On the use and misuse of cerebral hemodynamics terminology using transcranial Doppler ultrasound: a call for standardization.

Cerebral hemodynamics, e.g., cerebral blood flow, can be measured and quantified using many different methods, with transcranial Doppler ultrasound (TCD) being one of the most commonly used approaches. In human physiology, the terminology used to describe metrics of cerebral hemodynamics are inconsistent and in some instances technically inaccurate; this is especially true when evaluating, reporting, and interpreting measures from TCD. Therefore, this perspective article presents recommended terminology when reporting cerebral hemodynamic data. We discuss the current use and misuse of the terminology in the context of using TCD to measure and quantify cerebral hemodynamics and present our rationale and consensus on the terminology that we recommend moving forward. For example, one recommendation is to discontinue the use of the term "cerebral blood flow velocity" in favor of "cerebral blood velocity" with precise indication of the vessel of interest. We also recommend clarity when differentiating between discrete cerebrovascular regulatory mechanisms, namely, cerebral autoregulation, neurovascular coupling, and cerebrovascular reactivity. This will be a useful guide for investigators in the field of cerebral hemodynamics research.