Vista - Custom Listbox, binding problem

Hello

I'm a beginner with WPF.
I try to customize a listbox for view thumbnail image.
At the application start up :

Dim Images As List(Of String) = New List(Of String)
....
Listbox1.ItemsSource = Images

This code works great.
....
<ListBox Name="Listbox"
ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemTemplate >
<DataTemplate>
<Image Width="128" Height="100"
Source="{Binding}"> </Image>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

But if i want only the necessary BitmapImage width ,that don't work
....
<ListBox Name="Listbox"
ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemTemplate >
<DataTemplate>
<Image Width="128" Height="100" >
<Image.Source>
<BitmapImage DecodePixelWidth="200" UriSource="{Binding}" />
</Image.Source>
</Image>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

Could you help me

Thanks