Brain Structure Brain Structure Alterations Revealed Alterations Revealed

Using MRI in an Ethanol Using MRI in an Ethanol Mouse ModelMouse Model

Why a mouse model?Why a mouse model?

•Ethically acceptableEthically acceptable

•Abundant with relatively low costsAbundant with relatively low costs

•Approximately 99% of mice Approximately 99% of mice

have genes that have a homologue have genes that have a homologue

in the human genomein the human genome

Magnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI)

•9.4T Magnet used9.4T Magnet used

•Based on the detection of oscillating magnetic field Based on the detection of oscillating magnetic field produced by a set of hydrogen nucleiproduced by a set of hydrogen nuclei

•Tool for non-invasive detection of abnormal Tool for non-invasive detection of abnormal morphological patternsmorphological patterns

•20 Mice were scanned for approximately an hour each20 Mice were scanned for approximately an hour each

•MICe Software used to manipulate MR imagesMICe Software used to manipulate MR images

Image RegistrationImage Registration

Process of determining the optimal spatial Process of determining the optimal spatial transformation that best aligns a given source transformation that best aligns a given source image to a given target imageimage to a given target image

Objective is to achieve the maximum similarity Objective is to achieve the maximum similarity between all of the MR images, in order to construct between all of the MR images, in order to construct an unbiased average imagean unbiased average image

Feature-based and intensity-based approachesFeature-based and intensity-based approaches

Registration is very complex, it uses an algorithm Registration is very complex, it uses an algorithm that considers a transformation model, a similarity that considers a transformation model, a similarity measure and optimizationmeasure and optimization

Group-wise RegistrationGroup-wise Registration

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

Importance of AveragingImportance of Averaging

Average ImageAverage Image

Top view

Side viewFront view

124 Slices84 Slices

55 Slices

Brain AtlasBrain Atlas

Hippocampus

Ventricles

HippocampusHippocampus VentriclesVentricles

Why does alcohol affect the ventricles Why does alcohol affect the ventricles more than the hippocampus?more than the hippocampus?

•Alcohol known to kill brain cells and decrease brain Alcohol known to kill brain cells and decrease brain volumevolume

•Ventricles are fluid-filled sacs and therefore much more Ventricles are fluid-filled sacs and therefore much more susceptible to change in volume compared to the more susceptible to change in volume compared to the more rigid hippocampus regionrigid hippocampus region

•Function of hippocampus lies in long-term memory, which Function of hippocampus lies in long-term memory, which is not usually associated with the effects of alcoholis not usually associated with the effects of alcohol

However,However,

•While it has been agreed that alcohol decreases While it has been agreed that alcohol decreases brain volume in general, it has been shown to brain volume in general, it has been shown to increase ventricular volume in humansincrease ventricular volume in humans

•Perhaps long term alcoholism has dramatic effects Perhaps long term alcoholism has dramatic effects on the ventricleson the ventricles

•Mouse brain model is not always reliable for Mouse brain model is not always reliable for predicting similar physiological effects in humans!predicting similar physiological effects in humans!

Brain atlases are exceptionally useful in Brain atlases are exceptionally useful in determining abnormal morphological patternsdetermining abnormal morphological patterns

Brain ventricles in mice significantly decreased in Brain ventricles in mice significantly decreased in size when introduced to alcohol, while the size when introduced to alcohol, while the hippocampus did nothippocampus did not

Many Thanks to:Many Thanks to:

Supervisor: Dr. Ravi MenonSupervisor: Dr. Ravi Menon

Technical Support and Guidance: Dr. Alex LiTechnical Support and Guidance: Dr. Alex Li

Site: Robarts Research InstituteSite: Robarts Research Institute

Thank you for listening, any Thank you for listening, any questions?questions?