What does the ring use to measure radiation exposure?

Text Box: The Panasonic UD-807 extremity dosimeter measures radiation exposure due to x, beta, and gamma radiations with a single lithium borate phosphor (Li2B4O7:Cu) chip. Of all the TLD phosphors in common use today, Li2B4O7:Cu is most closely equivalent to human tissue.  Other types of dedicated extremity dosimeters include the Harshaw DXT-RAD and EXT-RAD, both using a single LiF phosphor. The Panasonic UD-802 whole body dosimeter can also be configured for use as a wrist or ankle dosimeter.  This dosimeter incorporates four TL phosphors behind varying filters - two of Li2B4O7:Cu and two of CaSO4:Tm.  This dosimeter configuration is more versatile in that it is capable of differentiating more radiation types and energies than is possible from a single element TLD used in the extremity dosimeter. However, it does have a disadvantage of a significantly larger physical size when compared to dedicated extremity dosimeters.