Fig 3. Phantom dosimetry measurement.

EBT-3 films were calibrated by ion chamber under large field conditions. All beam profiles and corresponding percentage depth dose were measured using two films as shown: one is on the surface perpendicular to radiation beam (A) and one sandwiched between two small phantom blocks parallel to radiation beam (B). The circles indicate the film areas used for volume-average dose calculation estimates. The following assumption was made for volume-averaged tumor dose and EUD calculations: dose value does not vary +/-1cm along the direction parallel to the same valleys/peaks.