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Published on: February 21, 2018
Markers of cochlear inflammation using MRI
Johann Le Floc'h1, Winston Tan, Ravindra S Telang
1Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand.
Purpose:
To quantify spatial and temporal inflammation-induced changes in vascular permeability and macrophage infiltration in guinea-pig (GP) cochlea using MRI.
Materials And Methods:
GPs were injected with lipopolysaccharide (LPS) to induce cochlear inflammation. One group was injected with a gadolinium based contrast agent (GBCA) and dynamic contrast enhanced (DCE)-MRI was performed at 4, 7, and 10 days after LPS treatment. A two-compartment pharmacokinetic model was used to determine the apparent rate constant of GBCA extravasation (K(trans) ). A second group was injected with ultrasmall superparamagnetic iron oxide particles (USPIOs) and studied at 2, 3, and 7 days after LPS treatment to detect tissue USPIO uptake and correlate with histology. For both groups, control GPs were scanned similarly.
Results:
The signal enhancement increased substantially and more rapidly at day 4 in LPS-treated than in control cochlea shortly following GBCA injection. K(trans) of LPS-treated cochlea was maximum on day 4 at 0.0218 ± 0.0032 min(-1) and then decreased to control level at 0.0036 ± 0.0004 min(-1) by day 10. In the second group, the relative signal intensity and T2 in cochlear perilymphatic spaces on day 2 decreased, on average, by 54% and 45%, respectively, compared with baseline and then remained under control levels by day 7. This suggests the infiltration of inflammatory cells, although unconfirmed by histology.
Conclusion:
This provides the first measurement of cochlear vascular permeability using MRI and a quantitative evaluation of the development of cochlear inflammation. MRI holds considerable potential for the assessment of disease processes such as clinical diagnosis of conditions such as labyrinthitis.
Insights
Magnetic resonance imaging (MRI) quantified cochlear inflammation and vascular changes in guinea pigs. This study provides a novel method for assessing inner ear disease and diagnosis.
Area of Science:
- Biomedical imaging
- Inner ear research
- Inflammation studies
Background:
- Cochlear inflammation is challenging to assess non-invasively.
- Understanding vascular permeability and macrophage infiltration is crucial for diagnosing inner ear diseases.
Purpose of the Study:
- To quantify spatial and temporal changes in vascular permeability and macrophage infiltration in the guinea pig cochlea using MRI.
- To establish MRI as a tool for evaluating cochlear inflammation.
Main Methods:
- Induced cochlear inflammation in guinea pigs using lipopolysaccharide (LPS).
- Utilized dynamic contrast-enhanced MRI (DCE-MRI) with gadolinium-based contrast agents (GBCAs) to measure vascular permeability (Ktrans).
- Employed ultrasmall superparamagnetic iron oxide particles (USPIOs) to detect macrophage infiltration and correlated with histology.
Main Results:
- LPS-treated cochlea showed significantly increased vascular permeability (Ktrans) peaking at day 4.
- GBCA extravasation returned to control levels by day 10.
- USPIO uptake indicated inflammatory cell infiltration by day 2, persisting until day 7.
Conclusions:
- This study presents the first MRI-based measurement of cochlear vascular permeability.
- MRI offers a quantitative method for evaluating the development of cochlear inflammation.
- MRI shows potential for clinical diagnosis of inner ear conditions like labyrinthitis.
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