Margin calculation for multiple lung metastases treated with single-isocenter SBRT

Intra- and inter-fraction breath-hold variations and margins for radiotherapy of abdominal targets

“…1 σ intrafraction 3.9 mm See Fig. 1 σ machine 0.6 mm 90th percentile of the maximum measured radius during routinely performed Winston-Lutz tests [29] α 2.5 90% of population, 3D [26] , [27] β heterogeneous 0.31/0.85 For 65%/80% isodose prescription [29] N obs 3 Number of fractions in treatments from which errors were derived Prescription Fractions ( N treat ) Margin EBH SI ( M SI,EBH ) Margin ITV ( M ITV ) Threshold motion amplitude ( h th ) 65% isodose 3 9.9 mm 5.0 mm 6.5 mm 5 8.5 mm 4.7 mm 5.1 mm 6 8.2 mm 4.6 mm 4.8 mm 8 7.6 mm 4.3 mm 4.4 mm 10 7.3 mm 4.1 mm 4.3 mm 80% isodose 3 12.2 mm 6.0 mm 8.3 mm 5 11.1 mm 5.7 mm 7.2 mm 6 10.7 mm 5.6 mm 6.8 mm 8 10.3 mm 5.4 mm 6.5 mm 10 10.0 mm 5.2 mm 6.4 mm …”

“…Since the intrafraction EBH reproducibility errors were based on a median of 3 fractions per patient, N obs = 3 was used. Values for were assessed in a previous study [29] and is the value to reach a certain population coverage. Margins were calculated for N treat = 3,5,6,8 and 10.…”