Растягивание изображения WPF для заполнения не растягивается до границ его родителей

вот мой XAML и как он выглядит:

<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>

Я просто хочу, чтобы изображение игры растягивалось, чтобы заполнить границы холста, который находится внутри круглой границы.

почему он этого не делает?