TCD stands for transcranial Doppler, a non-invasive diagnostic technique that uses ultrasound to examine intracranial vascular hemodynamics.
Transcranial Doppler clinically assesses cerebral blood flow, aiding in the diagnosis and management of stroke, vasospasm, and other vascular conditions.
It is mainly used for neurodegenerative disease examinations. As it is a painless examination, it is simple and convenient, providing important reference value for diagnosing cerebral arteriosclerosis, cerebral vascular spasm, and occlusion.
The Doppler probe is mainly placed in areas with thin skull bones and natural orifices to understand the blood flow situation within the intracranial vessels. Depending on the placement of the probe, different vascular blood flow signals can be detected. For example, placing the probe on the temple can obtain blood flow signals of the middle cerebral artery, anterior cerebral artery, and posterior cerebral artery; placing it on the midline of the occipital lobe can obtain blood flow signals of the vertebral artery and basilar artery; and placing it on the closed eyelid can obtain blood flow signals of the ophthalmic artery and internal carotid artery segment.
In recent years, the clinical application of TCD has become increasingly widespread. It has a high diagnostic value for detecting ischemic cerebrovascular diseases caused by severe intracranial artery stenosis or occlusion, cerebral vascular spasm caused by subarachnoid hemorrhage, arteriovenous malformations, cerebral arteriosclerosis, cerebral hypoperfusion, and aneurysms. It plays a role that cannot be replaced by head CT or magnetic resonance imaging.
The development of Transcranial Doppler began in the late 1980s when Rune Aaslid and his colleagues introduced the technology as a non-invasive method to measure blood flow velocity in the major cerebral arteries. This innovation built upon earlier work with Doppler ultrasound, which had been used primarily for peripheral vascular assessments. TCD initially faced challenges due to the difficulty in penetrating the skull, but advancements in ultrasound technology and the understanding of acoustic windows allowed for better imaging of the brain’s blood vessels.
Over the years, it has evolved with improvements in transducer technology, signal processing, and data analysis, making it a valuable tool in neurology and neurocritical care for assessing cerebrovascular diseases, monitoring high-risk patients, and guiding therapeutic interventions. Today, TCD is widely used in clinical settings and research, contributing significantly to the understanding and management of cerebrovascular disorders.
