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Contrast Enhancement of Cochlea after Direct Microneedle Intracochlear Injection of Gadodiamide through the Round
Chaoqun Zhou1, Sharon J Feng2, Stephen Leong3
1Department of Mechanical Engineering, Columbia University, New York, NY.
Rationale And Objectives:
The potential of contrast-enhanced MRI for diagnosing endolymphatic hydrops is limited by long wait times following intravenous (IV) or intratympanic (IT) delivery, high contrast dosages, and inconsistent signal intensity enhancements. This study investigates microneedle-mediated intracochlear (IC) gadodiamide injection for consistent and efficient contrast delivery with minimal contrast dosage.
Materials And Methods:
A 100 µm diameter microneedle with 35 µm lumen was used to inject 1 µL of diluted gadodiamide (17.4 mM) into a guinea pig cochlea via the round window membrane. Serial MRI imaging was performed in a post-mortem animal using a 9.4 T small-animal MRI. Maximum intensity projections of MRI scans were generated to visualize diffusion of contrast within cochlea over time; mean intensities in defined regions of interest (ROIs) were calculated. Contrast diffusion time and intensity enhancements were determined.
Results:
Contrast was observed in the basal turn of scala tympani (ST) and scala vestibuli (SV) in the first MRI scan for all subjects which was acquired as early as 35 min after injection. Two-tailed paired t-tests confirmed that contrast reached the first two turns of ST and SV within 60 min, and the second half of third turns and apical turns of ST and SV within 90 min (p < 0.05). Intensity enhancements, defined as the percentage increase of the ROI mean intensity in the injection side compared to the contralateral side, exceeded 100% in the first turn and ranged from 12% to 32% in the third and apical turns of ST and SV at 90 min after injection.
Conclusions:
IC gadodiamide enables controllable and efficient contrast delivery with significantly lower contrast dosage, making it a viable alternative for contrast-enhanced cochlear MRI.
Insights
Intracochlear gadodiamide injection via microneedles offers efficient contrast delivery for cochlear MRI, overcoming limitations of traditional methods. This technique allows for lower contrast dosages and consistent signal enhancement in diagnosing endolymphatic hydrops.
Area of Science:
- Otolaryngology
- Radiology
- Biomedical Engineering
Background:
- Current contrast-enhanced MRI for endolymphatic hydrops diagnosis faces challenges including long wait times, high contrast doses, and variable signal enhancement.
- Intravenous (IV) and intratympanic (IT) contrast delivery methods are limited in efficiency and consistency for cochlear imaging.
Purpose of the Study:
- To investigate the efficacy of microneedle-mediated intracochlear (IC) gadodiamide injection for improved contrast delivery in cochlear MRI.
- To assess the potential for consistent and efficient contrast distribution with reduced contrast dosage using the IC microneedle technique.
Main Methods:
- A 100 µm diameter microneedle with a 35 µm lumen was used to inject 1 µL of diluted gadodiamide (17.4 mM) into the guinea pig cochlea via the round window membrane.
- Serial 9.4 T small-animal MRI scans were performed post-mortem to visualize contrast diffusion over time.
- Maximum intensity projections and region of interest (ROI) mean intensities were analyzed to determine contrast diffusion time and signal enhancement.
Main Results:
- Contrast was visible in the basal turns of the scala tympani (ST) and scala vestibuli (SV) within 35 minutes post-injection in all subjects.
- Contrast reached the first two turns of ST and SV within 60 minutes, and the apical turns within 90 minutes (p < 0.05).
- Intensity enhancements exceeded 100% in the basal turn and ranged from 12% to 32% in apical turns at 90 minutes.
Conclusions:
- Intracochlear gadodiamide injection using microneedles provides controllable and efficient contrast delivery for cochlear MRI.
- This method significantly reduces contrast dosage, presenting a viable alternative to current contrast-enhanced MRI techniques for diagnosing endolymphatic hydrops.
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