kb/data/en.wikipedia.org/wiki/Arterial_spin_labelling-1.md

title	chunk	source	category	tags	date_saved	instance
Arterial spin labelling	2/2	https://en.wikipedia.org/wiki/Arterial_spin_labelling	reference	science, encyclopedia	2026-05-05T10:03:41.600359+00:00	kb-cron

== Analysis of ASL images == ASL maps can mainly be analyzed using the same tools to analyze fMRI and VBM. Many ASL-specific toolboxes have been developed to assist in ASL analysis, such as BASIL (Bayesian inference for arterial spin labelling MRI), part of the FSL neuroimaging package and also Ze Wang's ASL toolbox (using MATLAB) to assist in the subtraction and averaging of the tagged/control pairs. A visual quality check is often needed to make sure that the perfusion map is valid (such as correct registration, or correct segmentation of non-cerebral materials such as the dura mater). A whole brain/voxel-wise approach can be analyzed by registering the ASL map into MNI space for group comparisons. A region of interest approach can be analyzed by registering the ASL map into a selected cluster, or an atlas, like a standard (such as the Harvard-Oxford Cortical atlas) or an individual atlas developed by software like FreeSurfer. The recommended procedure of ASL registration for voxel-wise analysis is to register the perfusion map to a gray matter segmentation of each individual in a non-rigid procedure. Gray matter often requires more oxygenation and is the source of more brain activity compared to white matter. Therefore, gray matter CBF is often higher than white matter CBF. The single value of gray matter CBF is often isolated in order to give a broad overview of CBF differences. Gray matter and white matter CBF can be localized using atlases or Freesurfer. ASL functional connectivity can be designed with parameters conducive to a long scan time. Studies have suggested that ASL complement resting state fMRI findings well but can differentiate between resting brain networks (such as the default mode network) less.

== Comparison with fMRI == Functional MRI (fMRI) has been the modality of choice to visualize brain activity, and takes advantages of a range of techniques that can be used to interpret it. However, the signal that fMRI is acquiring is BOLD signal, which does not directly correlate with blood flow. Cerebral blood flow on the other hand does, allowing for cardiovascular disease (CVD) and inflammatory risk factor analysis, and disorders (such as schizophrenia and bipolar disorder) that have comorbid effects with CVD. ASL imaging can be a useful tool to complement fMRI and vice versa.

== Clinical use == In cerebral infarction, the penumbra has decreased perfusion. Besides acute and chronic neurovascular diseases, the value of ASL has been demonstrated in brain tumors, epilepsy and neurodegenerative disease, such as Alzheimer's disease, frontotemporal dementia and Parkinson disease. Additionally, DP-pCASL has promising potential for assessing blood-brain barrier integrity in patients with ischemic stroke. Although the primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, ASL is another method of obtaining contrast. There have been research to apply ASL to renal imaging, pancreas imaging, and placenta imaging. A challenge to this sort of non-cerebral perfusion is motion due to breathing. Additionally, there is a lot less development on the segmentation of theses specific organs, so the studies are relatively small scale.

== Safety == ASL is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error like other MRI techniques. ASL, like other MRI modalities generate a fair amount of acoustic noise during the scan, so earplugs are advised.

== References ==

== External links == mriquestions.com [1]