Physics:Inversion recovery
Inversion recovery is a magnetic resonance imaging sequence that provides high contrast between tissue and lesion. It can be used to provide high T1 weighted image, high T2 weighted image, and to suppress the signals from fat, blood, or cerebrospinal fluid.[1]
Fluid-attenuated inversion recovery
Fluid-attenuated inversion recovery (FLAIR)[2] is an inversion-recovery pulse sequence used to nullify the signal from fluids. For example, it can be used in brain imaging to suppress cerebrospinal fluid so as to bring out periventricular hyperintense lesions, such as multiple sclerosis plaques. By carefully choosing the inversion time TI (the time between the inversion and excitation pulses), the signal from any particular tissue can be suppressed.
Turbo inversion recovery magnitude
Turbo inversion recovery magnitude (TIRM) measures only the magnitude of a turbo spin echo after a preceding inversion pulse, thus is phase insensitive.[3]
TIRM is superior in the assessment of osteomyelitis and in suspected head and neck cancer.[4][5] Osteomyelitis appears as high intensity areas.[6] In head and neck cancers, TIRM has been found to both give high signal in tumor mass, as well as low degree of overestimation of tumor size by reactive inflammatory changes in the surrounding tissues.[7]
Double inversion recovery
Double inversion recovery is a sequence that suppresses both cerebrospinal fluid and white matter, and samples the remaining transverse magnetisation in fast spin echo, where the majority of the signals are from the grey matter. Thus, this sequence is useful in detecting small changes on the brain cortex such as focal cortical dysplasia and hippocampal sclerosis in those with epilepsy. These lesions are difficult to detect in other MRI sequences.[8]
Efficiency
The tissue or fluid to suppress (e.g., cerebrospinal fluid) and the tissue of interest (e.g. white/gray matter) typically have very different T1 values, e.g. T1 = 4000 ms and T1 = 920 ms.[9] Maximizing the signal from the tissue of interest while maintaining suppression of the tissue to suppress leads to optimal expressions for the sequence timing parameters.[10] In the example used (FLAIR) these are TI = 1710 ms and TR = 4759 ms.
In certain uses of inversion recovery, the tissue of interest and tissue to suppress are the same, e.g. at tissue boundaries[11], in which case the optimal timing parameters are TR = 3.57T1 and TI = 0.67T1.
History
Erwin Hahn first used inversion recovery technique to determine the value of T1 (the time taken for longitudinal magnetisation to recover 63% of its maximum value) for water in 1949, 3 years after the nuclear magnetic resonance was discovered.[1]
References
- ↑ 1.0 1.1 "MRI: use of the inversion recovery pulse sequence". Clinical Radiology 53 (3): 159–76. March 1998. doi:10.1016/s0009-9260(98)80096-2. PMID 9528866.
- ↑ "MR of the brain using fluid-attenuated inversion recovery (FLAIR) pulse sequences". AJNR. American Journal of Neuroradiology 13 (6): 1555–1564. 1992. PMID 1332459.
- ↑ "Chapter 2.4: Image Contrasts and Imaging Sequences". Magnetic Resonance Tomography. Springer Science & Business Media. 2007. p. 59. ISBN 978-3-540-29355-2. https://books.google.com/books?id=C4Tuzckp3oQC&pg=PA59.
- ↑ "Turbo inversion recovery magnitude". https://radiopaedia.org/articles/turbo-inversion-recovery-magnitude-1.
- ↑ "Comparison of turbo inversion recovery magnitude (TIRM) with T2-weighted turbo spin-echo and T1-weighted spin-echo MR imaging in the early diagnosis of acute osteomyelitis in children". Pediatric Radiology 28 (11): 846–850. November 1998. doi:10.1007/s002470050479. PMID 9799315.
- ↑ "Chronic osteomyelitis of the left femur". http://clinical-mri.com/chronic-osteomyelitis-of-the-left-femur/.
- ↑ "Diagnostic evaluation of magnetic resonance imaging with turbo inversion recovery sequence in head and neck tumors". European Archives of Oto-Rhino-Laryngology 262 (8): 634–639. August 2005. doi:10.1007/s00405-004-0878-x. PMID 15668813.
- ↑ "Utility of double inversion recovery MRI in paediatric epilepsy". The British Journal of Radiology 89 (1057). 2016. doi:10.1259/bjr.20150325. PMID 26529229.
- ↑ Bernstein, Matt (2004). Handbook of MRI Pulse Sequences. Elsevier. pp. 961. ISBN 978-0-12-092861-3.
- ↑ Bydder, Mark; Ali, Fadil; Condron, Paul; Cornfeld, Daniel M.; Newburn, Gil; Kwon, Eryn E.; Tayebi, Maryam; Scadeng, Miriam et al. (December 2024). "Validation of an ultrahigh contrast divided subtracted inversion recovery technique using a standard T 1 phantom" (in en). NMR in Biomedicine 37 (12). doi:10.1002/nbm.5269. ISSN 0952-3480. https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/nbm.5269.
- ↑ Middlebrooks, Erik H; Okromelidze, Lela; Lin, Chen; Jain, Ayushi; Westerhold, Erin; Ritaccio, Anthony; Quiñones-Hinojosa, Alfredo; Gupta, Vivek et al. (December 2021). "Edge-enhancing gradient echo with multi-image co-registration and averaging (EDGE-MICRA) for targeting thalamic centromedian and parafascicular nuclei" (in en). The Neuroradiology Journal 34 (6): 667–675. doi:10.1177/19714009211021781. ISSN 1971-4009. PMID 34121497. PMC 8649196. https://journals.sagepub.com/doi/10.1177/19714009211021781.
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