WPF Image étirer pour remplir de ne pas étirer les limites de ses parents

Voici mon XAML et à quoi ça ressemble:

<Window x:Class="GameLenseWpf.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="450" Width="350" MinHeight="450" MinWidth="350">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="0.15*" />
<RowDefinition />
</Grid.RowDefinitions>
<Image Grid.Row="0" Stretch="Fill" Source="Image/topBarBg.png" />
<StackPanel Orientation="Horizontal" Grid.Row="0">
<TextBlock Text="Platform" 
Foreground="White" 
FontFamily="Georgia"
FontSize="15" 
Margin="10"
HorizontalAlignment="Center"
VerticalAlignment="Center"/>
<ComboBox x:Name="cmbPlatform" 
Margin="10"
FontFamily="Georgia"
FontSize="15"
MinHeight="30"
MinWidth="140"
VerticalAlignment="Center"
VerticalContentAlignment="Center" SelectionChanged="cmbPlatform_SelectionChanged">
<ComboBoxItem>All Platforms</ComboBoxItem>
<ComboBoxItem>Playstation 3</ComboBoxItem>
<ComboBoxItem>XBox 360</ComboBoxItem>
<ComboBoxItem>Wii</ComboBoxItem>
<ComboBoxItem>PSP</ComboBoxItem>
<ComboBoxItem>DS</ComboBoxItem>
</ComboBox>
</StackPanel>
<Image x:Name="imgAbout" Grid.Row="0" Source="Image/about.png" 
Height="16" HorizontalAlignment="Right"
VerticalAlignment="Center"
Margin="0 0 10 0"    />
<ListBox Grid.Row="1" x:Name="lstGames" Background="#343434" Padding="5"
ScrollViewer.HorizontalScrollBarVisibility="Disabled"
HorizontalContentAlignment="Stretch">
<ListBox.Resources>
<Style TargetType="ListBoxItem">
<Style.Resources>
<!-- SelectedItem with focus -->
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
Color="Transparent" />
<!-- SelectedItem without focus -->
<SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}"
Color="Transparent" />
<!-- SelectedItem text foreground -->
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}"
Color="Black" />
</Style.Resources>
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
</Style>
</ListBox.Resources>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="120" Margin="0 10" >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="90"/>
<ColumnDefinition />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />                            
</Grid.RowDefinitions>
<Border BorderBrush="#202020" BorderThickness="5" CornerRadius="4" Panel.ZIndex="0">
<Canvas Grid.Row="0" Grid.Column="0" >
<Image Source="{Binding ImageUrl}" Canvas.Left="0" Canvas.Top="0" Stretch="UniformToFill"/>
<Image Source="Image/youtube.png" Canvas.Bottom="0" Canvas.Right="0" Height="20" Width="20" />
</Canvas>                           
</Border>
<StackPanel Grid.Row="0" Grid.Column="1" Margin="12 0 0 0">
<StackPanel Orientation="Horizontal">
<TextBlock Text="Title:" FontFamily="Arial" Foreground="White"/>
<TextBlock Text="{Binding Title}" FontFamily="Arial" Foreground="White" />
</StackPanel>
<StackPanel Orientation="Horizontal">
<TextBlock Text="Release Date:" FontFamily="Arial" Foreground="White" />
<TextBlock Text="{Binding ReleaseDate}" FontFamily="Arial" Foreground="White" />
</StackPanel>
<TextBlock Text="Synopsis" FontFamily="Arial" Foreground="White" />
<TextBox Background="#454545" Foreground="White" TextWrapping="Wrap" Text="{Binding Synopsis}" MaxHeight="73" />
</StackPanel>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>

WPF Image étirer pour remplir de ne pas étirer les limites de ses parents

Je veux juste jeux image pour étirer pour remplir la toile limites, qui est à l'intérieur du rond à la frontière.

Pourquoi n'est-il pas le faire?