Trans-Cranial Doppler sonography (TCD)
Trans-Cranial Doppler (TCD) sonography is a non-invasive method of measuring cerebral blood flow velocity (CBFV) from the basal intra-cerebral vessels through the intact skull. Pulses of ultrasound penetrate the skull at a number of ‘acoustic windows’, which include: temporal, orbital, foraminal and submandibular, insonating vessels at particular depths, with the returning ‘echo’ displayed as a Doppler waveform. The mean velocity, peak systolic velocity, diastolic velocity, and pulsatility index (all cm/sec) of the insonated vessel are provided; indicating the speed of the flow of blood and the variability of blood velocity. This technique can be combined with our other neuroimaging devices; the Near-Infrared Spectroscopy (NIRS) and electroencephalogram (EEG), within the same study and even at the same time if needed. This device provides a unique means of monitoring the provision of neural fuel during human nutrition research trials.