Imaging for early stage breast cancer

Margin calculation recipe

mean setup error (systematic) daily setup error (random )

2,0

1,5

1,0

0,5

0,0

-2,0

-1,5 -1,0

-0,5

0,0

0,5

1,0

1,5

2,0

-0,5

-1,0

-1,5

-2,0

Measurements for many patients and many fractions

Σ: population systematic error = SD of overall population mean setup error

σ: population random error = average of SDs of individual daily random error

CTV - PTV margin = 2.5 • Σ + 0.7 • σ

van Herk et al. IJROBP 47:1121-1135, 2000