To investigate the effectiveness of edge detector for depth dose measurement in buildup region of 6 and 10 MV FFF photon beams

Commissioning is one of the most important parts of the entire QA programme for both the treatment planning systems (TPS) and the planning process. Dosimetric parameters such as percentage depth dose, profiles and output factors are important for the commissioning of treatment planning systems in radiotherapy. Nowadays, along with nominal photon beams, flattening filter free (FFF) beams are being used for the treatments where high dose is required in single or few fractions. Since FFF beam uses very high dose in very short time, the accurate measurement of dosimetric data for FFF beam becomes very important. Thimble ionization chamber with volumes of the order of 0.1-0.2 cc is commonly used for these types of measurements. The disadvantage of 0.1-0.2 cc chamber is they are not suitable for the measurement of PDD in shallow depths due to the wrong estimation of surface doses. A buildup region is the most sensitive region of PDD curve, which if not measured accurately, would lead to wrong dose calculations by TPS