- Transcranial Doppler Ultrasound (TCD) is a noninvasive, inexpensive and portable imaging modality, which obtains information about the blood flow velocity in large intracranial arteries. TCD has several advantages in the investigation and treatment of acute ischemic stroke, but is inappropriately used in rehabilitation. Normal blood flow velocity in the middle cerebral artery (MCA) of the damaged hemisphere after stroke is associated with better rehabilitation outcome. Improved blood supply to the damaged hemisphere is associated with a favorable outcome, oppositely to the undamaged hemisphere. The decreased blood flow velocity in the damaged MCA is associated with orthostatic hypotension symptoms after stroke. Those patients are in high risk for developing syncopal reactions and should be elevated from supine position and treated on tilt table with caution, especially at the beginning of the rehabilitation. The performance of speech tasks is associated in aphasia stroke patients with much lower left hemisphere activation in comparison with the healthy subjects. High blood flow velocity in the right MCA was found to be a good prognostic sign for language ability. Arterial blood flow shift towards the left hemisphere during speech tasks is associated with poor language ability. The TCD technology can be an important additional tool for monitoring rehabilitation process, predicting functional outcome, evaluating brain reorganization strategies and developing new therapeutic modalities in post-stroke rehabilitation.