204 Petrovic B et al. / Verification of EDW in three ways 15 MV, 10x10 cm build up, open eld vs. pro le in non wedge direction ,-1099 ,-1002 ,-889 ,-810 ,-703 ,-599 ,-501 ,-398 -30 ,-042 ,-99 ,-10 ,103 ,198 ,296 40 ,984 ,602 ,699 ,803 90 ,979 distance from central axis (mm) FIGURE 3. Open field profiles overlap with the EDW profiles in non wedged direction (example is 10 cm x10 cm field). 15 MV, 10x10 wedge 60 deg build up, 50 mm, 100 mm, 200 mm 120 100 80 ) % ( D P 60 40 20 0 160 140 120 100 ) % ( D P 80 60 40 20 0 distance from central axis (mm) FIGURE 4. CA 24 profiles in comparison with hard wedge profiles, 10 cm x10 cm field, 60 deg wedge. Profile measurements Radiol Oncol 2010; 44(3): 199-206. open ﬁeld EDW 15 deg EDW 30 deg EDW 45 deg EDW 60 deg CA 24 hard These calculated profiles, as well as the profiles obtained by CA 24, and EPID, were compared to the profiles of hard wedges obtained using Blue phantom and CC13 ionization chambers, collected upon commissioning and acceptance tests of this linear accelerator. Hard wedges measurements and open field measurements The measured data of open fields and for hard wedges, collected during commissioning and ac- ceptance tests of the Varian 2100C linac were used for this study. Only additional measurements for the field 4x4 cm2 were collected during this survey for all wedge angles and depths, since Varian rec- ommendations for commissioning do not include this field size as mandatory. Results Percentage depth doses The percentage depth dose curves of the open fields (measured by CC13 chambers), hard wedged fields (measured also by CC13 chambers), EDW fields (measured by linear array CA 24- PDD val- ues extracted from profiles) and calculated by XIO, were compared. Generally speaking, the PDDs of open fields and EDW fields do not differ more than 0.5%. PDDs of open fields have a higher surface dose than the PDDs of hard wedged fields (dose extrapolated to the surface of water- 0 cm depth) (Figure 1). This comes from the beam hardening under the mechanical wedge. The beam hardening effect is also clearly visible on the tail of the PDD curve of the mechanical wedge and gives the dif- ference of around 2%. PDDs generated from profiles measured by CA 24 and calculated by XIO are practically identical (result of modelling the EDW in TPS). The PDDs with EPID could not be obtained at this stage, since only measurements in build up were possible. EPID profiles in build up compared to linear array measurements in build up Profiles were obtained in direction of the moving jaw, showing the wedged shaped distribution.