How do I bind a sub-element of an XML array item to a DataGridColumn?

Question

Problem

I have an XML file with an array of items. I can correctly bind to the list of items and also to attributes on the node. However, I cannot get any sub elements bound and not sure what XPath or Path to use. How do I bind a sub-element of an array item to a DataGridColumn?

More details

I have a .rdl file, which is basically XML, and would like to add images in bulk, which SSRS doesn't do. To get around this I created a WPF application with an XmlDataProvider as so:

<UserControl.DataContext>
    <XmlDataProvider x:Name="dpReport" Source="MyFile.rdl" XPath="rd:Report/rd:EmbeddedImages/rd:EmbeddedImage" />
</UserControl.DataContext>

I had to add the rd prefix in the XAML and in the NameTable in the code-behind otherwise it wouldn't bind.

I have a DataGrid, which is binding to the list correctly, and a column which is binding to the attribute Name correctly. However, I would also like to bind to the MIMEType and ImageData sub-elements. How would I do this?

Simplified DataGrid Xaml

<DataGrid x:Name="lstImages" AutoGenerateColumns="False" ItemsSource="{Binding}" Grid.Row="2">
    <DataGrid.Columns>      
        <DataGridTextColumn Header="Name" Binding="{Binding XPath=@Name,Mode=TwoWay}"/>
        <!-- MIMEType Here -->
    </DataGrid.Columns>
</DataGrid>

XPaths attempted:

I have attempted to use variants of the following Bindings:

<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=MIMEType}"/>
<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=MIMEType/text()}"/>
<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=/MIMEType[1]/text()}"/>
<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=MIMEType[1]/text()}"/>
<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=(/MIMEType/text())[0]}"/>
<DataGridTextColumn Header="MimeType" Binding="{Binding XPath=(MIMEType/text())[0]}"/>