The most common clinical methods to check for thrombosis are ultrasound of the neck blood vessels, CT of the head blood vessels, and cerebral angiography with MRI, which can clearly observe whether the patient has thrombosis and the site of thrombosis. 2. Therefore, the most common means of initial screening in clinical practice is through ultrasound of the cervical vessels and Doppler examination of the intracranial vessels, which are generally noninvasive and have precise localization of the thrombus. However, for deeper vessels, such as capillaries or deeper parts of the brain, the thrombus is not visible and may require CTA to clarify.