In this multicenter study, carotid artery color doppler flow imaging and transcranial color code doppler or transcranial doppler will be used to screen the extra-/intra-cranial vessels in chinese populations with transient ischemic attack and ischemic stroke. The aim of this study is to investigate the extra-/intra-cranial atherosclerosis distribution pattern in chinese populations and analyze the influencing factors of atherosclerosis distribution pattern.