Semi-quantification of Endolymphatic Size on MR Imaging after Intravenous Injection of Single-dose Gadodiamide: Comparison between Two Types of Processing Strategies

Abstract

Purpose: Many inner ear disorders, including M áeni àere's disease, are believed to be based on endolymphatic hydrops. We evaluated a newly proposed method for semi-quantiˆcation of endolymphatic size in patients with suspected endolymphatic hydrops that uses 2 kinds of processed magnetic resonance (MR) images.Methods: Twenty-four consecutive patients underwent heavily T 2 -weighted (hT 2 W) MR cisternography (MRC), hT 2 W 3-dimensional (3D) ‰uid-attenuated inversion recovery (FLAIR) with inversion time of 2250 ms (positive perilymph image, PPI), and hT 2 W-3D-IR with inversion time of 2050 ms (positive endolymph image, PEI) 4 hours after intravenous administration of single-dose gadolinium-based contrast material (IV-SD-GBCM). Two images were generated using 2 new methods to process PPI, PEI, and MRC. Three radiologists contoured the cochlea and vestibule on MRC, copied regions of interest (ROIs) onto the 2 kinds of generated images, and semi-quantitatively measured the size of the endolymph for the cochlea and vestibule by setting a threshold pixel value.Results: Each observer noted a strong linear correlation between endolymphatic size of both the cochlea and vestibule of the 2 kinds of generated images. The Pearson correlation coe‹cients (r) were 0.783, 0.734, and 0.800 in the cochlea and 0.924, 0.930, and 0.933 in the vestibule (Pº0.001, for all). In both the cochlea and vestibule, repeated-measures analysis of variance showed no statistically signiˆcant diŠerence between observers.Conclusion: Use of the 2 kinds of generated images generated from MR images obtained 4 hours after IV-SD-GBCM might enable semi-quantiˆcation of endolymphatic size with little observer dependency.

The Technical and Clinical Features of 3D-FLAIR in Neuroimaging

“…11). 37,38,[101][102][103][104][105][106][107][108] In summary, 3D-FLAIR using VFA-TSE has several unique advantages for clinical neuroimaging as shown below: 1) Thinner slices and multi-planar reformation capability, 2) Higher flow sensitivity, 3) High sensitivity to subtle T 1 changes in fluid, 4) Free from CSF inflow artifacts, 5) Reasonable scan time, and 6) A 3D dataset that allows computer-aided analysis. Familiarity with these features of 3D-FLAIR imaging and proper use of 3D-FLAIR are important in order for radiologists to obtain useful information for patient management.…”

Time Course for Measuring Endolymphatic Size in Healthy Volunteers Following Intravenous Administration of Gadoteridol

“…All volunteers underwent heavily T 2 -weighted magnetic resonance cisternography (MRC) for anatomical reference of the fluid space and hT 2 W-3D-FLAIR (positive perilymph image: PPI) with inversion time of 2250 ms according to the clinical protocol of our hospital for evaluating endolymphatic hydrops. [19][20][21] We also obtained a positive endolymph image (PEI) with a shorter inversion time (TI) of 2050 ms. 22 We set parameters as previously reported. 22,23 hours after IV-SD-GBCM.…”

“…21 We obtained a HYDROPS2-Mi2 (HYDROPS2 image Multiplied with heavily T 2 -weighted MR cisternography, Image #2 in the present study) image by multiplying the MRC and HYDROPS2. 20 Our aim in multiplying MRC onto HYDROPS and HYDROPS2 images was to set to zero the signal intensity value of bony structures possibly included in the ROI (i.e., osseous spiral lamina, interscalar septum, and bony wall of the labyrinth). Without multiplication, such bony structures might show non-zero negative signal intensity value because of the low signal-to-noise ratio of HYDROPS and HYDROPS2, which would result in the overestimation of the size of the area of the endolymph.…”

“…20 We defined the ROI of the slice of the cochlea to include the middle part of the cochlea and that of the slice of the vestibule to include the middle part of the vestibule. These ROIs drawn on MRC for each time point were copied and pasted onto Images #1 and #2.…”

“…20 The purpose of the current study was to measure the size of the endolymphatic space in healthy volunteers at various time points after IV-SD-GBCM using the proposed semiquantitative methods and to determine the optimal timing for evaluating the endolymphatic space.…”