1032 / 1245
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