నైరూప్య

Measurement of cerebral perfusion using MRI

Egbert JW Bleeker and Matthias JP van Osch

Cerebral perfusion MRI is becoming an increasingly important method for diagnosing and staging brain diseases. MRI provides the opportunity of combining perfusion imaging with high-quality anatomical imaging and is therefore, for most brain diseases, the modality of choice. Perfusion MRI techniques can be categorized into two different groups based on tracer type. First, dynamic susceptibility contrast (DSC)-MRI is a method based on the injection of an exogenous tracer, a gadolinium-based contrast agent, in the arm vein. By means of fast T2‑ or T2*‑weighted imaging the first passage of the contrast agent through the brain tissue is monitored. The second technique, arterial spin labeling (ASL), is a completely noninvasive technique that employs water protons as an endogenous tracer. In this article, the crucial elements for correct perfusion measurements by DSC‑MRI and ASL are discussed. In DSC-MRI, the conversion from signal changes to contrast agent concentration, the arterial input function measurement and the deconvolution method are the most important elements. Whereas in ASL, the efficiency of the labeling method, correction for relaxation processes and M0-calibration methods can be considered the most essential components of blood flow quantification.