Environmental Engineering Reference
In-Depth Information
8.2 MethodandResults
Mathematical. therapy. planning. is. performed.. Radiation. therapy. is. done.
with. the. Nucletron. Microelectronic. Classic. and. RTP. is. performed. by.
Nucletron's.Plato.(Nucletron.B..V.,.Veenendaal,.the.Netherlands)..The.expo-
sure.time.is.1.minute.in.the.zero.point.of.the.body.coordinate..In.the.study,.
absorption.calculations.are.performed.for.eight.treatment.points,.from.
p
1
.to.
p
8
.as.
p
0
.(0,.2.cm,.0),.
p
1
.(−2.cm,.2.cm,.0),.
p
2
.(2.cm,.−2.cm,.0),.
p
3
.(0,.2.cm, 2.cm),.
p
4
. (0,. 2. cm,. 0),.
p
5
. (0,. 5. cm,. 0),.
p
6
. (2. cm,. 4. cm,. 0),.
p
7
. (−2. cm,. 4. cm,. 0),. and.
p
8
.(0,.4.cm,.2.cm).
The.dosimeters. are. calculated. in.the.designed. geometry.. First.of.all,. one.
needs.to.choose.a.point.source.or.cylindrical. source.in.order.to.determine.
the. geometry. factor.. According. to. the. Technical. Guide. (TG). 41,. the. point.
source.is.described.as.
1/r
2
and.the.line.source.as.β
/
(
L × r × sin
θ)..Equation.(8.1).
shows.the.calculation.of.dosage.in.brachytherapy..Figure 8.1.shows.the.line.
source.case..The.calculated.doses.are.compared.to.the.RTP.doses.in.Table 8.3.
y
Variable point
P
P(r
,
θ)
β
θ
1
θ
Line source
L
θ
2
x
FIGURE 8.1
Diagram.of.the.line.source.case.
TABLE 8.3
Calculated.Doses.versus.RTP.Doses
Cal. D
(r,
θ
)
Dif.
(%)
Var.
r
θ
g(r)
φ
an
RTP D(r,
θ
)
p
0
1.9990
. 0.0000
1.0105
0.6450
79.2162
92.4
−14.27
p
1
2.8277
45.0371
1.0149
0.9607
59.2186
59.3
−0.14
p
2
2.8277
44.9629
1.0149
0.9607
59.2185
56.7
4.33
p
3
2.8277
45.0372
1.0149
0.9606
59.2185
59.0
0.37
p
4
1.9990
. 0.0000
1.0105
0.6450
79.2162
88.4
−10.39
p
5
4.9990
. 0.0000
0.9956
0.6960
13.4665
14.6
−7.76
p
6
4.4721
26.5843
1.0047
0.8947
21.8361
22.1
−1.19
p
7
4.4721
26.5843
1.0047
0.8947
21.8361
22.2
−1.64
p
8
4.4721
26.5843
1.0047
0.8947
21.8361
22.1
−1.19
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