IONIZATION AND DETECTION 



111 



shows a lead-collimated scintillation counter, useful, for instance, for ex- 

 ploring the thyroid after radioactive iodine has been administered. External 

 exploration of the organ for determination of size is known as scintography. 

 Mechanical devices have been designed which control the exploration and 

 print a map of the intensity of radiation from that area of the throat. 



(4) Chemical Reactions Induced in Aqueous Solutions: Water is broken up into 

 H and OH, and these very reactive products undergo reactions with solutes 

 to produce new chemicals. Oxidations or reductions, molecular rearrange- 

 ments, polymerization of plastics, and corrosion of metals have all been used 

 as detectors. Important quantitative aspects of absorption of ionizing radia- 

 tion by aqueous tissues are developed in Chapter 9. 



Figure 5-6. Collimated Scintillation Counter. Top: disassembled to show photo- 

 multiplier assembly. Bottom: assembled. With collimator (left) attached, the 

 instrument can be used for scintography — tor detailed external mapping of the 

 human body, above the liver for example, following internal administration of 

 the appropriate radioactively-labeled chemicals. (Photographs courtesy of 

 Burndepts Ltd., Erith, England.) 



