Gamma imaging is at the interface of medicine and physics and thus its teaching is important in both
fields. Pedagogic literature highlights the benefits of interactive demonstrations in teaching: an
increase in enjoyment and interest, as well as improvement in academic achievement. However gamma
imaging uses radioactive sources, which are potentially dangerous and thus their use is tightly
controlled. We have developed a demonstration which uses a localised exothermic reaction within a
rag doll as an analogue of radioactivity. This can be safely used in classrooms to demonstrate the
principles of gamma imaging. The tool is easy to make, cheap, robust and portable. The supplementary
material in this paper gives teacher notes and a description of how to make the rag doll
demonstrator. We have tested the tool using six participants, acting as ‘teachers’, who carried out
the demonstration and described the doll as easy to use, and the ‘tumour’ clearly identifiable.
Th…