Increased signal intensity with delayed post contrast 3D-FLAIR MRI sequence using constant flip angle and long repetition time for inner ear evaluation - 22/10/21

Doi : 10.1016/j.diii.2021.10.003

Samir Osman ^a, Charlotte Hautefort ^b,^c, Arnaud Attyé ^d, Alexis Vaussy ^e, Emmanuel Houdart ^a,^b, Michael Eliezer ^a,^b,^⁎
^a Department of Neuroradiology, Lariboisière University Hospital, Assistance Publique Hôpitaux de Paris, 75010 Paris, France
^b Université de Paris, Faculté de Médecine, 75010 Paris, France
^c Department of Head and Neck Surgery, Lariboisière University Hospital, Assistance Publique Hôpitaux de Paris, 75010 Paris, France
^d Department of Neuroradiology and MRI, Grenoble Alpes University Hospital, SFR RMN Neurosciences, 38000 Grenoble, France
^e Siemens Healthineers, 93200 Saint-Denis, France

^⁎Corresponding author.

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Highlights

•	After intravenous administration of gadolinium-based contrast agent, gadolinium passagethrough the blood-labyrinth barrier is weak leading to low concentration of gadolinium in the perilymphatic space.
•	Elongation of the repetition time (TR) increases the signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) while preserving diagnostic accuracy.
•	The sensitivity of 3D-FLAIR sequences to low concentration gadolinium in the perilymphatic space is increased (+34.4%) by elongation of the TR.

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Abstract

Purpose

The purpose of this study was to compare the degree of perilymphatic enhancement between 4 hour post-contrast constant flip angle three-dimensional fluid attenuated inversion recovery (3D-FLAIR) images obtained with short repetition time (TR) and those obtained with long TR.

Materials and methods

This single-center, prospective study included patients who underwent MRI of the inner ear with heavily T2-weighted sequence, 3D-FLAIR sequence with a “short” TR of 10,000 ms (s3D-FLAIR) and with a “long” TR of 16,000 ms (l3D-FLAIR). Signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) obtained with s3D-FLAIR and l3D-FLAIR were quantitatively assessed using region of interest (ROI) method and compared. The morphology of the endolymphatic space on both sequences was also evaluated.

Results

From March 2020 to July 2020, 20 consecutive patients were enrolled (9 women and 11 men; mean age, 52.1 ± 14.5 [SD] years; age range: 29–75 years). On l3D-FLAIR images, mean SIR (21.1 ± 8.8 [SD]; range: 7.6–46.1) was significantly greater than that on s3D-FLAIR images (15.7 ± 6.7 [SD]; range: 5.9–33.4) (P < 0.01). On l3D-FLAIR images, mean CNR (17 ± 8.5 [SD]; range: 2–40) was significantly greater than that on s3D-FLAIR images (12 ± 6.3 [SD]; range: 3.2–29.8) (P < 0.01). Kappa value for inter-rater agreement for endolymphatic hydrops, vestibular atelectasis and perilymphatic fistula were 0.93 (95% CI: 0.74–1), 1 (95% CI: 0.85–1) and 1 (95% CI: 0.85–1) respectively.

Conclusion

This study demonstrates that the sensitivity of 3D-FLAIR sequences to low concentration gadolinium in the perilymphatic space is improved by elongation of the TR, with SIR and CNR increased by +34.4% and +41.3% respectively.

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Keywords : 3D-FLAIR, Endolymphatic hydrops, Inner ear, Magnetic resonance imaging (MRI)

Abbreviations : 3D, CI, CNR, EH, FLAIR, l3D-FLAIR, MRI, ROI, s3D-FLAIR, SD, SI, SIR, SNR, TE, TR