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MRI of Perfusion: Principles and Clinical Applications.

The principle and clinical application of measurement of cerebral blood perfusion (CBP) using MRI are described. Purposes of measuring CBP using MRI are wide-ranging. Generally, it is used to diagnose cerebro-vascular disorders or brain tumors. There are two types of measuring methods. One is dynamic susceptibility contrast (DSC) method using a contrast agent as a tracer. Another is an arterial spin labeling (ASL) method using protons in arterial blood as an endogenous tracer, instead of bio-exogenous tracer. Basic theory of ASL method was published in the 1990s, recently, its clinical application has been spreading rapidly by the technological innovations. ASL method is attractive as a way to measure CBP because of its non-invasiveness (no radiation-exposure, not need intravenous injection or blood sampling), and the imaging time is about 5 minutes, thereby the measurement can be repeated. The analysis of DSC method has not been standardized, though various valuable parameters are provided. And the prerequisite of DSC method is uncertain in vivo. On the other hand, the result of ASL is affected by the post labeling delay, and limited to the arterial information.