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Reference dose with air-filled ionisation chambers
o
o
ref
ref
QQ,
Qw, D,
Q
Qw,
k
N M D
f
f
⋅
⋅
=
0
0
0
0
0
oQQ,
Q
Q
water
air
Q
Q
water
air
Q
Q
water
air
Q
air
Q
Q
water
air
Q
air
p
S
p
S
p
S
e
W
p
S
e
W
k
ρ
ρ
≈
ρ
ρ
=
IAEA, TRS-398 (2000)
Determination of dose in small fields
Eklund & Ahnesjo, PMB, 53 (2008) 4231-4247
Note!
There are differences in Sw,air
between beams with and without
flattening filter (see
Xiong and Rogers , Med Phys 35(5)
(2008), p2104 )