perfusionsMRI

Perfusion MRI is a set of magnetic resonance imaging techniques that measure tissue perfusion and hemodynamics, primarily within the brain. It includes both contrast-enhanced methods, such as dynamic susceptibility contrast (DSC) and dynamic contrast-enhanced (DCE) imaging, and non-contrast methods, notably arterial spin labeling (ASL). These techniques provide parameters that describe blood flow and the behavior of blood in the microvasculature.

DSC uses gadolinium-based contrast and rapid T2*-weighted imaging to track the first pass of contrast through the cerebral vasculature. Through deconvolution with an arterial input function, it yields cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). DCE employs T1-weighted dynamic imaging and pharmacokinetic modeling to estimate perfusion and permeability parameters such as Ktrans, Ve, and Kep, offering information about vascular leakage and extracellular/extravascular space.

ASL is a non-contrast approach that labels inflowing arterial blood and measures the resulting signal change to derive CBF maps. Variants include pseudo-continuous ASL (pCASL) and pulsed ASL. ASL is particularly advantageous for patients with contraindications to gadolinium, though it can have lower signal-to-noise and is sensitive to labeling efficiency and transit times.

Clinical applications span evaluation of acute ischemic stroke (perfusion-diffusion mismatch and tissue viability), tumor characterization and treatment planning, and monitoring therapy in oncology and neurovascular disorders. It can aid in distinguishing recurrent tumor from treatment-related changes and in assessing cerebral hemodynamics in conditions such as moyamoya and migraines.

Limitations and considerations include sensitivity to motion, contrast leakage effects in DSC, and the need for standardized post-processing and acquisition protocols to enable reliable cross-site comparisons.