Add blur effect to Image in WPF Application

I want to add blur effect on image. here is my code

        <Image  Name="imgBackground" Stretch="None" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.ColumnSpan="2" Grid.RowSpan="2" Source="../../Images/first.png" ClipToBounds="False" SnapsToDevicePixels="False">
            <Image.Effect>
                <BlurEffect KernelType="Gaussian" Radius="100" RenderingBias="Quality" />
            </Image.Effect>
        </Image>

But the only problem is it make all edges white. how can I remove them. I dont want white edges effect