Table 1 Machine specific parameters for both linacs and the TPSs parameters used for this study

SAD (cm)

100

90

Linac calibration

At the maximum dose point: 100 MU correspond to 1 Gy

Effective leaf width (mm)

0.5

0.415

Field size at isocentre (cm²)

40 × 40

27.4 × 24.1

Multileaf collimator

Rounded leaf edges

double-stacked, double-focused leaves

IMRT technique

VMAT

ssIMRT

Photon energy (MV)

6

6

Flattening filter

FF

FFF

Static magnetic field (T)

–

0.35

TPS parameters:

Calculation grid size (cm³)

0.3 × 0.3 × 0.3

0.3 × 0.3 × 0.3

Statistical uncertainty (%)

1

1

Dose calculation algorithm

XVMC

KMC