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Relationships between quantities
TPR from data measured isocentrically
cm
SAD
100
=
cm z
ref
10
=
z
cm SSD
90
=
cm SSD
90
≠
cm z
ref
10
=
SAD SDD
≠
A
B
C
(
)
(
)
(
)
+
×
×
+
×
=
cm
z cm
A S
A S
cm
z cm z A
PDD
z A TPR
EqSq
SAD
iso
p
EqSq
SAD
iso
p
EqSq
SAD cm cm
EqSq
SAD
100
90
100
90
100
;
;
2
10,
90
Is the equivalent square field at SAD for the determination of phantom scatter
PDD normalised at reference depth to 100
EqSq
SAD
A