Abstract
PurposeHeavily T2-weighted 3D FLAIR (hT2w-3D-FLAIR) sequence with constant flip angle (CFA) has been reported as being more sensitive to low concentrations of gadolinium (Gd) enabling endolymphatic hydrops (EH) visualization. The purpose of this study was to compare signal-to-noise (SNR) ratio, detection rate of EH, and increased perilymphatic enhancement (PE) as well as diagnostic accuracy in diagnosing definite Menière’s disease (MD), using 3D-SPACE FLAIR versus conventional 3D-TSE FLAIR.MethodsThis retrospective study included 29 definite MD patients who underwent a 4-h delayed intravenous (IV) Gd-enhanced 3D-TSE FLAIR and 3D-SPACE FLAIR MRI between February 2019 and February 2020. MR images were qualitatively and quantitatively analyzed twice by 2 experienced head and neck radiologists. Qualitative assessment included grading of cochlear and vestibular EH and visual comparison of PE. Quantitative assessment of PE was performed by placing a region of interest (ROI) and ratio calculation in the basal turn of the cochlea and the brainstem.ResultsThe intra- and inter-reader reliability for grading of EH and PE was excellent (0.7 < kappa < 0.9) for 3D-SPACE FLAIR and exceeded the values for 3D-TSE FLAIR (0.5 < kappa < 0.9) The combination of EH and visual assessment of PE has the highest diagnostic accuracy in diagnosing definite MD on 3D-SPACE FLAIR with a sensitivity of 0.91 and a specificity of 0.98 resulting in a sensitivity raise of 6% compared to 3D-TSE FLAIR.ConclusionFour-hour delayed IV Gd-enhanced 3D-SPACE FLAIR sequence has a higher sensitivity and reproducibility than 3D-TSE FLAIR for the visualization of EH and increased PE in definite MD patients.
Highlights
In the past decade, it has become feasible to discriminate endolymphatic hydrops (EH)—the morphological substrate of Menière’s disease (MD)—using delayed post-gadolinium (Gd) magnetic resonance imaging (MRI) [1,2,3,4,5,6]
The intravenous gadolinium (IV) administration has been widely adopted as the method of choice for hydrops imaging over the intratympanic (IT) method, with three-dimensional (3D) turbo spin-echo (TSE) fluid-attenuated inversion recovery (FLAIR) sequence as the sequence of choice over 3D REAL inversion recovery (IR) sequences, the former being more sensitive to T1-shortening [1, 2, 4, 6]
3D REAL IR was a single sequence developed for the IT administration of Gd—in which by adapting the inversion time endolymphatic space, perilymphatic space, and surrounding bone can be separately visualized—it has nowadays evolved for IV Gd use into a process of subtraction of imaging series with a different inversion time and/or a heavily T2-weighted MR cisternography (MRC) sequence [7,8,9,10]. 3D TSE FLAIR does not require this complex postprocessing involving subtraction of imaging series like 3D REAL IR sequences, being time-consuming, and with potential misregistration [2, 6]
Summary
It has become feasible to discriminate endolymphatic hydrops (EH)—the morphological substrate of Menière’s disease (MD)—using delayed post-gadolinium (Gd) magnetic resonance imaging (MRI) [1,2,3,4,5,6]. 3D REAL IR was a single sequence developed for the IT administration of Gd—in which by adapting the inversion time endolymphatic space, perilymphatic space, and surrounding bone can be separately visualized—it has nowadays evolved for IV Gd use into a process of subtraction of imaging series with a different inversion time and/or a heavily T2-weighted MR cisternography (MRC) sequence [7,8,9,10]. As compared to the 3D TSE FLAIR, 3D SPACE FLAIR has a higher radiofrequency (RF) receiver bandwidth with a constant (CFA) or variable flip angle (VFA), resulting in a higher echo train length and a longer echo time (TE) for the SPACE FLAIR. The increased repetition time (TR) and TE give much more heavily T2-weighted images, which benefits signal-to-noise ratio (SNR)
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