Supplementary Material for: Diverse Patterns of Perilymphatic Space Enhancement in the Rat Inner Ear after Intratympanic Injection of Two Different Types of Gadolinium: A 9.4-Tesla Magnetic Resonance Study

Objective: To compare the quality of perilymphatic
enhancement in the rat inner ear after intratympanic injection of two
types of gadolinium with a 9.4-tesla micro-MRI. Materials and Methods:
Gadolinium was injected into the middle ear in 6 Sprague-Dawley rats
via the transtympanic route. The left ear was injected with
Gd-DO3A-butrol first, and then the right ear was injected with Gd-DOTA.
MR images of the inner ear were acquired 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,
and 4 h after intratympanic (IT) injection using an Agilent MRI system
9.4T/160/AS. The normalized signal intensity was quantitatively analyzed
at the scala vestibuli (SV), scala media, and scala tympani (ST) using a
Marosis M-view system. Then the normalized signal intensities (SIs)
were compared between the two contrast agents. Results:
For Gd-DO3A-butrol, the SI was as low as 1.0-1.5 throughout 1-4 h at the
SV and ST of the basal turn. The maximum SI was 1.5 ± 0.5 at the SV (2
h) and 1.3 ± 0.5 at the ST (2 h). For Gd-DOTA, the 1-hour postinjection
SI at the basal turn was 2.5 ± 0.5 at the SV, 1.6 ± 0.3 at the ST, and
1.2 ± 0.3 at the scala media. In the apical turn, the maximum SI was
reached after 2.5 h. The maximum SI in the apical turn was 1.8 ± 0.4 at
the SV (3.5 h), 1.8 ± 0.4 at the ST (4 h), and 1.4 ± 0.3 at the scala
media (4 h). Conclusions: We were able to clearly
visualize and separate the ST and SV using IT Gd and 9.4-tesla
micro-MRI. We recommend using Gd-DO3A-butrol over Gd-DOTA and to perform
the MRI 2.5 h after using IT Gd in the rat inner ear.