《厉害了，我的国》：绘中国发展 为祖国点赞
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At the time the article was created Frank Gaillard had no recorded disclosures.
View Frank Gaillard's current disclosuresAt the time the article was last revised Paul Ryan had no financial relationships to ineligible companies to disclose.
View Paul Ryan's current disclosures- ASL MR perfusion
Arterial spin labeling (ASL) MR perfusion is an MR perfusion technique which does not require intravenous administration of contrast (unlike DSC perfusion?and DCE perfusion). Instead, it exploits the ability of MRI to magnetically label arterial blood below the imaging slab. The parameter most commonly derived is cerebral blood flow (CBF). It is a non-invasive and non-ionizing MRI technique that measures tissue perfusion (blood flow) by using magnetically-labeled arterial blood water protons as an endogenous tracer.
ASL is a very suitable technique to use in pediatrics, patients with impaired renal function, pregnancy and those who may need serial follow-up 1.
A number of techniques have been described to achieve ASL perfusion,?classified based on the magnetic labeling process 2:
pulsed (PASL)
continuous (CASL)
pseudocontinuous (PCASL)
velocity-selective ASL (VS-ASL)?
The PCASL technique is recommended because it provides superior labeling efficiency and better signal-to-noise ratio (SNR) when compared to the other methods 3.
Basic principles?
The main idea in ASL is to obtain a labeled image or tagged image and a control image, in which the static tissue signals are identical but the magnetization of the inflowing blood is different. The water molecules in the arterial blood are magnetically labeled (tagged) by using a radiofrequency pulse that saturates water protons. Subtraction between labeled (tagged) and control images eliminate the static signals and the remaining signals are linear measures to the perfusion, which is proportionate to the cerebral blood flow (CBF). ASL SNR is very low because the signal from the tagged blood is only 0.5-1.5% of the entire tissue signal. As such, a 3T field strength is recommended to improve SNR along with background suppression, best achieved using 3D segmented readout methods such as 3D GRASE or 3D multiecho (RARE) stack of spirals 3. ASL data must be acquired before gadolinium administration since gadolinium will cause T1 shortening leading to a decrease in the measurable signals in both the labeled and controlled images 1,4.
Clinical applications?
cerebrovascular imaging
neuro-oncology
ictal and interictal imaging
neuroinflammation
dementia and neurocognitive disorders
Quiz questions
References
- 1. Iutaka T, de Freitas M, Omar S et al. Arterial Spin Labeling: Techniques, Clinical Applications, and Interpretation. Radiographics. 2023;43(1):e220088. doi:10.1148/rg.220088 - Pubmed
- 2. Essig M, Shiroishi M, Nguyen T et al. Perfusion MRI: The Five Most Frequently Asked Technical Questions. AJR Am J Roentgenol. 2013;200(1):24-34. doi:10.2214/AJR.12.9543 - Pubmed
- 3. Alsop D, Detre J, Golay X et al. Recommended Implementation of Arterial Spin‐labeled Perfusion MRI for Clinical Applications: A Consensus of the ISMRM Perfusion Study Group and the European Consortium for ASL in Dementia. Magnetic Resonance in Med. 2014;73(1):102-16. doi:10.1002/mrm.25197 - Pubmed
- 4. Haller S, Zaharchuk G, Thomas D, Lovblad K, Barkhof F, Golay X. Arterial Spin Labeling Perfusion of the Brain: Emerging Clinical Applications. Radiology. 2016;281(2):337-56. doi:10.1148/radiol.2016150789 - Pubmed
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