applications of ultrasound in the pediatric population with neurological and neurosurgical disease therefore include diagnostic techniques, image-guided interventions, and even intraopera­tive navigation.

TCD has been used to measure cerebral blood ow (CBF) velocity in the circle of Willis and the vertebrobasilar system, both diagnostically and to adjust treatment strate­gies in neurovascular disease and raised ICP [3–5]. The parameters assessed include peak systolic and diastolic velocity, mean velocity, resistance index (RI), and pulsatility index (PI). The measurements are usually taken over regions of the skull with the thinnest bony win­dows, i.e., the temporal region, through the eye, and at the back of the head. A recent study in children found TCD to be an excellent rst­line examination for identifying patients likely to need invasive ICP monitoring, while another study, also in children with severe traumatic brain injury, found the PI to be a less reliable indicator of absolute ICP values [6, 7]. TCD remains an attractive alternative to invasive ICP because of its ability to detect cerebral ischemia, relative cost-effectiveness, and wide­spread availability. It is however limited by the requirement for trained operators and user variability. Two-depth TCD assessment has also demonstrated a good relationship with ICP, but also has certain limitations in accu­rately reecting ICP [8].