Objective        To observe the relationship between the anterior clinoid process (ACP) of internal carotid artery (ICA) and ophthalmic arterial branch by multi-slice spiral computed tomography (MSCT) with three-dimensional imaging reconstruction.       Methods       A total of 100 patients’ (including 200 sides) ophthalmic artery (OA) opening was observed on the axial thin slice and volume rendering (VR) images. The anterior segment of axial ICA were divided into 3 parts according to its position from the axial superior surface of ICA

namely

the anterior-medial one-third

anterior-median one-third

and anterior-lateral one-third. Then the opening position of ophthalmic artery was recorded respectively. The VR technique was used to reconstruct the skull

by removing along superorbital 1.5-cm-superoccipital tuberosity 1.0 cm plane and the left or right lateral sagittal planes 1 cm to the lateral rim of the ACP in the simulation. Then the rest skull was divided into left and right parts along and median sagittal plane and integrated with the VR reconstruction of ICA with different color image respectively. The sagittal anatomy relationships between the ACP and ophthalmic artery opening position from the sagittal anterior surface of ICA were observed and recorded respectively.       Results        In 100 patients’ (200 sides) OA

52.00% (left 29.00% and right 23.00%) came from above the medial one-third of the axial superior surface of ICA

45.00% (left 19.50% and right 25.50%) from the median one-third

and 3% (right 1.50% and left 1.50%) from the lateral one-third. OA originated from proximally to the distal ring in 6% (left 3.00% and right 3.00%)

distally in 76.50% (left 39.00% and right 37.50%)

or closed to the distal ring in 17.50% (left 9.00% and right 8.50%).       Conclusion        MSCT scanning clearly shows the relationship between the ACP

clinoid segment of ICA and OA opening

which can provide useful imaging information for the selection of operative approaches and removal of ACP in microsurgical operation.