Thermoluminescent dosimeter

Thermoluminescent dosimeter (TLD) is a passive radiation detection device that is used for personal dose monitoring or to measure patient dose. 

  • plastic holder
  • nickel-coated aluminium card with TLD discs
    • the discs are made of a thermoluminescent material, commonly calcium sulphate doped with dysprosium (CaSO4:Dy) or lithium fluoride (LiF)
      • nearly tissue equivalent, although not at all x-ray energies 3
    • the discs are 0.8 mm thick and have a 1.35 mm diameter
  • three filters against each disc
    • top: aluminium and copper
    • middle: perspex
    • lower: open

When the radiation falls on TLD, the electrons are excited and store energy. After a varied period (can be one month, bimonthly, quarterly or even biannual), the TLD badges are sent for reading. The TLD reader consists of a heater. On getting heated, the excited electrons again come back to the ground state and emit light which is then read by a photomultiplier 1.

If a radiation worker is wearing a lead apron, the TLD badge can be worn under the lead apron (to reflect body dose) or outside the lead apron (to reflect extremity/thyroid dose) 1. TLDs can measure doses from 0.01 mGy to 10 Gy 2

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Article information

rID: 36761
Tag: refs
Synonyms or Alternate Spellings:
  • TLD
  • Thermoluminescent dosimeter badge
  • TLD badge

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Cases and figures

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    TLD - opened up
    Figure 1: TLD badge opened up
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    Nickel coated alu...
    Figure 2: TLD card with discs
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