Editing Magnetic resonance imaging (section)

=== Quantitative MRI ===
Most MRI focuses on qualitative interpretation of MR data by acquiring spatial maps of relative variations in signal strength which are "weighted" by certain parameters.<ref name="Gulani-Sieberlich-QMRI-2020">{{cite book|last1=Gulani|first1=Vikas|last2=Nicole|first2=Sieberlich|date=2020|title=Quantitative Magnetic Resonance Imaging|chapter=Quantitative MRI: Rationale and Challenges|publisher=Academic Press|page=xxxvii-li|doi=10.1016/B978-0-12-817057-1.00001-9 |doi-access=free |isbn=9780128170571|s2cid=234995365 |s2cid-access=free |name-list-style=amp }}</ref> Quantitative methods instead attempt to determine spatial maps of accurate tissue relaxometry parameter values or magnetic field, or to measure the size of certain spatial features.

Examples of quantitative MRI methods are:

* T1-mapping (notably used in [[cardiac magnetic resonance imaging]]<ref name="pmid27354273">{{cite journal| last1=Captur |first1=G |last2=Manisty |first2=C |last3=Moon |first3=JC| title=Cardiac MRI evaluation of myocardial disease. | journal=Heart | year= 2016 | volume= 102 | issue= 18 | pages= 1429–35 | pmid=27354273 | doi=10.1136/heartjnl-2015-309077 | pmc= | s2cid=23647168 | url=https://pubmed.ncbi.nlm.nih.gov/27354273  }}</ref>)
* T2-mapping<ref name="pmid34008045">{{cite journal| last1=Cobianchi Bellisari |first1=F |last2=De Marino |first2=L |last3=Arrigoni |first3=F |last4=Mariani |first4=S |last5=Bruno |first5=F |last6=Palumbo |first6=P | display-authors=etal| title=T2-mapping MRI evaluation of patellofemoral cartilage in patients submitted to intra-articular platelet-rich plasma (PRP) injections. | journal=Radiol Med | year= 2021 | volume= 126 | issue= 8 | pages= 1085–1094 | pmid=34008045 | doi=10.1007/s11547-021-01372-6 |doi-access=free | pmc=8292236 }}</ref>
* [[Quantitative susceptibility mapping]] (QSM)
* Quantitative fluid flow MRI (i.e. some [[cerebrospinal fluid flow MRI]]<ref name="Radiopedia-CSFflow">{{Cite journal|last1=Gaillard|first1=Frank |first2=Henry |last2=Knipe |doi=10.53347/rID-37401 |doi-access=free |title=CSF flow studies {{!}} Radiology Reference Article |date=13 Oct 2021 |url=https://radiopaedia.org/articles/csf-flow-studies?lang=us|access-date=2021-11-24|website=Radiopaedia|language=en-US}}</ref>)
* [[Magnetic resonance elastography]] (MRE)<ref>{{cite book |url=https://www.onlinelibrary.wiley.com/doi/book/10.1002/9783527696017 |title=Magnetic Resonance Elastography &#124; Wiley Online Books |year=2016 |doi=10.1002/9783527696017 |last1=Hirsch |first1=Sebastian |last2=Braun |first2=Jürgen |last3=Sack |first3=Ingolf |isbn=9783527696017 |access-date=2022-03-06 |archive-date=2022-03-05 |archive-url=https://web.archive.org/web/20220305222408/https://onlinelibrary.wiley.com/doi/book/10.1002/9783527696017 |url-status=dead }}</ref>

Quantitative MRI aims to increase the [[reproducibility]] of MR images and interpretations, but has historically require longer scan times.<ref name="Gulani-Sieberlich-QMRI-2020"/>

Quantitative MRI (or qMRI) sometimes more specifically refers to multi-parametric quantitative MRI, the mapping of multiple tissue relaxometry parameters in a single imaging session.<ref name="pmid33763021">{{cite journal| vauthors=Seiler A, Nöth U, Hok P, Reiländer A, Maiworm M, Baudrexel S | display-authors=etal| title=Multiparametric Quantitative MRI in Neurological Diseases. | journal=Front Neurol | year= 2021 | volume= 12 | issue=  | pages= 640239 | pmid=33763021 | doi=10.3389/fneur.2021.640239 | pmc=7982527 | doi-access=free}}</ref>
Efforts to make multi-parametric quantitative MRI faster have produced sequences which map multiple parameters simultaneously, either by building separate encoding methods for each parameter into the sequence,<ref name="pmid18666127">{{cite journal| vauthors=Warntjes JB, Leinhard OD, West J, Lundberg P| title=Rapid magnetic resonance quantification on the brain: Optimization for clinical usage. | journal=Magn Reson Med | year= 2008 | volume= 60 | issue= 2 | pages= 320–9 | pmid=18666127 | doi=10.1002/mrm.21635 | pmc= | s2cid=11617224 | doi-access=free }}</ref>
or by fitting MR signal evolution to a multi-parameter model.<ref name="pmid22378141">{{cite journal| vauthors=Ehses P, Seiberlich N, Ma D, Breuer FA, Jakob PM, Griswold MA | display-authors=etal| title=IR TrueFISP with a golden-ratio-based radial readout: fast quantification of T1, T2, and proton density. | journal=Magn Reson Med | year= 2013 | volume= 69 | issue= 1 | pages= 71–81 | pmid=22378141 | doi=10.1002/mrm.24225 | pmc= | s2cid=24244167| doi-access=free }}</ref><ref name="pmid23486058">{{cite journal| vauthors=Ma D, Gulani V, Seiberlich N, Liu K, Sunshine JL, Duerk JL | display-authors=etal| title=Magnetic resonance fingerprinting. | journal=Nature | year= 2013 | volume= 495 | issue= 7440 | pages= 187–92 | pmid=23486058 | doi=10.1038/nature11971 | pmc=3602925 | bibcode=2013Natur.495..187M}}</ref>