Dose Course 2018_Flipping book

Point detectors for in vivo dosimetry

Before irradiation

Irradiation

readout heating

(G

)T

 D dT



Conduction band Forbidden band Valence band

TLD

trap

trap

trap

Sensitivity: material;reader

light

h  > 3,6eV

D I

T 

N

P

N

P

Diode

Sensitivity: doping; pre-irradiation dose

MOSFET structure

I

(sat)= I

(dif)

I

(sat) + I

(ion) > I N

(dif)

n

N

n

n

I

= 0

total

MOSFET • Capable of dose measurements immediately after irradiation or can be sampled in predefined time intervals (on-line dosimetry) • Can operate in active (negative bias on gate during radiation) or M etal O xide S emiconductor F ield E ffect T ransistor •

V

D  

Threshold

Sensitivity: thickness SiO2; bias during irradiation

passive mode

Soubra, Cygler, Mackay, Med. Phys. 21(4) , 567-572, 1994

Cygler, MOSFET dosimetry, AAPM Summer School 2009