Quantification of relative cerebral blood flow change by flow‐sensitive alternating inversion recovery (FAIR) technique: Application to functional mapping

Abstract

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.

FAIR true‐FISP perfusion imaging of the kidneys

“…The relevant perfusion signal in the final image (after subtraction) arises from the spins flowing into the imaging plane from outside. General influences of inflow, outflow, and dephasing effects of fast flow in echoplanar approaches have been discussed in former works (e.g., [3][4][5][6]. Following aspects of True-FISP sequences should be especially considered for the intended application: 1) Most spins from capillary blood stay inside the excited slice for a relatively long time and are expected to experience many RF excitation pulses of the True-FISP sequence: For example, at velocities of 1-2 mm/s and for a TR of 5 ms the blood displacement in the capillaries during 60 repetitions is only 0.3-0.6 mm, which is clearly smaller than the common slice thickness of ϳ5-10 mm.…”

“…The experiment is repeated without labeling the arterial blood and the image signals are subtracted to yield a difference signal directly reflecting local perfusion. Examples of this group of perfusion imaging techniques include signal targeting with alternating radio-frequency (STAR) (3), and flow-sensitive alternating inversion recovery (FAIR) (4,5) techniques. Several pulsed ASL approaches have been described in detail and compared in a review article from Calamante et al (6).…”

Correlation between arterial blood volume obtained by arterial spin labelling and cerebral blood volume in intracranial tumours

“…As an alternative to DSC-MRI, with regard to cerebral blood flow (CBF) quantification, arterial spin labelling (ASL) techniques have shown considerable potential [10][11][12][13]. ASL does not require injection of contrast agent and is thus completely non-invasive.…”

FAIR‐TrueFISP imaging of cerebral perfusion in areas of high magnetic susceptibility differences at 1.5 and 3 Tesla

“…Since ASL spin preparation does not rely on susceptibility changes, the ASL scheme can be used for perfusion quantification in brain areas of high susceptibility changes. A commonly applied ASL preparation is the flow-sensitive alternating inversion recovery (FAIR) (8,9) scheme. The most extensively used data acquisition technique for ASL is EPI (8 -10), which is extremely sensitive to susceptibility artifacts.…”