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Abstract

Arterial Spin Labeling (ASL) is a magnetic resonance imaging (MRI) method to map
the cerebral blood flow (CBF). ASL present a non-invasive alternative to the contrast
agent techniques used typically to study vascular and neuronal diseases such as
stroke, arteriostenosis, schizophrenia, alzheimer, epilepsy …. ASL techniques are
capable of providing quantitative information about local tissue blood flow by tracking
the inflow of magnetically labeled arterial blood into an imaging slice. The delivery of
the tagged water to each image voxel is measured. Because ASL is completely
noninvasive, the tagging can be repeated many times to obtain a high signal-to-noise
ratio (SNR). ASL produces perfusion maps of human brain with higher spatial and
temporal resolution than any other existing technique. Furthermore, ASL has
extensively been used to study brain function mostly simultaneously with the blood oxygenated level dependent (BOLD) signal. BOLD signal provide a high functional
contrast to noise ratio, but the analysis and interpretation of BOLD contrast functional
data is complicated by the fact that the MRI signal change is related to the underlying
neuronal activation through CBF, CBV and oxidative metabolism (CMRO2). In contrast to baseline BOLD signal, baseline CBF measured using ASL provides valuable information of the brain’s respective state. In addition, ASL techniques are an important tool to study the physiological basis of functional neuroimaging techniques such as BOLD signal. In the study presented at the conference, we evaluated critically three different ASL sequences and compared established methods to determine absolute values of CBF from ASL data.