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Conduction

band

Forbidden

band

Valence

band

trap

Before

irradiation

trap

Irradiation

trap

readout

heating

light

TLD

Diode

MOSFET

D dT

)T

(G

D I

T

D

V

Threshold

 

I

n

(sat)=

I

N

(dif)

I

total

= 0

N

P

h

> 3,6eV

N

P

I

n

(sat) + I

n

(ion) >

I

N

(dif)

Sensitivity:

material;reader

Sensitivity:

doping; pre-irradiation dose

Sensitivity:

thickness SiO2;

bias during irradiation

Point detectors for in vivo dosimetry

MOSFET st ruct ure

M

etal

O

xide

S

emiconductor

F

ield

E

ffect

T

ransistor

• 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

Cygler, MOSFET dosimetry, AAPM Summer School 2009

passive mode

Soubra, Cygler, Mackay, Med. Phys.

21(4)

, 567-572, 1994