research article Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements Borislava Petrovic1, Aleksandra Grzadziel2, Laza Rutonjski1, Krzysztof Slosarek2 1 Department of Radiotherapy, Institute of Oncology Vojvodina, Sremska Kamenica, Serbia 2 Radiotherapy and Brachytherapy Planning Department, Comprehensive Cancer Centre, Maria Sklodowska Curie Memorial Institute, Gliwice, Poland Received 8 March 2010 Accepted 19 May 2010 Correspondence to: Borislava Petrovic MSc, Department of Radiotherapy, Institute of oncology Vojvodina, Institutski put 4, 21204 Sremska Kamenica. E-mail: nsbim@eunet.rs Disclosure: No potential conflicts of interest were disclosed. Introduction. Enhanced dynamic wedges (EDW) are known to increase drastically the radiation therapy treatment efficiency. This paper has the aim to compare linear array measurements of EDW with the calculations of treatment planning system (TPS) and the electronic portal imaging device (EPID) for 15 MV photon energy. Materials and methods. The range of different field sizes and wedge angles (for 15 MV photon beam) were measured by the linear chamber array CA 24 in Blue water phantom. The measurement conditions were applied to the calculations of the commercial treatment planning system XIO CMS v.4.2.0 using convolution algorithm. EPID measurements were done on EPID-focus distance of 100 cm, and beam parameters being the same as for CA24 measurements. Results. Both depth doses and profiles were measured. EDW linear array measurements of profiles to XIO CMS TPS calculation differ around 0.5%. Profiles in non-wedged direction and open field profiles practically do not differ. Percentage depth doses (PDDs) for all EDW measurements show the difference of not more than 0.2%, while the open field PDD is almost the same as EDW PDD. Wedge factors for 60 deg wedge angle were also examined, and the dif- ference is up to 4%. EPID to linear array differs up to 5%. Conclusions. The implementation of EDW in radiation therapy treatments provides clinicians with an effective tool for the conformal radiotherapy treatment planning. If modelling of EDW beam in TPS is done correctly, a very good agreement between measurements and calculation is obtained, but EPID cannot be used for reference measure- ments. Key words: enhanced dynamic wedge; linear array; EPID Introduction Mechanical wedge filters (hard wedges) are often used in the treatment planning as compensators of dose inhomogeneities in the photon therapy. Nowadays, they are often replaced by Enhanced Dynamic Wedge (EDW). EDW is a technical so- lution of Varian Medical Systems, but also other manufactureres have solutions which achieve the same result (Elekta- omni wedge, Siemens- vir- tual wedge). The EDW technique achieves wedge- shaped dose distributions by the computer-con- trolled movement of one of the collimator jaws un- der the simultaneous adjustment of dose rate and speed of the moving jaw. The relationship between the number of delivered monitor units and the po- sition of the moving jaw is governed by lookup ta- bles referred to as ”Segmented Treatment Tables” Radiol Oncol 2010; 44(3): 199-206. doi:10.2478/v10019-010-0037-5 199