Peripheral dose measurement in high-energy photon radiotherapy with the implementation of MOSFET

Figure 1 Geometry set-up of the peripheral dose measurements in a water phantom where a is the distance from the edge of the field (from 1 to 18 cm) where the MOSFET dosimeter was placed, and d_max is 1. 5 and 3.3 cm for 6 and 18 MV, respectively. This shape represents the MOSFET dosimeter.

Figure 2 Effect of depth on percentage peripheral dose for 6 and 18 MV beams for various field sizes at (A) 5 cm off axis distance and (B) 15 cm off axis distance.

Figure 3 Percentage peripheral dose at surface vs distance from the field edge for various field sizes and both energies.

Figure 4 Effect of distance on percentage peripheral dose, using the 6 MV beam, for various depths for (A) 5 cm × 5 cm and (B) 15 cm × 15 cm.

Figure 5 Percentage peripheral dose obtained with metal oxide semiconductor field effect transistor and the ionization chamber for various field sizes as a function of distance from the surface using the (A) 6 MV and (B) 18 MV beam. MOSFET: Metal oxide semiconductor field effect transistor.

Figure 6 Coefficient of variation vs dose.