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]

The Collaborative International Dictionary of English v.0.48:

Autoradiogram \Au`to*ra"di*o*gram\, n. [Auto- + radiogram.]
   (Biochemistry)
   an image produced upon photographic film by exposure of the
   film to a radioactive substance in close proximity to
   (usually in contact with) the film.

   Note: Recording the distribution of radioactive materials on
         an autoradiogram is a technique much used in
         biochemical research as part of analytical procedures,
         in which radioactively labeled substances are subjected
         to a separation process (such as electrophoresis) which
         can help to characterize the substance, and the
         resulting distribution of the labeled substance is
         recorded on an autoradiogram. In microbiology and cell
         biology, autoradiograms may be made on the same film as
         a photomicrograph, permitting observation of the
         distribution of labeled compounds within a cell.
         [PJC]