![]() ![]() TCD is conducted using either transcranial color-coded duplex sonography, in which it is displayed a two-dimensional color-coded image or once the desired blood vessel is insonated, blood flow velocities may be measured using Pulsed wave (PW) Doppler. ![]() The probe can then be fixed to the scalp with a headband so that the same angle of insonation for continuous flow velocity recordings is maintained throughout the examination. In clinical practice, the most frequently used transducer is a Pulsed Doppler sectorial probe with a 2.0–3.5 MHz emission frequency. In this review, we will describe physical principles underlying TCD, flow indices most frequently used in clinical practice, and critical care indications for this imaging modality. Other clinical applications of TCD include monitoring of cerebral circulation and embolization during cardiopulmonary bypass, carotid endarterectomies, and carotid artery stenting. Moreover TCD allows for intraoperative monitoring, evaluation of vasomotor function, and assessment of cerebral microembolism due to right to left cardiac shunts. TCD has important clinical application in the management of patients with sickle-cell disease, brain stem death, and raised intracranial pressure (ICP). It allows to investigate cerebral pressure autoregulation and for the clinical evaluation of cerebral autoregulatory reserve. It is also useful on both adults and children to diagnose and monitor vasospasm (VSP) after subarachnoid hemorrhage (SAH) of different etiologies (aneurysm rupture and traumatic brain injury ), and cerebral hemodynamic changes after stroke including cryptogenic stroke. TCD examinations have gained an important role in the very early phase of critical cerebral pathologies, as well as during follow-up of patients with chronic CVDs. It is inexpensive, repeatable, and allows continuous bedside monitoring of CBFV, which is particularly useful in the intensive care setting. TCD ultrasonography involves the use of a low-frequency (≤2 MHz) transducer, placed on the scalp, to insonate the basal cerebral arteries through relatively thin bone windows and to measure the cerebral blood flow velocity (CBFV) and its alteration in different cerebrovascular diseases (CVDs) and traumatic brain injuries. Transcranial Doppler (TCD) ultrasonography is a noninvasive ultrasound (US) study, which was introduced in clinical practice in 1982, since then it has been extensively applied on both outpatient and inpatient settings. ![]()
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