Brain Structure Alterations Revealed Using MRI in an Ethanol Mouse Model

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Brain Structure Alterations Revealed Using MRI in
an Ethanol Mouse Model

• Mark Shewfelt
• April 4, 2012

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Introduction

• Why a mouse model?
• Ethically acceptable
• Abundant with relatively low costs
• Approximately 99 of mice
• have genes that have a homologue
• in the human genome

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Theory

• Magnetic Resonance Imaging (MRI)
• 9.4T Magnet used
• Based on the detection of oscillating magnetic
  field produced by a set of hydrogen nuclei
• Tool for non-invasive detection of abnormal
  morphological patterns
• 20 Mice were scanned for approximately an hour
  each
• MICe Software used to manipulate MR images

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Image Registration

• Process of determining the optimal spatial
  transformation that best aligns a given source
  image to a given target image
• Objective is to achieve the maximum similarity
  between all of the MR images, in order to
  construct an unbiased average image
• Feature-based and intensity-based approaches
• Registration is very complex, it uses an
  algorithm that considers a transformation model,
  a similarity measure and optimization

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Group-wise Registration

• Each individual image is associated with a
  deformation field that aligns it with the
  consensus average

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Importance of Averaging
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Average Image
124 Slices
84 Slices
Side view
Front view
55 Slices
Top view
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Brain Atlas
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Methods
Hippocampus
Ventricles
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Results
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Results
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Results

• Hippocampus

• Ventricles

Student t-test for alcohol versus control, equal variances not assumed Student t-test for alcohol versus control, equal variances not assumed
Sample size (Both the same) 3
Significance Value 0.05
Significance (1-tailed) 0.2480 ?
Student t-test for alcohol versus control, equal variances not assumed Student t-test for alcohol versus control, equal variances not assumed
Sample size (Both the same) 3
Significance Value 0.05
Significance (1-tailed) 0.0076 ?
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Discussion

• Why does alcohol affect the ventricles more than
  the hippocampus?
• Alcohol known to kill brain cells and decrease
  brain volume
• Ventricles are fluid-filled sacs and therefore
  much more susceptible to change in volume
  compared to the more rigid hippocampus region
• Function of hippocampus lies in long-term memory,
  which is not usually associated with the effects
  of alcohol

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Discussion

• However,
• While it has been agreed that alcohol decreases
  brain volume in general, it has been shown to
  increase ventricular volume in humans
• Perhaps long term alcoholism has dramatic effects
  on the ventricles
• Mouse brain model is not always reliable for
  predicting similar physiological effects in
  humans!

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Conclusion

• Brain atlases are exceptionally useful in
  determining abnormal morphological patterns
• Brain ventricles in mice significantly decreased
  in size when introduced to alcohol, while the
  hippocampus did not

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Acknowledgements

• Many Thanks to
• Supervisor Dr. Ravi Menon
• Technical Support and Guidance Dr. Alex Li
• Site Robarts Research Institute

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• Thank you for listening, any questions?