Inversion recovery

MRI sequence

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 (CSF).[1]

## Fluid-attenuated inversion recovery

[edit]

Main article: 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

[edit]

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

[edit]

Double inversion recovery is a sequence that suppresses both cerebrospinal fluid (CSF) 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]

## History

[edit]

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

[edit]

1. ^ a b Bydder GM, Hajnal JV, Young IR (March 1998). "MRI: use of the inversion recovery pulse sequence". Clinical Radiology. 53 (3): 159–76. doi:10.1016/s0009-9260(98)80096-2. PMID 9528866.
2. ^ De Coene B, Hajnal JV, Gatehouse P, Longmore DB, White SJ, Oatridge A, et al. (1992). "MR of the brain using fluid-attenuated inversion recovery (FLAIR) pulse sequences". AJNR. American Journal of Neuroradiology. 13 (6): 1555–1564. PMC 8332405. PMID 1332459.
3. ^ Reiser MF, Semmler W, Hricak H (2007). "Chapter 2.4: Image Contrasts and Imaging Sequences". Magnetic Resonance Tomography. Springer Science & Business Media. p. 59\. ISBN 978-3-540-29355-2.
4. ^ Weerakkody Y. "Turbo inversion recovery magnitude". Radiopaedia. Retrieved 2017-10-21.
5. ^ Hauer MP, Uhl M, Allmann KH, Laubenberger J, Zimmerhackl LB, Langer M (November 1998). "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. doi:10.1007/s002470050479. PMID 9799315. S2CID 29075661.
6. ^ Ai T. "Chronic osteomyelitis of the left femur". Clinical-MRI. Retrieved 2017-10-21.
7. ^ Sadick M, Sadick H, Hörmann K, Düber C, Diehl SJ (August 2005). "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. doi:10.1007/s00405-004-0878-x. PMID 15668813. S2CID 24575696.
8. ^ Soares BP, Porter SG, Saindane AM, Dehkharghani S, Desai NK (2016). "Utility of double inversion recovery MRI in paediatric epilepsy". The British Journal of Radiology. 89 (1057): 20150325. doi:10.1259/bjr.20150325. PMC 4985945. PMID 26529229.