跨过颅缝。