X-ray images from Thulium

Here is an interesting video clip that was recently posted to a radiography forum. It was produced by the British Pathe Co. in the 1950's and talks about a battle-field "X-ray" unit, which uses a radioactive material called Thulium to make an x-ray image. The
image is formed on a Polaroid style film and presumably processed by the old
Polaroid camera method. Although called an "X-ray Unit" it actually uses Gamma rays to produce the image.