Transcranial Doppler cannot detect carotid plaque. Transcranial Doppler, or transcranial Doppler ultrasound, examines intracranial blood vessels. It is a noninvasive examination method that evaluates the hemodynamics of the arteries at the base of the skull by utilizing the naturally weak part of the skull as a sound window for detection, and is mainly used for the diagnosis of cerebral arterial stenosis and occlusion and the determination of collateral compensation, monitoring of microemboli in the cerebral blood flow, subarachnoid hemorrhage, and the detection of cerebral arterial spasm. Carotid plaque is mainly detected by carotid ultrasound. Carotid ultrasound is one of the effective means to diagnose and evaluate carotid artery wall lesions, which can detect early carotid atherosclerosis lesions and enable patients to prevent and treat them in time; carotid stenosis and occlusion of moderate to severe carotid arteries can be diagnosed in time, and it can be used as a strong basis for the selection of carotid artery endarterectomy in the clinic. Carotid ultrasound and transcranial Doppler ultrasound can be used to observe the intracranial and extracranial hemodynamic changes of ischemic cerebrovascular disease in a timely and accurate manner, which can improve the detection rate of intracranial and extracranial cerebrovascular disease and the diagnostic correctness, and provide a reliable and objective basis of imaging and dynamics for the selection of different clinical treatments and obtaining effective therapeutic effects.