Transcranial Doppler (TCD) ultrasonography uses a pulsed Doppler transducer for assessment of intra- cerebral blood flow. It is a noninvasive, real-time bedside monitoring tool to measure arterial flow velocities. In patients with aneurysmal subarachnoid hemorrhage (aSAH), TCD is primarily used in detection of cerebral vasospasm 1) , but has been broadly utilised for non-invasive ICP monitoring due to its ability to detect changes in cerebral blood flow velocity (FV) derived from ICP variations. TCD has also been used for non-invasive estimation of cerebral perfusion pressure (CPP), based on some parameters derived from FV, such as diastolic flow velocity (FVd) 2) and critical closing pressure (CrCP) 3). Considering the assumption that CPP equals the difference of arterial blood pressure (ABP) and ICP, nICP can be estimated as nICP = ABP – nCPP.
The Transcranial Doppler (TCD) and the more recent Transcranial Color Doppler (TCCD) are tests that measure the blood flow velocity through the brain's blood vessels. Used to help in the diagnosis of emboli, stenosis, vasospasm from a subarachnoid hemorrhage, and other problems.
TCD is effective to detect Sickle Cell Disease, (in order) established for Ischemic cerebrovascular disease, Subarachnoid hemorrhage, Arteriovenous malformations and Cerebral circulatory arrest and possibly useful for Perioperative monitoring and Menigeal infection.
The equipment used for these tests is becoming increasingly portable, making it possible for a clinician to travel to a hospital, doctor's office or nursing home for both inpatient and outpatient studies. It is often used in conjunction with other tests such as MRI, MRA, carotid duplex ultrasound and CT scans.
TCD-based indices, mean velocity index, Mx and autoregulation index (ARI).
Transcranial Doppler (TCD) ultrasonography is an important tool for noninvasive detection and monitoring of vasospasm and other pathological conditions of the intracranial vessels.
Provides excellent orientation, also allowing diagnostic procedures on pathological vascular structures.
Three patients who underwent computed tomographic angiography scanning for reasons not related to this study were examined by neuronavigated image-guided TCD. The Doppler probe was fitted with reflective markers and tracked by a commercially available Kolibri image guidance system.
Image-guided TCD allowed identification of all major intracranial vessels. Unilateral acquisition of reliable Doppler signals for the internal carotid artery, carotid T, middle cerebral artery, middle cerebral artery bifurcation, and anterior cerebral artery required 14 ± 6 minutes. Preregistration of these targets and detection by neuronavigation alone shortened examination times significantly to 8 ± 2 minutes. Registering the optimal examination trajectories on the neuronavigational device and applying navigational pilot software shortened times for repetitive examination further to 4 ± 1 minutes and ensured that the examination was done at the exact same spot under the same angle as in previous examinations.
Image guidance can be applied easily and efficiently to TCD. It provides anatomic orientation and may help to standardize investigation protocols, define pathological vascular territories for repeat investigations, and thus reduce interinvestigator variations. Image guidance may also extend the use of TCD to situations of a pathological or variant vascular anatomy 4).