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Example
100cm SSD spine field 8cm*15cm,
Prescription single fraction 8Gy, prescribed to 7cm depth.
Calculated EqSq
Look up in BIR supl 25: 10.3cm
=1016.5
Max dose in many clinical settings
for a single beam is 1000MU
What do we do?
Basic Dose Caculation
Principles 2012
38
“Willow” 6MV PDD* Output
Depth
Equivalent Square Field Size (cm)
(cm)
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
9.5 10 10.5
Dmax (1.5) 93.6 94.5 95.4 95.7 95.9 96.6 97.3 97.7 98.2 98.5 98.8 99.4 100.0 100.2
2.0
92.7 93.7 94.7 94.8 94.8 95.5 96.1 96.6 97.1 97.4 97.7 98.3 99.0 99.1
2.5
90.5 91.5 92.6 92.8 93.0 93.5 94.1 94.6 95.1 95.4 95.8 96.3 96.9 97.1
3.0
88.0 89.1 90.1 90.4 90.7 91.2 91.8 92.3 92.8 93.2 93.6 94.3 95.0 95.2
3.5
85.8 86.9 88.0 88.3 88.7 89.2 89.8 90.3 90.8 91.2 91.6 92.1 92.6 93.0
4.0
83.7 84.7 85.7 86.0 86.3 87.0 87.7 88.2 88.6 89.1 89.5 90.2 90.8 91.1
4.5
81.3 82.2 83.1 83.6 84.2 84.9 85.6 86.1 86.5 87.0 87.4 88.0 88.6 89.0
5.0
79.1 80.0 80.8 81.5 82.2 82.8 83.4 84.0 84.5 84.9 85.4 86.0 86.7 87.0
5.5
76.7 77.9 79.0 79.3 79.6 80.5 81.3 81.9 82.4 82.8 83.3 84.0 84.7 84.9
6.0
74.7 75.6 76.5 77.2 77.8 78.5 79.1 79.7 80.3 80.9 81.6 82.1 82.5 82.8
6.5
72.5 73.6 74.7 75.2 75.7 76.6 77.4 77.9 78.4 78.8 79.2 79.9 80.5 80.8
7.0
70.5 71.5 72.5 73.1 73.7 74.4 75.1 75.8 76.4 76.9 77.3 77.8 78.4 78.8
7.5
68.3 69.5 70.7 71.2 71.6 72.4 73.2 73.8 74.3 74.8 75.3 76.1 76.8 77.1
8.0
66.4 67.5 68.5 69.2 69.8 70.5 71.2 71.9 72.6 72.9 73.3 74.1 74.8 75.1
8.5
64.5 65.6 66.6 67.3 67.9 68.6 69.3 70.0 70.7 71.1 71.5 72.2 72.9 73.2
9.0
62.5 63.6 64.8 65.4 66.1 66.7 67.4 68.1 68.7 69.1 69.5 70.3 71.1 71.4
9.5
60.8 61.9 63.0 63.5 64.1 64.8 65.5 66.2 66.9 67.5 68.0 68.6 69.2 69.5
10.0
58.8 59.9 61.1 61.7 62.3 63.1 63.8 64.5 65.1 65.6 66.1 66.8 67.5 67.9
10.5
57.1 58.3 59.5 60.0 60.4 61.2 62.1 62.7 63.2 63.8 64.4 65.0 65.6 65.9
11.0
55.5 56.6 57.7 58.2 58.7 59.5 60.4 61.0 61.6 62.2 62.8 63.4 64.0 64.4
11.5
53.9 55.0 56.0 56.5 57.1 57.9 58.8 59.4 60.1 60.6 61.1 61.6 62.2 62.7
12.0
52.3 53.4 54.4 55.0 55.6 56.3 57.1 57.7 58.4 58.9 59.4 60.1 60.8 61.2