Perfusion MRI
Perfusion MRI | |
---|---|
Purpose | perfusion scanning via MRI |
Perfusion MRI or perfusion-weighted imaging (PWI) is
Clinical use
In
Sequences
There are 3 main techniques for perfusion MRI:
- Dynamic susceptibility contrast (DSC): T2*-weighted) quantifies susceptibility-induced signal loss.[2]
- Dynamic contrast enhanced (DCE): Measuring shortening of the gadolinium contrast bolus[3]
- Arterial spin labelling (ASL): Magnetic labeling of arterial blood below the imaging slab, without the need of gadolinium contrast[4]
It can also be argued that diffusion MRI models, such as intravoxel incoherent motion, also attempt to capture perfusion.
Dynamic susceptibility contrast
In Dynamic susceptibility contrast MR imaging (DSC-MRI, or simply DSC),
Dynamic contrast-enhanced imaging
Dynamic contrast-enhanced (DCE) imaging gives information about physiological tissue characteristics such transport from blood to tissue and blood volume. It is typically used to measure how a contrast agent moves from the blood to the tissue. The concentration of the contrast agent is measured as it passes from the blood vessels to the
The contrast agents used for DCE-MRI are often
Pharmacokinetic modelling of gadolinium in DCE-MRI is complex and requires choosing a model. There are a variety of models, which describe tissue structure differently, including size and structure of plasma fraction, extravascular extracellular space, and the resulting parameters relating to permeability, surface area, and transfer constants.[7] DCE-MRI can also provide model-independent parameters, such as T1 (which is not technically part of the contrast scan and can be acquired independently) and (initial) area under the gadolinium curve (IAUGC, often given with number of seconds from injection - i.e., IAUGC60), which may be more reproducible.[8] Accurate measurement of T1 is required for some pharmacokinetic models, which can be estimated from 2 pre-gadolinium images of varying excitation pulse flip angle,[9] though this method is not intrinsically quantitative.[10] Some models require knowledge of the arterial input function, which may be measured on a per patient basis or taken as a population function from literature, and can be an important variable for modelling.[11]
Arterial spin labelling
Arterial spin labelling (ASL) has the advantage of not relying on an injected contrast agent, instead inferring perfusion from a drop in signal observed in the imaging slice arising from inflowing spins (outside the imaging slice) having been selectively inverted or saturated. A number of ASL schemes are possible, the simplest being flow alternating inversion recovery (FAIR) which requires two acquisitions of identical parameters with the exception of the out-of-slice inversion; the difference in the two images is theoretically only from inflowing spins, and may be considered a 'perfusion map'.
References
- ^ PMID 22468186.
- ^ Frank Gaillard; et al. "Dynamic susceptibility contrast (DSC) MR perfusion". Radiopaedia. Retrieved 2017-10-14.
- ^ Frank Gaillard; et al. "Dynamic contrast enhanced (DCE) MR perfusion". Radiopaedia. Retrieved 2017-10-15.
- ^ Frank Gaillard; et al. "Arterial spin labelling (ASL) MR perfusion". Radiopaedia. Retrieved 2017-10-15.
- ^ Paul S. Tofts. "T1-weighted DCE Imaging Concepts: Modelling, Acquisition and Analysis" (PDF). paul-tofts-phd.org.uk. Retrieved 22 June 2013.
- S2CID 20718331.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - S2CID 20718331.
- PMID 25773937.
- PMID 3626789.
- PMID 16466927.
- PMID 24083460.