Walsh-ordered hadamard time-encoded pseudocontinuous ASL (WH pCASL) : Walsh-Ordered Hadamard Time-Encoded pCASL

Relative cerebral blood flow changes can be measured by a novel simple blood flow measurement technique with endogenous water protons as a tracer based on flow-sensitive alternating inversion recovery (FAIR). Two inversion recovery (IR) images are acquired by interleaving slice-selective inversion and nonselective inversion. During the inversion delay time after slice-selective inversion, fully magnetized blood spins move into the imaging slice and exchange with tissue water. The signal enhancement (FAIR image) measured by the signal difference between two images is directly related to blood flow. For functional MR imaging studies, two IR images are alternatively and repeatedly acquired during control and task periods. Relative signal changes in the FAIR images during the task periods represent the relative regional cerebral blood flow changes. The FAIR technique has been successfully applied to functional brain mapping studies in humans during finger opposition movements. The technique is capable of generating microvascular-based functional maps.