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15

Dose and monitor unit calculation

Warsaw 2017

Measured

Calculated

Type

Dose (Gy)

MU (Dose/MU)

meas

Dose MU

(Dose/

MU)

calc

d(i) /d%(i)

5x5

Open

0.557

100

0.00557

1.00 184.78 0.00541

0.971 / -2.9%

60º

Wedge

0.152

100

0.00152

1.00 677.73 0.00148

0.969 / -3.1%

10x10

Open

0.614

100

0.00614

1.00 165.46 0.00604

0.984 / -1.6%

60º

Wedge

0.173

100

0.00173

1.00 579.46 0.00173

1.000 / 0.0%

20x20

Open

0.673

100

0.00673

1.00 149.80 0.00668

0.993 / -0.7%

60º

Wedge

0.197

100

0.00197

1.00 527.66 0.00189

0.964 / -3.6%

30x30

Open

0.694

100

0.00694

1.00 145.35 0.00688

0.991 / -0.9%

60º

Wedge

0.206

100

0.00206

1.00 509.46 0.00196

0.951 / -4.9%

5x20

Open

0.597

100

0.00597

1.00 168.16 0.00595

0.997 / -0.3%

60º

Wedge

0.167

100

0.00167

1.00 593.02 0.00169

1.010 / +1.0%

20x5

Open

0.589

100

0.00589

1.00 172.77 0.00579

0.983 / -1.7%

60º

Wedge

0.164

100

0.00164

1.00 622.97 0.00162

0.979 / -2.1%

Data from point measurements using an ionization chamber positioned at 20 cm depth along

the central beam axis in a large water phantom, source-skin distance 90 cm, irradiated with a

beam of 18 MV x-rays.