The Collaborative International Dictionary of English v.0.48:

radiograph \ra"di*o*graph\ (r[=a]"d[i^]*[-o]*gr[a^]f), n.
   [Radio- + -graph.]
   1. An instrument for measuring and recording solar radiation.
      [Webster 1913 Suppl.]

   2. An image or picture produced upon a sensitive surface, as
      of a photographic or fluorescent plate, by some form of
      penetrating radiation other than light, as X-rays, beta
      rays, etc.; esp., a picture of the internal structure of
      opaque objects traversed by the rays; a skiagraph. When
      the picture is produced upon photographic film by X-rays,
      the picture is usually called an X-ray photo or X-ray.
      When an image is produced on photographic film by a
      radioactive substance in close proximity to the film, in a
      manner so as to record the spatial distribution of the
      radioactive substance, the resulting image is called an
      autoradiograph or autoradiogram.
      [Webster 1913 Suppl. +PJC]