When TLD material is irradiated and subsequently heated, it will emit light which is related to:  

 

·         Absorbed dose in the material  

·         Phosphor conformity  

·         Reproducibility of the heating cycle  

·         Reader sensitivity  

·         Energy of the radiation  

·         Linearity of light emitted per unit dose  

·         Retention of emitted TLD phosphor light  

 

Each year, IROC Houston commissions a new batch of TLD powder to be used in our mailed TLD program. Each batch of powder yields nearly 100,000 capsules. The commissioning process includes verifying the fading correction, non-linearity correction, energy correction and dose response (sensitivity). The TLD dose is determined as follows:

 

D = S x V/mg x K_F x K_L x K_E x K_ISQ x PSF / DDF x K_DECAY

 

S            =        System sensitivity determined each session  

V/mg      =        Sample response per unit mass  

K_F          =        Fading correction (range 5-160 days)  

K_L          =        Non-linearity correction (doses 50 - 600 cGy)  

K_E          =        Energy correction (photons: ⁶⁰Co - 25 MV, electrons: 5 - 25 MeV)  

K_ISQ       =        Inverse square correction  

F            =        Peak scatter factor for dose to full phantom  

DDF       =        Depth dose factor

K_DECAY   =        Decay correction for ⁶⁰Co measurements